package main

import (
	"fmt"
	"reflect"
	"strconv"
	"strings"

	"github.com/z7zmey/php-parser/freefloating"
	"github.com/z7zmey/php-parser/node"
	"github.com/z7zmey/php-parser/node/expr"
	"github.com/z7zmey/php-parser/node/expr/assign"
	"github.com/z7zmey/php-parser/node/expr/binary"
	"github.com/z7zmey/php-parser/node/name"
	"github.com/z7zmey/php-parser/node/scalar"
	"github.com/z7zmey/php-parser/node/stmt"

	"php2go/parseutil"
)

func nodeTypeString(n node.Node) string {
	return reflect.TypeOf(n).String()
}

type parseErr struct {
	n        node.Node
	childErr error
}

func (pe parseErr) Error() string {
	positionStr := ""
	if posn := pe.n.GetPosition(); posn != nil {
		positionStr = fmt.Sprintf(" on line %d", posn.StartLine)
	}

	return fmt.Sprintf("Parsing %s%s: %s", nodeTypeString(pe.n), positionStr, pe.childErr.Error())
}

func (pe parseErr) Unwrap() error {
	return pe.childErr
}

//

type arityErr struct {
	funcName                     string
	got                          int
	expected, expectedUpperRange int
}

func (ae arityErr) Error() string {
	if ae.expected != ae.expectedUpperRange {
		return fmt.Sprintf("Call to '%s' expected %d to %d argument(s), got %d", ae.funcName, ae.expected, ae.expectedUpperRange, ae.got)
	} else {
		return fmt.Sprintf("Call to '%s' expected %d argument(s), got %d", ae.funcName, ae.expected, ae.got)
	}
}

//

type ParseContext int

const (
	TopLevelContext         ParseContext = iota // We are free to inject entire additional statements
	RvalueFreeContext                           // We are free to make `x, ok := foo(); ok` transformations e.g. for array_key_exists()/isset()
	RvalueRestrictedContext                     // We are not free to make semicolon transformations
)

//

type conversionState struct {
	currentClassName       string
	currentClassParentName string
	currentErrHandler      string
	currentFunctionName    string
	currentMethodName      string
	currentNamespace       string
	currentTraitName       string // TODO
	importPackages         map[string]struct{}
}

//

func normaliseCommentStrFragment(s string) string {
	if len(s) == 0 {
		return s
	}

	lines := strings.Split(s, "\n")
	for i, _ := range lines {
		lines[i] = strings.TrimLeft(lines[i], "\t\r\n ")
		if strings.HasPrefix(lines[i], `//`) {
			lines[i] = lines[i][2:]
		}
	}
	return `/*` + strings.TrimRight(strings.Join(lines, "\n"), "\n") + ` */`
}

func normaliseCommentStr(s string) string {

	// A comment may be injected at any point in the source tree
	// It's not necessarily valid to use line comments (`//`) mid-AST
	// Avoid the problem by unconditionally transforming to range comments (`/**/`)

	extents := strings.Split(s, `/*`)
	ret := make([]string, 0, len(extents)*2)
	for _, extent := range extents {
		parts := strings.SplitN(extent, `*/`, 2) // any further */ after this has no effect
		if len(parts) == 1 {
			// No range comment, only line comment/whitespace
			// Transform single range only
			ret = append(ret, normaliseCommentStrFragment(parts[0]))

		} else { // len(parts) == 2
			// Range comment part is OK
			// Only second middle part needs normalising
			ret = append(ret, `/*`+parts[0]+`*/`, normaliseCommentStrFragment(parts[1]))

		}
	}

	return strings.Join(ret, "")
}

func (this *conversionState) convert(n node.Node) (string, error) {

	// Get any whitespace/comments attached to this node
	// FIXME we are not calling convert() on some interior nodes of statements - some comments may be lost(!!)
	freePrefix := ""
	freeSuffix := ""

	if ff := n.GetFreeFloating(); ff != nil && !ff.IsEmpty() {
		for positionType, elements := range *ff {
		element:
			for _, element := range elements {
				if element.StringType == freefloating.TokenType {
					// Skip <?php
					continue element
				}
				if element.StringType == freefloating.WhiteSpaceType {
					// We can't insert arbitrary whitespace
					// TODO the number of newlines would be fine ONLY IF this is a *stmt
					continue element
				}

				switch positionType {
				default:
					fallthrough
				case freefloating.Start:
					freePrefix += element.Value

				case freefloating.End, freefloating.AltEnd:
					freeSuffix += element.Value
				}
			}
		}
	}

	// Convert the node itself
	ret, err := this.convertNoFreeFloating(n)
	if err != nil {
		return "", err
	}

	//if len(freePrefix) > 0 && !(strings.HasSuffix(freePrefix, "\n") || strings.HasSuffix(freePrefix, `*/`)) {
	//	freePrefix += "\n"
	//}

	freePrefix = normaliseCommentStr(freePrefix)
	freeSuffix = normaliseCommentStr(freeSuffix)

	return freePrefix + ret + freeSuffix, nil
}

func (this *conversionState) convertNoFreeFloating(n_ node.Node) (string, error) {

	switch n := n_.(type) {

	//
	// node
	//

	case *node.Root:

		// Hoist all declarations first, and put any top-level code into a generated main() function
		declarations := []string{}
		statements := []string{}
		packageName := `main`

		for _, s := range n.Stmts {

			switch s := s.(type) {
			case *stmt.Class, *stmt.Function, *stmt.Interface:
				this.currentErrHandler = "return nil, err\n"

				sm, err := this.convert(s)
				if err != nil {
					return "", parseErr{s, err}
				}

				// Declaration - emit immediately (hoist)
				declarations = append(declarations, sm)

			case *stmt.Namespace:
				if len(s.Stmts) > 0 {
					return "", parseErr{s, fmt.Errorf("please use `namespace Foo;` instead of blocks")}
				}
				namespace, err := this.resolveName(s.NamespaceName)
				if err != nil {
					return "", err
				}
				packageName = namespace
				this.currentNamespace = packageName

			default:
				this.currentErrHandler = "panic(err)\n" // top-level init/main behaviour

				sm, err := this.convert(s)
				if err != nil {
					return "", parseErr{s, err}
				}

				// Top-level function code - deter emission
				statements = append(statements, sm)
			}

		}

		// Emit
		ret := "package main\n\n"
		if len(this.importPackages) > 0 {
			ret += "import (\n"
			for packageName, _ := range this.importPackages {
				ret += "\t" + quoteGoString(packageName) + "\n"
			}
			ret += ")\n"
		}

		if len(declarations) > 0 {
			ret += strings.Join(declarations, "\n") + "\n"
		}

		if len(statements) > 0 {
			topFunc := `init`
			if packageName == `main` {
				topFunc = `main`
			}

			ret += "func " + topFunc + "() {\n"
			ret += "\t" + strings.Join(statements, "\t") // Statements already added their own newline
			ret += "}\n"
		}

		return ret, nil

	case *node.Identifier:
		return n.Value, nil

	case Literal:
		// We expect literal statements to act like a *Stmt, i.e. be emitted with a trailing NL
		return n.Value + "\n", nil

	//
	// stmt
	//

	case *stmt.StmtList:
		// TODO keep track of variable types within this scope

		ret := "{\n" // new variable scope
		for _, s := range n.Stmts {
			line, err := this.convert(s)
			if err != nil {
				return "", parseErr{s, err}
			}

			ret += line // Statements already added a trailing newline
		}
		return ret + "}\n", nil

	case *stmt.Class:
		ret := ""

		prevClassName := this.currentClassName // almost certainly empty-string
		prevClassParentName := this.currentClassParentName

		className := n.ClassName.(*node.Identifier).Value
		this.currentClassName = className
		memberVars := []string{}
		memberConsts := []string{}
		memberFuncs := []string{}

		if n.Extends != nil {
			parentName, err := this.resolveName(n.Extends.ClassName)
			if err != nil {
				return "", parseErr{n, err}
			}

			memberVars = append(memberVars, parentName+" // parent")
			this.currentClassParentName = parentName
		} else {
			this.currentClassParentName = ""
		}

		// Walk all child nodes of the class
		for _, s_ := range n.Stmts {
			switch s := s_.(type) {

			case *stmt.PropertyList:
				// Class member variable

				// Doc comment
				// TODO scan for `@var {type}` strings

				// Name
				prop, ok := s.Properties[0].(*stmt.Property)
				if !ok {
					return "", parseErr{s, fmt.Errorf("unexpected propertylist structure")}
				}
				name := prop.Variable.(*expr.Variable).VarName.(*node.Identifier).Value

				// Type (unknown)
				memberType := unknownVarType

				// 'Modifiers' - protected public readonly ...
				// prop.Modifiers

				memberVars = append(memberVars, name+" "+memberType.AsGoString())

			case *stmt.ClassConstList:
				// Class constant
				// Go doesn't have class constants - convert it to just a package const, prefixed with the const name
				// TODO detect, intercept and re-reroute any future references to these consts!
				// That might need a separate compiler pass
				for _, c_ := range s.Consts {
					c, ok := c_.(*stmt.Constant)
					if !ok {
						return "", parseErr{c_, fmt.Errorf("expected stmt.Constant")}
					}

					name, err := applyVisibilityModifier(c.ConstantName.(*node.Identifier).Value, s.Modifiers)
					if err != nil {
						return "", parseErr{c_, err}
					}

					constExpr, err := this.convert(c.Expr)
					if err != nil {
						return "", parseErr{c.Expr, err}
					}

					memberConsts = append(memberConsts, className+name+" = "+constExpr)
				}

			case *stmt.ClassMethod:
				// Function name
				// If function is public/private/protected, set the first character to upper/lowercase
				funcName, err := applyVisibilityModifier(s.MethodName.(*node.Identifier).Value, s.Modifiers)
				if err != nil {
					return "", parseErr{s, err}
				}

				prevMethodName := this.currentMethodName
				this.currentMethodName = funcName

				// TODO implement abstract methods as method functions

				// Doc comment
				// TODO scan for `@param {type}` strings

				isConstructor := (strings.ToLower(funcName) == `__construct` || strings.ToLower(funcName) == strings.ToLower(className))

				if isConstructor {
					// Constructor functions get transformed to NewFoo() (*Foo, error)

					// We need to force the return type
					returnType := name.NewName([]node.Node{name.NewNamePart(className)})

					// We also need prefix + suffix statements
					allStmts := make([]node.Node, 0, 2+len(s.Stmt.(*stmt.StmtList).Stmts))
					allStmts = append(allStmts, Literal{`this := &` + className + `{}`}) // TODO also insert variable type into the scope
					allStmts = append(allStmts, s.Stmt.(*stmt.StmtList).Stmts...)
					allStmts = append(allStmts, Literal{`return this, nil`})

					// Method body
					funcStmt, err := this.convertFunctionCommon(s.Params, returnType, true /* always use ptr return */, allStmts)
					if err != nil {
						return "", parseErr{s, err}
					}
					memberFuncStmt := "func " + constructorName(className) + funcStmt + "\n"
					memberFuncs = append(memberFuncs, memberFuncStmt)

				} else {

					// Check if this is a static method
					hasStatic, err := hasModifier(s.Modifiers, `static`)
					if err != nil {
						return "", parseErr{s, err}
					}

					// Method body
					funcStmt, err := this.convertFunctionCommon(s.Params, s.ReturnType, s.ReturnsRef, s.Stmt.(*stmt.StmtList).Stmts)
					if err != nil {
						return "", parseErr{s, err}
					}

					if hasStatic {
						memberFuncs = append(memberFuncs, "func "+className+funcName+funcStmt+"\n")
					} else {
						memberFuncs = append(memberFuncs, "func (this *"+className+") "+funcName+funcStmt+"\n")
					}

				}

				// Reinstate stack
				this.currentMethodName = prevMethodName

			default:
				return "", parseErr{s, fmt.Errorf("Class '%s' contained unexpected AST node; expected PropertyList / ClassMethod", className)}
			}
		}

		// Write out any class constants
		if len(memberConsts) == 1 {
			ret += "const " + memberConsts[0] + "\n"
		} else if len(memberConsts) > 1 {
			ret += "const (\n" + strings.Join(memberConsts, "\n") + ")\n"
		}

		// Create struct typedef containing all explicit properties
		ret += "type " + className + " struct {\n"
		ret += "\t" + strings.Join(memberVars, "\n\t") + "\n"
		ret += "}\n"

		// Create all member functions
		ret += strings.Join(memberFuncs, "\n\n")

		if n.Implements != nil {
			for _, ifaceName_ := range n.Implements.InterfaceNames {
				ifaceName, err := this.resolveName(ifaceName_)
				if err != nil {
					return "", parseErr{ifaceName_, err}
				}

				// Add extra interface assertion statement
				ret += "var _ " + ifaceName + " = &" + className + "{} // interface assertion\n"

			}
		}

		// Done
		// Reinstate parent state before returning
		this.currentClassName = prevClassName
		this.currentClassParentName = prevClassParentName
		return ret, nil

	case *stmt.Interface:

		ifaceName := n.InterfaceName.(*node.Identifier).Value

		ret := "type " + ifaceName + " interface {\n"

		for _, ss := range n.Stmts {
			classMethod, ok := ss.(*stmt.ClassMethod)
			if !ok {
				return "", parseErr{ss, fmt.Errorf("expected stmt.ClassMethod")}
			}

			methodName, err := applyVisibilityModifier(classMethod.MethodName.(*node.Identifier).Value, classMethod.Modifiers)
			if err != nil {
				return "", parseErr{ss, err}
			}

			// TODO classMethod.PhpDocComment

			arglist, err := this.convertFunctionCommon(classMethod.Params, classMethod.ReturnType, classMethod.ReturnsRef, nil)
			if err != nil {
				return "", parseErr{ss, err}
			}

			ret += methodName + arglist + "\n"
		}

		ret += "}\n"

		return ret, nil

	case *stmt.Function:
		// Top-level function definition
		// TODO parse doc comment
		// FIXME is this the same as a closure?
		funcName := n.FunctionName.(*node.Identifier).Value

		if funcName == `super` {
			return "", parseErr{n, fmt.Errorf("Function name '%s' probably will not function correctly", funcName)}
		}

		// All top-level functions like this are public; ensure function name starts
		// with an uppercase letter
		funcName = toPublic(funcName)

		// Convert body
		prevFuncName := this.currentFunctionName
		this.currentFunctionName = funcName

		funcStmt, err := this.convertFunctionCommon(n.Params, n.ReturnType, n.ReturnsRef, n.Stmts)
		if err != nil {
			// FIXME an early-return will trash the `this` state around currentFunctionName, etc
			// That's OK for now since we don't practically have any error handling than an unmitigated panic
			return "", parseErr{n, err}
		}

		this.currentFunctionName = prevFuncName

		ret := "func " + funcName + funcStmt + "\n"
		return ret, nil

	case *stmt.Return:
		child, err := this.convert(n.Expr)
		if err != nil {
			return "", parseErr{n, err}
		}

		ret := "return " + child + ", nil\n"
		return ret, nil

	case *stmt.Throw:
		// throw (expr);
		// Treat as an err return
		// FIXME we don't know the default return type for the function we're in

		// PHP can only throw objects, not literals/scalars
		// If the expr is just new Exception, we can convert it to errors.New()

		//if str, ok := n.Expr.(*scalar.String); ok {
		//	return "return nil, errors.New(" + str.Value + ")\n", nil
		//}

		child, err := this.convert(n.Expr)
		if err != nil {
			return "", parseErr{n, err}
		}

		return "return nil, " + child + "\n", nil

	case *stmt.For:

		var preinit, finit string
		var err error = nil

		if len(n.Init) == 0 {
			// No initialiser in loop

		} else if len(n.Init) == 1 {
			finit, err = this.convert(n.Init[0])
			if err != nil {
				return "", parseErr{n, err}
			}

		} else {
			// We can handle the case of multiple init statements by hoisting them
			// above the loop. There is no negative impact on PHP scoping rules, but
			// it may cause an extra local variable after the loop that may result
			// in type mismatch (can be fixed by using an extra scope).
			for _, initStmt := range n.Init {
				singleInitStmt, err := this.convert(initStmt)
				if err != nil {
					return "", parseErr{initStmt, err}
				}

				preinit += singleInitStmt + "\n"
			}
		}

		if len(n.Cond) != 1 {
			return "", parseErr{n, fmt.Errorf("for loop can only have 1 cond clause, found %d", len(n.Cond))}
		}
		fcond, err := this.convert(n.Cond[0])
		if err != nil {
			return "", parseErr{n, err}
		}

		if len(n.Loop) != 1 {
			return "", parseErr{n, fmt.Errorf("for loop can only have 1 loop clause, found %d", len(n.Loop))}
		}
		loopStmt := n.Loop[0]
		if preinc, ok := loopStmt.(*expr.PreInc); ok {
			// It's idiomatic to do for (,, ++i) but preincrement doesn't exist in Go
			// Luckily for the case of a for loop, we can just swap it to postincrement
			loopStmt = expr.NewPostInc(preinc.Variable)
		} else if predec, ok := loopStmt.(*expr.PreDec); ok { // Likewise
			loopStmt = expr.NewPostDec(predec.Variable)
		}

		floop, err := this.convert(loopStmt)
		if err != nil {
			return "", parseErr{n, err}
		}

		body, err := this.convert(convertToStmtList(n.Stmt))
		if err != nil {
			return "", parseErr{n, err}
		}

		return preinit + "for " + finit + "; " + fcond + "; " + floop + " " + body + "\n", nil

	case *stmt.Foreach:
		iterand, err := this.convert(n.Expr)
		if err != nil {
			return "", parseErr{n, err}
		}

		valueReceiver, err := this.convert(n.Variable)
		if err != nil {
			return "", parseErr{n, err}
		}

		keyReceiver := `_`
		if n.Key != nil {
			keyReceiver, err = this.convert(n.Key)
			if err != nil {
				return "", parseErr{n, err}
			}
		}

		body, err := this.convert(convertToStmtList(n.Stmt))
		if err != nil {
			return "", parseErr{n, err}
		}

		return "for " + keyReceiver + ", " + valueReceiver + " := range " + iterand + " " + body + "\n", nil

	case *stmt.While:
		cond, err := this.convert(n.Cond)
		if err != nil {
			return "", parseErr{n, err}
		}

		body, err := this.convert(convertToStmtList(n.Stmt))
		if err != nil {
			return "", parseErr{n, err}
		}

		return "for " + cond + " " + body + "\n", nil

	case *stmt.Do:
		cond, err := this.convert(n.Cond)
		if err != nil {
			return "", parseErr{n, err}
		}

		bodyStmts := convertToStmtList(n.Stmt)
		bodyStmts.Stmts = append(bodyStmts.Stmts, Literal{"if " + cond + "{\nbreak\n}"})

		body, err := this.convert(bodyStmts)
		if err != nil {
			return "", parseErr{n, err}
		}

		return "for " + cond + " " + body + "\n", nil

	case *stmt.Expression:

		// Special case
		if fncall, ok := n.Expr.(*expr.FunctionCall); ok {
			if fnname, err := this.resolveName(fncall.Function); err == nil && fnname == "super" {
				// Call to parent constructor

				if this.currentClassParentName == "" {
					return "", parseErr{n, fmt.Errorf("Call to parent constructor outside of class context")}
				}

				// We need to call the parent constructor function (NewX) with these arguments
				funcArgs, err := this.convertFuncCallArgsCommon(fncall.ArgumentList)
				if err != nil {
					return "", parseErr{n, err}
				}

				// Then we need to overwrite the embedded value type with the received pointer
				// That's not 100% safe in all cases if the *this pointer is leaked
				// within the constructor, but, our generated code will never do that
				// TODO replace our NewX constructors with split NewX + newXInPlace(??)

				// No need to use a child scope for the temporary name -
				// super() is a reserved name in PHP anyway
				ret := "super, err := " + constructorName(this.currentClassParentName) + "(" + strings.Join(funcArgs, ", ") + ")\n"
				ret += "if err != nil {\n"
				ret += this.currentErrHandler //"return err\n"
				ret += "}\n"
				ret += "this." + this.currentClassParentName + " = *super // copy by value\n"
				return ret, nil
			}

			if fnname, err := this.resolveName(fncall.Function); err == nil && fnname == "define" {
				// define() gets converted to const

				if len(fncall.ArgumentList.Arguments) != 2 {
					return "", parseErr{fncall, arityErr{"define", len(fncall.ArgumentList.Arguments), 2, 2}}
				}

				defineName := fncall.ArgumentList.Arguments[0].(*node.Argument).Expr // that much is always possible
				defineNameStr, ok := defineName.(*scalar.String)
				if !ok {
					return "", parseErr{fncall, fmt.Errorf("can't handle a complex expression in define() name")}
				}

				rawDefineName, err := phpUnquote(defineNameStr.Value)
				if err != nil {
					return "", parseErr{fncall, err}
				}

				// Convert to a final Const statement
				return this.convert(stmt.NewConstList([]node.Node{stmt.NewConstant(node.NewIdentifier(rawDefineName), fncall.ArgumentList.Arguments[1].(*node.Argument).Expr, "")}))
			}
		}

		// Assignment expressions can take on better error-handling behaviour
		// when we know the assignment is a top-level expression
		if a, ok := n.Expr.(*assign.Assign); ok {
			return this.convertAssignAssign(a, true)
		}

		// Non-assignment expression
		child, err := this.convert(n.Expr)
		if err != nil {
			return "", parseErr{n, err}
		}

		// If this is a simple expression (func call; indirect/method call; assignment of func/method call) then
		// we need to propagate errors
		switch n.Expr.(type) {
		case *expr.FunctionCall, *expr.StaticCall, *expr.New:
			ret := "_, err = " + child + "\n"
			ret += "if err != nil {\n"
			ret += this.currentErrHandler
			ret += "}\n"
			return ret, nil

		default:
			// Some other kind of general expression - no special error handling needed
			ret := child + "\n" // standalone expression statement

			return ret, nil
		}

	case *stmt.Echo:
		// Convert into fmt.Print
		args := make([]string, 0, len(n.Exprs))
		for _, expr := range n.Exprs {
			exprGo, err := this.convert(expr)
			if err != nil {
				return "", parseErr{n, err}
			}

			args = append(args, removeParens(exprGo))
		}

		this.importPackages["fmt"] = struct{}{}

		return "fmt.Print(" + strings.Join(args, ", ") + ")\n", nil // newline - standalone statement

	case *stmt.InlineHtml:
		// Convert into fmt.Print

		this.importPackages["fmt"] = struct{}{}
		return "fmt.Print(" + quoteGoString(n.Value) + ")\n", nil // newline - standalone statement

	case *stmt.ConstList:
		consts := make([]string, 0, len(n.Consts))
		for _, c_ := range n.Consts {
			c, ok := c_.(*stmt.Constant)
			if !ok {
				return "", parseErr{c_, fmt.Errorf("expected stmt.Constant")}
			}

			// TODO c.PhpDocComment

			constName := c.ConstantName.(*node.Identifier).Value

			rvalue, err := this.convert(c.Expr)
			if err != nil {
				return "", parseErr{c, err}
			}

			consts = append(consts, constName+" = "+rvalue)
		}

		if len(n.Consts) == 1 {
			return "const " + consts[0] + "\n", nil
		} else {
			return "const (\n" + strings.Join(consts, "\n") + ")\n", nil
		}

	case *stmt.If:

		hasCondAssign, err := hasInteriorAssignment(n.Cond)
		if err != nil {
			return "", parseErr{n, err}
		}
		if hasCondAssign {
			return "", parseErr{n.Cond, fmt.Errorf("please remove assignment from if-expression")}
		}

		cond, err := this.convert(n.Cond)
		if err != nil {
			return "", parseErr{n, err}
		}

		body, err := this.convert(convertToStmtList(n.Stmt))
		if err != nil {
			return "", parseErr{n, err}
		}

		//

		// `elseif` is a valid PHP keyword; but `else if` gets treated as `else { if ()`
		// If our discovered `else` clause has exactly one child If statement,
		// rewrite it as an else-if clause (and recurse)
		for n.Else != nil {
			els, ok := n.Else.(*stmt.Else)
			if !ok {
				return "", parseErr{n, fmt.Errorf("expected stmt.Else")}
			}

			elif, ok := els.Stmt.(*stmt.If)
			if !ok {
				break // exit loop
			}

			n.AddElseIf(stmt.NewElseIf(elif.Cond, elif.Stmt))
			for _, extraElif := range elif.ElseIf {
				n.AddElseIf(extraElif)
			}
			n.Else = elif.Else // Wipe from future processing
		}

		//

		ret := "if " + cond + body
		for _, elif := range n.ElseIf {
			elif, ok := elif.(*stmt.ElseIf)
			if !ok {
				return "", parseErr{n, fmt.Errorf("expected stmt.ElseIf")}
			}

			cond, err := this.convert(elif.Cond)
			if err != nil {
				return "", parseErr{n, err}
			}

			body, err := this.convert(convertToStmtList(elif.Stmt))
			if err != nil {
				return "", parseErr{n, err}
			}

			ret = strings.TrimRight(ret, "\n")
			ret += " else if " + cond + body
		}

		if n.Else != nil {
			els, ok := n.Else.(*stmt.Else)
			if !ok {
				return "", parseErr{n, fmt.Errorf("expected stmt.Else")}
			}

			body, err := this.convert(convertToStmtList(els.Stmt))
			if err != nil {
				return "", parseErr{n, err}
			}

			ret = strings.TrimRight(ret, "\n")
			ret += " else  " + body
		}

		return ret, nil

	case *stmt.Switch:
		cond, err := this.convert(n.Cond)
		if err != nil {
			return "", parseErr{n, err}
		}

		cases := make([]string, 0, len(n.CaseList.Cases))
		for _, ncase := range n.CaseList.Cases {
			switch ncase.(type) {
			case *stmt.Default, *stmt.Case:
				caseStr, err := this.convert(ncase)
				if err != nil {
					return "", parseErr{n, err}
				}
				cases = append(cases, caseStr)

			default:
				return "", parseErr{ncase, fmt.Errorf("expected Case/Default")}
			}
		}

		// TODO use dead code elimination after `break` to clean up redundant fallthrough statements
		return "switch " + cond + " {\n" + strings.Join(cases, "\n") + "}\n", nil

	case *stmt.Case:
		// Add a `fallthrough` to the end
		// TODO then use dead code elimination to clean them up
		stmtBody, err := this.convert(stmt.NewStmtList(n.Stmts))
		if err != nil {
			return "", parseErr{n, err}
		}

		cond, err := this.convert(n.Cond)
		if err != nil {
			return "", parseErr{n, err}
		}

		return "case " + cond + ":\n" + stmtBody + "\nfallthrough\n", nil

	case *stmt.Default:
		// Add a `fallthrough` to the end
		// TODO then use dead code elimination to clean them up
		stmtBody, err := this.convert(stmt.NewStmtList(n.Stmts))
		if err != nil {
			return "", parseErr{n, err}
		}

		return "default: " + stmtBody + "\nfallthrough\n", nil

	case *stmt.Break:
		if n.Expr != nil {
			return "", parseErr{n, fmt.Errorf("break {expr} is not yet supported")} // TODO implement numbered break
		}

		return "break\n", nil

	case *stmt.Continue:
		if n.Expr != nil {
			return "", parseErr{n, fmt.Errorf("continue {expr} is not yet supported")} // TODO implement numbered continue
		}

		return "continue\n", nil

	case *stmt.Try:

		// Generate an if err != nil {} block that we can bring up whenever
		// an error is raised in a body function call

		// TODO put finally() code somewhere (before/after err checking??)

		handler := ""
		if len(n.Catches) == 0 {
			handler = "// suppress error"
		} else {

			catchVars := []string{}
			catchIfs := []string{}

			for _, catch_ := range n.Catches {
				catch, ok := catch_.(*stmt.Catch)
				if !ok {
					return "", parseErr{n, fmt.Errorf("expected stmt.Catch")}
				}

				catchVar := catch.Variable.(*expr.Variable).VarName.(*node.Identifier).Value

				catchBody, err := this.convert(stmt.NewStmtList(catch.Stmts))
				if err != nil {
					return "", parseErr{catch_, err}
				}

				for _, typename_ := range catch.Types {
					typename, err := this.resolveName(typename_)
					if !ok {
						return "", parseErr{catch_, err}
					}

					if typename == `Exception` {
						// PHP base type - catches all exceptions

						catchStmt := catchBody
						catchIfs = append(catchIfs, catchStmt)

					} else {

						tempCatchVar := catchVar
						if len(catch.Types) > 1 {
							tempCatchVar += "" + typename
						}

						// It's common for PHP types to have 'Exception' in the suffix
						// We are probably free to elide that (stylistically)
						if strings.HasSuffix(tempCatchVar, `Exception`) {
							tempCatchVar = tempCatchVar[0 : len(tempCatchVar)-9]
						}

						catchVars = append(catchVars, tempCatchVar+"*"+typename)

						this.importPackages["errors"] = struct{}{}
						catchStmt := "if errors.As(err, &" + tempCatchVar + ") {\n"
						if len(catch.Types) > 1 {
							catchStmt += catchVar + " := " + tempCatchVar + " // rename\n"
						}
						catchStmt += catchBody // contains its own {}
						catchStmt += "}"       // but without trailing NL

						catchIfs = append(catchIfs, catchStmt)
					}
				}
			}

			handler = ""
			if len(catchVars) == 1 {
				handler += "var " + catchVars[0] + "\n"
			} else {
				handler += "var (\n" + strings.Join(catchVars, "\n") + "\n)\n"
			}
			handler += strings.Join(catchIfs, " else ") + "\n"
		}

		// Store the handler to be used going forwards
		previousErrHandler := this.currentErrHandler
		this.currentErrHandler = handler

		body, err := this.convert(stmt.NewStmtList(n.Stmts))
		if err != nil {
			return "", parseErr{n, err}
		}

		// Reinstate parent error handler
		this.currentErrHandler = previousErrHandler
		return body, nil // Try/catch behaviour is transparently encoded in err handlers

	case *stmt.Nop:
		return "", nil

	//
	// assign
	//

	case *assign.Assign:
		return this.convertAssignAssign(n, false /* no reason to believe we are a top-level statement */)

	// Go has a limited set of assignment shorthands:
	//
	// ```
	//     assign_op = [ add_op | mul_op ] "=" .
	//
	//     [...]
	//
	//     add_op     = "+" | "-" | "|" | "^" .
	//     mul_op     = "*" | "/" | "%" | "<<" | ">>" | "&" | "&^" .
	// ```

	case *assign.BitwiseAnd:
		return this.convertAssignment(n, n.Variable, n.Expression, false, `&=`)

	case *assign.BitwiseOr:
		return this.convertAssignment(n, n.Variable, n.Expression, false, `|=`)

	case *assign.BitwiseXor:
		return this.convertAssignment(n, n.Variable, n.Expression, false, `^=`)

	case *assign.Coalesce:
		// Null coaslecing assignment expression - $x ??= $y;
		// We don't have a natural equivalent for the coalescing operator
		// We don't have an implementation of *binary.Coalesce yet either
		// But when we do this will need an rvalue transformation to use it

		return this.convert(assign.NewAssign(n.Variable, binary.NewCoalesce(n.Variable, n.Expression))) // FIXME also handle position/freefloating

	case *assign.Concat:
		return this.convertAssignment(n, n.Variable, n.Expression, false, `+=`)

	case *assign.Div:
		return this.convertAssignment(n, n.Variable, n.Expression, false, `/=`)

	case *assign.Minus:
		return this.convertAssignment(n, n.Variable, n.Expression, false, `-=`)

	//case *assign.Mod:
	// TODO

	case *assign.Mul:
		return this.convertAssignment(n, n.Variable, n.Expression, false, `*=`)

	case *assign.Plus:
		return this.convertAssignment(n, n.Variable, n.Expression, false, `+=`)

	//case *assign.Pow:
	// TODO

	//case *assign.Reference:

	case *assign.ShiftLeft:
		return this.convertAssignment(n, n.Variable, n.Expression, false, `<<=`)

	case *assign.ShiftRight:
		return this.convertAssignment(n, n.Variable, n.Expression, false, `>>=`)

	//
	// name
	//

	case *name.Name:
		return this.resolveName(n)

	//
	// expr
	//

	case *expr.FunctionCall:
		// All our generated functions return err, but this AST node may be in a single-rvalue context
		// TODO do something more intelligent here
		// We can't necessarily hoist the whole call, in case we are on the right-hand side of a && operator

		// We might be calling by name, or, we might be calling by an rvalue expression
		// e.g. foo()()() or $x()
		// Use full conversion logic for name resolution
		funcName, err := this.convert(n.Function)
		if err != nil {
			return "", parseErr{n, err}
		}

		callParams, err := this.convertFuncCallArgsCommon(n.ArgumentList)
		if err != nil {
			return "", parseErr{n, err}
		}

		// FIXME need to support `this.currentErrHandler`

		// Transform some PHP standard library functions to their Go equivalents
		// TODO check namespacing for collision prevention
		if funcName == `strlen` || funcName == `count` || funcName == `sizeof` {
			funcName = `len`

		} else if funcName == `explode` {
			if len(callParams) != 2 {
				return "", parseErr{n, arityErr{funcName, len(callParams), 2, 2}}
			}
			this.importPackages["strings"] = struct{}{}
			funcName = `strings.Split`
			callParams[0], callParams[1] = callParams[1], callParams[0] // need to reverse function argument order

		} else if funcName == `implode` {
			if len(callParams) != 2 {
				return "", parseErr{n, arityErr{funcName, len(callParams), 2, 2}}
			}

			this.importPackages["strings"] = struct{}{}
			funcName = `strings.Join`
			callParams[0], callParams[1] = callParams[1], callParams[0] // need to reverse function argument order

		} else if funcName == `sprintf` {
			this.importPackages["fmt"] = struct{}{}
			funcName = `fmt.Sprintf`

		} else if funcName == `trim` {
			if len(callParams) != 1 {
				return "", parseErr{n, arityErr{funcName, len(callParams), 2, 2}}
			}

			this.importPackages["strings"] = struct{}{}
			funcName = `strings.TrimSpace`

		} else if funcName == `rtrim` {
			if len(callParams) != 1 {
				return "", parseErr{n, arityErr{funcName, len(callParams), 1, 1}}
			}

			this.importPackages["strings"] = struct{}{}
			this.importPackages["unicode"] = struct{}{}
			funcName = `strings.TrimRightFunc`
			callParams = append(callParams, `unicode.IsSpace`)

		} else if funcName == `ltrim` {
			if len(callParams) != 1 {
				return "", parseErr{n, arityErr{funcName, len(callParams), 1, 1}}
			}

			this.importPackages["strings"] = struct{}{}
			this.importPackages["unicode"] = struct{}{}
			funcName = `strings.TrimLeftFunc`
			callParams = append(callParams, `unicode.IsSpace`)

		} else if funcName == `strtolower` {
			if len(callParams) != 1 {
				return "", parseErr{n, arityErr{funcName, len(callParams), 1, 1}}
			}

			this.importPackages["strings"] = struct{}{}
			funcName = `strings.ToLower`

		} else if funcName == `strtoupper` {
			if len(callParams) != 1 {
				return "", parseErr{n, arityErr{funcName, len(callParams), 1, 1}}
			}

			this.importPackages["strings"] = struct{}{}
			funcName = `strings.ToUpper`

		} else if funcName == `file_get_contents` {
			if len(callParams) != 2 {
				return "", parseErr{n, arityErr{funcName, len(callParams), 1, 1}}
			}

			this.importPackages["io/ioutil"] = struct{}{}
			funcName = `ioutil.ReadFile` // (string filename)

		} else if funcName == `file_put_contents` {
			if len(callParams) != 2 {
				return "", parseErr{n, arityErr{funcName, len(callParams), 2, 2}}
			}

			this.importPackages["io/ioutil"] = struct{}{}
			funcName = `ioutil.WriteFile` // (string filename, []byte data, int perm)

			callParams[1] = `[]byte(` + callParams[1] + `)`
			callParams = append(callParams, `0644`) // default file permissions

		} else if funcName == `str_replace` {
			// str_replace( mixed $search , mixed $replace , mixed $subject [, int &$count ] )
			// n.b. str_replace also supports arrays, that strings.Replace() doesn't do
			if !(len(callParams) == 3 || len(callParams) == 4) {
				return "", parseErr{n, arityErr{funcName, len(callParams), 3, 4}}
			}

			this.importPackages["strings"] = struct{}{}
			funcName = `strings.Replace` // (s, old, new string, n int) string
			callParams[0], callParams[1], callParams[2] = callParams[2], callParams[0], callParams[1]

			if len(callParams) == 3 {
				callParams = append(callParams, `-1`) // replaceAll
				// There is a strings.ReplaceAll() added in go1.12 (2018), which is still pretty recent i.e. not in Debian Stable (buster)
			}

		} else if funcName == `extract` {
			return "", parseErr{n, fmt.Errorf("Unsupported dynamic function `\\extract()`")}

		} else if funcName == `var_dump` {
			// This is mostly called for debugging purposes. Printf should be good enough
			this.importPackages["fmt"] = struct{}{}
			callParams = append([]string{`"%#v\n"`}, callParams...) // Insert extra 1st parameter
			funcName = `fmt.Printf`

		} else if funcName == `max` {
			this.importPackages["math"] = struct{}{}
			funcName = `math.Max` // n.b. only works on 2 integers, not as wide as PHP's version

		} else if funcName == `min` {
			this.importPackages["math"] = struct{}{}
			funcName = `math.Max` // n.b. only works on 2 integers, not as wide as PHP's version

		} else if funcName == `floor` {
			this.importPackages["math"] = struct{}{}
			funcName = `math.Floor`

		} else if funcName == `var_export` || funcName == `print_r` {

			if len(callParams) == 1 {
				this.importPackages["fmt"] = struct{}{}
				callParams = append([]string{`"%#v\n"`}, callParams...) // Insert extra 1st parameter
				funcName = `fmt.Printf`

			} else if len(callParams) == 2 {
				// Returning form
				this.importPackages["fmt"] = struct{}{}
				callParams = append([]string{`"%#v\n"`}, callParams...) // Insert extra 1st parameter
				funcName = `fmt.Sprintf`

			} else {
				return "", parseErr{n, arityErr{funcName, len(callParams), 3, 4}}

			}

		} else if funcName == `substr` {
			// substr($string, $start [, $length]) => new string
			// In Go all strings are immutable, and slicing an existing string produces a new immutable string so that works out

			if len(callParams) == 2 {
				return "(" + callParams[0] + ")[" + callParams[1] + ":]", nil

			} else if len(callParams) == 3 {
				// if lnum, ok := n.ArgumentList.Arguments[1].

				if callParams[1] == `0` {
					return "(" + callParams[0] + ")[:" + callParams[2] + "]", nil
				}

				// WARNING: We are doubling up on the first parameter
				// This is a problem if it's not necessarily constant
				return "(" + callParams[0] + ")[" + callParams[1] + ":" + callParams[1] + `+` + callParams[2] + "]", nil

			} else {
				return "", parseErr{n, arityErr{funcName, len(callParams), 2, 3}}
			}

		} else if funcName == `rename` {
			if len(callParams) != 2 {
				return "", parseErr{n, arityErr{funcName, len(callParams), 2, 2}}
			}

			this.importPackages["os"] = struct{}{}
			funcName = `os.Rename`

		}

		return funcName + "(" + strings.Join(callParams, ", ") + ")", nil // expr only, no semicolon/newline

	case *expr.StaticCall:
		className, err := this.resolveName(n.Class)
		if err != nil {
			return "", parseErr{n, err}
		}

		funcName, err := this.convert(n.Call)
		if err != nil {
			return "", parseErr{n, err}
		}

		callTarget := className + "." + funcName
		if className == "self" {
			if this.currentClassName == "" {
				return "", parseErr{n, fmt.Errorf("Made a self::Static method call while not in class context")}
			}
			// We're making a static call, and we renamed those to be top-level functions
			callTarget = this.currentClassName + funcName
		}

		callParams, err := this.convertFuncCallArgsCommon(n.ArgumentList)
		if err != nil {
			return "", parseErr{n, err}
		}

		// FIXME need to support `this.currentErrHandler`

		return callTarget + "(" + strings.Join(callParams, ", ") + ")", nil // expr only, no semicolon/newline

	case *expr.New:
		// new foo(xx)
		// Transparently convert to calling constructor function.
		nn, err := this.resolveName(n.Class)
		if err != nil {
			return "", parseErr{n, err}
		}
		// FIXME if there is a package specifier embedded in the result name,
		// the `New` will appear in the wrong place
		nn = `New` + nn

		// Convert resolved back to node.Name
		transparentNameNode := name.NewName([]node.Node{name.NewNamePart(nn)})

		return this.convert(expr.NewFunctionCall(transparentNameNode, n.ArgumentList))

	case *expr.ClassConstFetch:
		// We converted class constants to package-level constants
		className, err := this.resolveName(n.Class)
		if err != nil {
			return "", parseErr{n, err}
		}

		constName := n.ConstantName.(*node.Identifier).Value
		// TODO fix up visibility modifier

		// Special case: `::class` is just the string name of the class
		if constName == `class` {
			// This can be known statically (e.g. MyClass::class --> "MyClass") but
			// isn't generally known non-statically
			if _, ok := n.Class.(*name.Name); ok {
				// Static
				return quoteGoString(className), nil

			} else if className == `self` {
				return quoteGoString(this.currentClassName), nil

			} else {
				// Dynamic
				// Translate to reflect
				// this.importPackages["reflect"] = struct{}{}
				// return `reflect.TypeOf(` + className + `).String()`, nil

				// Actually PHP doesn't support using ::class on variables
				return "", parseErr{n, fmt.Errorf(`PHP Fatal error: Dynamic class names are not allowed in compile-time ::class fetch`)}
			}
		}

		return className + constName, nil

	case *expr.Closure:
		// Need to decide what to do with `this` binding
		// TODO figure out what it means to use `this` in all types of nested closures

		if n.Static {
			return "", parseErr{n, fmt.Errorf("use of `static` in closure implies `this`-insensitive, but we can't make that true")}
		}

		// TODO n.PhpDocComment
		// TODO n.ClosureUse

		body, err := this.convertFunctionCommon(n.Params, n.ReturnType, n.ReturnsRef, n.Stmts)
		if err != nil {
			return "", parseErr{n, err}
		}

		return "(func" + strings.TrimRight(body, " \n") + ")", nil

	case *expr.Exit:
		// die(0) - set process exit code and exit
		// die("message") - print to stdout and exit 0
		// die - exit 0

		this.importPackages["os"] = struct{}{}

		if n.Expr == nil {
			return "os.Exit(0)", nil
		}

		child, err := this.convert(n.Expr)
		if err != nil {
			return "", parseErr{n, err}
		}

		// Although it might have been a more complex string expression - we
		// don't currently know that
		// TODO type inference
		switch n.Expr.(type) {
		case *scalar.String:
			this.importPackages["fmt"] = struct{}{}
			return "fmt.Print(" + child + ")\nos.Exit(0)", nil // hopefully die() was standalone, and not "or die"
		default:
			return "os.Exit(" + child + ")", nil
		}

	case *expr.Eval:
		return "", parseErr{n, fmt.Errorf("Unsupported use of eval()")}

	case *expr.PreInc:
		// """In Go, i++ is a statement, not an expression. So you can't use its value in another expression such as a function call."""
		v, err := this.convert(n.Variable)
		if err != nil {
			return "", parseErr{n, err}
		}

		return "++" + v, nil

	case *expr.PostInc:
		// """In Go, i++ is a statement, not an expression. So you can't use its value in another expression such as a function call."""
		v, err := this.convert(n.Variable)
		if err != nil {
			return "", parseErr{n, err}
		}

		return v + "++", nil

	case *expr.UnaryMinus:
		v, err := this.convert(n.Expr)
		if err != nil {
			return "", parseErr{n, err}
		}

		return "-(" + v + ")", nil

	case *expr.UnaryPlus:
		v, err := this.convert(n.Expr)
		if err != nil {
			return "", parseErr{n, err}
		}

		return "+(" + v + ")", nil

	case *expr.MethodCall:
		// Foo->Bar(Baz)
		parent, err := this.convert(n.Variable)
		if err != nil {
			return "", parseErr{n, err}
		}

		child, err := this.convert(n.Method)
		if err != nil {
			return "", parseErr{n, err}
		}

		args, err := this.convertFuncCallArgsCommon(n.ArgumentList)
		if err != nil {
			return "", parseErr{n, err}
		}

		// FIXME need to support `this.currentErrHandler`

		return parent + "." + child + "(" + strings.Join(args, ", ") + ")", nil

	case *expr.PropertyFetch:
		// Foo->Bar
		parent, err := this.convert(n.Variable)
		if err != nil {
			return "", parseErr{n, err}
		}

		child, err := this.convert(n.Property)
		if err != nil {
			return "", parseErr{n, err}
		}

		return parent + "." + child, nil

	case *expr.Variable:
		return n.VarName.(*node.Identifier).Value, nil

	case *expr.ConstFetch:
		constRef, err := this.resolveName(n.Constant)
		if err != nil {
			return "", err
		}

		// Handle PHP reserved constants
		// @ref https://www.php.net/manual/en/reserved.constants.php

		if constRef == `PHP_EOL` {
			// Not 100% accurate, but realistically this works on Windows too nowadays
			return `"\n"`, nil

		} else if constRef == `PHP_INT_MAX` {
			// Go has math.MaxInt64 in the Math package, etc
			// But we don't know if this package will maybe be built on a 32-bit platform
			// And we are generating plain `int` types, not necessarily int64 everywhere

			// @ref https://stackoverflow.com/a/54421330
			this.importPackages["math/bits"] = struct{}{}
			return `((1 << bits.UintSize) / -2 /* INT_MAX */)`, nil

		} else if constRef == `PHP_VERSION` {
			return quoteGoString(fmt.Sprintf("%d.%d.%d%s", phpVersionMajor, phpVersionMinor, phpVersionPatch, phpVersionExtra)), nil

		} else if constRef == `PHP_MAJOR_VERSION` {
			return fmt.Sprintf("%d", phpVersionMajor), nil

		} else if constRef == `PHP_MINOR_VERSION` {
			return fmt.Sprintf("%d", phpVersionMinor), nil

		} else if constRef == `PHP_RELEASE_VERSION` {
			return fmt.Sprintf("%d", phpVersionPatch), nil

		} else if constRef == `PHP_VERSION_ID` {
			return fmt.Sprintf("%d%02d%02d", phpVersionMajor, phpVersionMinor, phpVersionPatch), nil

		} else if constRef == `PHP_EXTRA_VERSION` {
			return quoteGoString(phpVersionExtra), nil

		} else if constRef == `PHP_ZTS` {
			return "true /* PHP_ZTS */", nil

		} else if constRef == `PHP_DEBUG` {
			return "false /* PHP_DEBUG */", nil

		} else if constRef == `PHP_MAXPATHLEN` {
			// Not 100% accurate
			// Go filesystem functions can transparently handle long paths
			// PHP on Linux has a max path of 4096 by default
			// Just use that
			return "4096 /* MAXPATHLEN */", nil

		} else if constRef == `PHP_OS` || constRef == `PHP_OS_FAMILY` {
			// Not 100% accurate, but the right idea
			this.importPackages["runtime"] = struct{}{}
			return `runtime.GOOS`, nil

		}

		// No const transformation was required
		return constRef, nil

	case *expr.Array:
		return this.convertArrayLiteralCommon(n.Items)

	case *expr.ShortArray:
		return this.convertArrayLiteralCommon(n.Items)

	case *expr.BooleanNot:
		rhs, err := this.convert(n.Expr)
		if err != nil {
			return "", parseErr{n, err}
		}

		return "!(" + rhs + ")", nil

	case *expr.Ternary:
		cond, err := this.convert(n.Condition)
		if err != nil {
			return "", parseErr{n, err}
		}

		iftrue, err := this.convert(n.IfTrue)
		if err != nil {
			return "", parseErr{n, err}
		}

		iffalse, err := this.convert(n.IfFalse)
		if err != nil {
			return "", parseErr{n, err}
		}

		// FIXME this is (A) not idiomatic, and (B) doesn't work in assignment expressions
		return "(func() unknown {\nif (" + cond + ") {\nreturn (" + iftrue + ")\n} else {\nreturn (" + iffalse + ")\n } })()", nil

	case *expr.ArrayDimFetch:
		// Might be x[foo], might be x[] (i.e. append() call)
		// In order to make the append() transformation, we need to lookahead
		// for ArrayDimFetch in the `*assign.Assign` case
		vv, err := this.convert(n.Variable)
		if err != nil {
			return "", parseErr{n, err}
		}

		if n.Dim == nil {
			return "", parseErr{n, fmt.Errorf("found '%s[]' outside of lvalue assignment context", vv)}
		}

		idx, err := this.convert(n.Dim)
		if err != nil {
			return "", parseErr{n, err}
		}

		return vv + `[` + idx + `]`, nil // Same syntax as PHP

	//
	// binary
	//

	case *binary.BitwiseAnd:
		return this.convertBinaryCommon(n.Left, n.Right, `&`)

	case *binary.BitwiseOr:
		return this.convertBinaryCommon(n.Left, n.Right, `|`)

	case *binary.BitwiseXor:
		return this.convertBinaryCommon(n.Left, n.Right, `^`) // n.b. Go only supports this for integers; PHP also supports it for bools

	case *binary.BooleanAnd:
		return this.convertBinaryCommon(n.Left, n.Right, `&&`)

	case *binary.BooleanOr:
		return this.convertBinaryCommon(n.Left, n.Right, `||`)

	//case *binary.Coalesce:
	// TODO this can't be expressed in an rvalue context in Go (unless we create a typed closure..?)

	case *binary.Concat:
		return this.convertBinaryCommon(n.Left, n.Right, `+`) // PHP uses + for numbers, `.` for strings; Go uses `+` in both cases

	case *binary.Div:
		return this.convertBinaryCommon(n.Left, n.Right, `/`) // PHP will upgrade ints to floats, Go won't

	case *binary.Equal:
		return this.convertBinaryCommon(n.Left, n.Right, `==`) // Type-lax equality comparator

	case *binary.GreaterOrEqual:
		return this.convertBinaryCommon(n.Left, n.Right, `>=`)

	case *binary.Greater:
		return this.convertBinaryCommon(n.Left, n.Right, `>`)

	case *binary.Identical:
		return this.convertBinaryCommon(n.Left, n.Right, `==`) // PHP uses `===`, Go is already type-safe

	case *binary.LogicalAnd:
		// This is the lexer token when using `and` in PHP. It's equivalent to
		// `&&` but has different precedence
		// e.g. $a = $b && $c   ==> $a = ($b && $c)
		//      $a = $b and $c  ==> ($a = $b) and $c
		// So far, we are relying on the PHP parser having already having handled
		// the precedence difference - transform to `&&` unconditionally
		return this.convertBinaryCommon(n.Left, n.Right, `&&`)

	case *binary.LogicalOr:
		// As above
		return this.convertBinaryCommon(n.Left, n.Right, `||`)

	case *binary.LogicalXor:
		// As above
		return this.convertBinaryCommon(n.Left, n.Right, `^`) // n.b. Go only supports this for integers; PHP also supports it for bools

	case *binary.Minus:
		return this.convertBinaryCommon(n.Left, n.Right, `-`)

	case *binary.Mod:
		// Go doesn't have a built-in operator for mod - convert to a call to math.Mod()
		rval, err := this.convert(n.Left)
		if err != nil {
			return "", parseErr{n, err}
		}

		modulo, err := this.convert(n.Right)
		if err != nil {
			return "", parseErr{n, err}
		}

		this.importPackages["math"] = struct{}{}
		return `math.Mod(` + rval + `, ` + modulo + `)`, nil

	case *binary.Mul:
		return this.convertBinaryCommon(n.Left, n.Right, `*`)

	case *binary.NotEqual:
		return this.convertBinaryCommon(n.Left, n.Right, `!=`) // Type-lax equality comparator

	case *binary.NotIdentical:
		return this.convertBinaryCommon(n.Left, n.Right, `!=`) // PHP uses `!==`, Go is already type-safe

	case *binary.Plus:
		return this.convertBinaryCommon(n.Left, n.Right, `+`) // PHP uses + for numbers, `.` for strings; Go uses `+` in both cases

	case *binary.Pow:
		// Go doesn't have a built-in operator for mod - convert to a call to math.Pow()

		base, err := this.convert(n.Left)
		if err != nil {
			return "", parseErr{n, err}
		}

		exponent, err := this.convert(n.Right)
		if err != nil {
			return "", parseErr{n, err}
		}

		this.importPackages["math"] = struct{}{}
		return `math.Pow(` + base + `, ` + exponent + `)`, nil

	case *binary.ShiftLeft:
		return this.convertBinaryCommon(n.Left, n.Right, `<<`)

	case *binary.ShiftRight:
		return this.convertBinaryCommon(n.Left, n.Right, `>>`)

	case *binary.SmallerOrEqual:
		return this.convertBinaryCommon(n.Left, n.Right, `<=`)

	case *binary.Smaller:
		return this.convertBinaryCommon(n.Left, n.Right, `<`)

	case *binary.Spaceship:
		// The spaceship operator returns -1 / 0 / 1 based on a gteq/leq comparison
		// Go doesn't have a built-in spaceship operator
		// The primary use case is in user-definded sort comparators, where Go
		//  uses bools instead ints anyway.
		// Subtraction is a reasonable substitute
		return this.convertBinaryCommon(n.Left, n.Right, `-`)

	//
	// scalar
	//

	case *scalar.Lnumber:
		// Integer (maybe with 0b / 0x / '0' prefix)
		return n.Value, nil // number formats are compatible

	case *scalar.Dnumber:
		// Float (maybe with period / scientific notation)
		return n.Value, nil // number formats are compatible

	case *scalar.String:
		// We need to transform the string format - e.g. Go does not support
		// single-quoted strings
		rawValue, err := phpUnquote(n.Value)
		if err != nil {
			return "", parseErr{n, err}
		}

		return quoteGoString(rawValue), nil // Go source code quoting format

	case *scalar.EncapsedStringPart:
		// The n.Value that we receive here does not contain quotes at all
		// But it is still a fragment of a double-quoted string
		rawValue, err := phpUnquote(`"` + strings.Replace(n.Value, `"`, `\"`, -1) + `"`)
		if err != nil {
			return "", parseErr{n, err}
		}

		return quoteGoString(rawValue), nil // Go source code quoting format

	case *scalar.Encapsed:
		return this.convertEncapsedString(n.Parts)

	case *scalar.Heredoc:
		return this.convertEncapsedString(n.Parts)

	case *scalar.MagicConstant:
		// magic constants are case-insensitive
		switch strings.ToLower(n.Value) {
		case `__file__`, `__dir__`:
			// These are normally used in PHP for finding the absolute webroot directory (e.g. dirname(__FILE__) in index.php)
			// The letter of the law would be to replace them with the *.go file/dir
			// We could even emit a runtime call to get the Go file/line: @ref https://github.com/golang/go/issues/12876#issuecomment-146878684
			// But in practice, the current working directory might be preferable
			return `""`, nil

		case `__line__`:
			return fmt.Sprintf("%d", n.Position.StartLine), nil

		case `__namespace__`:
			return this.currentNamespace, nil

		case `__function__`:
			if this.currentFunctionName == "" {
				return "", parseErr{n, fmt.Errorf("use of __FUNCTION__ outside of a function")}
			}
			return this.currentFunctionName, nil

		case `__class__`:
			if this.currentClassName == "" {
				return "", parseErr{n, fmt.Errorf("use of __CLASS__ outside of a class")}
			}
			return this.currentClassName, nil

		case `__method__`:
			if this.currentMethodName == "" {
				return "", parseErr{n, fmt.Errorf("use of __METHOD__ outside of a class method")}
			}
			return this.currentMethodName, nil

		case `__trait__`:
			if this.currentTraitName == "" {
				return "", parseErr{n, fmt.Errorf("use of __TRAIT__ outside of a trait")}
			}
			return this.currentTraitName, nil

		default:
			return "", parseErr{n, fmt.Errorf("unrecognized magic constant '%s'", n.Value)}
		}

	//
	//
	//

	default:
		return "", fmt.Errorf("unsupported node type %s", nodeTypeString(n))
	}
}

func hasModifier(modifiers []node.Node, search string) (bool, error) {

	for _, mod := range modifiers {
		ident, ok := mod.(*node.Identifier)
		if !ok {
			return false, parseErr{mod, fmt.Errorf("expected node.Identifier")}
		}

		if strings.ToLower(ident.Value) == strings.ToLower(search) {
			return true, nil
		}
	}

	return false, nil
}

// applyVisibilityModifier renames a function to use an upper/lowercase first
// letter based on PHP visibility modifiers.
func applyVisibilityModifier(funcName string, modifiers []node.Node) (string, error) {

	hasPublic, err := hasModifier(modifiers, "public")
	if err != nil {
		return "", err
	}

	hasPrivate, err := hasModifier(modifiers, "private")
	if err != nil {
		return "", err
	}

	hasProtected, err := hasModifier(modifiers, "protected")
	if err != nil {
		return "", err
	}

	if (hasPublic && !hasPrivate && !hasProtected) /* explicitly public */ ||
		(!hasPublic && !hasPrivate && !hasProtected) /* no modifiers defaults to public */ {
		return toPublic(funcName), nil

	} else if !hasPublic && (hasPrivate || hasProtected) {
		return toPrivate(funcName), nil

	} else {
		return "", fmt.Errorf("unexpected combination of modifiers")
	}
}

func toPublic(name string) string {
	nFirst := name[0:1]
	uFirst := strings.ToUpper(nFirst)
	if nFirst == uFirst {
		return name // avoid making more heap garbage
	}

	return uFirst + name[1:]
}

func toPrivate(name string) string {
	nFirst := name[0:1]
	lFirst := strings.ToLower(nFirst)
	if nFirst == lFirst {
		return name // avoid making more heap garbage
	}

	return lFirst + name[1:]
}

func constructorName(className string) string {
	return `New` + className
}

// removeParens removes surrounding parentheses from an expression.
// This is only safe in cases where there is ambiguously a single rvalue wanted,
// e.g. between ( and , in a function call argument
func removeParens(expr string) string {
	for len(expr) > 2 && expr[0] == '(' && expr[len(expr)-1] == ')' && !strings.HasSuffix(expr, `()`) {
		expr = expr[1 : len(expr)-1]
	}
	return expr
}

// asSingleExpression makes the expr into a single expression that is safe for
// embedding in a larger statement e.g. multiple string concatenation.
func asSingleExpression(expr string) string {
	return `(` + removeParens(expr) + `)`
	// TODO simplify this in cases where we can tell it is already a single expression e.g. quoted strings, number literals, variable literals, ...
}

func quoteGoString(s string) string {

	if !strings.Contains(s, "`") && strings.Count(s, "\n") >= 3 { // TODO make the heuristic configurable
		// Use backtick-delimited multiline string
		return "`" + s + "`"
	} else {
		// Can't trivially represent it with backticks, or it's not multiline "enough" to bother - use full Go quoting
		return strconv.Quote(s)
	}
}

func (this *conversionState) convertEncapsedString(parts []node.Node) (string, error) {
	// This is used for string interpolation: `echo "bar $ref";`
	// And also for heredocs
	// Child nodes are either EncapsedStringPart or expr.**
	ret := make([]string, 0, len(parts))
	for _, part := range parts {
		pp, err := this.convert(part)
		if err != nil {
			return "", parseErr{part, err}
		}

		if _, ok := part.(*scalar.EncapsedStringPart); !ok {
			// Subexpression - should probably parenthesise just in case
			pp = asSingleExpression(pp)
		}

		ret = append(ret, pp)
	}

	return `(` + strings.Join(ret, ` + `) + `)`, nil
}

// resolveName turns a `*name.Name` node into a Go string.
func (this *conversionState) resolveName(n node.Node) (string, error) {
	// TODO support namespace lookups

	ret := unknownVarType.AsGoString()
	if n == nil || n == node.Node(nil) {
		return ret, nil
	}

	switch n := n.(type) {
	case *name.FullyQualified:
		if len(n.Parts) != 1 {
			return "", parseErr{n, fmt.Errorf("name has %d parts, expected 1", len(n.Parts))}
		}
		ret = n.Parts[0].(*name.NamePart).Value

	case *name.Name:
		if len(n.Parts) != 1 {
			return "", parseErr{n, fmt.Errorf("name has %d parts, expected 1", len(n.Parts))}
		}
		ret = n.Parts[0].(*name.NamePart).Value

	case *node.Identifier:
		ret = n.Value // e.g. `array`

	default:
		return "", fmt.Errorf("unexpected name type %#v", n)
	}

	// Handle class lookups
	if strings.ToLower(ret) == "parent" {
		if this.currentClassParentName == "" {
			return "", parseErr{n, fmt.Errorf("Lookup of 'parent' while not in an inherited child class context")}
		}
		return `this.` + this.currentClassParentName, nil

	} else if strings.ToLower(ret) == "self" {
		// Let it through as-is
		// return "", parseErr{n, fmt.Errorf("Lookup of 'self::' should have been resolved already")}
		/*
			if this.currentClassName == "" {
				return "", parseErr{n, fmt.Errorf("Lookup of 'self' while not in class context")}
			}
			return `this`, nil
		*/
	} else if strings.ToLower(ret) == "static" {
		return "", parseErr{n, fmt.Errorf("'static::' is not yet supported")}

	} else if strings.ToLower(ret) == "true" {
		return "true", nil

	} else if strings.ToLower(ret) == "false" {
		return "false", nil

	} else if strings.ToLower(ret) == "null" {
		return "nil", nil

	}

	return ret, nil
}

func (this *conversionState) convertAssignAssign(n *assign.Assign, isTopLevelStatement bool) (string, error) {
	return this.convertAssignment(n, n.Variable, n.Expression, isTopLevelStatement, `=`)
}

func (this *conversionState) convertAssignment(n, nLValue, nRValue node.Node, isTopLevelStatement bool, operator string) (string, error) {

	rvalue, err := this.convert(nRValue)
	if err != nil {
		return "", parseErr{n, err}
	}

	if dimf, ok := nLValue.(*expr.ArrayDimFetch); ok && dimf.Dim == nil {

		if operator != `=` {
			return "", parseErr{n, fmt.Errorf("can't yet handle complex shorthand append assignment operator statement")}
		}

		// Special handling for the case of foo[] = bar
		// Transform into append()
		arrayVar, err := this.convert(dimf.Variable)
		if err != nil {
			return "", parseErr{dimf, err}
		}

		ret := arrayVar + ` = append(` + arrayVar + `, ` + removeParens(rvalue) + `)`
		if isTopLevelStatement {
			ret += "\n"
		}
		return ret, nil

	} else {

		// Normal assignment

		lvalue, err := this.convert(nLValue) // might be a more complicated lvalue
		if err != nil {
			return "", parseErr{n, err}
		}

		// TODO this may need to use `:=`

		if isTopLevelStatement {
			rvalue = removeParens(rvalue) // safe in top-level assignment context

			// If this is a simple expression (func call; indirect/method call; assignment of func/method call) then
			// we need to propagate errors
			switch nRValue.(type) {
			case *expr.FunctionCall, *expr.StaticCall, *expr.New:

				if operator != `=` {
					// We need to perform the variable assignment + err check, but we are in shorthand assignment context
					// and can't just mess with the left hand of the expression
					// Need to create a temporary accumulator variable
					return "", parseErr{n, fmt.Errorf("can't yet handle err value extraction for function call in shorthand append assignment operator statement")}
				}

				ret := lvalue + ", err = " + rvalue + "\n"
				ret += "if err != nil {\n"
				ret += this.currentErrHandler
				ret += "}\n"
				return ret, nil

			default:
				ret := lvalue + " = " + rvalue + "\n" // Just the basic assignment - with trailing NL
				return ret, nil
			}

		} else {
			return lvalue + " " + operator + " " + rvalue, nil // Just the basic assignment - without trailing NL

		}
	}

}

// convertToStmtList asserts that the node is either a StmtList or wraps it in a
//  single-stmt StmtList if not.
// Loop bodies may be a StmtList if it is wrapped in {}, or a single statement
//  if it is not; we want to enforce the use of {} for all loop bodies
func convertToStmtList(n node.Node) *stmt.StmtList {
	if sl, ok := n.(*stmt.StmtList); ok {
		return sl // It's already a StmtList
	}

	return stmt.NewStmtList([]node.Node{n})
}

func (this *conversionState) convertBinaryCommon(left, right node.Node, goBinaryOperator string) (string, error) {

	// PHP uses + for numbers, `.` for strings; Go uses `+` in both cases
	// Assume PHP/Go have the same associativity here
	lhs, err := this.convert(left)
	if err != nil {
		return "", parseErr{left, err}
	}

	rhs, err := this.convert(right)
	if err != nil {
		return "", parseErr{right, err}
	}

	// In case of an rvalue assignment expression, we need extra parens
	if _, ok := left.(*assign.Assign); ok {
		lhs = "(" + lhs + ")"
	}
	if _, ok := right.(*assign.Assign); ok {
		rhs = "(" + rhs + ")"
	}

	// We can elide even more parens in case of some commutative operators
	// We can only do this in the left-associative case
	// FIXME Plus and Concat aren't necessarily commutative together even though they both have + here(!!)
	if _, ok := left.(*binary.Plus); ok && goBinaryOperator == `+` {
		lhs = removeParens(lhs)
	}
	if _, ok := left.(*binary.Concat); ok && goBinaryOperator == `+` {
		lhs = removeParens(lhs)
	}

	// Done
	return "(" + lhs + " " + goBinaryOperator + " " + rhs + ")", nil
}

func (this *conversionState) convertFuncCallArgsCommon(args *node.ArgumentList) ([]string, error) {

	callParams := make([]string, 0, len(args.Arguments))
	for _, arg_ := range args.Arguments {
		arg, ok := arg_.(*node.Argument)
		if !ok {
			return nil, parseErr{arg_, fmt.Errorf("expected node.Argument")}
		}

		rvalue, err := this.convert(arg.Expr)
		if err != nil {
			return nil, parseErr{arg, err}
		}
		if arg.IsReference {
			rvalue = "&" + rvalue
		}
		if arg.Variadic {
			rvalue = "..." + rvalue
		}

		callParams = append(callParams, removeParens(rvalue))
	}

	return callParams, nil
}

func (this *conversionState) convertArrayLiteralCommon(items []node.Node) (string, error) {
	// Array literal
	// We need to know the type. See if we can guess it from the first child element
	// At least, we may be able to determine if this is a map or an array

	entries := []string{}
	keyType := unknownVarType
	valType := unknownVarType

	// TODO support unpack operator (...)

	nChars := 0

	isMapType := false
	for idx, itm_ := range items {
		itm, ok := itm_.(*expr.ArrayItem)
		if !ok {
			return "", parseErr{itm_, fmt.Errorf("expected ArrayItem")}
		}

		// If there is a trailing comma in the definition,
		// the parser produces an empty ArrayItem with no detail information
		if itm.Key == nil && itm.Val == nil && idx == len(items)-1 {
			break
		}

		if idx == 0 {
			isMapType = (itm.Key != nil)
		} else {
			thisElemIsMapType := (itm.Key != nil)
			if isMapType != thisElemIsMapType {
				return "", parseErr{itm, fmt.Errorf("Can't represent array and map in a single type (idx[0].isMap=%v != idx[%d].isMap=%v)", isMapType, idx, thisElemIsMapType)}
			}
		}

		vv, err := this.convert(itm.Val)
		if err != nil {
			return "", parseErr{itm, err}
		}

		if itm.Key != nil {
			kv, err := this.convert(itm.Key)
			if err != nil {
				return "", parseErr{itm, err}
			}
			entries = append(entries, kv+`: `+vv+`,`)

			nChars += len(kv) + len(vv) + 4 // assume an extra trailing space
		} else {
			entries = append(entries, vv+`,`)
			nChars += len(vv) + 2
		}

	}

	// Heuristic decision whether to break array literal onto multiple lines
	// We have to do this because gofmt does not care about long lines otherwise
	maybeNewline := " "
	if nChars > 60 {
		maybeNewline = "\n"
	}

	if isMapType {
		return `map[` + keyType.AsGoString() + `]` + valType.AsGoString() + `{` + maybeNewline + strings.Join(entries, maybeNewline) + maybeNewline + `}`, nil
	} else {
		return `[]` + valType.AsGoString() + `{` + maybeNewline + strings.Join(entries, maybeNewline) + maybeNewline + `}`, nil
	}
}

func (this *conversionState) convertFunctionCommon(params []node.Node, returnType node.Node, returnsRef bool, bodyStmts []node.Node) (string, error) {

	// TODO scan function and see if it contains any return statements at all
	// If not, then we only need an err return parameter, not anything else

	funcParams := []string{}
	for _, param := range params {
		param, ok := param.(*node.Parameter) // shadow
		if !ok {
			return "", parseErr{param, fmt.Errorf("expected node.Parameter")}
		}

		// VariableType: might be nil for untyped parameters
		paramType, err := this.resolveName(param.VariableType)
		if err != nil {
			return "", parseErr{param, err}
		}
		if param.ByRef {
			paramType = "*" + paramType
		}
		if param.Variadic {
			paramType = "..." + paramType
		}

		// Name
		paramName := param.Variable.(*expr.Variable).VarName.(*node.Identifier).Value

		funcParams = append(funcParams, paramName+" "+paramType)
	}

	// ReturnType
	funcReturn, err := this.resolveName(returnType)
	if err != nil {
		return "", parseErr{returnType, err}
	}
	if returnsRef {
		funcReturn = "*" + funcReturn
	}

	// Build function prototype
	ret := "(" + strings.Join(funcParams, ", ") + ") (" + funcReturn + ", error) "

	// Recurse through body statements

	if bodyStmts != nil {
		fullBody, err := this.convert(stmt.NewStmtList(bodyStmts))
		if err != nil {
			return "", err
		}

		ret += fullBody + "\n"
	}

	// Done
	// No extra trailing newline in case this is part of a large expression
	return ret, nil
}

// hasInteriorAssignment recursively walks a node, to determine if it contains
// any assignment expressions
func hasInteriorAssignment(n node.Node) (hasAnyAssign bool, err error) {

	err = parseutil.SimpleWalk(n, func(n node.Node) error {
		if _, ok := n.(*assign.Assign); ok {
			hasAnyAssign = true
		}
		return nil
	})

	return // named return
}