package main

import (
	"database/sql"
	"fmt"
	"path/filepath"
	"unsafe"

	"github.com/ying32/govcl/vcl"
	"github.com/ying32/govcl/vcl/types"
)

const (
	sqliteTablesCaption = "Tables"
)

type sqliteLoadedDatabase struct {
	displayName string
	path        string
	db          *sql.DB
	nav         *vcl.TTreeNode

	arena []*navData // keepalive
}

func (ld *sqliteLoadedDatabase) DisplayName() string {
	return ld.displayName
}

func (ld *sqliteLoadedDatabase) RootElement() *vcl.TTreeNode {
	return ld.nav
}

func (ld *sqliteLoadedDatabase) Keepalive(ndata *navData) {
	ld.arena = append(ld.arena, ndata)
}

func (ld *sqliteLoadedDatabase) RenderForNav(f *TMainForm, ndata *navData) {

	if len(ndata.bucketPath) == 0 {
		// Top-level
		f.propertiesBox.SetText("Please select...")
		f.contentBox.SetEnabled(false)
		f.contentBox.Clear()

	} else if len(ndata.bucketPath) == 1 {
		// Category (tables, ...)
		f.propertiesBox.SetText("Please select...")
		f.contentBox.SetEnabled(false)
		f.contentBox.Clear()

	} else if len(ndata.bucketPath) == 2 && ndata.bucketPath[0] == sqliteTablesCaption {
		// Render for specific table
		tableName := ndata.bucketPath[1]

		// Get some basic properties
		r := ld.db.QueryRow(`SELECT sql FROM sqlite_schema WHERE name = ?;`, tableName)
		var schemaStmt string
		err := r.Scan(&schemaStmt)
		if err != nil {
			schemaStmt = fmt.Sprintf("* Failed to describe table %q: %s", tableName, err.Error())
		}

		// Display table properties
		f.propertiesBox.SetText(fmt.Sprintf("Selected table %q\n\nSchema:\n\n%s", tableName, schemaStmt))

		f.contentBox.SetEnabled(false)
		f.contentBox.Clear()

		// Load column details
		// Use SELECT form instead of common PRAGMA table_info so we can just get names
		// We could possibly get this from the main data select, but this will
		// work even when there are 0 results
		columnNames, err := ld.sqliteGetColumnNamesForTable(tableName)
		if err != nil {
			vcl.ShowMessageFmt("Failed to load columns for table %q: %s", tableName, err.Error())
			return
		}

		populateColumns(columnNames, f.contentBox)

		// Select count(*) so we know to display a warning if there are too many entries
		// TODO

		// Select * with small limit
		datar, err := ld.db.Query(`SELECT * FROM ` + tableName + ` LIMIT 1000`) // WARNING can't prepare this parameter, but it comes from the DB (trusted)
		if err != nil {
			vcl.ShowMessageFmt("Failed to load data for table %q: %s", tableName, err.Error())
			return
		}
		defer datar.Close()
		populateRows(datar, f.contentBox)

		// We successfully populated the data grid
		f.contentBox.SetEnabled(true)

	} else {
		// ??? unknown

	}

}

func (ld *sqliteLoadedDatabase) sqliteGetColumnNamesForTable(tableName string) ([]string, error) {
	colr, err := ld.db.Query(`SELECT name FROM pragma_table_info(?)`, tableName)
	if err != nil {
		return nil, fmt.Errorf("Query: %w", err)
	}
	defer colr.Close()

	var ret []string

	for colr.Next() {

		var columnName string
		err = colr.Scan(&columnName)
		if err != nil {
			return nil, fmt.Errorf("Scan: %w", colr.Err())
		}

		ret = append(ret, columnName)
	}
	if colr.Err() != nil {
		return nil, colr.Err()
	}

	return ret, nil
}

func populateColumns(names []string, dest *vcl.TListView) {
	dest.Columns().Clear()
	for _, columnName := range names {
		col := dest.Columns().Add()
		col.SetCaption(columnName)
		col.SetWidth(MY_WIDTH)
		col.SetAlignment(types.TaLeftJustify)
	}
}

func populateRows(rr *sql.Rows, dest *vcl.TListView) {

	numColumns := int(dest.Columns().Count())

	for rr.Next() {
		fields := make([]interface{}, numColumns)
		pfields := make([]interface{}, numColumns)
		for i := 0; i < numColumns; i += 1 {
			pfields[i] = &fields[i]
		}

		err := rr.Scan(pfields...)
		if err != nil {
			vcl.ShowMessageFmt("Failed to load data: %s", err.Error())
			return
		}

		dataEntry := dest.Items().Add()
		dataEntry.SetCaption(formatAny(fields[0]))
		for i := 1; i < len(fields); i += 1 {
			dataEntry.SubItems().Add(formatAny(fields[i]))
		}

	}
	if rr.Err() != nil {
		vcl.ShowMessageFmt("Failed to load data: %s", rr.Err().Error())
		return
	}
}

func (ld *sqliteLoadedDatabase) ExecQuery(query string, resultArea *vcl.TListView) {
	rr, err := ld.db.Query(query)
	if err != nil {
		vcl.ShowMessage(err.Error())
		return
	}

	defer rr.Close()

	resultArea.SetEnabled(false)
	resultArea.Clear()

	columns, err := rr.Columns()
	if err != nil {
		vcl.ShowMessage(err.Error())
		return
	}

	populateColumns(columns, resultArea)

	populateRows(rr, resultArea)

	resultArea.SetEnabled(true)
}

func (ld *sqliteLoadedDatabase) NavChildren(ndata *navData) ([]string, error) {

	if len(ndata.bucketPath) == 0 {
		// The top-level children are always:
		return []string{sqliteTablesCaption}, nil
	}

	if len(ndata.bucketPath) == 1 && ndata.bucketPath[0] == sqliteTablesCaption {
		rr, err := ld.db.Query(`SELECT name FROM sqlite_master WHERE type='table' ORDER BY name ASC;`)
		if err != nil {
			return nil, err
		}
		defer rr.Close()

		var gather []string
		for rr.Next() {
			var tableName string
			err = rr.Scan(&tableName)
			if err != nil {
				return nil, err
			}

			gather = append(gather, tableName)
		}
		if rr.Err() != nil {
			return nil, rr.Err()
		}

		return gather, nil
	}

	if len(ndata.bucketPath) == 2 {
		return nil, nil // Never any deeper children
	}

	return nil, fmt.Errorf("unknown nav path %#v", ndata.bucketPath)
}

func (ld *sqliteLoadedDatabase) Close() {
	_ = ld.db.Close()
	ld.arena = nil
}

var _ loadedDatabase = &sqliteLoadedDatabase{} // interface assertion

//

func (f *TMainForm) sqliteAddDatabaseFromFile(path string) {

	// TODO load in background thread to stop blocking the UI
	db, err := sql.Open("sqlite3", path)
	if err != nil {
		vcl.ShowMessage(fmt.Sprintf("Failed to load database '%s': %s", path, err.Error()))
		return
	}

	ld := &sqliteLoadedDatabase{
		path:        path,
		displayName: filepath.Base(path),
		db:          db,
	}

	ld.nav = f.Buckets.Items().Add(nil, ld.displayName)
	ld.nav.SetImageIndex(imgDatabase)
	ld.nav.SetSelectedIndex(imgDatabase)
	ld.nav.SetHasChildren(true) // dynamically populate in OnNavExpanding
	navData := &navData{
		ld:             ld,
		childrenLoaded: false,      // will be loaded dynamically
		bucketPath:     []string{}, // empty = root
	}
	ld.nav.SetData(unsafe.Pointer(navData))

	f.dbs = append(f.dbs, ld)
	f.Buckets.SetSelected(ld.nav) // Select new element

	ld.Keepalive(navData)
}