package main

import (
	"errors"
	"fmt"
	"path/filepath"
	"sort"
	"strings"
	"time"
	"unsafe"

	"github.com/ying32/govcl/vcl"
	"go.etcd.io/bbolt"
	"go.etcd.io/bbolt/version"
)

const (
	boltFilter = "Bolt database|*.db|All files|*.*"
)

type boltLoadedDatabase struct {
	displayName string
	path        string
	db          *bbolt.DB
	nav         *vcl.TTreeNode

	arena []*navData // keepalive
}

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

func (ld *boltLoadedDatabase) DriverName() string {
	return "Bolt " + version.Version
}

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

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

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

	// Load properties

	bucketDisplayName := strings.Join(ndata.bucketPath, `/`)
	content := fmt.Sprintf("Selected database: %#v\n\n\nSelected bucket: %q\n", ld.db.Stats(), bucketDisplayName)
	f.propertiesBox.SetText(content)

	// Load data
	// Bolt always uses Key + Value as the columns
	colKey := f.contentBox.Columns().Add()
	colKey.Title().SetCaption("Key")
	colVal := f.contentBox.Columns().Add()
	colVal.Title().SetCaption("Value")

	err := ld.db.View(func(tx *bbolt.Tx) error {
		b := boltTargetBucket(tx, ndata.bucketPath)
		if b == nil {
			// no such bucket
			return nil
		}

		// Valid
		c := b.Cursor()
		for k, v := c.First(); k != nil; k, v = c.Next() {
			rpos := f.contentBox.RowCount()
			f.contentBox.SetRowCount(rpos + 1)
			f.contentBox.SetCells(0, rpos, formatUtf8(k))
			f.contentBox.SetCells(1, rpos, formatUtf8(v))
		}
		return nil
	})
	if err != nil {
		return err
	}

	// Valid
	vcl_stringgrid_columnwidths(f.contentBox)
	f.contentBox.SetEnabled(true)
	return nil
}

func (n *boltLoadedDatabase) ApplyChanges(f *TMainForm, ndata *navData) error {
	if n.db.IsReadOnly() {
		return errors.New("Database was opened read-only")
	}

	// We have rendered row IDs, need to convert back to a bolt primary key
	// TODO stash the real key inside f.contentBox.Objects()
	// FIXME breaks if you try and edit the primary key(!)
	primaryKeyForRendered := func(rowid int32) []byte {
		return []byte(f.contentBox.Cells(0, rowid))
	}

	return n.db.Update(func(tx *bbolt.Tx) error {

		// Get current bucket handle
		b := boltTargetBucket(tx, ndata.bucketPath)

		// Edit
		for rowid, _ /*editcells*/ := range f.updateRows {
			k := primaryKeyForRendered(rowid)
			v := f.contentBox.Cells(1, rowid) // There's only one value cell
			err := b.Put(k, []byte(v))
			if err != nil {
				return fmt.Errorf("Updating cell %q: %w", formatUtf8(k), err)
			}
		}

		// Delete by key (affects rowids after re-render)
		for rowid, _ := range f.deleteRows {
			k := primaryKeyForRendered(rowid)
			err := b.Delete(k)
			if err != nil {
				return fmt.Errorf("Deleting cell %q: %w", formatUtf8(k), err)
			}
		}

		// Insert all new entries
		for rowid, _ := range f.insertRows {
			k := primaryKeyForRendered(rowid)
			v := f.contentBox.Cells(1, rowid) // There's only one value cell
			err := b.Put(k, []byte(v))
			if err != nil {
				return fmt.Errorf("Inserting cell %q: %w", formatUtf8(k), err)
			}
		}

		// Done
		return nil
	})
}

func (ld *boltLoadedDatabase) NavChildren(ndata *navData) ([]string, error) {
	// In the bolt implementation, the nav is a recursive tree of child buckets
	return boltChildBucketNames(ld.db, ndata.bucketPath)
}

func (ld *boltLoadedDatabase) NavContext(ndata *navData) (ret []contextAction, err error) {
	ret = append(ret, contextAction{"Add bucket...", ld.AddChildBucket})

	if len(ndata.bucketPath) > 0 {
		ret = append(ret, contextAction{"Delete bucket", ld.DeleteBucket})
	}

	return
}

func (ld *boltLoadedDatabase) AddChildBucket(ndata *navData) error {
	bucketName := ""
	if !vcl.InputQuery(APPNAME, "Enter a name for the new bucket:", &bucketName) {
		return nil // cancel
	}

	err := ld.db.Update(func(tx *bbolt.Tx) error {
		parent := boltTargetBucket(tx, ndata.bucketPath)
		if parent != nil {
			_, err := parent.CreateBucket([]byte(bucketName))
			return err
		}

		// Top-level
		_, err := tx.CreateBucket([]byte(bucketName))
		return err
	})
	if err != nil {
		return fmt.Errorf("Error adding bucket: %w", err)
	}
	return nil
}

func (ld *boltLoadedDatabase) DeleteBucket(ndata *navData) error {
	err := ld.db.Update(func(tx *bbolt.Tx) error {
		// Find parent of this bucket.
		if len(ndata.bucketPath) >= 2 {
			// child bucket
			parent := boltTargetBucket(tx, ndata.bucketPath[0:len(ndata.bucketPath)-1])
			return parent.DeleteBucket([]byte(ndata.bucketPath[len(ndata.bucketPath)-1]))
		} else {
			// top-level bucket
			return tx.DeleteBucket([]byte(ndata.bucketPath[0]))
		}
	})
	if err != nil {
		return fmt.Errorf("Error deleting bucket %q: %w", strings.Join(ndata.bucketPath, `/`), err)
	}
	return nil
}

func (ld *boltLoadedDatabase) ExecQuery(query string, resultArea *vcl.TStringGrid) error {
	return ErrNotSupported
}

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

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

//

func (f *TMainForm) boltAddDatabaseFromFile(path string, readonly bool) {
	// TODO load in background thread to stop blocking the UI

	opts := bbolt.Options{
		Timeout:  1 * time.Second,
		ReadOnly: readonly,
	}

	db, err := bbolt.Open(path, 0644, &opts)
	if err != nil {
		vcl.ShowMessage(fmt.Sprintf("Failed to load database '%s': %s", path, err.Error()))
		return
	}

	ld := &boltLoadedDatabase{
		path:        path,
		displayName: filepath.Base(path),
		db:          db,
	}
	if readonly {
		ld.displayName += " (read-only)"
	}

	ld.nav = f.Buckets.Items().Add(nil, ld.displayName)
	ld.nav.SetHasChildren(true) // dynamically populate in OnNavExpanding
	ld.nav.SetImageIndex(imgDatabase)
	ld.nav.SetSelectedIndex(imgDatabase)
	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)
}

func boltTargetBucket(tx *bbolt.Tx, path []string) *bbolt.Bucket {

	// If we are already deep in buckets, go directly there to find children
	if len(path) == 0 {
		return nil
	}

	b := tx.Bucket([]byte(path[0]))
	if b == nil {
		return nil // unexpectedly missing
	}

	for i := 1; i < len(path); i += 1 {
		b = b.Bucket([]byte(path[i]))
		if b == nil {
			return nil // unexpectedly missing
		}
	}

	return b // OK
}

func boltChildBucketNames(db *bbolt.DB, path []string) ([]string, error) {
	var nextBucketNames []string

	err := db.View(func(tx *bbolt.Tx) error {

		// If we are already deep in buckets, go directly there to find children
		if len(path) > 0 {
			b := tx.Bucket([]byte(path[0]))
			if b == nil {
				return fmt.Errorf("Root bucket %q: %w", path[0], ErrNavNotExist)
			}

			for i := 1; i < len(path); i += 1 {
				b = b.Bucket([]byte(path[i]))
				if b == nil {
					return fmt.Errorf("Bucket %q: %w", strings.Join(path[0:i], `/`), ErrNavNotExist)
				}
			}

			// Find child buckets of this bucket
			b.ForEachBucket(func(bucketName []byte) error {
				nextBucketNames = append(nextBucketNames, string(bucketName))
				return nil
			})

		} else {
			// Find root bucket names
			return tx.ForEach(func(bucketName []byte, _ *bbolt.Bucket) error {
				nextBucketNames = append(nextBucketNames, string(bucketName))
				return nil
			})
		}

		// OK
		return nil
	})
	if err != nil {
		return nil, err
	}

	sort.Strings(nextBucketNames)

	return nextBucketNames, nil
}