package main

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

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

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) 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) {

	// 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

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

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

		// Valid
		f.contentBox.Clear()

		c := b.Cursor()
		for k, v := c.First(); k != nil; k, v = c.Next() {
			dataEntry := f.contentBox.Items().Add()
			dataEntry.SetCaption(formatUtf8(k))
			dataEntry.SubItems().Add(formatUtf8(v))
		}
		return nil
	})
	if err != nil {
		vcl.ShowMessage(fmt.Sprintf("Failed to load data for bucket %q: %s", bucketDisplayName, err.Error()))
		return
	}

	// Valid
	f.contentBox.SetEnabled(true)
}

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)
}

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

//

func (f *TMainForm) addDatabaseFromFile(path string) {
	// TODO load in background thread to stop blocking the UI
	db, err := bbolt.Open(path, 0644, &bbolt.Options{Timeout: 1 * time.Second})
	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,
	}

	ld.nav = f.Buckets.Items().Add(nil, ld.displayName)
	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)

	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("Unexpected missing root bucket %q", path[0])
			}

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

			// 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
}