package engine

import (
	"context"
	"fmt"
	"time"

	"robotfs/store"
	"robotfs/utils"
)

type FileSystemManager struct {
	meta    store.MetaStore
	storage *StorageManager
}

func NewFileSystemManager(meta store.MetaStore, storage *StorageManager) *FileSystemManager {
	return &FileSystemManager{
		meta:    meta,
		storage: storage,
	}
}

func (f *FileSystemManager) BeginTransaction(ctx context.Context) (context.Context, error) {
	return f.meta.BeginTransaction(ctx)
}

func (f *FileSystemManager) CommitTransaction(ctx context.Context) error {
	return f.meta.CommitTransaction(ctx)
}

func (f *FileSystemManager) RollbackTransaction(ctx context.Context) error {
	return f.meta.RollbackTransaction(ctx)
}

var (
	Root = &utils.Entry{
		FullPath:             utils.FullPath("/"),
		IsDir:                true,
		CreateTime:           time.Now().Unix(),
		LastModificationTime: time.Now().Unix(),
	}
)

func (f *FileSystemManager) FindEntry(ctx context.Context, p utils.FullPath) (entry *utils.Entry, err error) {
	if p == "/" {
		return nil, nil
	}

	entry, err = f.meta.FindEntry(ctx, p)
	if err != nil {
		return nil, err
	}

	return
}

func (f *FileSystemManager) MakeDirectory(ctx context.Context, path utils.FullPath) error {
	if string(path) == "/" {
		return nil
	}

	if entry, _ := f.FindEntry(ctx, path); entry != nil {
		return fmt.Errorf("directory %s already exists", path)
	}

	parentDir, _ := path.DirAndName()
	if parentDir != "/" {
		if parentEntry, _ := f.FindEntry(ctx, utils.FullPath(parentDir)); parentEntry == nil {
			return fmt.Errorf("parent directory %s does not exist", parentDir)
		}
	}

	entry := utils.MakeEntry(path, true)
	return f.meta.InsertEntry(ctx, entry)
}

func (f *FileSystemManager) ListDirectoryEntries(ctx context.Context, p utils.FullPath, startFileName string, inclusive bool, limit int64) (entries []*utils.Entry, hasMore bool, err error) {

	_, err = f.StreamListDirectoryEntries(ctx, p, startFileName, inclusive, limit+1, func(entry *utils.Entry) bool {
		entries = append(entries, entry)
		return true
	})

	hasMore = int64(len(entries)) >= limit+1
	if hasMore {
		entries = entries[:limit]
	}

	return entries, hasMore, err
}

func (f *FileSystemManager) StreamListDirectoryEntries(ctx context.Context, p utils.FullPath, startFileName string, inclusive bool, limit int64, eachEntryFunc store.ListEachEntryFunc) (lastFileName string, err error) {

	lastFileName, err = f.doListDirectoryEntries(ctx, p, startFileName, inclusive, limit, eachEntryFunc)
	return
}

func (f *FileSystemManager) doListDirectoryEntries(ctx context.Context, p utils.FullPath, startFileName string, inclusive bool, limit int64, eachEntryFunc store.ListEachEntryFunc) (lastFileName string, err error) {
	lastFileName, err = f.meta.ListDirectoryEntries(ctx, p, startFileName, inclusive, limit, func(entry *utils.Entry) bool {
		select {
		case <-ctx.Done():
			return false
		default:
			return eachEntryFunc(entry)
		}
	})
	return
}

func (f *FileSystemManager) Shutdown() error {
	if f.meta != nil {
		f.meta.Shutdown()
	}

	return nil
}