package browser

import (
	"fmt"
	"path/filepath"
	"time"

	"pad/internal/io/pool"
	"pad/internal/io/pool/mock"
)

var ErrDirNotFound = fmt.Errorf("directory not found")

type BrowserManager struct {
	state      *BrowserState
	workerPool *pool.WorkerPool
	fs         *mock.FileSystem
	dirPath    string
}

func NewBrowserManager(state *BrowserState, wp *pool.WorkerPool, fs *mock.FileSystem) (*BrowserManager, error) {
	return &BrowserManager{
		state:      state,
		workerPool: wp,
		fs:         fs,
	}, nil
}

func (bm *BrowserManager) NavigateTo(dirPath string) {
	fmt.Printf("NavigateTo: %s\n", dirPath)
	bm.dirPath = dirPath
	navigateToDirectory(bm.state, dirPath)
	bm.state.Loading = true

	// Dispatch BuildIndexTask to the worker pool.
	// In a real app, this would be a task that reads and sorts the directory.
	task := pool.NewBuildIndexTask(dirPath, bm.fs)
	bm.workerPool.Dispatch(task)
}

func (bm *BrowserManager) OnScroll() {
	if bm.state.TotalEntries == 0 {
		return
	}

	// Identify unloaded pages in the visible + prefetch range
	minPage, maxPage := computeVisiblePageRange(bm.state)
	var pagesToLoad []int
	for i := minPage; i <= maxPage; i++ {
		if page, ok := bm.state.Pages[i]; !ok || !page.Loaded {
			pagesToLoad = append(pagesToLoad, i)
		}
	}

	fmt.Printf("OnScroll: minPage=%d, maxPage=%d, pagesToLoad=%v\n", minPage, maxPage, pagesToLoad)

	// Dispatch LoadPagesTask for unloaded pages
	if len(pagesToLoad) > 0 {
		fmt.Printf("OnScroll: Dispatching LoadPagesTask for pages %v\n", pagesToLoad)
		task := pool.NewLoadPagesTask(bm.dirPath, pagesToLoad, bm.fs)
		bm.workerPool.Dispatch(task)
	}

	// Evict distant pages to save memory
	bm.state.EvictPages()
}

func (bm *BrowserManager) HandleResult(result pool.Result) {
	if !result.IsBrowserResult() {
		return
	}

	switch result.TaskType {
	case pool.TypeBuildIndex:
		if result.Success {
			bm.handleBuildIndexSuccess(result)
		} else {
			bm.handleError(result)
		}
	case pool.TypeLoadPages:
		if result.Success {
			bm.handleLoadPagesSuccess(result)
		} else {
			bm.handleError(result)
		}
	}
}

func (bm *BrowserManager) handleBuildIndexSuccess(result pool.Result) {
	fmt.Printf("handleBuildIndexSuccess: TotalEntries=%d\n", len(result.Data.([]mock.DirEntry)))
	bm.state.Loading = false

	// In the mock implementation, BuildIndexTask returns []mock.DirEntry.
	// We need to convert these to browser.Entry and build the SortIndex.
	entries := result.Data.([]mock.DirEntry)
	
	var browserEntries []Entry
	// Add ".." entry if not at root
	if bm.dirPath != "/" && bm.dirPath != "." {
		browserEntries = append(browserEntries, Entry{
			Path:    filepath.Dir(bm.dirPath),
			Name:    "..",
			Size:    0,
			ModTime: time.Now(),
			IsDir:   true,
		})
	}
	
	for _, e := range entries {
		info, _ := e.Info()
		browserEntries = append(browserEntries, Entry{
			Path:    filepath.Join(bm.dirPath, e.Name()),
			Name:    e.Name(),
			Size:    info.Size(),
			ModTime: info.ModTime(),
			IsDir:   e.IsDir(),
		})
	}

	// Build the sorted index with position maps
	bm.state.SortIndex = &DirectoryIndex{
		Path:       bm.dirPath,
		EntryCount: len(browserEntries),
		Entries:    browserEntries,
		SortOrders: make(map[string][]int),
	}

	// Compute position maps for all sort modes
	for mode := SortMode(0); mode < SortMode(modeCount()); mode++ {
		key := sortModeKey(mode)
		if key != "" {
			bm.state.SortIndex.SortOrders[key] = buildPositionMap(browserEntries, mode)
		}
	}

	bm.state.TotalEntries = len(browserEntries)
	fmt.Printf("handleBuildIndexSuccess: TotalEntries set to %d\n", bm.state.TotalEntries)

	// Trigger initial page load
	bm.OnScroll()
}

func (bm *BrowserManager) handleLoadPagesSuccess(result pool.Result) {
	// In a real implementation, LoadPagesTask would return the actual entry data.
	// In our current mock/placeholder, it just returns the page indices.
	// We'll load the data from the SortIndex.
	pageIndices := result.Data.([]int)

	for _, idx := range pageIndices {
		page := loadPageFromIndex(bm.state, idx)
		if page != nil {
			bm.state.Pages[idx] = page
		}
	}
}

func (bm *BrowserManager) handleError(result pool.Result) {
	fmt.Printf("handleError: TaskType=%s, Error=%v\n", result.TaskType, result.Error)
	bm.state.Loading = false
	// For now, just reset the state or log the error.
	// In production, we'd show a toast or error message.
	if bm.state.CurrentPath == bm.dirPath {
		bm.state.Reset()
	}
}