package handler

import (
	"context"
	"fmt"
	"log/slog"
	"strconv"
	"strings"
	"time"

	tgbot "github.com/go-telegram/bot"

	"uptodownBot/internal/domain"
)

func (h *Handler) handlePlaylist(ctx context.Context, chatID int64, userID int64, url string, info *domain.MediaInfo) {
	state := &domain.PlaylistState{
		Entries:  info.PlaylistEntries,
		Page:     0,
		PerPage:  10,
		Selected: make(map[string]bool),
	}

	ss := &stepState{
		URL:           url,
		MediaInfo:     info,
		PlaylistState: state,
		CreatedAt:     time.Now(),
	}
	h.setUserStepState(chatID, ss)

	h.sendMediaPreview(ctx, chatID, info)

	kb := playlistNavKeyboard(state, 0)
	h.sendWithKB(ctx, chatID, fmt.Sprintf("Playlist: %s (%d videos)\n\nSelect videos to download:", info.Title, info.PlaylistCount), kb)
}

func (h *Handler) getPlaylistState(chatID int64) *domain.PlaylistState {
	ss := h.getUserStepState(chatID)
	if ss == nil {
		return nil
	}
	return ss.PlaylistState
}

func (h *Handler) handlePlaylistPage(ctx context.Context, chatID int64, msgID int, userID int64, pageStr string) {
	state := h.getPlaylistState(chatID)
	if state == nil {
		return
	}
	page, err := strconv.Atoi(pageStr)
	if err != nil {
		return
	}
	totalPages := (len(state.Entries) + state.PerPage - 1) / state.PerPage
	if page < 0 || page >= totalPages {
		return
	}
	state.Page = page

	selectedCount := countSelected(state)
	kb := playlistNavKeyboard(state, selectedCount)
	ss := h.getUserStepState(chatID)
	title := ""
	if ss != nil {
		title = ss.MediaInfo.Title
	}
	h.editText(ctx, chatID, msgID, fmt.Sprintf("Playlist: %s (%d videos)", title, len(state.Entries)), &kb)
}

func (h *Handler) handlePlaylistEntry(ctx context.Context, chatID int64, msgID int, userID int64, entryID string) {
	state := h.getPlaylistState(chatID)
	if state == nil {
		return
	}
	state.Selected[entryID] = !state.Selected[entryID]

	selectedCount := countSelected(state)
	kb := playlistNavKeyboard(state, selectedCount)
	ss := h.getUserStepState(chatID)
	title := ""
	if ss != nil {
		title = ss.MediaInfo.Title
	}
	h.editText(ctx, chatID, msgID, fmt.Sprintf("Playlist: %s (%d videos)", title, len(state.Entries)), &kb)
}

func (h *Handler) handlePlaylistSelectAll(ctx context.Context, chatID int64, msgID int, userID int64) {
	state := h.getPlaylistState(chatID)
	if state == nil {
		return
	}

	allSelected := true
	for _, e := range state.Entries {
		if !state.Selected[e.ID] {
			allSelected = false
			break
		}
	}
	for _, e := range state.Entries {
		state.Selected[e.ID] = !allSelected
	}

	selectedCount := 0
	if !allSelected {
		selectedCount = len(state.Entries)
	}
	kb := playlistNavKeyboard(state, selectedCount)
	ss := h.getUserStepState(chatID)
	title := ""
	if ss != nil {
		title = ss.MediaInfo.Title
	}
	h.editText(ctx, chatID, msgID, fmt.Sprintf("Playlist: %s (%d videos)", title, len(state.Entries)), &kb)
}

func (h *Handler) handlePlaylistConfirm(ctx context.Context, chatID int64, msgID int, userID int64) {
	if job := h.getActiveJob(userID); job != nil {
		h.sendText(ctx, chatID, "You already have an active download. Cancel it first.")
		return
	}

	state := h.getPlaylistState(chatID)
	if state == nil {
		return
	}

	var selected []domain.PlaylistEntry
	for _, e := range state.Entries {
		if state.Selected[e.ID] {
			selected = append(selected, e)
		}
	}
	if len(selected) == 0 {
		h.editText(ctx, chatID, msgID, "No videos selected.", nil)
		return
	}

	h.clearStepState(chatID)

	// Parent context for the entire playlist — cancelling this stops all entries
	playlistCtx, playlistCancel := context.WithCancel(context.Background())
	h.setCancelFunc(userID, playlistCancel)

	h.editText(ctx, chatID, msgID, fmt.Sprintf("Downloading %d videos...", len(selected)), nil)

	// Run the playlist loop in a goroutine so the handler is free to process
	// cancel callbacks and other updates concurrently.
	go func() {
		for i, entry := range selected {
			if playlistCtx.Err() != nil {
				break
			}

			info, err := h.YtDlp.GetMediaInfo(entry.URL)
			if err != nil {
				h.sendText(playlistCtx, chatID, fmt.Sprintf("Playlist entry (%d/%d) failed: %s", i+1, len(selected), err.Error()))
				continue
			}

			prefs, prefErr := h.Repo.GetOrCreatePreferences(userID)
			if prefErr != nil {
				prefs = &domain.UserPreferences{
					DefaultMediaType:   domain.MediaTypeVideoAudio,
					DefaultAudioFormat: "best",
					DefaultVideoFormat: "best",
				}
			}

			formatID := prefs.DefaultVideoFormat
			if prefs.DefaultMediaType == domain.MediaTypeAudio {
				formatID = prefs.DefaultAudioFormat
			}
			ff := &domain.Format{ID: formatID}
			for i := range info.Formats {
				if info.Formats[i].ID == formatID {
					ff = &info.Formats[i]
					break
				}
			}

			job := &domain.DownloadJob{
				ID:             h.generateJobID(),
				UserID:         userID,
				ChatID:         chatID,
				MessageID:      0,
				URL:            entry.URL,
				MediaType:      prefs.DefaultMediaType,
				SelectedFormat: ff,
				FormatString:   "",
				Language:       prefs.DefaultLanguage,
				Status:         domain.StatusDownloading,
				Title:          entry.Title,
				FileSize:       ff.Filesize,
				MaxFileSize:    h.maxFileSize,
				ProgressPrefix: fmt.Sprintf("Downloading (%d/%d)", i+1, len(selected)),
				Done:           make(chan struct{}),
			}

			ok := h.downloadPlaylistEntry(playlistCtx, userID, chatID, job)
			if !ok {
				break
			}
		}

		h.clearActiveJob(userID)
		h.sendText(playlistCtx, chatID, "Playlist downloads finished.")
	}()
}

// downloadPlaylistEntry handles a single entry in a playlist download.
// It returns false if the playlist should stop (cancelled/fatal).
func (h *Handler) downloadPlaylistEntry(ctx context.Context, userID, chatID int64, job *domain.DownloadJob) bool {
	if job.Done != nil {
		defer close(job.Done)
	}

	h.setActiveJob(userID, job)

	kb := progressKeyboard(0, "", "")
	progressHeader := job.ProgressPrefix + "\nDownloading: " + job.Title
	msg, sendErr := h.Bot.SendMessage(ctx, &tgbot.SendMessageParams{
		ChatID:      chatID,
		Text:        progressHeader,
		ReplyMarkup: &kb,
	})
	if sendErr != nil {
		slog.Error("send playlist progress msg failed", "error", sendErr)
		return true // non-fatal, continue to next
	}
	job.MessageID = msg.ID

	updates, dlErr := h.YtDlp.StartDownload(job, h.downloadDir)
	if dlErr != nil {
		errMsg := dlErr.Error()
		if job.StderrLog != "" {
			if lines := strings.SplitN(job.StderrLog, "\n", 2); len(lines) > 0 && lines[0] != "" {
				errMsg = strings.TrimSpace(lines[0])
			}
		}
		h.editText(ctx, chatID, job.MessageID, fmt.Sprintf("Download failed: %s", errMsg), nil)
		return true
	}

	h.trackDownloadProgress(ctx, job, updates)

	if job.Status == domain.StatusCompleted {
		h.handleDownloadCompletion(ctx, job)
	}

	return job.Status != domain.StatusCancelled
}

func countSelected(state *domain.PlaylistState) int {
	count := 0
	for _, s := range state.Selected {
		if s {
			count++
		}
	}
	return count
}