// Package service — download manager.
//
// DownloadService persists user-initiated downloads, dispatches them to
// the configured client (currently qBittorrent) and pushes live progress
// to the WS hub so the React UI can render a live table.
//
// Settings consumed (system Setting table):
//
//   qbittorrent.url       e.g. http://127.0.0.1:8080
//   qbittorrent.username  qBittorrent WebUI user
//   qbittorrent.password  qBittorrent WebUI password
//   qbittorrent.savepath  optional default save dir
//
// Settings can be updated at runtime via the admin UI; ReloadConfig()
// re-reads them and re-authenticates.
package service

import (
	"context"
	"errors"
	"sync"
	"time"

	"go.uber.org/zap"

	"github.com/ShukeBta/MediaStationGo/internal/model"
	"github.com/ShukeBta/MediaStationGo/internal/repository"
)

// DownloadService is the single download orchestrator.
type DownloadService struct {
	log     *zap.Logger
	repo    *repository.Container
	hub     *Hub
	qb      *QBitClient

	mu       sync.Mutex
	stopCh   chan struct{}
	pollOnce sync.Once
}

// NewDownloadService is the constructor.
func NewDownloadService(log *zap.Logger, repo *repository.Container, hub *Hub) *DownloadService {
	return &DownloadService{
		log:    log,
		repo:   repo,
		hub:    hub,
		qb:     NewQBitClient(log, QBitConfig{}),
		stopCh: make(chan struct{}),
	}
}

// Start kicks off the background poller (idempotent).
func (d *DownloadService) Start(ctx context.Context) {
	d.pollOnce.Do(func() {
		_ = d.ReloadConfig(ctx)
		go d.poll(ctx)
	})
}

// Stop terminates the poller.
func (d *DownloadService) Stop() {
	close(d.stopCh)
}

// ReloadConfig rebuilds the qBittorrent client from the system settings.
func (d *DownloadService) ReloadConfig(ctx context.Context) error {
	cfg := QBitConfig{}
	for _, key := range []struct{ from, into *string }{} {
		_ = key
	}
	get := func(k string) string {
		v, _ := d.repo.Setting.Get(ctx, k)
		return v
	}
	cfg.BaseURL = get("qbittorrent.url")
	cfg.Username = get("qbittorrent.username")
	cfg.Password = get("qbittorrent.password")
	d.qb.Configure(cfg)
	return nil
}

// AddDownload accepts a magnet URL / HTTP URL and persists a tracking row.
func (d *DownloadService) AddDownload(ctx context.Context, userID, urlStr, savePath string) (*model.DownloadTask, error) {
	if urlStr == "" {
		return nil, errors.New("empty url")
	}
	if savePath == "" {
		savePath, _ = d.repo.Setting.Get(ctx, "qbittorrent.savepath")
	}
	if err := d.qb.AddTorrent(ctx, urlStr, savePath); err != nil {
		return nil, err
	}
	t := &model.DownloadTask{
		UserID:   userID,
		Source:   "qbittorrent",
		URL:      urlStr,
		SavePath: savePath,
		Status:   "queued",
	}
	if err := d.repo.Download.Create(ctx, t); err != nil {
		return nil, err
	}
	return t, nil
}

// List returns every persisted download task augmented with live data
// from qBittorrent when available.
func (d *DownloadService) List(ctx context.Context) ([]model.DownloadTask, []QBitTorrent, error) {
	rows, err := d.repo.Download.List(ctx)
	if err != nil {
		return nil, nil, err
	}
	live, err := d.qb.List(ctx, "")
	if err != nil {
		// Network failure shouldn't break the page — return rows with no
		// live data and let the UI render the persisted snapshot.
		d.log.Debug("qbittorrent list failed", zap.Error(err))
		return rows, nil, nil
	}
	return rows, live, nil
}

// Delete removes a torrent (and optionally its files) from qBittorrent.
func (d *DownloadService) Delete(ctx context.Context, hash string, withFiles bool) error {
	return d.qb.Delete(ctx, hash, withFiles)
}

// poll fans out qBittorrent /torrents/info every 5 s as WS events. The
// payload is opaque to the client; the React store merges by hash.
func (d *DownloadService) poll(ctx context.Context) {
	t := time.NewTicker(5 * time.Second)
	defer t.Stop()
	for {
		select {
		case <-ctx.Done():
			return
		case <-d.stopCh:
			return
		case <-t.C:
		}
		live, err := d.qb.List(ctx, "")
		if err != nil {
			continue
		}
		d.hub.Publish("download", map[string]any{"torrents": live})
	}
}