package service

import (
	"fmt"
	"sort"
	"strconv"

	"github.com/fjurmanovic/sugarr/internal/client"
	"github.com/fjurmanovic/sugarr/internal/model"
	"github.com/fjurmanovic/sugarr/internal/utl/configs"
	"github.com/rs/zerolog/log"
)

// Recommender orchestrates the full recommendation pipeline.
type Recommender struct {
	cfg      *configs.Config
	jellyfin *client.JellyfinClient
	tmdb     *client.TMDbClient
	llm      *client.LLMClient    // nil if LLM disabled
	radarr   *client.RadarrClient // nil if Radarr disabled
}

func NewRecommender(cfg *configs.Config) *Recommender {
	r := &Recommender{
		cfg:      cfg,
		jellyfin: client.NewJellyfinClient(cfg),
		tmdb:     client.NewTMDbClient(cfg),
	}
	if cfg.LLMEnabled {
		r.llm = client.NewLLMClient(cfg)
	}
	if cfg.RadarrEnabled {
		r.radarr = client.NewRadarrClient(cfg)
	}
	return r
}

func (r *Recommender) Run() ([]model.Recommendation, error) {
	return r.RunWithCount(r.cfg.RecommendCount)
}

func (r *Recommender) RunWithCount(count int) ([]model.Recommendation, error) {
	// 1. Determine signal movies
	favorites, err := r.jellyfin.GetFavoriteMovies()
	if err != nil {
		return nil, fmt.Errorf("fetching favorites: %w", err)
	}

	var signalMovies, watchedMovies []model.Movie

	if len(favorites) >= r.cfg.MinRatedMovies {
		signalMovies = favorites
		log.Info().Msgf("Using %d favorite movies as signal", len(favorites))
	} else {
		watchedMovies, err = r.jellyfin.GetRecentlyWatched()
		if err != nil {
			return nil, fmt.Errorf("fetching recently watched: %w", err)
		}
		signalMovies = watchedMovies
		log.Info().Msgf("Not enough favorites (%d < %d), falling back to %d recently watched",
			len(favorites), r.cfg.MinRatedMovies, len(watchedMovies))
	}

	// 2. Build exclusion set from Jellyfin library
	library, err := r.jellyfin.GetAllMovies()
	if err != nil {
		log.Warn().Err(err).Msg("Could not fetch library; exclusion may be incomplete")
	}
	exclude := buildExclusionSet(library)

	// Also exclude movies already in Radarr
	if r.cfg.RadarrEnabled && r.radarr != nil {
		if existing, err := r.radarr.GetExisting(); err != nil {
			log.Warn().Err(err).Msg("Could not fetch Radarr library; exclusion may be incomplete")
		} else {
			for _, m := range existing {
				exclude[m.TmdbId] = true
			}
		}
	}

	// 3. Retry loop: each attempt requests only the remaining needed count.
	//    `seen` accumulates every TMDb-resolved movie across attempts so the
	//    LLM prompt excludes them by name, not just by ID.
	var recommendations []model.Recommendation
	var seen []model.Movie
	for attempt := 0; attempt <= r.cfg.RecommendMaxRetry && len(recommendations) < count; attempt++ {
		remaining := count - len(recommendations)
		if attempt > 0 {
			log.Info().Msgf("Retry %d/%d: need %d more recommendations", attempt, r.cfg.RecommendMaxRetry, remaining)
		}

		var suggestions []model.MovieSuggestion
		if r.cfg.LLMEnabled && r.llm != nil {
			prompt := client.BuildPrompt(favorites, watchedMovies, library, seen, remaining)
			suggestions, err = r.llm.Recommend(prompt)
			if err != nil {
				return recommendations, fmt.Errorf("llm recommendation failed: %w", err)
			}
			log.Info().Msgf("LLM returned %d suggestions (attempt %d)", len(suggestions), attempt+1)
		} else {
			suggestions = r.tmdbFallback(signalMovies, exclude, remaining)
			log.Info().Msgf("TMDb fallback returned %d suggestions (attempt %d)", len(suggestions), attempt+1)
		}

		before := len(recommendations)
		for _, s := range suggestions {
			if len(recommendations) >= count {
				break
			}
			tm, err := r.tmdb.SearchMovie(s.Title, s.Year)
			if err != nil || tm == nil {
				log.Debug().Msgf("Could not resolve: %s (%d)", s.Title, s.Year)
				continue
			}
			seen = append(seen, model.Movie{Name: tm.Title, Year: tm.Year, TMDbID: strconv.Itoa(tm.ID)})
			if exclude[tm.ID] {
				log.Debug().Msgf("Skipping (already in library): %s", tm.Title)
				continue
			}
			exclude[tm.ID] = true
			recommendations = append(recommendations, model.Recommendation{
				Title:  tm.Title,
				Year:   tm.Year,
				TMDbID: tm.ID,
				Reason: s.Reason,
			})
		}

		if len(recommendations) == before {
			log.Warn().Msgf("No new recommendations found on attempt %d, stopping retries", attempt+1)
			break
		}
	}

	return recommendations, nil
}

// tmdbFallback gathers TMDb similar/recommended movies across signal movies,
// ranks by occurrence frequency, and returns top N suggestions.
func (r *Recommender) tmdbFallback(signals []model.Movie, exclude map[int]bool, count int) []model.MovieSuggestion {
	freq := map[int]int{}
	meta := map[int]model.TMDbMovie{}

	for _, m := range signals {
		tmdbID, err := strconv.Atoi(m.TMDbID)
		if err != nil || tmdbID == 0 {
			continue
		}
		for _, list := range [][]model.TMDbMovie{
			mustGetList(r.tmdb.GetSimilar(tmdbID)),
			mustGetList(r.tmdb.GetRecommendations(tmdbID)),
		} {
			for _, tm := range list {
				if !exclude[tm.ID] {
					freq[tm.ID]++
					meta[tm.ID] = tm
				}
			}
		}
	}

	type entry struct{ id, count int }
	sorted := make([]entry, 0, len(freq))
	for id, c := range freq {
		sorted = append(sorted, entry{id, c})
	}
	sort.Slice(sorted, func(i, j int) bool { return sorted[i].count > sorted[j].count })

	suggestions := make([]model.MovieSuggestion, 0, count)
	for _, e := range sorted {
		if len(suggestions) >= count {
			break
		}
		tm := meta[e.id]
		suggestions = append(suggestions, model.MovieSuggestion{
			Title:  tm.Title,
			Year:   tm.Year,
			Reason: "Recommended by TMDb",
		})
	}
	return suggestions
}

// AutoRequest adds all recommendations to Radarr.
func (r *Recommender) AutoRequest(recs []model.Recommendation) {
	if r.radarr == nil {
		return
	}
	for _, rec := range recs {
		movie, err := r.radarr.Lookup(rec.TMDbID)
		if err != nil {
			log.Error().Err(err).Msgf("Radarr lookup failed for %s", rec.Title)
			continue
		}
		if err := r.radarr.AddMovie(*movie); err != nil {
			log.Error().Err(err).Msgf("Radarr add failed for %s", rec.Title)
			continue
		}
		log.Info().Msgf("Requested in Radarr: %s (%d)", rec.Title, rec.Year)
	}
}

// LLM returns the LLM client, or nil if not enabled.
func (r *Recommender) LLM() *client.LLMClient { return r.llm }

// Radarr returns the Radarr client, or nil if not enabled.
func (r *Recommender) Radarr() *client.RadarrClient { return r.radarr }

// Jellyfin returns the Jellyfin client.
func (r *Recommender) Jellyfin() *client.JellyfinClient { return r.jellyfin }

// TMDb returns the TMDb client.
func (r *Recommender) TMDb() *client.TMDbClient { return r.tmdb }

func buildExclusionSet(movies []model.Movie) map[int]bool {
	exclude := map[int]bool{}
	for _, m := range movies {
		if id, err := strconv.Atoi(m.TMDbID); err == nil && id != 0 {
			exclude[id] = true
		}
	}
	return exclude
}

func mustGetList(movies []model.TMDbMovie, _ error) []model.TMDbMovie {
	if movies == nil {
		return nil
	}
	return movies
}