package api

import (
	"context"
	"encoding/json"
	"net/http"
	"net/url"
	"strings"
	"sync"
	"time"

	"github.com/ponzischeme89/memby/server/internal/cache"
	"github.com/ponzischeme89/memby/server/internal/recommend"
	"github.com/ponzischeme89/memby/server/internal/store"
)

type activeHeroResponse struct {
	Placement string          `json:"placement"`
	Source    string          `json:"source"`
	Rows      []recommend.Row `json:"rows"`
}

// handleActiveHero gives every section the same server-owned resolver as Home. The client
// supplies only a placement; schedules, priorities, pins and ranking remain gateway data.
func (s *Server) handleActiveHero(w http.ResponseWriter, r *http.Request, sess store.Session) {
	placement := strings.ToLower(strings.TrimSpace(r.URL.Query().Get("placement")))
	if !store.ValidHeroPlacement(placement) {
		writeError(w, http.StatusBadRequest, "placement must be home, movies or tv_shows")
		return
	}
	now := time.Now()
	location := s.heroLocation()
	// Keyed by the revision the status poll publishes, which already carries the rotation
	// slot. That is what makes an operator's change reachable immediately without dropping
	// anything else the household has cached: the old entry is not invalidated, it is
	// simply no longer named. See heroRevision.
	key := cache.UserKey(sess.EmbyUserID, "hero:active:v2:"+placement+":"+
		heroRevision(s.currentHeroPolicy(r.Context()), sess.EmbyUserID, now, location))
	if raw, err := s.cache.Get(r.Context(), key); err == nil {
		w.Header().Set("X-Memby-Cache", "hit")
		writeRaw(w, http.StatusOK, raw)
		return
	}

	response, err := s.resolveActiveHero(r.Context(), sess, placement, now)
	if err != nil {
		s.writeUpstreamError(r.Context(), w, err, "could not resolve the section hero")
		return
	}
	raw, err := json.Marshal(response)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "could not build the section hero")
		return
	}
	if err := s.cache.Set(r.Context(), key, raw, s.cfg.SearchTTL); err != nil {
		s.loggerFor(r.Context()).Warn("section hero cache write failed", "placement", placement, "error", err)
	}
	w.Header().Set("X-Memby-Cache", "miss")
	writeRaw(w, http.StatusOK, raw)
}

func (s *Server) resolveActiveHero(ctx context.Context, sess store.Session, placement string, now time.Time) (activeHeroResponse, error) {
	itemType := "Movie"
	if placement == store.HeroPlacementTVShows {
		itemType = "Series"
	}
	if placement == store.HeroPlacementHome {
		itemType = "Movie,Series"
	}
	result, err := s.emby.Items(ctx, credentials(sess), rowParams(url.Values{
		"IncludeItemTypes": {itemType}, "Recursive": {"true"}, "Limit": {"64"},
		"SortBy": {"DateCreated,PremiereDate,SortName"}, "SortOrder": {"Descending"},
	}, fieldsRow))
	if err != nil {
		return activeHeroResponse{}, err
	}
	s.decorateItemRatings(ctx, result.Items)
	rows := []recommend.Row{{ID: "hero-candidates-" + placement, Kind: "catalogue", Items: result.Items}}

	policy := s.currentHeroPolicy(ctx)
	placementPolicy := policy.Placement(placement)
	pinned := filterHeroPlacement(s.pinnedHeroCandidates(ctx, placementPolicy.PinnedItemIDs), placement)
	location := s.heroLocation()
	scheduledIDs := activeHeroScheduleIDs(policy.Schedules, placement, sess.EmbyUserID, now, location)
	scheduled := filterHeroPlacement(s.pinnedHeroCandidates(ctx, scheduledIDs), placement)

	var candidates []heroCandidate
	if placement == store.HeroPlacementTVShows {
		candidates = append(s.heroPremiereCandidates(ctx, now), heroSeriesCandidates(rows)...)
		candidates = filterHeroPlacement(candidates, placement)
	} else if placement == store.HeroPlacementMovies {
		candidates = s.heroMoviePlacementCandidates(ctx, rows, now)
	} else {
		candidates = s.heroCandidates(ctx, rows, now)
	}
	pool := rankHeroCandidates(candidates, now, heroPoolLimit)
	organic := rotateHeroCandidates(pool, heroVariationSeed(sess.EmbyUserID, heroRotationSlot(now, location)+":"+placement), heroRowLimit)
	ranked := mergePinnedHeroCandidates(append(pinned, scheduled...), candidates, organic, heroRowLimit)

	source := "automatic"
	if len(pinned) > 0 {
		source = "manual"
	} else if len(scheduled) > 0 {
		source = "scheduled"
	}
	response := activeHeroResponse{Placement: placement, Source: source, Rows: []recommend.Row{}}
	if len(ranked) == 0 {
		response.Source = "fallback"
		return response, nil
	}
	items := make([]json.RawMessage, 0, len(ranked))
	for index, candidate := range ranked {
		items = append(items, injectHeroFields(candidate.Item, heroLabel(candidate, now), heroReasonForPosition(candidate, index, placementPolicy.PrimeSubtitle, now, location)))
	}
	response.Rows = append(response.Rows, recommend.Row{ID: "hero-" + placement, Title: "Featured", Kind: heroRowKind, Items: items})
	s.loggerFor(ctx).Debug("section hero resolved", "placement", placement, "source", source, "items", len(items))
	return response, nil
}

// Movies needs Radarr's real availability date, but never needs to wait for Sonarr. Home
// intentionally combines both; keeping this path narrow is what makes section preloading
// inexpensive even when one integration is unavailable.
func (s *Server) heroMoviePlacementCandidates(ctx context.Context, rows []recommend.Row, now time.Time) []heroCandidate {
	movies, facts := heroMovieCandidates(rows)
	var releases heroReleaseIndex
	var providers map[string]string
	var wg sync.WaitGroup
	wg.Add(2)
	go func() { defer wg.Done(); releases = s.heroReleaseIndex(ctx, now) }()
	go func() { defer wg.Done(); providers = s.heroProviderIDs(ctx, facts) }()
	wg.Wait()
	for index := range movies {
		fact := facts[movies[index].ID]
		if release, ok := releases.lookup(providers[movies[index].ID], fact.Name, heroYearOf(fact)); ok {
			movies[index].ReleasedAt = release.at
			movies[index].Estimated = release.estimated
		}
	}
	return movies
}

func filterHeroPlacement(candidates []heroCandidate, placement string) []heroCandidate {
	out := make([]heroCandidate, 0, len(candidates))
	for _, candidate := range candidates {
		isMovie := candidate.Kind == heroMovie
		if placement == store.HeroPlacementMovies && isMovie {
			out = append(out, candidate)
		}
		if placement == store.HeroPlacementTVShows && !isMovie {
			out = append(out, candidate)
		}
		if placement == store.HeroPlacementHome {
			out = append(out, candidate)
		}
	}
	return out
}

func heroSeriesCandidates(rows []recommend.Row) []heroCandidate {
	out := make([]heroCandidate, 0, heroCandidateLimit)
	seen := map[string]bool{}
	for _, row := range rows {
		for _, raw := range row.Items {
			fact, ok := heroFactsOf(raw)
			if !ok || seen[fact.ID] || !fact.Playable || !strings.EqualFold(fact.Type, "Series") {
				continue
			}
			seen[fact.ID] = true
			rating, rated := heroRatingOf(raw)
			out = append(out, heroCandidate{ID: fact.ID, Name: fact.Name, Kind: heroSeries, Item: raw, ReleasedAt: fact.Premiere, Rating: rating, Rated: rated})
			if len(out) == heroCandidateLimit {
				return out
			}
		}
	}
	return out
}