package api

import (
	"encoding/json"
	"math/rand/v2"
	"net/http"
	"net/url"
	"strconv"
	"sync"

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

// Field sets mirror what each TV row actually renders. Asking Emby for less is the
// single biggest lever on home-screen latency, so keep these tight.
const (
	fieldsContinue    = "RunTimeTicks,SeriesName,PrimaryImageAspectRatio"
	fieldsNextUp      = "Overview,ProductionYear,RunTimeTicks,SeriesName,PrimaryImageAspectRatio"
	fieldsRow         = "ProductionYear,RunTimeTicks,PrimaryImageAspectRatio"
	fieldsDetail      = "Overview,Genres,MediaStreams,ProductionYear,OfficialRating,CommunityRating,RunTimeTicks,PrimaryImageAspectRatio"
	fieldsScreensaver = "Overview,Taglines,Genres,ProductionYear,CommunityRating,Studios,OfficialRating,RunTimeTicks"

	rowImageTypes         = "Backdrop,Primary,Logo"
	screensaverImageTypes = "Backdrop,Logo"
)

type homeResponse struct {
	// Rows is the home screen as the server wants it drawn: order, titles and kinds all
	// decided here, so a new row (a recommendation strip, a seasonal collection) ships
	// without touching the TV app. The client renders whatever arrives.
	Rows []recommend.Row `json:"rows"`

	// The four fixed rows are also sent flat. They are what the client caches for an
	// instant cold start, and what the direct-to-Emby path still produces.
	ContinueWatching []json.RawMessage `json:"continueWatching"`
	NextUp           []json.RawMessage `json:"nextUp"`
	Favorites        []json.RawMessage `json:"favorites"`
	LatestMovies     []json.RawMessage `json:"latestMovies"`

	// Partial is true when at least one row failed upstream. The TV shows what arrived
	// and flags a refresh error rather than blanking the screen.
	Partial bool `json:"partial"`

	// Deliberately no update verdict here: this payload is cached per user, and the
	// verdict depends on the *client's* version, so a cached body would hand one TV's
	// answer to another running a different build. The client asks /v1/update instead.
}

// handleHome answers the entire launcher in one round trip.
func (s *Server) handleHome(w http.ResponseWriter, r *http.Request, sess store.Session) {
	ctx := r.Context()
	limit := queryInt(r, "limit", 24, 100)
	key := cache.UserKey(sess.EmbyUserID, "home:"+itoa(limit))

	if raw, err := s.cache.Get(ctx, key); err == nil {
		w.Header().Set("X-Memby-Cache", "hit")
		writeRaw(w, http.StatusOK, raw)
		return
	}

	cred := credentials(sess)
	var (
		mu        sync.Mutex
		failures  int
		out       homeResponse
		sonarrRow *recommend.Row
		wg        sync.WaitGroup
	)

	run := func(dest *[]json.RawMessage, fetch func() (*emby.ItemsResult, error)) {
		wg.Add(1)
		go func() {
			defer wg.Done()
			result, err := fetch()
			mu.Lock()
			defer mu.Unlock()
			if err != nil {
				failures++
				s.log.Warn("home row failed", "error", err)
				return
			}
			*dest = result.Items
		}()
	}

	run(&out.ContinueWatching, func() (*emby.ItemsResult, error) {
		return s.emby.Items(ctx, cred, rowParams(url.Values{
			"Filters":          {"IsResumable"},
			"IncludeItemTypes": {"Movie,Episode"},
			"Recursive":        {"true"},
			"SortBy":           {"DatePlayed"},
			"SortOrder":        {"Descending"},
			"Limit":            {itoa(limit)},
		}, fieldsContinue))
	})
	run(&out.NextUp, func() (*emby.ItemsResult, error) {
		return s.emby.NextUp(ctx, cred, rowParams(url.Values{
			"Limit": {itoa(limit)},
		}, fieldsNextUp))
	})
	run(&out.Favorites, func() (*emby.ItemsResult, error) {
		return s.emby.Items(ctx, cred, rowParams(url.Values{
			"Filters":          {"IsFavorite"},
			"IncludeItemTypes": {"Movie,Series"},
			"Recursive":        {"true"},
			"SortBy":           {"SortName"},
			"SortOrder":        {"Ascending"},
			"Limit":            {itoa(limit)},
		}, fieldsRow))
	})
	run(&out.LatestMovies, func() (*emby.ItemsResult, error) {
		return s.emby.Items(ctx, cred, rowParams(url.Values{
			"IncludeItemTypes": {"Movie"},
			"Recursive":        {"true"},
			"SortBy":           {"DateCreated"},
			"SortOrder":        {"Descending"},
			"Limit":            {itoa(limit)},
		}, fieldsRow))
	})
	if s.sonarr != nil && supportsSonarrSchedule(r) {
		wg.Add(1)
		go func() {
			defer wg.Done()
			row, err := s.sonarrAiringTodayRow(ctx)
			if err != nil {
				s.log.Warn("sonarr calendar row failed", "error", err)
				return
			}
			mu.Lock()
			sonarrRow = row
			mu.Unlock()
		}()
	}

	wg.Wait()

	if failures == 4 {
		writeError(w, http.StatusBadGateway, "could not reach the emby server")
		return
	}
	out.Partial = failures > 0
	ensureSlices(&out)

	// Recommendations are read from their own long-lived cache. A miss means this
	// response ships without them and a rebuild starts in the background — the home
	// screen never waits on the engine.
	recommendations := s.cachedRecommendations(ctx, sess.EmbyUserID)
	if recommendations == nil {
		s.refreshRecommendationsInBackground(sess)
	}
	rows := baseRows(out)
	if sonarrRow != nil {
		// The schedule is most useful beside Next Up, before personal collections.
		rows = append(rows[:2], append([]recommend.Row{*sonarrRow}, rows[2:]...)...)
	}
	out.Rows = append(rows, recommendations...)

	body, err := json.Marshal(out)
	if err != nil {
		s.log.Error("home encode failed", "error", err)
		writeError(w, http.StatusInternalServerError, "could not build the home payload")
		return
	}
	// A partial payload is served but never cached: the next request should retry.
	if !out.Partial {
		if err := s.cache.Set(ctx, key, body, s.cfg.HomeTTL); err != nil {
			s.log.Warn("home cache write failed", "error", err)
		}
	}
	w.Header().Set("X-Memby-Cache", "miss")
	writeRaw(w, http.StatusOK, body)
}

// Older clients render unknown rows but do not understand MembyPlayable=false, so they
// could try to send a synthetic Sonarr id to Emby. The feature ships with 0.1.54.
func supportsSonarrSchedule(r *http.Request) bool {
	version := clientVersion(r)
	return version != "" && appupdate.CompareVersions(version, "0.1.54") >= 0
}

// handleScreensaver serves the backdrop pool. The pool is cached and shuffled per
// request, so the Dream still looks random without re-querying Emby every few seconds.
func (s *Server) handleScreensaver(w http.ResponseWriter, r *http.Request, sess store.Session) {
	ctx := r.Context()
	limit := queryInt(r, "limit", 200, 400)
	key := cache.UserKey(sess.EmbyUserID, "screensaver:"+itoa(limit))

	var items []json.RawMessage
	if raw, err := s.cache.Get(ctx, key); err == nil {
		_ = json.Unmarshal(raw, &items)
	}

	if items == nil {
		result, err := s.emby.Items(ctx, credentials(sess), url.Values{
			"IncludeItemTypes": {"Movie,Series"},
			"Recursive":        {"true"},
			"Filters":          {"HasBackdrop"},
			"SortBy":           {"Random"},
			"Limit":            {itoa(limit)},
			"Fields":           {fieldsScreensaver},
			"ImageTypeLimit":   {"1"},
			"EnableImageTypes": {screensaverImageTypes},
			"EnableUserData":   {"true"},
		})
		if err != nil {
			s.writeUpstreamError(w, err, "could not load screensaver items")
			return
		}
		items = result.Items
		if raw, err := json.Marshal(items); err == nil {
			_ = s.cache.Set(ctx, key, raw, s.cfg.ScreensaverTTL)
		}
	}

	shuffled := make([]json.RawMessage, len(items))
	copy(shuffled, items)
	rand.Shuffle(len(shuffled), func(i, j int) { shuffled[i], shuffled[j] = shuffled[j], shuffled[i] })

	writeJSON(w, http.StatusOK, map[string]any{"items": shuffled})
}

func (s *Server) handleSearch(w http.ResponseWriter, r *http.Request, sess store.Session) {
	ctx := r.Context()
	term := r.URL.Query().Get("q")
	if len(term) < 2 {
		writeJSON(w, http.StatusOK, map[string]any{"items": []json.RawMessage{}})
		return
	}
	limit := queryInt(r, "limit", 40, 100)
	key := cache.UserKey(sess.EmbyUserID, "search:"+itoa(limit)+":"+term)

	if raw, err := s.cache.Get(ctx, key); err == nil {
		w.Header().Set("X-Memby-Cache", "hit")
		writeRaw(w, http.StatusOK, raw)
		return
	}

	// The imported library answers search from Postgres, which is the difference
	// between "instant" and "one round trip to Emby per keystroke". An empty result
	// falls through to Emby, so search still works before the first import completes.
	items, err := s.store.SearchLibrary(ctx, term, limit)
	if err != nil {
		s.log.Warn("library search failed; falling back to emby", "error", err)
		items = nil
	}
	if len(items) == 0 {
		result, err := s.emby.Items(ctx, credentials(sess), rowParams(url.Values{
			"SearchTerm":       {term},
			"IncludeItemTypes": {"Movie,Series,Episode"},
			"Recursive":        {"true"},
			"Limit":            {itoa(limit)},
		}, fieldsRow))
		if err != nil {
			s.writeUpstreamError(w, err, "search failed")
			return
		}
		items = result.Items
	}

	body, err := json.Marshal(map[string]any{"items": nonNil(items)})
	if err != nil {
		writeError(w, http.StatusInternalServerError, "could not build search results")
		return
	}
	if err := s.cache.Set(ctx, key, body, s.cfg.SearchTTL); err != nil {
		s.log.Warn("search cache write failed", "error", err)
	}
	w.Header().Set("X-Memby-Cache", "miss")
	writeRaw(w, http.StatusOK, body)
}

// baseRows describes the four fixed rows.
//
// Titles live here rather than in the app so wording can change server-side. They are
// emitted even when empty: the client draws its own "Nothing in progress" message, and a
// row that vanishes as you watch things is more jarring than an empty one.
func baseRows(h homeResponse) []recommend.Row {
	return []recommend.Row{
		{ID: "continue", Title: "Continue Watching", Kind: "continue", Items: h.ContinueWatching},
		{ID: "next-up", Title: "Next Up", Kind: "nextup", Items: h.NextUp},
		{ID: "favorites", Title: "Favourites", Kind: "favorites", Items: h.Favorites},
		{ID: "latest-movies", Title: "Recently Added Movies", Kind: "latest", Items: h.LatestMovies},
	}
}

// rowParams applies the query shape every list endpoint shares.
func rowParams(params url.Values, fields string) url.Values {
	params.Set("Fields", fields)
	params.Set("ImageTypeLimit", "1")
	params.Set("EnableImages", "true")
	params.Set("EnableImageTypes", rowImageTypes)
	params.Set("EnableTotalRecordCount", "false")
	params.Set("EnableUserData", "true")
	return params
}

// ensureSlices keeps empty rows as [] rather than null, so kotlinx.serialization can
// decode them into non-null List fields.
func ensureSlices(h *homeResponse) {
	h.ContinueWatching = nonNil(h.ContinueWatching)
	h.NextUp = nonNil(h.NextUp)
	h.Favorites = nonNil(h.Favorites)
	h.LatestMovies = nonNil(h.LatestMovies)
}

func nonNil(items []json.RawMessage) []json.RawMessage {
	if items == nil {
		return []json.RawMessage{}
	}
	return items
}

func itoa(v int) string { return strconv.Itoa(v) }