package search

import (
	"context"
	"encoding/base64"
	"log/slog"
	"net/http"
	"strconv"
	"strings"

	"github.com/google/uuid"

	"pipu/api/internal/api/gen"
	"pipu/api/internal/auth"
	"pipu/api/internal/library"
	"pipu/api/internal/platform/apperr"
)

// Коды ошибок поиска.
const (
	CodeUnavailable = "search.unavailable"
	CodeQueryEmpty  = "validation.query_empty"
)

// Handler реализует search-часть gen.StrictServerInterface.
type Handler struct {
	dto     library.DTO
	meili   *Meili
	catalog *library.Store
	indexer *Indexer
	aff     *Affinity
	log     *slog.Logger
}

// NewHandler создаёт обработчик поиска.
func NewHandler(
	meili *Meili, catalog *library.Store, indexer *Indexer, aff *Affinity, dto library.DTO, log *slog.Logger,
) *Handler {
	return &Handler{meili: meili, catalog: catalog, indexer: indexer, aff: aff, dto: dto, log: log}
}

type limits struct{ artists, albums, tracks, offset int }

type found struct {
	artists, albums, tracks []string
	exactArtists            []string
	totals                  [3]int
}

func (h *Handler) query(ctx context.Context, q string, l limits) (found, error) {
	var queries []MultiQuery
	add := func(index string, n int) {
		if n > 0 {
			attrs := []string{"id"}
			if index == IndexArtists {
				attrs = append(attrs, "name", "name_translit")
			}
			queries = append(queries, MultiQuery{IndexUID: index, Q: q, Limit: n, Offset: l.offset, MatchingStrategy: "all", AttributesToRetrieve: attrs})
		}
	}
	add(IndexArtists, l.artists)
	add(IndexAlbums, l.albums)
	add(IndexTracks, l.tracks)
	res, err := h.meili.MultiSearch(ctx, queries)
	if err != nil {
		h.log.WarnContext(ctx, "search failed", "err", err)
		return found{}, apperr.New(http.StatusServiceUnavailable, CodeUnavailable, "search is unavailable")
	}
	var f found
	i := 0
	for k, n := range []int{l.artists, l.albums, l.tracks} {
		if n == 0 {
			continue
		}
		f.totals[k] = res[i].Total
		switch k {
		case 0:
			f.artists = res[i].IDs
			f.exactArtists = res[i].ExactIDs
		case 1:
			f.albums = res[i].IDs
		case 2:
			f.tracks = res[i].IDs
		}
		i++
	}
	return f, nil
}

func (f found) empty() bool { return len(f.artists)+len(f.albums)+len(f.tracks) == 0 }

// run ищет q, а если ничего не нашлось — тот же запрос в другой раскладке.
func (h *Handler) run(ctx context.Context, q string, l limits) (found, string, error) {
	q = strings.TrimSpace(q)
	if q == "" {
		return found{}, "", apperr.Validation("q", CodeQueryEmpty, "query is empty", nil)
	}
	f, err := h.query(ctx, q, l)
	if err != nil || !f.empty() || l.offset > 0 {
		return f, "", err
	}
	alt := SwitchLayout(q)
	if alt == "" {
		return f, "", nil
	}
	f2, err := h.query(ctx, alt, l)
	if err != nil || f2.empty() {
		return f, "", err
	}
	return f2, alt, nil
}

func ids(raw []string) []uuid.UUID {
	out := make([]uuid.UUID, 0, len(raw))
	for _, s := range raw {
		if id, err := uuid.Parse(s); err == nil {
			out = append(out, id)
		}
	}
	return out
}

// hydrate превращает найденные id в DTO; индекс может отставать от БД — удалённое пропускается.
func (h *Handler) hydrate(ctx context.Context, f found, corrected string) (gen.SearchResults, error) {
	out := gen.SearchResults{Artists: []gen.ArtistRef{}, Albums: []gen.AlbumSummary{}, Tracks: []gen.Track{}}
	out.Totals.Artists, out.Totals.Albums, out.Totals.Tracks = f.totals[0], f.totals[1], f.totals[2]
	if corrected != "" {
		out.CorrectedQuery = &corrected
	}
	if len(f.artists) > 0 {
		refs, err := h.catalog.ArtistsByIDs(ctx, ids(f.artists))
		if err != nil {
			return out, err
		}
		for _, a := range refs {
			out.Artists = append(out.Artists, gen.ArtistRef{Id: a.ID, Name: a.Name})
		}
	}
	if len(f.albums) > 0 {
		rows, err := h.catalog.AlbumsByIDs(ctx, ids(f.albums))
		if err != nil {
			return out, err
		}
		for _, a := range rows {
			out.Albums = append(out.Albums, h.dto.AlbumSummary(a))
		}
	}
	if len(f.tracks) > 0 {
		rows, err := h.catalog.TracksByIDs(ctx, ids(f.tracks))
		if err != nil {
			return out, err
		}
		if out.Tracks, err = h.dto.Tracks(ctx, rows); err != nil {
			return out, err
		}
	}
	return out, nil
}

// SearchSuggest реализует gen.StrictServerInterface.
func (h *Handler) SearchSuggest(ctx context.Context, req gen.SearchSuggestRequestObject) (gen.SearchSuggestResponseObject, error) {
	want := limits{artists: 3, albums: 3, tracks: 5}
	l := want
	if h.aff != nil {
		l = limits{artists: want.artists * suggestPool, albums: want.albums * suggestPool, tracks: want.tracks * suggestPool}
	}
	f, corrected, err := h.run(ctx, req.Params.Q, l)
	if err != nil {
		return nil, err
	}
	f = h.personal(ctx, f, want)
	out, err := h.hydrate(ctx, f, corrected)
	if err != nil {
		return nil, err
	}
	return gen.SearchSuggest200JSONResponse(out), nil
}

// personal оставляет в подсказках по want.* лучших с учётом вкуса пользователя.
// Без пользователя или при сбое — просто первые по релевантности.
func (h *Handler) personal(ctx context.Context, f found, want limits) found {
	var aff map[uuid.UUID]float64
	if p, ok := auth.PrincipalFrom(ctx); ok && h.aff != nil {
		all := ids(append(append(append([]string{}, f.artists...), f.albums...), f.tracks...))
		var err error
		if aff, err = h.aff.Of(ctx, p.UserID, all); err != nil {
			h.log.WarnContext(ctx, "suggest personalization failed", "err", err)
		}
	}
	f.artists = personalizeArtists(f.artists, f.exactArtists, aff, want.artists)
	f.albums = personalize(f.albums, aff, want.albums)
	f.tracks = personalize(f.tracks, aff, want.tracks)
	return f
}

// Search реализует gen.StrictServerInterface.
func (h *Handler) Search(ctx context.Context, req gen.SearchRequestObject) (gen.SearchResponseObject, error) {
	typ := gen.All
	if req.Params.Type != nil {
		typ = *req.Params.Type
	}
	limit := 30
	if req.Params.Limit != nil {
		limit = min(max(*req.Params.Limit, 1), 100)
	}
	offset := 0
	if req.Params.Cursor != nil {
		raw, err := base64.RawURLEncoding.DecodeString(*req.Params.Cursor)
		if err == nil {
			offset, err = strconv.Atoi(string(raw))
		}
		if err != nil || offset < 0 {
			return nil, apperr.Validation("cursor", "validation.cursor_invalid", "malformed cursor", nil)
		}
	}
	var l limits
	switch typ {
	case gen.Artists:
		l = limits{artists: limit, offset: offset}
	case gen.Albums:
		l = limits{albums: limit, offset: offset}
	case gen.Tracks:
		l = limits{tracks: limit, offset: offset}
	default:
		l = limits{artists: 6, albums: 6, tracks: 20}
	}
	f, corrected, err := h.run(ctx, req.Params.Q, l)
	if err != nil {
		return nil, err
	}
	out, err := h.hydrate(ctx, f, corrected)
	if err != nil {
		return nil, err
	}
	if typ != gen.All {
		total := f.totals[0] + f.totals[1] + f.totals[2]
		if offset+limit < total {
			next := base64.RawURLEncoding.EncodeToString([]byte(strconv.Itoa(offset + limit)))
			out.NextCursor = &next
		}
	}
	return gen.Search200JSONResponse(out), nil
}

// ReindexSearch реализует gen.StrictServerInterface.
func (h *Handler) ReindexSearch(ctx context.Context, _ gen.ReindexSearchRequestObject) (gen.ReindexSearchResponseObject, error) {
	p, ok := auth.PrincipalFrom(ctx)
	if !ok || !auth.Can(p.Role, auth.PermManageLibrary) {
		return nil, apperr.Forbidden(auth.CodeForbidden, "not allowed")
	}
	h.indexer.Trigger()
	return gen.ReindexSearch202Response{}, nil
}