package wave

import (
	"context"
	"encoding/json"
	"fmt"

	"github.com/google/uuid"

	"pipu/api/internal/api/gen"
)

// Онбординг вкуса (docs/recommendations.md#7): новый пользователь отмечает исполнителей и жанры — рекомендатель
// берёт их как начальный вкус, пока своей истории мало. Пропуск сохраняется пустым выбором.

const (
	onboardingArtists = 40
	onboardingGenres  = 24
	// История, после которой онбординг уже не предлагается: вкус и так виден по прослушиваниям.
	onboardingMinHistory = 10
)

// GetOnboarding реализует gen.StrictServerInterface.
func (h *Handler) GetOnboarding(ctx context.Context, _ gen.GetOnboardingRequestObject) (gen.GetOnboardingResponseObject, error) {
	p, err := principal(ctx)
	if err != nil {
		return nil, err
	}
	out := gen.GetOnboarding200JSONResponse{}
	var done bool
	var plays int
	if err := h.pool.QueryRow(ctx, `
		SELECT EXISTS (SELECT 1 FROM user_profiles_rec WHERE user_id = $1 AND onboarding IS NOT NULL),
			(SELECT count(*) FROM user_track_stats WHERE user_id = $1)`, p.UserID).Scan(&done, &plays); err != nil {
		return nil, fmt.Errorf("wave: onboarding state: %w", err)
	}

	rows, err := h.pool.Query(ctx, `
		SELECT a.id, a.name, count(*) AS n,
			(SELECT al.id FROM albums al WHERE al.album_artist_id = a.id
				ORDER BY (SELECT count(*) FROM tracks t WHERE t.album_id = al.id) DESC, al.id LIMIT 1)
		FROM artists a JOIN track_artists ta ON ta.artist_id = a.id AND ta.role = 'main'
		GROUP BY a.id ORDER BY n DESC, a.name LIMIT $1`, onboardingArtists)
	if err != nil {
		return nil, fmt.Errorf("wave: onboarding artists: %w", err)
	}
	type artist struct {
		id, album *uuid.UUID
		name      string
		n         int
	}
	var artists []artist
	for rows.Next() {
		var a artist
		var id uuid.UUID
		if err := rows.Scan(&id, &a.name, &a.n, &a.album); err != nil {
			rows.Close()
			return nil, fmt.Errorf("wave: onboarding artists: %w", err)
		}
		a.id = &id
		artists = append(artists, a)
	}
	rows.Close()
	dto := h.dto
	for _, a := range artists {
		item := struct {
			CoverColors []string  `json:"cover_colors"`
			CoverUrl    *string   `json:"cover_url"`
			Id          uuid.UUID `json:"id"`
			Name        string    `json:"name"`
			TrackCount  int       `json:"track_count"`
		}{Id: *a.id, Name: a.name, TrackCount: a.n, CoverColors: []string{}}
		if a.album != nil {
			if al, err := h.catalog.Album(ctx, *a.album); err == nil {
				sum := dto.AlbumSummary(al)
				item.CoverUrl, item.CoverColors = sum.CoverUrl, sum.CoverColors
			}
		}
		out.Artists = append(out.Artists, item)
	}

	grows, err := h.pool.Query(ctx, `
		SELECT g.name, count(DISTINCT tg.track_id) AS n FROM track_genres tg JOIN genres g ON g.id = tg.genre_id
		GROUP BY g.name ORDER BY n DESC, g.name LIMIT $1`, onboardingGenres)
	if err != nil {
		return nil, fmt.Errorf("wave: onboarding genres: %w", err)
	}
	for grows.Next() {
		var g struct {
			Name       string `json:"name"`
			TrackCount int    `json:"track_count"`
		}
		if err := grows.Scan(&g.Name, &g.TrackCount); err != nil {
			grows.Close()
			return nil, fmt.Errorf("wave: onboarding genres: %w", err)
		}
		out.Genres = append(out.Genres, g)
	}
	grows.Close()
	if out.Artists == nil {
		out.Artists = []struct {
			CoverColors []string  `json:"cover_colors"`
			CoverUrl    *string   `json:"cover_url"`
			Id          uuid.UUID `json:"id"`
			Name        string    `json:"name"`
			TrackCount  int       `json:"track_count"`
		}{}
	}
	if out.Genres == nil {
		out.Genres = []struct {
			Name       string `json:"name"`
			TrackCount int    `json:"track_count"`
		}{}
	}
	out.Required = !done && plays < onboardingMinHistory && len(out.Artists) > 0
	return out, nil
}

// SaveOnboarding реализует gen.StrictServerInterface.
func (h *Handler) SaveOnboarding(ctx context.Context, req gen.SaveOnboardingRequestObject) (gen.SaveOnboardingResponseObject, error) {
	p, err := principal(ctx)
	if err != nil {
		return nil, err
	}
	ids := req.Body.ArtistIds
	if ids == nil {
		ids = []uuid.UUID{}
	}
	genres := req.Body.Genres
	if genres == nil {
		genres = []string{}
	}
	raw, _ := json.Marshal(map[string]any{"artist_ids": ids, "genres": genres})
	if _, err := h.pool.Exec(ctx, `
		INSERT INTO user_profiles_rec (user_id, onboarding, updated_at) VALUES ($1, $2, now())
		ON CONFLICT (user_id) DO UPDATE SET onboarding = EXCLUDED.onboarding, updated_at = now()`,
		p.UserID, raw); err != nil {
		return nil, fmt.Errorf("wave: save onboarding: %w", err)
	}
	return gen.SaveOnboarding204Response{}, nil
}