package store

import (
	"context"
	"fmt"
	"time"

	"github.com/jackc/pgx/v5"

	"gitea.d-ma.be/mathias/tapir/internal/domain"
)

// UpsertVideo persists a video's metadata and returns its durable store id (the
// videos.id UUID). It is idempotent on (user_id, provider, provider_video_id):
// the same provider video for a user always resolves to the same row and the
// same returned id, so the run loop can use that id as the stable dedup key
// across restarts (it matches summaries.video_id once a summary exists).
//
// This lives in a separate file from store.go on purpose: the Sink port only
// carries a domain.Summary (no title/channel), so video metadata is persisted
// here, out of the delivery path, to keep the reader's rows readable.
//
// subscription_id is intentionally left NULL at Stage 0: the YouTube
// Subscription.ID is a provider resource id, not the UUID that column expects,
// and the subscriptions table is not part of this slice (data-model.md).
func (s *Store) UpsertVideo(ctx context.Context, v domain.Video) (string, error) {
	if v.UserID == "" {
		return "", fmt.Errorf("store: upsert video: empty user id")
	}
	if v.ProviderVideoID == "" {
		return "", fmt.Errorf("store: upsert video: empty provider video id")
	}

	provider := string(v.Provider)
	if provider == "" {
		provider = string(domain.ProviderYouTube)
	}

	var id string
	if err := s.withUser(ctx, v.UserID, func(tx pgx.Tx) error {
		// Ensure the owning user exists (FK target) — same as the Deliver path.
		if _, err := tx.Exec(ctx,
			`INSERT INTO users (id) VALUES ($1) ON CONFLICT (id) DO NOTHING`,
			v.UserID); err != nil {
			return fmt.Errorf("store: upsert user: %w", err)
		}

		if err := tx.QueryRow(ctx,
			`INSERT INTO videos (user_id, provider, provider_video_id, title, url, published_at, channel_title, duration_s)
			 VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
			 ON CONFLICT (user_id, provider, provider_video_id) DO UPDATE SET
			     title         = EXCLUDED.title,
			     url           = EXCLUDED.url,
			     published_at  = EXCLUDED.published_at,
			     channel_title = COALESCE(NULLIF(EXCLUDED.channel_title, ''), videos.channel_title),
			     duration_s    = COALESCE(EXCLUDED.duration_s, videos.duration_s)
			 RETURNING id`,
			v.UserID, provider, v.ProviderVideoID, v.Title, v.URL, nullTime(v.PublishedAt), v.ChannelTitle, nullDuration(v.DurationSeconds),
		).Scan(&id); err != nil {
			return fmt.Errorf("store: upsert video: %w", err)
		}
		return nil
	}); err != nil {
		return "", err
	}
	return id, nil
}

// nullTime maps the zero time to NULL so an unknown published_at is stored as
// SQL NULL rather than year 0001.
func nullTime(t time.Time) *time.Time {
	if t.IsZero() {
		return nil
	}
	return &t
}

// nullDuration maps an unknown duration (0) to SQL NULL so the upsert's
// COALESCE(EXCLUDED.duration_s, videos.duration_s) preserves a previously-known
// value instead of clobbering it with 0 (ADR-028; the channel_title backfill
// stance, migration 014).
func nullDuration(seconds int) *int {
	if seconds <= 0 {
		return nil
	}
	return &seconds
}

// NewestUnsummarizedVideoIDs returns up to limit of the user's videos that have
// no summary yet, newest first (published_at DESC, NULLS LAST). It caps the
// connect-time onboarding burst (Feature 1) at a fixed count: the caller marks
// these for summarization through the shared rate gate. RLS-scoped via withUser,
// so it only ever sees the requesting user's rows. limit <= 0 returns nil.
func (s *Store) NewestUnsummarizedVideoIDs(ctx context.Context, userID string, limit int) ([]string, error) {
	if limit <= 0 {
		return nil, nil
	}
	var ids []string
	if err := s.withUser(ctx, userID, func(tx pgx.Tx) error {
		rows, err := tx.Query(ctx,
			`SELECT v.id
			   FROM videos v
			  WHERE v.user_id = $1
			    AND NOT EXISTS (
			          SELECT 1 FROM summaries su
			           WHERE su.user_id = v.user_id AND su.video_id = v.id)
			  ORDER BY v.published_at DESC NULLS LAST, v.seen_at DESC
			  LIMIT $2`, userID, limit)
		if err != nil {
			return fmt.Errorf("store: newest unsummarized: %w", err)
		}
		defer rows.Close()
		for rows.Next() {
			var id string
			if err := rows.Scan(&id); err != nil {
				return fmt.Errorf("store: scan newest unsummarized: %w", err)
			}
			ids = append(ids, id)
		}
		return rows.Err()
	}); err != nil {
		return nil, err
	}
	return ids, nil
}

// OnboardBurstVideoIDs returns up to limit of the user's unsummarized videos for
// the connect-time onboarding burst (ADR-028), newest-first but quality-aware: a
// video is excluded when its duration is KNOWN and outside [minSeconds, maxSeconds]
// — dropping Shorts (below min) and multi-hour livestream VODs (above max) that
// would waste a scarce caption fetch on a poor first impression. A NULL/unknown
// duration is kept (degrade-open) but ranked AFTER known-good rows, so a freshly
// enriched good pick wins when both exist. minSeconds<=0 / maxSeconds<=0 each
// disable that bound (0/0 == pure newest-first, the reversibility lever).
// RLS-scoped via withUser; limit <= 0 returns nil.
func (s *Store) OnboardBurstVideoIDs(ctx context.Context, userID string, limit, minSeconds, maxSeconds int) ([]string, error) {
	if limit <= 0 {
		return nil, nil
	}
	var ids []string
	if err := s.withUser(ctx, userID, func(tx pgx.Tx) error {
		rows, err := tx.Query(ctx,
			`SELECT v.id
			   FROM videos v
			  WHERE v.user_id = $1
			    AND NOT EXISTS (
			          SELECT 1 FROM summaries su
			           WHERE su.user_id = v.user_id AND su.video_id = v.id)
			    AND NOT (
			          v.duration_s IS NOT NULL
			          AND ( ($3 > 0 AND v.duration_s < $3)
			             OR ($4 > 0 AND v.duration_s > $4) ))
			  ORDER BY (v.duration_s IS NOT NULL) DESC,
			           v.published_at DESC NULLS LAST, v.seen_at DESC
			  LIMIT $2`, userID, limit, minSeconds, maxSeconds)
		if err != nil {
			return fmt.Errorf("store: onboard burst videos: %w", err)
		}
		defer rows.Close()
		for rows.Next() {
			var id string
			if err := rows.Scan(&id); err != nil {
				return fmt.Errorf("store: scan onboard burst video: %w", err)
			}
			ids = append(ids, id)
		}
		return rows.Err()
	}); err != nil {
		return nil, err
	}
	return ids, nil
}

// DistinctChannels returns the user's distinct, non-empty source channel titles
// (the channels they have videos from), alphabetically — the option list for the
// feed's channel filter. RLS-scoped via withUser.
func (s *Store) DistinctChannels(ctx context.Context, userID string) ([]string, error) {
	var out []string
	if err := s.withUser(ctx, userID, func(tx pgx.Tx) error {
		rows, err := tx.Query(ctx,
			`SELECT DISTINCT channel_title FROM videos
			  WHERE user_id = $1 AND channel_title IS NOT NULL AND channel_title <> ''
			  ORDER BY channel_title`, userID)
		if err != nil {
			return fmt.Errorf("store: distinct channels: %w", err)
		}
		defer rows.Close()
		for rows.Next() {
			var c string
			if err := rows.Scan(&c); err != nil {
				return fmt.Errorf("store: scan channel: %w", err)
			}
			out = append(out, c)
		}
		return rows.Err()
	}); err != nil {
		return nil, err
	}
	return out, nil
}