package store

import (
	"context"
	"fmt"
	"strings"
	"time"
)

// MediaRequest is one viewer's ask, as recorded.
//
// The status a card shows is not here: it is derived per read from the *arrs and the
// library, for the reason the schema gives. The one exception is LastStatus, which is not
// the card's status but the memory of it — the only way to notice that something changed.
type MediaRequest struct {
	MediaType   string    `json:"mediaType"`
	ForeignID   int       `json:"foreignId"`
	Title       string    `json:"title"`
	Year        int       `json:"year,omitempty"`
	PosterURL   string    `json:"posterUrl,omitempty"`
	RequestedAt time.Time `json:"requestedAt"`
	// LastStatus is the state this request was in the last time anything looked, and it is
	// the only piece of request state that is stored. See the schema comment: an arrival is
	// a difference between two observations rather than a property of one, and the viewer is
	// told about it once.
	LastStatus string `json:"-"`
}

// OwnedMediaRequest is a stored ask with the person who made it, which the per-viewer read
// does not need to carry because it was asked for by user. The ready sweep looks at the
// whole household in one query, so there it is the point.
type OwnedMediaRequest struct {
	MediaRequest
	UserID string
}

// RequestUsage is the operator-facing use of the request feature. A recorded request is
// one that Memby has already handed to Radarr or Sonarr; their later download state is
// deliberately not duplicated here.
type RequestUsage struct {
	UserID      string    `json:"userId"`
	Requests    int64     `json:"requests"`
	LastRequest time.Time `json:"lastRequest,omitempty"`
}

func (s *Store) RequestUsage(ctx context.Context) ([]RequestUsage, error) {
	rows, err := s.pool.Query(ctx, `SELECT emby_user_id, count(*), max(requested_at)
		FROM media_requests GROUP BY emby_user_id`)
	if err != nil {
		return nil, fmt.Errorf("store: request usage: %w", err)
	}
	defer rows.Close()
	out := []RequestUsage{}
	for rows.Next() {
		var value RequestUsage
		if err := rows.Scan(&value.UserID, &value.Requests, &value.LastRequest); err != nil {
			return nil, err
		}
		out = append(out, value)
	}
	return out, rows.Err()
}

// MediaRequestLimit caps what one viewer's page will read back. A household that has been
// asking for things for two years should not turn the page into an unbounded query, and
// nobody scrolls past the most recent hundred by remote.
const MediaRequestLimit = 100

// SaveMediaRequest records an ask, or refreshes one already held.
//
// The repeat is deliberately an update rather than a no-op: asking again is how somebody
// says they still want it, and the page is ordered by when they asked.
func (s *Store) SaveMediaRequest(ctx context.Context, userID string, req MediaRequest) error {
	userID = strings.TrimSpace(userID)
	if userID == "" || req.ForeignID <= 0 {
		return fmt.Errorf("store: media request needs a user and a foreign id")
	}
	// last_status is deliberately absent from the UPDATE. Asking again is somebody saying
	// they still want it, not a reason to re-announce an arrival they were already told
	// about — and re-seeding it here would make a second press of Request the way to make
	// the gateway repeat itself.
	_, err := s.pool.Exec(ctx, `
		INSERT INTO media_requests
			(emby_user_id, media_type, foreign_id, title, year, poster_url, last_status, requested_at)
		VALUES ($1, $2, $3, $4, $5, $6, $7, now())
		ON CONFLICT (emby_user_id, media_type, foreign_id) DO UPDATE
		SET title        = EXCLUDED.title,
		    year         = EXCLUDED.year,
		    poster_url   = EXCLUDED.poster_url,
		    requested_at = now()`,
		userID, req.MediaType, req.ForeignID, req.Title, req.Year, req.PosterURL, req.LastStatus)
	if err != nil {
		return fmt.Errorf("store: save media request: %w", err)
	}
	return nil
}

// MediaRequests returns one viewer's asks, most recent first.
func (s *Store) MediaRequests(ctx context.Context, userID string) ([]MediaRequest, error) {
	rows, err := s.pool.Query(ctx, `
		SELECT media_type, foreign_id, title, year, poster_url, last_status, requested_at
		FROM media_requests
		WHERE emby_user_id = $1
		ORDER BY requested_at DESC
		LIMIT $2`, strings.TrimSpace(userID), MediaRequestLimit)
	if err != nil {
		return nil, fmt.Errorf("store: read media requests: %w", err)
	}
	defer rows.Close()

	requests := []MediaRequest{}
	for rows.Next() {
		var req MediaRequest
		if err := rows.Scan(
			&req.MediaType, &req.ForeignID, &req.Title, &req.Year, &req.PosterURL,
			&req.LastStatus, &req.RequestedAt,
		); err != nil {
			return nil, fmt.Errorf("store: scan media request: %w", err)
		}
		requests = append(requests, req)
	}
	return requests, rows.Err()
}

// DeleteMediaRequest removes a viewer's ask from their own page.
//
// It deliberately does not touch Radarr or Sonarr. The title may well have been downloaded
// by now, and other people may have asked for it too — this only says the viewer no longer
// wants it listed among theirs.
func (s *Store) DeleteMediaRequest(
	ctx context.Context, userID, mediaType string, foreignID int,
) error {
	_, err := s.pool.Exec(ctx, `
		DELETE FROM media_requests
		WHERE emby_user_id = $1 AND media_type = $2 AND foreign_id = $3`,
		strings.TrimSpace(userID), mediaType, foreignID)
	if err != nil {
		return fmt.Errorf("store: delete media request: %w", err)
	}
	return nil
}

// AllMediaRequests reads the whole household's asks, newest first, with the person attached.
//
// The per-viewer read above is what a page needs; this is what the ready sweep needs, and
// the difference is worth one query rather than one per account: a household of six with
// eighty requests between them is one read, and the sweep has to look at all of them anyway
// because two people can be waiting for the same film.
//
// It is bounded like the per-viewer read. A sweep that fell behind on a household which had
// been asking for things for two years must not become an unbounded query on a timer.
func (s *Store) AllMediaRequests(ctx context.Context, limit int) ([]OwnedMediaRequest, error) {
	if limit <= 0 {
		limit = MediaRequestSweepLimit
	}
	rows, err := s.pool.Query(ctx, `
		SELECT emby_user_id, media_type, foreign_id, title, year, poster_url, last_status, requested_at
		FROM media_requests
		ORDER BY requested_at DESC
		LIMIT $1`, limit)
	if err != nil {
		return nil, fmt.Errorf("store: read all media requests: %w", err)
	}
	defer rows.Close()

	requests := []OwnedMediaRequest{}
	for rows.Next() {
		var req OwnedMediaRequest
		if err := rows.Scan(
			&req.UserID, &req.MediaType, &req.ForeignID, &req.Title, &req.Year,
			&req.PosterURL, &req.LastStatus, &req.RequestedAt,
		); err != nil {
			return nil, fmt.Errorf("store: scan media request: %w", err)
		}
		requests = append(requests, req)
	}
	return requests, rows.Err()
}

// MediaRequestSweepLimit caps what one pass of the ready sweep will look at.
const MediaRequestSweepLimit = 500

// RequestReadySurfaceWindow is how long a freshly arrived request stays pinned to the front
// of Continue Watching with a REQUEST READY tag if the viewer never plays it. Past this the
// age-out clears it: an arrival nobody has acted on in a fortnight is no longer news, and a
// pin that outstays its welcome is worse than one that lapses.
const RequestReadySurfaceWindow = 14 * 24 * time.Hour

// SurfacedReadyRequest is one arrival still worth pinning: which title, and the Emby item id
// the card opens and dedupes against.
type SurfacedReadyRequest struct {
	MediaType  string
	ForeignID  int
	Title      string
	Year       int
	PosterURL  string
	ItemID     string
	SurfacedAt time.Time
}

// MarkRequestReadySurfaced records that a request has become watchable and should be pinned.
//
// The guard is the whole of the idempotency: the ready sweep calls this on every observed
// transition to "available", and only the first one — before anything has cleared it — takes
// effect. A request cleared by playback or the age-out is never re-pinned here; a genuinely
// new ask is a fresh row with both timestamps null.
func (s *Store) MarkRequestReadySurfaced(
	ctx context.Context, userID, mediaType string, foreignID int, itemID string,
) error {
	itemID = strings.TrimSpace(itemID)
	if itemID == "" {
		return fmt.Errorf("store: request ready needs an item id")
	}
	_, err := s.pool.Exec(ctx, `
		UPDATE media_requests
		SET ready_surfaced_at = now(), ready_item_id = $4
		WHERE emby_user_id = $1 AND media_type = $2 AND foreign_id = $3
		  AND ready_surfaced_at IS NULL AND ready_cleared_at IS NULL`,
		strings.TrimSpace(userID), mediaType, foreignID, itemID)
	if err != nil {
		return fmt.Errorf("store: mark request ready surfaced: %w", err)
	}
	return nil
}

// SurfacedReadyRequests reads one viewer's still-pinned arrivals, newest first.
//
// The window and the cleared check are both in the query so the caller never has to think
// about either: a row past RequestReadySurfaceWindow, or one playback has cleared, simply
// does not come back. This is the read Home makes beside its Emby fan-out.
func (s *Store) SurfacedReadyRequests(
	ctx context.Context, userID string,
) ([]SurfacedReadyRequest, error) {
	cutoff := time.Now().Add(-RequestReadySurfaceWindow)
	rows, err := s.pool.Query(ctx, `
		SELECT media_type, foreign_id, title, year, poster_url, ready_item_id, ready_surfaced_at
		FROM media_requests
		WHERE emby_user_id = $1
		  AND ready_surfaced_at IS NOT NULL
		  AND ready_cleared_at IS NULL
		  AND ready_surfaced_at > $2
		  AND ready_item_id <> ''
		ORDER BY ready_surfaced_at DESC`,
		strings.TrimSpace(userID), cutoff)
	if err != nil {
		return nil, fmt.Errorf("store: read surfaced ready requests: %w", err)
	}
	defer rows.Close()

	out := []SurfacedReadyRequest{}
	for rows.Next() {
		var req SurfacedReadyRequest
		if err := rows.Scan(
			&req.MediaType, &req.ForeignID, &req.Title, &req.Year,
			&req.PosterURL, &req.ItemID, &req.SurfacedAt,
		); err != nil {
			return nil, fmt.Errorf("store: scan surfaced ready request: %w", err)
		}
		out = append(out, req)
	}
	return out, rows.Err()
}

// ClearRequestReadySurfaced retires the pin for whichever of a viewer's requests point at
// the given Emby item id — the film itself, or the series an episode belongs to. It returns
// how many rows it touched so the caller can skip a cache invalidation that would change
// nothing.
func (s *Store) ClearRequestReadySurfaced(
	ctx context.Context, userID string, itemIDs ...string,
) (int64, error) {
	ids := make([]string, 0, len(itemIDs))
	for _, id := range itemIDs {
		if id = strings.TrimSpace(id); id != "" {
			ids = append(ids, id)
		}
	}
	if len(ids) == 0 {
		return 0, nil
	}
	tag, err := s.pool.Exec(ctx, `
		UPDATE media_requests
		SET ready_cleared_at = now()
		WHERE emby_user_id = $1 AND ready_item_id = ANY($2)
		  AND ready_surfaced_at IS NOT NULL AND ready_cleared_at IS NULL`,
		strings.TrimSpace(userID), ids)
	if err != nil {
		return 0, fmt.Errorf("store: clear request ready surfaced: %w", err)
	}
	return tag.RowsAffected(), nil
}

// ExpireStaleReadyRequests clears every pin past RequestReadySurfaceWindow across the whole
// household in one statement, and returns the users whose Home cache is now stale. The ready
// sweep runs this so SurfacedReadyRequests never has to lean on its own window clause to
// hide a row that should have been retired days ago.
func (s *Store) ExpireStaleReadyRequests(ctx context.Context) ([]string, error) {
	cutoff := time.Now().Add(-RequestReadySurfaceWindow)
	rows, err := s.pool.Query(ctx, `
		UPDATE media_requests
		SET ready_cleared_at = now()
		WHERE ready_surfaced_at IS NOT NULL AND ready_cleared_at IS NULL
		  AND ready_surfaced_at <= $1
		RETURNING emby_user_id`, cutoff)
	if err != nil {
		return nil, fmt.Errorf("store: expire stale ready requests: %w", err)
	}
	defer rows.Close()

	seen := map[string]bool{}
	users := []string{}
	for rows.Next() {
		var userID string
		if err := rows.Scan(&userID); err != nil {
			return nil, err
		}
		if !seen[userID] {
			seen[userID] = true
			users = append(users, userID)
		}
	}
	return users, rows.Err()
}

// SetMediaRequestStatus records what a request was last seen doing.
//
// Written only when the state actually moved, so a sweep over a household where nothing has
// changed — which is almost every sweep — costs no writes at all.
func (s *Store) SetMediaRequestStatus(
	ctx context.Context, userID, mediaType string, foreignID int, status string,
) error {
	_, err := s.pool.Exec(ctx, `
		UPDATE media_requests SET last_status = $4
		WHERE emby_user_id = $1 AND media_type = $2 AND foreign_id = $3`,
		strings.TrimSpace(userID), mediaType, foreignID, status)
	if err != nil {
		return fmt.Errorf("store: set media request status: %w", err)
	}
	return nil
}