// Package store persists gateway sessions in Postgres.
package store

import (
	"context"
	_ "embed"
	"errors"
	"fmt"
	"time"

	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"
)

//go:embed schema.sql
var schema string

// ErrNotFound is returned when a token does not match a live session.
var ErrNotFound = errors.New("store: session not found")

func isNoRows(err error) bool { return errors.Is(err, pgx.ErrNoRows) }

type Session struct {
	TokenHash          []byte
	EmbyUserID         string
	EmbyToken          string
	Username           string
	ServerID           string
	DeviceID           string
	DeviceName         string
	ClientVersion      string
	ClientProtocol     string
	ClientCapabilities []string
	LastSeenAt         time.Time
}

type KnownUser struct {
	ID       string    `json:"id"`
	Username string    `json:"username"`
	LastSeen time.Time `json:"lastSeen"`
}

type KnownClient struct {
	DeviceName   string    `json:"deviceName"`
	Username     string    `json:"username"`
	Version      string    `json:"version"`
	Protocol     string    `json:"protocol"`
	Capabilities []string  `json:"capabilities"`
	LastSeen     time.Time `json:"lastSeen"`
}

// KnownClients gives the feature console compatibility evidence without exposing
// gateway or Emby credentials. Stale sessions remain useful rollout information.
func (s *Store) KnownClients(ctx context.Context) ([]KnownClient, error) {
	rows, err := s.pool.Query(ctx, `
		SELECT device_name, username, client_version, client_protocol,
			client_capabilities, last_seen_at
		FROM sessions ORDER BY last_seen_at DESC LIMIT 100`)
	if err != nil {
		return nil, fmt.Errorf("store: list known clients: %w", err)
	}
	defer rows.Close()
	clients := []KnownClient{}
	for rows.Next() {
		var client KnownClient
		if err := rows.Scan(&client.DeviceName, &client.Username, &client.Version,
			&client.Protocol, &client.Capabilities, &client.LastSeen); err != nil {
			return nil, fmt.Errorf("store: scan known client: %w", err)
		}
		clients = append(clients, client)
	}
	return clients, rows.Err()
}

// KnownUsers returns one entry per Emby user that has signed in to the gateway.
func (s *Store) KnownUsers(ctx context.Context) ([]KnownUser, error) {
	rows, err := s.pool.Query(ctx, `
		SELECT DISTINCT ON (emby_user_id) emby_user_id, username, last_seen_at
		FROM sessions
		ORDER BY emby_user_id, last_seen_at DESC`)
	if err != nil {
		return nil, fmt.Errorf("store: list known users: %w", err)
	}
	defer rows.Close()
	users := []KnownUser{}
	for rows.Next() {
		var user KnownUser
		if err := rows.Scan(&user.ID, &user.Username, &user.LastSeen); err != nil {
			return nil, fmt.Errorf("store: scan known user: %w", err)
		}
		users = append(users, user)
	}
	return users, rows.Err()
}

type Store struct {
	pool *pgxpool.Pool
}

func Open(ctx context.Context, databaseURL string) (*Store, error) {
	pool, err := pgxpool.New(ctx, databaseURL)
	if err != nil {
		return nil, fmt.Errorf("store: connect: %w", err)
	}
	if err := pool.Ping(ctx); err != nil {
		pool.Close()
		return nil, fmt.Errorf("store: ping: %w", err)
	}
	return &Store{pool: pool}, nil
}

func (s *Store) Close() { s.pool.Close() }

func (s *Store) Ping(ctx context.Context) error { return s.pool.Ping(ctx) }

// RecordSearch stores a normalized query for future per-user ranking analysis.
func (s *Store) RecordSearch(ctx context.Context, userID, query string) error {
	_, err := s.pool.Exec(ctx,
		`WITH inserted AS (
			INSERT INTO search_history (emby_user_id, query) VALUES ($1, $2)
			RETURNING id
		)
		DELETE FROM search_history
		WHERE emby_user_id = $1
		  AND occurred_at < now() - interval '30 days'`,
		userID, query)
	return err
}

// RecentSearches returns a user's distinct queries in most-recently-used order.
// Case-only duplicates collapse to the spelling used most recently.
func (s *Store) RecentSearches(
	ctx context.Context,
	userID string,
	since time.Time,
	limit int,
) ([]string, error) {
	rows, err := s.pool.Query(ctx, `
		SELECT query
		FROM (
			SELECT DISTINCT ON (lower(query)) query, occurred_at
			FROM search_history
			WHERE emby_user_id = $1 AND occurred_at >= $2
			ORDER BY lower(query), occurred_at DESC
		) AS latest
		ORDER BY occurred_at DESC
		LIMIT $3`,
		userID, since, limit)
	if err != nil {
		return nil, fmt.Errorf("store: recent searches: %w", err)
	}
	defer rows.Close()

	queries := make([]string, 0, limit)
	for rows.Next() {
		var query string
		if err := rows.Scan(&query); err != nil {
			return nil, fmt.Errorf("store: scan recent search: %w", err)
		}
		queries = append(queries, query)
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("store: read recent searches: %w", err)
	}
	return queries, nil
}

// Migrate applies the schema. It is idempotent, so it runs on every boot.
func (s *Store) Migrate(ctx context.Context) error {
	if _, err := s.pool.Exec(ctx, schema); err != nil {
		return fmt.Errorf("store: migrate: %w", err)
	}
	return nil
}

// CreateSession records every signed-in TV without an account-level device cap.
// Re-authenticating the same stable device replaces its token.
// The replaced hash is returned so its Redis entry can be invalidated immediately.
func (s *Store) CreateSession(ctx context.Context, sess Session) ([]byte, error) {
	tx, err := s.pool.Begin(ctx)
	if err != nil {
		return nil, fmt.Errorf("store: begin session: %w", err)
	}
	defer func() { _ = tx.Rollback(ctx) }()

	if _, err := tx.Exec(ctx, `SELECT pg_advisory_xact_lock(hashtextextended($1, 0))`, sess.EmbyUserID); err != nil {
		return nil, fmt.Errorf("store: lock user sessions: %w", err)
	}

	var previousHash []byte
	err = tx.QueryRow(ctx, `
		SELECT token_hash FROM sessions
		WHERE emby_user_id = $1 AND device_id = $2`,
		sess.EmbyUserID, sess.DeviceID).Scan(&previousHash)
	if err != nil && !errors.Is(err, pgx.ErrNoRows) {
		return nil, fmt.Errorf("store: find device session: %w", err)
	}

	_, err = tx.Exec(ctx, `
		INSERT INTO sessions (
			token_hash, emby_user_id, emby_token, username, server_id, device_id, device_name,
			client_version, client_protocol, client_capabilities
		)
		VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10)
		ON CONFLICT (emby_user_id, device_id) DO UPDATE SET
			token_hash   = EXCLUDED.token_hash,
			emby_token   = EXCLUDED.emby_token,
			username     = EXCLUDED.username,
			server_id    = EXCLUDED.server_id,
			device_name  = EXCLUDED.device_name,
			client_version  = EXCLUDED.client_version,
			client_protocol = EXCLUDED.client_protocol,
			client_capabilities = EXCLUDED.client_capabilities,
			last_seen_at = now()`,
		sess.TokenHash, sess.EmbyUserID, sess.EmbyToken, sess.Username,
		sess.ServerID, sess.DeviceID, sess.DeviceName, sess.ClientVersion, sess.ClientProtocol,
		sess.ClientCapabilities)
	if err != nil {
		return nil, fmt.Errorf("store: create session: %w", err)
	}
	if err := tx.Commit(ctx); err != nil {
		return nil, fmt.Errorf("store: commit session: %w", err)
	}
	return previousHash, nil
}

func (s *Store) SessionByTokenHash(ctx context.Context, hash []byte) (Session, error) {
	var sess Session
	err := s.pool.QueryRow(ctx, `
		SELECT token_hash, emby_user_id, emby_token, username, server_id, device_id,
			device_name, client_version, client_protocol, client_capabilities, last_seen_at
		FROM sessions WHERE token_hash = $1`, hash).
		Scan(&sess.TokenHash, &sess.EmbyUserID, &sess.EmbyToken, &sess.Username,
			&sess.ServerID, &sess.DeviceID, &sess.DeviceName, &sess.ClientVersion,
			&sess.ClientProtocol, &sess.ClientCapabilities, &sess.LastSeenAt)
	if errors.Is(err, pgx.ErrNoRows) {
		return Session{}, ErrNotFound
	}
	if err != nil {
		return Session{}, fmt.Errorf("store: load session: %w", err)
	}
	return sess, nil
}

// Touch records activity. Cheap enough to call on the auth path, and it is what the
// idle-expiry sweep reads.
func (s *Store) Touch(ctx context.Context, hash []byte) error {
	_, err := s.pool.Exec(ctx, `UPDATE sessions SET last_seen_at = now() WHERE token_hash = $1`, hash)
	return err
}

// UpdateSessionClientIdentity remembers the last non-empty identity supplied by a TV.
// Headerless image requests can then still be attributed to the correct app build.
func (s *Store) UpdateSessionClientIdentity(
	ctx context.Context,
	hash []byte,
	version, protocol string, capabilities []string,
) error {
	_, err := s.pool.Exec(ctx, `
		UPDATE sessions
		SET client_version = CASE WHEN $2 <> '' THEN $2 ELSE client_version END,
		    client_protocol = CASE WHEN $3 <> '' THEN $3 ELSE client_protocol END,
		    client_capabilities = CASE WHEN cardinality($4::text[]) > 0 THEN $4 ELSE client_capabilities END,
		    last_seen_at = now()
		WHERE token_hash = $1`,
		hash, version, protocol, capabilities)
	return err
}

func (s *Store) DeleteSession(ctx context.Context, hash []byte) error {
	_, err := s.pool.Exec(ctx, `DELETE FROM sessions WHERE token_hash = $1`, hash)
	return err
}

// SessionsForUser returns the TVs whose gateway tokens are still active for a user.
func (s *Store) SessionsForUser(ctx context.Context, userID string) ([]Session, error) {
	rows, err := s.pool.Query(ctx, `
		SELECT token_hash, emby_user_id, emby_token, username, server_id, device_id,
			device_name, client_version, client_protocol, client_capabilities, last_seen_at
		FROM sessions
		WHERE emby_user_id = $1
		ORDER BY last_seen_at DESC, device_name`, userID)
	if err != nil {
		return nil, fmt.Errorf("store: list user sessions: %w", err)
	}
	defer rows.Close()
	var sessions []Session
	for rows.Next() {
		var sess Session
		if err := rows.Scan(
			&sess.TokenHash, &sess.EmbyUserID, &sess.EmbyToken, &sess.Username,
			&sess.ServerID, &sess.DeviceID, &sess.DeviceName, &sess.ClientVersion,
			&sess.ClientProtocol, &sess.ClientCapabilities, &sess.LastSeenAt,
		); err != nil {
			return nil, fmt.Errorf("store: scan user session: %w", err)
		}
		sessions = append(sessions, sess)
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("store: list user session rows: %w", err)
	}
	return sessions, nil
}

// DeleteUserDevice revokes one device while scoping the delete to the authenticated user.
func (s *Store) DeleteUserDevice(ctx context.Context, userID, deviceID string) ([]byte, error) {
	var tokenHash []byte
	err := s.pool.QueryRow(ctx, `
		DELETE FROM sessions
		WHERE emby_user_id = $1 AND device_id = $2
		RETURNING token_hash`, userID, deviceID).Scan(&tokenHash)
	if errors.Is(err, pgx.ErrNoRows) {
		return nil, ErrNotFound
	}
	if err != nil {
		return nil, fmt.Errorf("store: delete user device: %w", err)
	}
	return tokenHash, nil
}

// RenameUserDevice changes only the display name and keeps the session/token intact.
func (s *Store) RenameUserDevice(ctx context.Context, userID, deviceID, deviceName string) error {
	tag, err := s.pool.Exec(ctx, `
		UPDATE sessions SET device_name = $3
		WHERE emby_user_id = $1 AND device_id = $2`, userID, deviceID, deviceName)
	if err != nil {
		return fmt.Errorf("store: rename user device: %w", err)
	}
	if tag.RowsAffected() == 0 {
		return ErrNotFound
	}
	return nil
}

// DeleteIdleSessions retires tokens unused for longer than idle, returning how many went.
func (s *Store) DeleteIdleSessions(ctx context.Context, idle time.Duration) (int64, error) {
	tag, err := s.pool.Exec(ctx,
		`DELETE FROM sessions WHERE last_seen_at < now() - $1::interval`,
		fmt.Sprintf("%d seconds", int64(idle.Seconds())))
	if err != nil {
		return 0, err
	}
	return tag.RowsAffected(), nil
}