import type {
  Notification,
  NotificationData,
  NotificationType,
} from "../model/interfaces.ts";
import { APIErrorCode, APIException } from "../model/interfaces.ts";
import { db, isNotificationRow, notificationRowToApi } from "../model/db.ts";
import { sendToUser } from "./ws-service.ts";

// ── Core CRUD ─────────────────────────────────────────────────────────────────

// sourceKey: if set, INSERT OR IGNORE — same (user_id, source_key) pair is a no-op.
function createNotification(
  userId: string,
  type: NotificationType,
  data: NotificationData,
  sourceKey: string | null = null,
): void {
  const id = crypto.randomUUID();
  const createdAt = new Date().toISOString();
  const dataJson = JSON.stringify(data);

  let changes: number;

  if (sourceKey) {
    // INSERT OR IGNORE: idempotent — same (user_id, source_key) pair is a no-op
    const result = db.prepare(
      `INSERT OR IGNORE INTO notifications (id, user_id, type, data, read, created_at, source_key)
       VALUES (?, ?, ?, ?, 0, ?, ?);`,
    ).run(id, userId, type, dataJson, createdAt, sourceKey);
    changes = result.changes as number;
  } else {
    const result = db.prepare(
      `INSERT INTO notifications (id, user_id, type, data, read, created_at, source_key)
       VALUES (?, ?, ?, ?, 0, ?, NULL);`,
    ).run(id, userId, type, dataJson, createdAt);
    changes = result.changes as number;
  }

  if (changes > 0) {
    sendToUser(userId, {
      type: "notification_created",
      notification: { id, userId, type, data, read: false, createdAt },
    });
  }
}

export function getNotificationsForUser(
  userId: string,
  page: number,
  limit: number,
): { items: Notification[]; total: number } {
  const offset = (page - 1) * limit;
  const rawRows = db.prepare(
    `SELECT * FROM notifications WHERE user_id = ? ORDER BY created_at DESC LIMIT ? OFFSET ?;`,
  ).all(userId, limit, offset) as Parameters<typeof isNotificationRow>[0][];

  const totalRow = db.prepare(
    `SELECT COUNT(*) as count FROM notifications WHERE user_id = ?;`,
  ).get(userId) as { count: number } | undefined;

  if (!rawRows.every(isNotificationRow)) {
    throw new APIException(
      APIErrorCode.SERVER_ERROR,
      500,
      "Malformed notification data",
    );
  }
  return {
    items: rawRows.map(notificationRowToApi),
    total: totalRow?.count ?? 0,
  };
}

export function getUnreadCount(userId: string): number {
  const row = db.prepare(
    `SELECT COUNT(*) as count FROM notifications WHERE user_id = ? AND read = 0;`,
  ).get(userId) as { count: number } | undefined;
  return row?.count ?? 0;
}

export function markAllRead(userId: string): void {
  db.prepare(`UPDATE notifications SET read = 1 WHERE user_id = ?;`).run(
    userId,
  );
}

export function markOneRead(notificationId: string, userId: string): void {
  db.prepare(
    `UPDATE notifications SET read = 1 WHERE id = ? AND user_id = ?;`,
  ).run(notificationId, userId);
}

// ── Trigger helpers ───────────────────────────────────────────────────────────

export function notifyUserNewFollower(
  followerId: string,
  followedUserId: string,
): void {
  const followerRow = db.prepare(
    `SELECT username FROM users WHERE id = ?;`,
  ).get(followerId) as { username: string } | undefined;

  if (!followerRow) return;

  createNotification(
    followedUserId,
    "user_followed",
    { followerId, followerUsername: followerRow.username },
    `user-followed:${followedUserId}:${followerId}`,
  );
}

export function notifyPlaylistOwnerNewFollower(
  followerId: string,
  playlistId: string,
): void {
  const followerRow = db.prepare(
    `SELECT username FROM users WHERE id = ?;`,
  ).get(followerId) as { username: string } | undefined;

  const playlistRow = db.prepare(
    `SELECT title, user_id FROM playlists WHERE id = ?;`,
  ).get(playlistId) as { title: string; user_id: string } | undefined;

  if (!followerRow || !playlistRow) return;
  if (followerId === playlistRow.user_id) return;

  createNotification(
    playlistRow.user_id,
    "playlist_followed",
    {
      followerId,
      followerUsername: followerRow.username,
      playlistId,
      playlistTitle: playlistRow.title,
    },
    `followed:${playlistId}:${followerId}`,
  );
}

export function notifyUserFollowersNewDump(
  dumperId: string,
  dumpId: string,
  dumpTitle: string,
): void {
  const posterRow = db.prepare(
    `SELECT username FROM users WHERE id = ?;`,
  ).get(dumperId) as { username: string } | undefined;
  if (!posterRow) return;

  const followerRows = db.prepare(
    `SELECT follower_id FROM follows WHERE followed_user_id = ?;`,
  ).all(dumperId) as { follower_id: string }[];

  for (const row of followerRows) {
    createNotification(
      row.follower_id,
      "user_dump_posted",
      { dumperId, dumperUsername: posterRow.username, dumpId, dumpTitle },
      `dump:${dumpId}`,
    );
  }
}

export function notifyDumpOwnerUpvote(
  voterId: string,
  dumpId: string,
): void {
  const voterRow = db.prepare(
    `SELECT username FROM users WHERE id = ?;`,
  ).get(voterId) as { username: string } | undefined;

  const dumpRow = db.prepare(
    `SELECT title, user_id FROM dumps WHERE id = ?;`,
  ).get(dumpId) as { title: string; user_id: string } | undefined;

  if (!voterRow || !dumpRow) return;
  if (voterId === dumpRow.user_id) return; // no self-notification

  createNotification(
    dumpRow.user_id,
    "dump_upvoted",
    {
      voterId,
      voterUsername: voterRow.username,
      dumpId,
      dumpTitle: dumpRow.title,
    },
    `upvote:${dumpId}:${voterId}`,
  );
}

export function notifyPlaylistFollowersNewDump(
  playlistId: string,
  playlistTitle: string,
  dumpId: string,
  dumpTitle: string,
): void {
  const followerRows = db.prepare(
    `SELECT follower_id FROM follows WHERE followed_playlist_id = ?;`,
  ).all(playlistId) as { follower_id: string }[];

  for (const row of followerRows) {
    createNotification(
      row.follower_id,
      "playlist_dump_added",
      { dumpId, dumpTitle, playlistId, playlistTitle },
      `pdump:${playlistId}:${dumpId}`,
    );
  }
}