import { APIErrorCode, APIException, type User } from "../model/interfaces.ts";
import { db, isUserRow, userRowToApi } from "../model/db.ts";
import { notifyDumpOwnerUpvote } from "./notification-service.ts";

export interface VoteResult {
  voteCount: number;
  /** Private dumps' vote counts go to their owner only. */
  isPrivate: boolean;
}

// Visibility of the dump, or a 404 when the user can't see it — voting must not
// confirm that a private dump exists.
function visibleDump(dumpId: string, userId: string): { isPrivate: boolean } {
  const row = db.prepare(
    `SELECT is_private, user_id FROM dumps WHERE id = ?;`,
  ).get(dumpId) as { is_private: number; user_id: string } | undefined;
  if (!row || (row.is_private && row.user_id !== userId)) {
    throw new APIException(APIErrorCode.NOT_FOUND, 404, "Dump not found");
  }
  return { isPrivate: Boolean(row.is_private) };
}

export function castVote(dumpId: string, userId: string): VoteResult {
  const { isPrivate } = visibleDump(dumpId, userId);
  let voteCount: number;
  try {
    db.exec("BEGIN;");
    db.prepare(
      `INSERT INTO votes (dump_id, user_id, created_at) VALUES (?, ?, ?);`,
    ).run(dumpId, userId, new Date().toISOString());
    db.prepare(
      `UPDATE dumps SET vote_count = vote_count + 1 WHERE id = ?;`,
    ).run(dumpId);
    const row = db.prepare(
      `SELECT vote_count FROM dumps WHERE id = ?;`,
    ).get(dumpId) as { vote_count: number } | undefined;
    db.exec("COMMIT;");
    voteCount = row?.vote_count ?? 0;
  } catch (err) {
    try {
      db.exec("ROLLBACK;");
    } catch { /* ignore if no active transaction */ }
    if (err instanceof Error && err.message.includes("UNIQUE constraint")) {
      throw new APIException(
        APIErrorCode.VALIDATION_ERROR,
        409,
        "Already voted",
      );
    }
    throw err;
  }
  // Notification is best-effort — must not prevent vote_ack from being sent
  try {
    notifyDumpOwnerUpvote(userId, dumpId);
  } catch { /* ignore */ }
  return { voteCount, isPrivate };
}

// No visibility check: taking back a vote on a dump that has since gone
// private is harmless, and it's the voter's own row.
export function removeVote(dumpId: string, userId: string): VoteResult {
  const row = db.prepare(`SELECT is_private FROM dumps WHERE id = ?;`).get(
    dumpId,
  ) as { is_private: number } | undefined;
  const isPrivate = Boolean(row?.is_private);
  try {
    db.exec("BEGIN;");
    const result = db.prepare(
      `DELETE FROM votes WHERE dump_id = ? AND user_id = ?;`,
    ).run(dumpId, userId);
    if (result.changes === 0) {
      db.exec("ROLLBACK;");
      throw new APIException(APIErrorCode.NOT_FOUND, 404, "Vote not found");
    }
    db.prepare(
      `UPDATE dumps SET vote_count = vote_count - 1 WHERE id = ?;`,
    ).run(dumpId);
    const count = db.prepare(
      `SELECT vote_count FROM dumps WHERE id = ?;`,
    ).get(dumpId) as { vote_count: number } | undefined;
    db.exec("COMMIT;");
    return { voteCount: count?.vote_count ?? 0, isPrivate };
  } catch (err) {
    if (err instanceof APIException) throw err;
    db.exec("ROLLBACK;");
    throw err;
  }
}

export function getUserVotes(userId: string): string[] {
  const rows = db.prepare(
    `SELECT dump_id FROM votes WHERE user_id = ?;`,
  ).all(userId) as { dump_id: string }[];
  return rows.map((r) => r.dump_id);
}

export function getDumpVoters(
  dumpId: string,
  page: number,
  limit: number,
): { items: User[]; total: number } {
  const offset = (page - 1) * limit;

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

  const rawRows = db.prepare(
    `SELECT u.id, u.username, u.password_hash, u.role, u.created_at, u.updated_at,
            u.avatar_mime, u.description, u.invited_by, u.email,
            i.username as invited_by_username
     FROM users u
     LEFT JOIN users i ON i.id = u.invited_by
     INNER JOIN votes v ON v.dump_id = ? AND v.user_id = u.id
     ORDER BY v.created_at DESC
     LIMIT ? OFFSET ?;`,
  ).all(dumpId, limit, offset);

  if (!rawRows.every(isUserRow)) {
    throw new APIException(
      APIErrorCode.SERVER_ERROR,
      500,
      "Malformed user data",
    );
  }

  return { items: rawRows.map(userRowToApi), total: totalRow?.count ?? 0 };
}