import type { createPinboard } from "./server.js";

export namespace PostgresDurabilityStore {
  /** Structurally a pg Pool or Client; the deployment supplies the driver. */
  export type Queryable = {
    query(
      text: string,
      values?: unknown[],
    ): Promise<{ rows: Record<string, unknown>[]; rowCount: number | null }>;
  };
}

/** DurabilityStore over the pinned host's `pinned_tray_index` table: a
 * `marked` row `(ns, id, tray_ns, tray_id)` means a tray has in-flight
 * work, so its instance needs waking; unmarked rows stay put. */
export class PostgresDurabilityStore implements createPinboard.DurabilityStore {
  private readonly db: PostgresDurabilityStore.Queryable;

  constructor(db: PostgresDurabilityStore.Queryable) {
    this.db = db;
  }

  async listMarked(
    cursor: string | null,
    limit: number,
  ): Promise<{
    entries: { env: string; hostname: string; ns: string; id: string }[];
    cursor: string | null;
  }> {
    if (!Number.isInteger(limit) || limit < 1) {
      throw new Error(`limit must be a positive integer: ${limit}`);
    }
    let after: [string, string, string] = ["", "", ""];
    if (cursor !== null) {
      const parsed: unknown = JSON.parse(cursor);
      if (
        !Array.isArray(parsed) ||
        parsed.length !== 3 ||
        parsed.some((part) => typeof part !== "string")
      ) {
        throw new Error(`malformed cursor: ${cursor}`);
      }
      after = parsed as [string, string, string];
    }
    const { rows } = await this.db.query(
      "SELECT DISTINCT ON (env, ns, id) env, hostname, ns, id " +
        "FROM pinned_tray_index " +
        "WHERE marked AND (env, ns, id) > ($1, $2, $3) " +
        "ORDER BY env, ns, id, hostname LIMIT $4",
      [after[0], after[1], after[2], limit],
    );
    const entries = rows.map((row) => ({
      env: String(row["env"]),
      hostname: String(row["hostname"]),
      ns: String(row["ns"]),
      id: String(row["id"]),
    }));
    const last = entries[entries.length - 1];
    return {
      entries,
      cursor:
        entries.length < limit || last === undefined
          ? null
          : JSON.stringify([last.env, last.ns, last.id]),
    };
  }
}