/**
 * Adds the `dump_backlinks` table, recording which dumps, comments and
 * descriptions link to a dump, and indexes `dumps.url`.
 *
 * Idempotent: safe to run against a fresh db (already created from schema.sql
 * with these) or an existing one that predates them.
 *
 * @module
 */

import type { DatabaseSync } from "node:sqlite";

/** Applies this migration to `db`. */
export function up(db: DatabaseSync): void {
  db.exec(`CREATE TABLE IF NOT EXISTS dump_backlinks (
    source_type  TEXT NOT NULL,
    source_id    TEXT NOT NULL,
    from_dump_id TEXT NOT NULL,
    to_dump_id   TEXT NOT NULL,
    created_at   TEXT NOT NULL,
    PRIMARY KEY (source_type, source_id, to_dump_id),
    FOREIGN KEY (from_dump_id) REFERENCES dumps(id) ON DELETE CASCADE,
    FOREIGN KEY (to_dump_id)   REFERENCES dumps(id) ON DELETE CASCADE
  );`);

  db.exec(
    `CREATE INDEX IF NOT EXISTS idx_dump_backlinks_to ON dump_backlinks(to_dump_id);`,
  );
  db.exec(
    `CREATE INDEX IF NOT EXISTS idx_dump_backlinks_from ON dump_backlinks(from_dump_id);`,
  );
  db.exec(
    `CREATE INDEX IF NOT EXISTS idx_dumps_url ON dumps(url);`,
  );
}