/**
 * Adds `dump_backlinks`, which records the links from a dump's note or
 * comments to other dumps, so a dump page can list the dumps related to it.
 * backlink-service fills it, and the index on `dumps.url` lets it find the
 * dumps an external link was posted as.
 *
 * @module
 */

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

/**
 * Run once by `runMigrations`. It doesn't scan the notes and comments already
 * posted, so their links are recorded only once they are edited.
 */
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);`,
  );
}