import { MigrationInterface, QueryRunner } from 'typeorm';

export class PhaseF31AssetChronologicalMerge1789844600000 implements MigrationInterface {
  name = 'PhaseF31AssetChronologicalMerge1789844600000';

  public async up(queryRunner: QueryRunner): Promise<void> {
    await queryRunner.query(`
      CREATE TABLE asset_merges (
        id uuid PRIMARY KEY DEFAULT gen_random_uuid(),
        source_asset_id uuid NOT NULL REFERENCES assets(id) ON DELETE RESTRICT,
        canonical_asset_id uuid NOT NULL REFERENCES assets(id) ON DELETE RESTRICT,
        reason text NOT NULL,
        merged_at timestamptz NOT NULL DEFAULT CURRENT_TIMESTAMP,
        merged_by uuid NULL REFERENCES users(id) ON DELETE SET NULL,
        source varchar(32) NOT NULL,
        request_id varchar(128) NULL,
        source_snapshot jsonb NOT NULL,
        canonical_snapshot jsonb NOT NULL,
        CONSTRAINT chk_asset_merges_distinct CHECK (source_asset_id <> canonical_asset_id),
        CONSTRAINT uq_asset_merges_source UNIQUE (source_asset_id)
      )
    `);
    await queryRunner.query(`CREATE INDEX idx_asset_merges_canonical ON asset_merges(canonical_asset_id)`);
    await queryRunner.query(`CREATE INDEX idx_asset_merges_merged_at ON asset_merges(merged_at)`);

    await queryRunner.query(`
      CREATE OR REPLACE FUNCTION protect_asset_merges_append_only()
      RETURNS trigger
      LANGUAGE plpgsql
      AS $$
      BEGIN
        RAISE EXCEPTION 'asset_merges es append-only; una fusión no puede editarse ni borrarse';
      END;
      $$
    `);
    await queryRunner.query(`
      CREATE TRIGGER trg_asset_merges_append_only
      BEFORE UPDATE OR DELETE ON asset_merges
      FOR EACH ROW EXECUTE FUNCTION protect_asset_merges_append_only()
    `);
  }

  public async down(queryRunner: QueryRunner): Promise<void> {
    await queryRunner.query('DROP TRIGGER IF EXISTS trg_asset_merges_append_only ON asset_merges');
    await queryRunner.query('DROP FUNCTION IF EXISTS protect_asset_merges_append_only()');
    await queryRunner.query('DROP TABLE IF EXISTS asset_merges');
  }
}