CREATE TABLE IF NOT EXISTS task_artifacts (
  id uuid PRIMARY KEY DEFAULT gen_random_uuid(),
  organization_id uuid NOT NULL REFERENCES organizations(id) ON DELETE CASCADE,
  task_id uuid NOT NULL REFERENCES tasks(id) ON DELETE CASCADE,
  execution_id uuid NOT NULL REFERENCES task_attempts(id) ON DELETE CASCADE,
  artifact_index integer NOT NULL CHECK (artifact_index >= 0),
  artifact_type text NOT NULL,
  file_name text NOT NULL,
  content_type text NOT NULL,
  byte_size bigint NOT NULL CHECK (byte_size > 0),
  sha256 text NOT NULL CHECK (sha256 ~ '^[a-f0-9]{64}$'),
  storage_backend text NOT NULL DEFAULT 'database' CHECK (storage_backend IN ('database', 'oss')),
  storage_key text,
  content_ciphertext text,
  created_at timestamptz NOT NULL DEFAULT now(),
  UNIQUE (task_id, execution_id, artifact_index),
  CHECK (
    (storage_backend = 'database' AND content_ciphertext IS NOT NULL AND storage_key IS NULL)
    OR (storage_backend = 'oss' AND storage_key IS NOT NULL AND content_ciphertext IS NULL)
  )
);

CREATE INDEX IF NOT EXISTS task_artifacts_org_task_idx
  ON task_artifacts (organization_id, task_id, created_at DESC);