CREATE TABLE IF NOT EXISTS threads (
  thread_id TEXT PRIMARY KEY,
  run_id TEXT NOT NULL,
  task_id TEXT NOT NULL,
  subject TEXT NOT NULL,
  created_by TEXT NOT NULL,
  assigned_to TEXT NOT NULL,
  status TEXT NOT NULL,
  priority TEXT NOT NULL DEFAULT 'normal',
  latest_message_id TEXT,
  created_at TEXT NOT NULL,
  updated_at TEXT NOT NULL
);

CREATE TABLE IF NOT EXISTS messages (
  message_id TEXT PRIMARY KEY,
  thread_id TEXT NOT NULL,
  from_agent TEXT NOT NULL,
  to_agent TEXT NOT NULL,
  kind TEXT NOT NULL,
  summary TEXT NOT NULL,
  body TEXT NOT NULL DEFAULT '',
  payload_json TEXT NOT NULL DEFAULT '{}',
  created_at TEXT NOT NULL,
  FOREIGN KEY(thread_id) REFERENCES threads(thread_id)
);

CREATE TABLE IF NOT EXISTS leases (
  thread_id TEXT PRIMARY KEY,
  agent_id TEXT NOT NULL,
  lease_token TEXT NOT NULL,
  claimed_at TEXT NOT NULL,
  expires_at TEXT NOT NULL,
  released_at TEXT
);

CREATE TABLE IF NOT EXISTS artifacts (
  artifact_id TEXT PRIMARY KEY,
  message_id TEXT NOT NULL,
  path TEXT NOT NULL,
  kind TEXT NOT NULL,
  metadata_json TEXT NOT NULL DEFAULT '{}',
  created_at TEXT NOT NULL,
  FOREIGN KEY(message_id) REFERENCES messages(message_id)
);

CREATE INDEX IF NOT EXISTS idx_threads_status_assigned
  ON threads(status, assigned_to, updated_at);

CREATE INDEX IF NOT EXISTS idx_messages_thread_created
  ON messages(thread_id, created_at);