-- A business task owns exactly one external Agent session. The external
-- session identifier and every conversational turn stay server-side and are
-- encrypted by the application before persistence.
CREATE TABLE IF NOT EXISTS agent_sessions (
  id uuid PRIMARY KEY DEFAULT gen_random_uuid(),
  organization_id uuid NOT NULL REFERENCES organizations(id) ON DELETE CASCADE,
  task_id uuid NOT NULL UNIQUE REFERENCES tasks(id) ON DELETE CASCADE,
  conversation_id text,
  provider text NOT NULL DEFAULT 'superagent',
  external_session_id_ciphertext text,
  status text NOT NULL DEFAULT 'pending'
    CHECK (status IN ('pending', 'active', 'recovering', 'expired', 'failed', 'closed')),
  current_turn integer NOT NULL DEFAULT 0 CHECK (current_turn >= 0),
  recovery_count integer NOT NULL DEFAULT 0 CHECK (recovery_count >= 0),
  last_error text,
  last_message_at timestamptz,
  created_at timestamptz NOT NULL DEFAULT now(),
  updated_at timestamptz NOT NULL DEFAULT now()
);

CREATE INDEX IF NOT EXISTS agent_sessions_conversation_idx
  ON agent_sessions (organization_id, conversation_id, updated_at DESC)
  WHERE conversation_id IS NOT NULL;

CREATE INDEX IF NOT EXISTS agent_sessions_pending_idx
  ON agent_sessions (organization_id, conversation_id, status, updated_at DESC)
  WHERE conversation_id IS NOT NULL AND status NOT IN ('closed', 'failed');

CREATE TABLE IF NOT EXISTS agent_session_messages (
  id uuid PRIMARY KEY DEFAULT gen_random_uuid(),
  organization_id uuid NOT NULL REFERENCES organizations(id) ON DELETE CASCADE,
  agent_session_id uuid NOT NULL REFERENCES agent_sessions(id) ON DELETE CASCADE,
  task_id uuid NOT NULL REFERENCES tasks(id) ON DELETE CASCADE,
  turn_no integer NOT NULL CHECK (turn_no > 0),
  role text NOT NULL CHECK (role IN ('user', 'assistant', 'system')),
  content_ciphertext text NOT NULL,
  status text NOT NULL DEFAULT 'queued'
    CHECK (status IN ('queued', 'sending', 'sent', 'replayed', 'failed')),
  idempotency_key text,
  error_code text,
  created_at timestamptz NOT NULL DEFAULT now(),
  sent_at timestamptz,
  UNIQUE (agent_session_id, turn_no, role)
);

CREATE UNIQUE INDEX IF NOT EXISTS agent_session_messages_idempotency_idx
  ON agent_session_messages (organization_id, idempotency_key)
  WHERE idempotency_key IS NOT NULL;

CREATE INDEX IF NOT EXISTS agent_session_messages_queue_idx
  ON agent_session_messages (agent_session_id, status, role, turn_no);

CREATE INDEX IF NOT EXISTS agent_session_messages_task_idx
  ON agent_session_messages (organization_id, task_id, turn_no);

-- Existing tasks were created before task-scoped sessions existed. Backfill a
-- pending session and preserve the already encrypted original instruction as
-- the first user turn. The application will attach conversation metadata when
-- a later message arrives.
INSERT INTO agent_sessions (organization_id, task_id, status, current_turn, created_at, updated_at)
SELECT t.organization_id, t.id,
       CASE WHEN t.status IN (
         'completed', 'cancelled', 'parse_failed', 'parse_blocked', 'blocked',
         'failed', 'dry_run', 'reconciliation_pending', 'execution_uncertain',
         'saved_unverified', 'operation_blocked'
       ) THEN 'closed' ELSE 'pending' END,
       1,
       t.created_at,
       t.updated_at
  FROM tasks t
 WHERE NOT EXISTS (
   SELECT 1 FROM agent_sessions s WHERE s.task_id = t.id
 );

INSERT INTO agent_session_messages
  (organization_id, agent_session_id, task_id, turn_no, role, content_ciphertext, status, created_at, sent_at)
SELECT t.organization_id, s.id, t.id, 1, 'user', t.original_text_ciphertext,
       CASE
         WHEN t.status = 'parse_queued' THEN 'queued'
         WHEN t.status = 'parse_running' THEN 'sending'
         ELSE 'sent'
       END,
       t.created_at,
       CASE WHEN t.status IN ('parse_queued', 'parse_running') THEN NULL ELSE t.created_at END
  FROM tasks t
  JOIN agent_sessions s ON s.task_id = t.id
 WHERE t.original_text_ciphertext IS NOT NULL
   AND NOT EXISTS (
     SELECT 1
       FROM agent_session_messages m
      WHERE m.agent_session_id = s.id
        AND m.turn_no = 1
        AND m.role = 'user'
   );