"""Fenced PostgreSQL job-queue statements.

Callers must execute each statement in a transaction and treat an empty
``RETURNING`` result as loss of the lease. No external model call should hold
the claim transaction open.
"""

CLAIM_JOB_SQL = """
WITH candidate AS (
    SELECT job.id
    FROM rag.background_jobs AS job
    WHERE job.attempt < job.max_attempts
      AND job.required_capability = ANY(CAST(:worker_capabilities AS text[]))
      AND (
        (job.status = 'QUEUED' AND job.run_after <= now())
        OR (job.status = 'RUNNING' AND job.lease_until < now())
      )
    ORDER BY job.priority DESC, job.run_after, job.created_at
    FOR UPDATE SKIP LOCKED
    LIMIT 1
)
UPDATE rag.background_jobs AS job
SET status = 'RUNNING',
    lease_owner = :worker_id,
    lease_token = gen_random_uuid(),
    lease_until = now() + make_interval(secs => CAST(:lease_seconds AS integer)),
    attempt = job.attempt + 1,
    updated_at = now(),
    finished_at = NULL
FROM candidate
WHERE job.id = candidate.id
RETURNING job.*
"""

HEARTBEAT_JOB_SQL = """
UPDATE rag.background_jobs AS job
SET lease_until = now() + make_interval(secs => CAST(:lease_seconds AS integer)),
    updated_at = now()
WHERE job.id = :job_id
  AND job.status = 'RUNNING'
  AND job.lease_owner = :worker_id
  AND job.lease_token = :lease_token
  AND job.lease_until >= now()
RETURNING job.id, job.lease_until
"""

COMPLETE_JOB_SQL = """
UPDATE rag.background_jobs AS job
SET status = 'SUCCEEDED',
    progress = 100,
    lease_owner = NULL,
    lease_token = NULL,
    lease_until = NULL,
    finished_at = now(),
    updated_at = now()
WHERE job.id = :job_id
  AND job.status = 'RUNNING'
  AND job.lease_owner = :worker_id
  AND job.lease_token = :lease_token
  AND job.lease_until >= now()
RETURNING job.*
"""

FAIL_OR_RETRY_JOB_SQL = """
UPDATE rag.background_jobs AS job
SET status = CASE
      WHEN job.attempt < job.max_attempts THEN 'QUEUED'
      ELSE 'FAILED'
    END,
    run_after = CASE
      WHEN job.attempt < job.max_attempts
        THEN now() + make_interval(
          secs => GREATEST(CAST(:retry_delay_seconds AS integer), 0)
        )
      ELSE job.run_after
    END,
    last_error_code = :error_code,
    last_error_message = left(:error_message, 2000),
    lease_owner = NULL,
    lease_token = NULL,
    lease_until = NULL,
    finished_at = CASE
      WHEN job.attempt < job.max_attempts THEN NULL
      ELSE now()
    END,
    updated_at = now()
WHERE job.id = :job_id
  AND job.status = 'RUNNING'
  AND job.lease_owner = :worker_id
  AND job.lease_token = :lease_token
  AND job.lease_until >= now()
RETURNING job.*
"""

REAP_EXPIRED_JOBS_SQL = """
WITH maintenance_lock AS (
    SELECT pg_try_advisory_xact_lock(CAST(:lock_key AS bigint)) AS acquired
),
expired AS (
    SELECT job.id
    FROM rag.background_jobs AS job
    CROSS JOIN maintenance_lock
    WHERE maintenance_lock.acquired
      AND job.status = 'RUNNING'
      AND job.lease_until < now()
    ORDER BY job.lease_until, job.created_at
    FOR UPDATE OF job SKIP LOCKED
    LIMIT CAST(:batch_size AS integer)
)
UPDATE rag.background_jobs AS job
SET status = CASE
      WHEN job.attempt < job.max_attempts THEN 'QUEUED'
      ELSE 'FAILED'
    END,
    run_after = CASE
      WHEN job.attempt < job.max_attempts THEN now()
      ELSE job.run_after
    END,
    last_error_code = 'WORKER_LEASE_EXPIRED',
    last_error_message = 'Worker lease expired before a fenced terminal update.',
    lease_owner = NULL,
    lease_token = NULL,
    lease_until = NULL,
    finished_at = CASE
      WHEN job.attempt < job.max_attempts THEN NULL
      ELSE now()
    END,
    updated_at = now()
FROM expired
WHERE job.id = expired.id
RETURNING job.*
"""