-- broker.broker_run
-- Executes a job by its ID, presenting the lease token it was claimed with.
--
-- p_retval is reserved for infra failures (bad job id, job not found, wrong
-- state, lease mismatch/expired, DB error). An executed-and-caught job
-- failure is a *successful* invocation: p_retval stays 0 and the outcome is
-- reported via p_job_status (0=requeued for retry, 2=completed, 3=dead-lettered)
-- so the caller commits the terminal/retry state instead of rolling it back.
--
-- On failure, if attempt_count < max_attempts the job is reset to pending
-- with exponential backoff (base 5s, capped at 300s); otherwise it is
-- dead-lettered as complete_status = 3.

CREATE OR REPLACE FUNCTION broker.broker_run(
    p_job_id BIGINT,
    p_lease_token UUID,
    OUT p_retval INTEGER,
    OUT p_errmsg TEXT,
    OUT p_job_status INTEGER
)
RETURNS RECORD
LANGUAGE plpgsql
AS $$
DECLARE
    v_job_record RECORD;
    v_execute_result TEXT;
    v_error_occurred BOOLEAN := false;
    v_backoff_base CONSTANT INTEGER := 5;
    v_backoff_cap CONSTANT INTEGER := 300;
    v_backoff_secs INTEGER;
BEGIN
    p_retval := 0;
    p_errmsg := '';
    p_job_status := NULL;
    v_execute_result := '';

    IF p_job_id IS NULL OR p_job_id <= 0 THEN
        p_retval := 1;
        p_errmsg := 'Invalid job ID';
        RETURN;
    END IF;

    SELECT id_broker_jobs, execute_str, job_language, complete_status, attempt_count, max_attempts, lease_token
    INTO v_job_record
    FROM broker.broker_jobs
    WHERE id_broker_jobs = p_job_id
    FOR UPDATE;

    IF NOT FOUND THEN
        p_retval := 2;
        p_errmsg := 'Job not found';
        RETURN;
    END IF;

    IF v_job_record.complete_status != 1 THEN
        p_retval := 3;
        p_errmsg := format('Job is not in running state (status: %s)', v_job_record.complete_status);
        RETURN;
    END IF;

    IF v_job_record.lease_token IS DISTINCT FROM p_lease_token THEN
        p_retval := 4;
        p_errmsg := 'Lease token mismatch or expired; job was reclaimed by another worker';
        RETURN;
    END IF;

    -- Execute the job
    BEGIN
        IF v_job_record.job_language IN ('sql', 'plpgsql') THEN
            EXECUTE v_job_record.execute_str;
            v_execute_result := 'Success';
        ELSE
            v_error_occurred := true;
            v_execute_result := format('Unsupported job language: %s', v_job_record.job_language);
        END IF;
    EXCEPTION
        WHEN OTHERS THEN
            v_error_occurred := true;
            v_execute_result := format('Error: %s', SQLERRM);
    END;

    IF v_error_occurred THEN
        IF v_job_record.attempt_count < v_job_record.max_attempts THEN
            v_backoff_secs := LEAST(POWER(2, v_job_record.attempt_count)::INTEGER * v_backoff_base, v_backoff_cap);

            UPDATE broker.broker_jobs
            SET complete_status = 0,  -- pending, retry
                available_at = NOW() + make_interval(secs => v_backoff_secs),
                error_msg = v_execute_result,
                execute_result = v_execute_result,
                lease_token = NULL,
                leased_at = NULL,
                lease_expires_at = NULL,
                updated_at = NOW()
            WHERE id_broker_jobs = p_job_id;

            p_job_status := 0;
        ELSE
            UPDATE broker.broker_jobs
            SET complete_status = 3,  -- failed (dead-letter, attempts exhausted)
                error_msg = v_execute_result,
                execute_result = v_execute_result,
                lease_token = NULL,
                leased_at = NULL,
                lease_expires_at = NULL,
                completed_at = NOW(),
                updated_at = NOW()
            WHERE id_broker_jobs = p_job_id;

            p_job_status := 3;
        END IF;
    ELSE
        UPDATE broker.broker_jobs
        SET complete_status = 2,  -- completed
            execute_result = v_execute_result,
            error_msg = NULL,
            lease_token = NULL,
            leased_at = NULL,
            lease_expires_at = NULL,
            completed_at = NOW(),
            updated_at = NOW()
        WHERE id_broker_jobs = p_job_id;

        p_job_status := 2;
    END IF;

EXCEPTION
    WHEN OTHERS THEN
        p_retval := 6;
        p_errmsg := SQLERRM;
        RAISE WARNING 'broker_run error: %', SQLERRM;
END;
$$;

COMMENT ON FUNCTION broker.broker_run IS 'Executes a leased job; reports outcome via p_job_status without forcing a rollback of the terminal/retry state';