"""Master main loop — composes the per-tick work (tick + reaper +
pickup guard) and runs it on a configurable cadence until a stop
event fires.

Per plan v9: the master is a long-running singleton per (owner, repo).
This module is the orchestrator that ties together the deterministic
pieces shipped in Phase 1d-1/1d-2 + later additions.

Currently composes:
- ``tick.run_tick()`` — advance state for any completed attempts
- ``reaper.reap_stale_attempts()`` — reset stale-heartbeat in_progress rows
- ``pickup_guard.transition_exhausted_to_stuck()`` — STUCK workflows
  whose attempts have been re-pended too many times

Deferred to Phase 1d-3+:
- Discovery (Forgejo poll for new PRs/issues + insert DISCOVERED rows)
- Per-workflow scheduling (after a state transition, enqueue the
  next attempt's workflow_attempts row with input_payload prefetched)
- Forgejo writes (status comments, labels, merges)
- MERGING state's actual Forgejo merge call
- Periodic reconciliation tick
- Backfill at startup
- Operator CLI server (HTTP / unix socket for controller-cli)
"""
from __future__ import annotations

import logging
import os
import threading
from collections.abc import Callable
from dataclasses import dataclass

from sqlalchemy.engine import Engine

from ..pickup_guard import (
    DEFAULT_MAX_PICKUPS,
    PickupGuardReport,
    transition_exhausted_to_stuck,
)
from ..reaper import ReaperReport, reap_stale_attempts
from .tick import TickReport, run_tick

logger = logging.getLogger(__name__)


@dataclass
class MasterConfig:
    """Per-master config; tunable via env vars."""

    tick_interval_s: float = float(
        os.environ.get("CONTROLLER_MASTER_TICK_INTERVAL_S", "30")
    )
    reaper_interval_s: float = float(
        os.environ.get("CONTROLLER_REAPER_INTERVAL_S", "60")
    )
    pickup_guard_max_pickups: int = DEFAULT_MAX_PICKUPS


@dataclass
class MasterTickReport:
    """Summary of one composite master tick."""

    tick: TickReport
    reaper: ReaperReport
    pickup_guard: PickupGuardReport


def run_master_iteration(
    engine: Engine, *, max_pickups: int = DEFAULT_MAX_PICKUPS,
) -> MasterTickReport:
    """Run one composite iteration: tick + reaper + pickup guard.

    Order matters:
    1. ``tick`` first: advance state machine for completed attempts;
       may produce new transitions that the reaper / pickup guard
       then notice.
    2. ``reaper`` next: reset stale-heartbeat in_progress rows.
       Post-reap, those attempts return to the pending pool +
       pickup_count is preserved (the guard uses it).
    3. ``pickup_guard`` last: STUCK any workflows whose pending
       attempts have hit MAX_PICKUPS. Runs AFTER the reaper so a
       just-reaped attempt's pickup_count is visible.
    """
    return MasterTickReport(
        tick=run_tick(engine),
        reaper=reap_stale_attempts(engine),
        pickup_guard=transition_exhausted_to_stuck(engine, max_pickups=max_pickups),
    )


def master_main_loop(
    engine: Engine,
    *,
    config: MasterConfig | None = None,
    stop_event: threading.Event | None = None,
    on_iteration: Callable[[MasterTickReport], None] | None = None,
) -> None:
    """Run the master loop until ``stop_event`` is set.

    The reaper runs less frequently than the tick by default (60s vs
    30s). We model this simply: each iteration runs the tick always;
    the reaper runs only when ``elapsed_since_last_reap >=
    reaper_interval_s``. (Plan v9 noted "reaper every 60s"; we honor
    it modulo the tick cadence.)
    """
    cfg = config or MasterConfig()
    stop = stop_event or threading.Event()
    last_reap_at_iteration = 0
    iteration = 0

    logger.info(
        "master loop starting: tick_interval=%.1fs reaper_interval=%.1fs max_pickups=%d",
        cfg.tick_interval_s, cfg.reaper_interval_s, cfg.pickup_guard_max_pickups,
    )

    try:
        while not stop.is_set():
            iteration += 1
            # Always run tick + pickup guard. Run reaper less often.
            tick_report = run_tick(engine)
            should_reap = (
                (iteration - last_reap_at_iteration) * cfg.tick_interval_s
                >= cfg.reaper_interval_s
            )
            reaper_report = (
                reap_stale_attempts(engine) if should_reap else ReaperReport()
            )
            if should_reap:
                last_reap_at_iteration = iteration
            pickup_report = transition_exhausted_to_stuck(
                engine, max_pickups=cfg.pickup_guard_max_pickups,
            )

            if on_iteration is not None:
                try:
                    on_iteration(MasterTickReport(
                        tick=tick_report,
                        reaper=reaper_report,
                        pickup_guard=pickup_report,
                    ))
                except Exception:
                    logger.exception("on_iteration callback raised")

            if (tick_report.transitions_applied
                    or reaper_report.rows_reaped
                    or pickup_report.workflows_stuck):
                logger.info(
                    "master iteration %d: transitions=%d reaped=%d stuck=%d",
                    iteration,
                    tick_report.transitions_applied,
                    reaper_report.rows_reaped,
                    pickup_report.workflows_stuck,
                )
            stop.wait(cfg.tick_interval_s)
    finally:
        logger.info("master loop stopped after %d iterations", iteration)


__all__ = [
    "MasterConfig",
    "MasterTickReport",
    "master_main_loop",
    "run_master_iteration",
]