"""
事件日志模块 — V2 可观测性基础设施。
JSONL 格式无限流式追加，与 state.json 互补：state.json 是当前快照，事件日志是完整时间线。
"""

from __future__ import annotations

import contextlib
import json
import logging
import os
import tempfile
from datetime import datetime, timezone
from pathlib import Path

logger = logging.getLogger(__name__)

# 事件类型常量 — 所有 emit 调用必须使用常量，禁止字符串字面量
TASK_DISPATCHED = "task.dispatched"
TASK_ENTERED = "task.entered"
TASK_FINISHED = "task.finished"
TASK_COMPLETED = "task.completed"
TASK_BLOCKED = "task.blocked"
MERGE_STARTED = "merge.started"
MERGE_COMPLETED = "merge.completed"
REPAIR_CREATED = "repair.created"
REPAIR_RESOLVED = "repair.resolved"
INTERVENTION_STALL = "intervention.stall"
XDB_CAPTURED = "xdb.captured"
DEBUG_SESSION = "debug.session"
CONTEXT_COMPACTED = "context.compacted"
DEPLOY_COMPLETED = "deploy.completed"
TEST_RUN = "test.run"
SEC_SCAN = "sec.scan"
REVIEW_SESSION = "review.session"
ENGINE_ENTERED = "engine.entered"
ENGINE_CYCLE = "engine.cycle"
ENG_REPLAN_TRIGGERED = "eng.replan.triggered"
ENG_BLOCKED = "eng.blocked"
WORKER_TIMEOUT = "worker.timeout"
WORKTREE_MERGE_CONFLICT = "worktree.merge.conflict"
ARC_REPLANNED = "arc.replanned"
ADR_CHANGE_DETECTED = "adr.change.detected"
ADR_INVALIDATION = "adr.invalidation"
ADR_UNFREEZED = "adr.unfreezed"
LOCK_ACQUIRED = "lock.acquired"
LOCK_RELEASED = "lock.released"
STALE_LOCK_CLEANED = "stale_lock.cleaned"


def now_iso() -> str:
    return datetime.now(timezone.utc).isoformat()


class EventLog:
    """结构化事件日志（JSONL 格式），支持轮转截断。

    P1-GAP18: 原子轮转 — open(tmp)+os.replace，每 N 次 emit 检查一次避免每次读文件。
    """

    MAX_LINES = 10000
    ROTATE_CHECK_EVERY = 128  # 每 128 次 emit 检查一次轮转

    def __init__(self, path: Path, max_lines: int = MAX_LINES):
        self._path = path
        self._max_lines = max_lines
        self._emit_count = 0  # P1-GAP18: 计数器，避免每次 emit 都读文件

    def emit(self, event_type: str, payload: dict | None = None) -> None:
        entry = {
            "ts": now_iso(),
            "type": event_type,
            **(payload or {}),
        }
        self._path.parent.mkdir(parents=True, exist_ok=True)
        with open(self._path, "a") as f:
            f.write(json.dumps(entry, ensure_ascii=False) + "\n")
        self._emit_count += 1
        if self._emit_count % self.ROTATE_CHECK_EVERY == 0:
            self._maybe_rotate()

    def _maybe_rotate(self) -> None:
        """原子轮转：先写临时文件，再 os.replace。"""
        if not self._path.exists():
            return
        try:
            with open(self._path, "r", encoding="utf-8", errors="replace") as f:
                lines = f.readlines()
            if len(lines) <= self._max_lines:
                return

            keep_count = self._max_lines // 2
            kept_lines = lines[-keep_count:] if len(lines) > keep_count else lines

            fd, tmp_path = tempfile.mkstemp(dir=self._path.parent, suffix=".tmp")
            os.close(fd)

            try:
                with open(tmp_path, "w", encoding="utf-8") as f:
                    f.writelines(kept_lines)
                os.replace(tmp_path, self._path)
                logger.info("rotated event log %s, kept %d/%d lines", self._path, len(kept_lines), len(lines))
            except Exception:
                with contextlib.suppress(Exception):
                    os.unlink(tmp_path)
                raise
        except OSError:
            pass