"""读取日志文件末尾 N 行（v1.1.18）。

按 level 过滤：默认 INFO+。适用于 RotatingFileHandler 落地的日志文件。
"""

from __future__ import annotations

import os
from pathlib import Path

from util.runtime_paths import get_logs_dir


DEFAULT_TAIL = 200
_LEVEL_ORDER = {
    "DEBUG": 10, "INFO": 20, "WARNING": 30, "ERROR": 40, "CRITICAL": 50,
}


def _resolve_log_path() -> Path:
    """解析日志文件路径。

    优先级：
      1. LOG_FILE env（绝对路径直接用，相对路径走 get_logs_dir()）
      2. 默认 get_logs_dir() / LOG_FILE_DEFAULT_NAME
    """
    raw = os.environ.get("LOG_FILE", "")
    if raw:
        p = Path(raw)
        if not p.is_absolute():
            p = get_logs_dir() / raw
        return p
    from util.constants import LOG_FILE_DEFAULT_NAME
    return get_logs_dir() / LOG_FILE_DEFAULT_NAME


def tail_log_file(tail: int = DEFAULT_TAIL, min_level: str = "INFO") -> dict:
    """读日志文件末尾 tail 行，过滤 level >= min_level。

    Returns:
        {
            "log_file": str,
            "exists": bool,
            "total_lines": int,
            "returned_lines": int,
            "lines": [str, ...],
            "min_level": str,
        }
    """
    log_path = _resolve_log_path()
    if not log_path.exists():
        return {
            "log_file": str(log_path),
            "exists": False,
            "total_lines": 0,
            "returned_lines": 0,
            "lines": [],
            "min_level": min_level,
        }

    text = log_path.read_text(encoding="utf-8", errors="replace")
    all_lines = text.splitlines()
    last_n = all_lines[-tail:] if tail > 0 else all_lines
    threshold = _LEVEL_ORDER.get(min_level.upper(), 20)

    filtered: list[str] = []
    for line in last_n:
        # 格式: "2026-09-15 12:34:56 [alert-contract-expiring-hr] INFO message"
        # 取第 4 个 token (INFO/DEBUG/...)
        parts = line.split()
        if len(parts) >= 4 and parts[1].count(":") >= 2 and parts[3] in _LEVEL_ORDER:
            line_level = parts[3]
            if _LEVEL_ORDER.get(line_level, 0) >= threshold:
                filtered.append(line)
        else:
            # 非标准行 / 解析不到 level：保留
            filtered.append(line)

    return {
        "log_file": str(log_path),
        "exists": True,
        "total_lines": len(all_lines),
        "returned_lines": len(filtered),
        "lines": filtered,
        "min_level": min_level,
    }