"""
Centralised application logging for DBClient.

Call ``setup_logging()`` once at startup (in main.py).
Then anywhere in the codebase:

    from app.utils.logger import get_logger
    log = get_logger(__name__)
    log.info("Connected to %s", host)
    log.error("Query failed", exc_info=True)   # includes full traceback

Log files are written to  ~/.dbclient/logs/dbclient.log
with daily rotation, keeping the last 7 files.

The module also installs:
  • sys.excepthook  — logs every uncaught exception with full traceback
  • threading.excepthook — logs uncaught exceptions in background threads
"""
from __future__ import annotations

import logging
import logging.handlers
import os
import sys
import threading
import traceback
from pathlib import Path

# ── Constants ─────────────────────────────────────────────────────────────────

APP_DIR  = Path.home() / ".dbclient"
LOG_DIR  = APP_DIR / "logs"
LOG_FILE = LOG_DIR / "dbclient.log"

# File: DEBUG and above  |  Console: WARNING and above
FILE_LEVEL    = logging.DEBUG
CONSOLE_LEVEL = logging.WARNING

# Rotate at midnight, keep 7 days of log files
BACKUP_COUNT = 7

LOG_FORMAT = (
    "[%(asctime)s] [%(levelname)-8s] [%(name)s:%(lineno)d]  %(message)s"
)
DATE_FORMAT = "%Y-%m-%d %H:%M:%S"

# ── Public helpers ────────────────────────────────────────────────────────────

def get_logger(name: str) -> logging.Logger:
    """Return a module-level logger.  Always call as ``get_logger(__name__)``."""
    return logging.getLogger(name)


def get_log_path() -> Path:
    """Return the absolute path of the current log file."""
    return LOG_FILE


# ── Setup ─────────────────────────────────────────────────────────────────────

def setup_logging(level: int = FILE_LEVEL) -> None:
    """
    Initialise the root logger.  Safe to call multiple times (idempotent).

    Parameters
    ----------
    level : int
        Minimum level written to the log file (default: DEBUG).
        The console handler always uses WARNING regardless of this setting.
    """
    LOG_DIR.mkdir(parents=True, exist_ok=True)

    root = logging.getLogger()
    if root.handlers:
        # Already configured — nothing to do
        return

    root.setLevel(logging.DEBUG)

    fmt = logging.Formatter(LOG_FORMAT, datefmt=DATE_FORMAT)

    # ── Rotating file handler (midnight rollover, 7-day retention) ────────────
    try:
        fh = logging.handlers.TimedRotatingFileHandler(
            str(LOG_FILE),
            when="midnight",
            backupCount=BACKUP_COUNT,
            encoding="utf-8",
            delay=False,
        )
        fh.setLevel(level)
        fh.setFormatter(fmt)
        root.addHandler(fh)
    except OSError as exc:
        # Can't write logs — at least print a warning
        print(f"[DBClient] WARNING: Could not open log file {LOG_FILE}: {exc}",
              file=sys.stderr)

    # ── Console handler (WARNING+ only, for developers) ───────────────────────
    ch = logging.StreamHandler(sys.stderr)
    ch.setLevel(CONSOLE_LEVEL)
    ch.setFormatter(fmt)
    root.addHandler(ch)

    # ── Silence noisy third-party libraries ───────────────────────────────────
    for noisy in ("pymysql", "psycopg2", "pyodbc", "urllib3", "PIL"):
        logging.getLogger(noisy).setLevel(logging.WARNING)

    _install_exception_hooks()

    log = get_logger(__name__)
    log.info("=" * 60)
    log.info("DBClient started  (Python %s)", sys.version.split()[0])
    log.info("Log file: %s", LOG_FILE)


# ── Unhandled exception hooks ─────────────────────────────────────────────────

def _install_exception_hooks() -> None:
    """Capture all uncaught exceptions — both in the main thread and workers."""
    _log = get_logger("dbclient.uncaught")

    # Main thread
    def _excepthook(exc_type, exc_value, exc_tb):
        if issubclass(exc_type, KeyboardInterrupt):
            sys.__excepthook__(exc_type, exc_value, exc_tb)
            return
        _log.critical(
            "Uncaught exception:\n%s",
            "".join(traceback.format_exception(exc_type, exc_value, exc_tb)),
        )
        # Still let Qt/Python print it to stderr so the developer sees it live
        sys.__excepthook__(exc_type, exc_value, exc_tb)

    sys.excepthook = _excepthook

    # Background threads (Python 3.8+)
    def _thread_excepthook(args):
        if args.exc_type is SystemExit:
            return
        _log.critical(
            "Uncaught exception in thread '%s':\n%s",
            getattr(args.thread, "name", "?"),
            "".join(traceback.format_exception(
                args.exc_type, args.exc_value, args.exc_tb
            )),
        )

    threading.excepthook = _thread_excepthook


# ── Qt message handler ─────────────────────────────────────────────────────────

def install_qt_message_handler() -> None:
    """
    Route Qt's own warning/critical messages into the Python log.
    Call AFTER QApplication is created.
    """
    try:
        from PyQt6.QtCore import qInstallMessageHandler, QtMsgType

        _log = get_logger("Qt")
        _level_map = {
            QtMsgType.QtDebugMsg:    logging.DEBUG,
            QtMsgType.QtInfoMsg:     logging.INFO,
            QtMsgType.QtWarningMsg:  logging.WARNING,
            QtMsgType.QtCriticalMsg: logging.ERROR,
            QtMsgType.QtFatalMsg:    logging.CRITICAL,
        }

        def _handler(msg_type, context, message):
            lvl = _level_map.get(msg_type, logging.WARNING)
            loc = ""
            if context.file:
                loc = f" [{context.file}:{context.line}]"
            _log.log(lvl, "%s%s", message, loc)

        qInstallMessageHandler(_handler)
    except Exception:
        pass  # Non-fatal — Qt messages just won't be logged