"""
Simple run-scoped logger for the template generator.

The log file under logs/ is erased and recreated at the start of every run
(see reset_log()) so it only ever reflects the most recent generation.
"""

import datetime
import os

ROOT_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
LOGS_DIR = os.path.join(ROOT_DIR, "logs")
LOG_FILE = os.path.join(LOGS_DIR, "template_generator.log")

_log_path = None


def reset_log():
    """Erases any previous log and starts a fresh one for this run."""
    global _log_path
    os.makedirs(LOGS_DIR, exist_ok=True)
    _log_path = LOG_FILE
    with open(_log_path, "w", encoding="utf-8") as f:
        f.write(f"Timetable generation log - started {datetime.datetime.now().isoformat()}\n")
        f.write("=" * 80 + "\n")
    return _log_path


def log_error(message):
    """Appends an ERROR line to the current run's log file and prints it."""
    _write("ERROR", message)


def log_warning(message):
    _write("WARNING", message)


def log_info(message):
    _write("INFO", message)


def _write(level, message):
    global _log_path
    if _log_path is None:
        os.makedirs(LOGS_DIR, exist_ok=True)
        _log_path = LOG_FILE
        if not os.path.exists(_log_path):
            # First-ever write with no prior reset_log() call in this
            # process (e.g. a phase_N command run without a preceding
            # clear_all): create the file fresh, but never truncate an
            # existing log — separate process invocations of phase_1/2/3
            # must all append to the same ongoing log.
            with open(_log_path, "w", encoding="utf-8") as f:
                f.write(f"Timetable generation log - started {datetime.datetime.now().isoformat()}\n")
                f.write("=" * 80 + "\n")
    line = f"[{datetime.datetime.now().strftime('%H:%M:%S')}] {level}: {message}"
    with open(_log_path, "a", encoding="utf-8") as f:
        f.write(line + "\n")
    print(line)