from typing import Optional
from apscheduler.schedulers.background import BackgroundScheduler
from apscheduler.triggers.cron import CronTrigger
from apscheduler.triggers.base import BaseTrigger
from app.utils.config import server_config
from app.utils.logger import logger
from app.utils.watcher import watcher_manager
from app.utils.sync_manager import sync_manager
import os

# Initialize the scheduler
scheduler = BackgroundScheduler()

def validate_cron_expression(expression: str) -> bool:
    """
    Validates a cron expression.
    Expected format: "minute hour day month day_of_week"
    """
    try:
        parts = expression.split()
        if len(parts) != 5:
            return False
        # Try to create a trigger to validate
        CronTrigger(
            minute=parts[0],
            hour=parts[1],
            day=parts[2],
            month=parts[3],
            day_of_week=parts[4]
        )
        return True
    except Exception:
        return False

def job_function():
    """
    The function to be executed by the scheduler.
    Triggers the sync process.
    """
    logger.info("Executing scheduled sync job...")
    try:
        sync_manager.run_sync(trigger_source="scheduler", wait=False)
    except Exception as e:
        logger.error(f"Error during scheduled sync job: {e}", exc_info=True)

def start_scheduler():
    """
    Starts the background scheduler if it's not already running.
    """
    if not scheduler.running:
        scheduler.start()
        logger.info("Scheduler started.")
    update_scheduler_job()

def _create_cron_trigger(cron_exp: str) -> Optional[CronTrigger]:
    """Helper to create a CronTrigger from a cron expression string."""
    try:
        # 5 parts: minute hour day month day_of_week
        parts = cron_exp.split()
        if len(parts) == 5:
            return CronTrigger(
                minute=parts[0],
                hour=parts[1],
                day=parts[2],
                month=parts[3],
                day_of_week=parts[4]
            )
        else:
            logger.error(f"Invalid cron expression format (needs 5 parts): {cron_exp}")
    except Exception as e:
        logger.error(f"Invalid cron expression: {cron_exp}, error: {e}")
    return None

def _create_daily_trigger(time_str: str) -> Optional[CronTrigger]:
    """Helper to create a CronTrigger for daily execution at a specific time."""
    try:
        hour, minute = map(int, time_str.split(':'))
        return CronTrigger(hour=hour, minute=minute)
    except ValueError:
        logger.error(f"Invalid daily time format: {time_str}")
    return None

def _create_weekly_trigger(days: list[int], time_str: str) -> Optional[CronTrigger]:
    """
    Helper to create a CronTrigger for weekly execution.
    days: List of integers 0-6 where 0 is Sunday, 1 is Monday, ..., 6 is Saturday.
    APScheduler expects: 0 = Monday, ..., 6 = Sunday.
    """
    # Convert Frontend days (0=Sun...6=Sat) to APScheduler days (0=Mon...6=Sun)
    aps_days = []
    for d in days:
        if d == 0: 
            aps_days.append(6) # Sunday
        else: 
            aps_days.append(d - 1) # Mon(1)->0, ..., Sat(6)->5
            
    days_str = ",".join(map(str, aps_days))
    
    try:
        hour, minute = map(int, time_str.split(':'))
        return CronTrigger(day_of_week=days_str, hour=hour, minute=minute)
    except ValueError:
        logger.error(f"Invalid weekly time format: {time_str}")
    return None

def update_scheduler_job():
    """
    Updates the scheduler jobs based on the current configuration.
    Reloads configuration, handles auto-watch, and sets up the sync job trigger.
    """
    scheduler.remove_all_jobs()
    
    # Reload config to get latest schedule settings
    server_config.load()
    logger.info("Configuration reloaded for scheduler update.")

    # Handle Auto Watch
    if server_config.schedule_auto_watch:
        # Ensure we have an absolute path
        local_path = os.path.abspath(server_config.local_path)
        watcher_manager.start(local_path)
        logger.info(f"Auto-watch started for path: {local_path}")
    else:
        watcher_manager.stop()
        logger.info("Auto-watch stopped.")

    mode = server_config.schedule_mode
    logger.info(f"Updating scheduler with mode: {mode}")
    
    if mode == "DISABLED":
        logger.info("Schedule is disabled. No jobs added.")
        return

    trigger: Optional[BaseTrigger] = None
    
    if mode == "CRON":
        trigger = _create_cron_trigger(server_config.schedule_cron)

    elif mode == "DAILY":
        trigger = _create_daily_trigger(server_config.schedule_daily_time)

    elif mode == "WEEKLY":
        trigger = _create_weekly_trigger(server_config.schedule_weekly_days, server_config.schedule_weekly_time)

    if trigger:
        scheduler.add_job(job_function, trigger)
        logger.info(f"Added scheduled job with mode '{mode}' and trigger: {trigger}")
    else:
        logger.warning(f"Failed to create trigger for mode '{mode}'. No job added.")

def get_next_run_time():
    """
    Returns the next run time of the scheduled job, if any.
    """
    jobs = scheduler.get_jobs()
    if not jobs:
        return None
    # Assuming only one job is scheduled for sync
    job = jobs[0]
    return job.next_run_time