"""Lambda handler — posts the weekly on-call schedule and previous week's pay summary
to Slack every Monday at 7am ET."""

import logging
import os
from datetime import datetime, timedelta
from zoneinfo import ZoneInfo

import boto3
from slack_sdk import WebClient

from src.blocks import build_pay_summary_blocks, build_week_schedule
from src.schedule import ShiftSchedule

logger = logging.getLogger()
logger.setLevel(logging.INFO)

EASTERN = ZoneInfo("America/New_York")

DAY_ORDER = ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"]


def _calculate_weekly_pay(schedule: ShiftSchedule, week_start: datetime) -> dict:
    """Calculate pay for a Mon–Sun week. Returns pay record dict."""
    rate = schedule.get_shift_rate()
    breakdown = []
    totals = {}

    for i in range(7):
        date = week_start + timedelta(days=i)
        date_str = date.strftime("%Y-%m-%d")
        day_name = DAY_ORDER[i]
        ext, name, source = schedule.resolve_shift(date_str, day_name)

        if source == "available":
            continue

        breakdown.append({
            "date": date_str,
            "date_label": date.strftime("%b %-d"),
            "day": day_name[:3],
            "name": name,
            "extension": ext,
            "rate": rate,
        })

        if name not in totals:
            totals[name] = {"shifts": 0, "total": 0.0, "extension": ext}
        totals[name]["shifts"] += 1
        totals[name]["total"] += rate

    return {
        "week_start": week_start.strftime("%Y-%m-%d"),
        "rate": str(rate),
        "breakdown": breakdown,
        "totals": totals,
    }


def handler(event, context):
    now = datetime.now(EASTERN)

    # DST guard — same pattern as the 3CX scheduler
    if now.hour != 7:
        logger.info("ET hour is %d, not 7am — skipping (wrong DST rule fired)", now.hour)
        return {"skipped": True}

    ssm = boto3.client("ssm")
    bot_token = ssm.get_parameter(
        Name=os.environ["SLACK_BOT_TOKEN_PARAM"], WithDecryption=True
    )["Parameter"]["Value"]
    channel_id = ssm.get_parameter(
        Name=os.environ["SHIFT_CHANNEL_PARAM"], WithDecryption=True
    )["Parameter"]["Value"]

    schedule = ShiftSchedule()
    slack = WebClient(token=bot_token)

    # --- Previous week's pay summary ---
    prev_monday = now - timedelta(days=7)
    prev_monday = prev_monday.replace(hour=0, minute=0, second=0, microsecond=0)
    pay_record = _calculate_weekly_pay(schedule, prev_monday)

    if pay_record["breakdown"]:
        week_key = prev_monday.strftime("%Y-%m-%d")
        schedule.save_pay_record(week_key, pay_record)

        prev_sunday = prev_monday + timedelta(days=6)
        week_label = f"{prev_monday.strftime('%b %-d')} to {prev_sunday.strftime('%b %-d')}"
        pay_blocks = build_pay_summary_blocks(
            week_label, pay_record["breakdown"], pay_record["totals"], float(pay_record["rate"])
        )
        slack.chat_postMessage(
            channel=channel_id,
            blocks=pay_blocks,
            text=f"After-Hours Pay — {week_label}",
        )
        logger.info("Posted pay summary for week of %s", week_key)

    # --- Two-week schedule ---
    blocks = build_week_schedule(schedule, start_date=now)

    end_date = now + timedelta(days=13)
    slack.chat_postMessage(
        channel=channel_id,
        blocks=blocks,
        text=f"After-Hours Schedule — {now.strftime('%b %-d')} to {end_date.strftime('%b %-d')}",
    )

    logger.info("Posted weekly schedule to channel %s", channel_id)
    return {"posted": True, "channel": channel_id, "pay_calculated": bool(pay_record["breakdown"])}