"""Lambda handler — syncs the DynamoDB roster from 3CX group members.

Runs daily via EventBridge. Pulls members from the configured 3CX group,
filters to Extension type only (excludes RingGroups, IVRs, Voicemail, etc.),
and syncs to DynamoDB. Preserves existing slack_user_id links.
"""

import logging
import os
from datetime import datetime
from zoneinfo import ZoneInfo

import boto3

from src.three_cx_client import ThreeCXClient
from src.schedule import ShiftSchedule

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

EASTERN = ZoneInfo("America/New_York")

# System extensions to exclude from roster sync
EXCLUDE_NAMES = {"Voicemail", "IVR", "Fax"}


def get_3cx_credentials() -> dict:
    ssm = boto3.client("ssm")
    prefix = os.environ.get("TCX_SSM_PREFIX", "/3cx-scheduler")
    params = ssm.get_parameters_by_path(Path=prefix, WithDecryption=True)
    creds = {}
    for p in params["Parameters"]:
        key = p["Name"].split("/")[-1]
        creds[key] = p["Value"]
    return creds


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

    # DST guard — two EventBridge rules fire, only one is at 6am ET
    force = event.get("force", False)
    if not force and now.hour != 6:
        logger.info("ET hour is %d, not 6am — skipping (wrong DST rule fired)", now.hour)
        return {"skipped": True}

    group_name = os.environ.get("SYNC_GROUP", "DEFAULT")

    logger.info("Starting roster sync from 3CX group '%s' at %s", group_name, now.isoformat())

    creds = get_3cx_credentials()
    client = ThreeCXClient(
        domain=creds["domain"],
        auth_mode="oauth",
        client_id=creds["client_id"],
        client_secret=creds["client_secret"],
    )

    members = client.get_group_members(group_name)
    # Only sync actual phone extensions, not ring groups, IVRs, etc.
    extensions = [
        m for m in members
        if m.get("Type") == "Extension" and m.get("MemberName") not in EXCLUDE_NAMES
    ]
    logger.info("Found %d extensions in 3CX group '%s' (filtered from %d members)", len(extensions), group_name, len(members))

    schedule = ShiftSchedule()
    current_roster = {item["SK"]: item for item in schedule.get_roster()}

    threecx_extensions = set()
    added = []
    updated = []

    for ext in extensions:
        number = str(ext.get("Number", ""))
        name = ext.get("MemberName", "").strip()

        if not number or not name:
            continue

        threecx_extensions.add(number)
        existing = current_roster.get(number)

        if existing:
            if existing.get("name") != name:
                schedule.table.update_item(
                    Key={"PK": "ROSTER", "SK": number},
                    UpdateExpression="SET #n = :name",
                    ExpressionAttributeNames={"#n": "name"},
                    ExpressionAttributeValues={":name": name},
                )
                updated.append(f"Ext {number}: {existing['name']} -> {name}")
        else:
            schedule.table.put_item(
                Item={
                    "PK": "ROSTER",
                    "SK": number,
                    "name": name,
                    "extension": number,
                    "slack_user_id": "",
                }
            )
            added.append(f"Ext {number}: {name}")

    removed = []
    # Only remove departed employees if we got results from 3CX
    # (prevents wiping roster on API errors or misconfigured group)
    if threecx_extensions:
        for ext_number, item in current_roster.items():
            if ext_number not in threecx_extensions:
                schedule.table.delete_item(Key={"PK": "ROSTER", "SK": ext_number})
                removed.append(f"Ext {ext_number}: {item.get('name', 'Unknown')}")
    elif current_roster:
        logger.warning("No 3CX extensions found but roster is non-empty — skipping removal to prevent data loss")

    result = {
        "group": group_name,
        "total_3cx": len(threecx_extensions),
        "added": added,
        "updated": updated,
        "removed": removed,
    }
    logger.info("Roster sync complete: %s", result)
    return result