"""
Email processor Lambda.

Triggered by S3 events when SES delivers an email.
Parses the raw email, sends it to Claude for structured extraction,
then writes the result to DynamoDB.
"""

import email
import json
import logging
import os
import re
from datetime import datetime
from email import policy

import anthropic
import boto3

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

s3 = boto3.client("s3")
dynamodb = boto3.resource("dynamodb")

WORK_ORDERS_TABLE = os.environ.get("WORK_ORDERS_TABLE", "WorkOrders")
COMMENTS_TABLE = os.environ.get("COMMENTS_TABLE", "WorkOrderComments")
ANTHROPIC_API_KEY_SECRET_ARN = os.environ.get("ANTHROPIC_API_KEY_SECRET_ARN")

EXTRACTION_PROMPT = """\
You are an email parser for a facilities maintenance work order system.
The emails come from Amazon's APM system (via Hexagon EAM / HxGN SmartCloud).

Analyze the following email and extract structured data. Return ONLY valid JSON with these fields:

{
  "email_type": "new_work_order" | "update" | "comment" | "cancellation",
  "work_order_id": "string or null",
  "description": "work order description or null",
  "status": "new" | "assigned" | "in_progress" | "on_hold" | "completed" | "cancelled" | "unknown",
  "site_code": "building/site code like WIL1, ZDL8, etc. or null",
  "building": "full building identifier or null",
  "address": "physical address or null",
  "severity": "severity level or null",
  "priority": "priority level or null",
  "date_reported": "ISO 8601 date or null",
  "scheduled_start": "ISO 8601 date or null",
  "due_date": "ISO 8601 date or null",
  "assigned_to": "person/team assigned or null",
  "commenter": "person who left a comment or null",
  "comment_text": "the comment text or null",
  "comment_time": "ISO 8601 datetime of the comment or null"
}

Rules:
- "email_type" detection:
  - "new_work_order": email announces a new WO assignment
  - "comment": email contains a new comment on an existing WO
  - "cancellation": email announces a WO has been cancelled
  - "update": any other update to an existing WO (status change, reassignment, etc.)
- Extract the site_code from the building field (e.g., "WIL1" from "building WIL1")
- Dates should be converted to ISO 8601 format
- If a field is not present in the email, set it to null
- Do NOT invent or infer data that is not explicitly in the email
"""


def get_anthropic_client() -> anthropic.Anthropic:
    """Create Anthropic client, fetching API key from Secrets Manager.

    Requires ANTHROPIC_API_KEY_SECRET_ARN to be set. The previous silent
    fallback to a plaintext ANTHROPIC_API_KEY env var is removed: a misconfigured
    deploy must fail loudly rather than quietly run on an unmanaged key.
    """
    if not ANTHROPIC_API_KEY_SECRET_ARN:
        raise RuntimeError(
            "ANTHROPIC_API_KEY_SECRET_ARN is not set; refusing to fall back to a "
            "plaintext API key. Configure the Secrets Manager ARN."
        )
    secrets = boto3.client("secretsmanager")
    secret = secrets.get_secret_value(SecretId=ANTHROPIC_API_KEY_SECRET_ARN)
    api_key = secret["SecretString"]
    return anthropic.Anthropic(api_key=api_key)


def parse_raw_email(raw_bytes: bytes) -> dict:
    """Parse a raw email into subject, sender, body text."""
    msg = email.message_from_bytes(raw_bytes, policy=policy.default)

    subject = msg.get("Subject", "")
    sender = msg.get("From", "")
    to = msg.get("To", "")
    cc = msg.get("Cc", "")
    date = msg.get("Date", "")

    body = ""
    if msg.is_multipart():
        for part in msg.walk():
            content_type = part.get_content_type()
            if content_type == "text/plain":
                body = part.get_content()
                break
            elif content_type == "text/html" and not body:
                body = part.get_content()
    else:
        body = msg.get_content()

    return {
        "subject": subject,
        "sender": sender,
        "to": to,
        "cc": cc,
        "date": date,
        "body": body,
    }


def extract_with_claude(email_data: dict) -> dict:
    """Send parsed email to Claude for structured extraction."""
    client = get_anthropic_client()

    email_text = (
        f"Subject: {email_data['subject']}\n"
        f"From: {email_data['sender']}\n"
        f"To: {email_data['to']}\n"
        f"CC: {email_data['cc']}\n"
        f"Date: {email_data['date']}\n"
        f"\n---\n\n"
        f"{email_data['body']}"
    )

    response = client.messages.create(
        model="claude-haiku-4-5-20251001",
        max_tokens=1024,
        messages=[
            {
                "role": "user",
                "content": f"{EXTRACTION_PROMPT}\n\nEMAIL:\n{email_text}",
            }
        ],
    )

    response_text = response.content[0].text

    # Extract JSON from response (handle markdown code blocks)
    json_match = re.search(r"```(?:json)?\s*(.*?)```", response_text, re.DOTALL)
    if json_match:
        response_text = json_match.group(1)

    return json.loads(response_text.strip())


def save_work_order(parsed: dict, s3_key: str):
    """Create or update a work order in DynamoDB."""
    table = dynamodb.Table(WORK_ORDERS_TABLE)
    work_order_id = parsed["work_order_id"]
    now = datetime.utcnow().isoformat()

    # Build update expression dynamically from non-null fields
    field_map = {
        "description": "description",
        "status": "wo_status",  # 'status' is a DynamoDB reserved word
        "site_code": "site_code",
        "building": "building",
        "address": "address",
        "severity": "severity",
        "priority": "priority",
        "date_reported": "date_reported",
        "scheduled_start": "scheduled_start",
        "due_date": "due_date",
        "assigned_to": "assigned_to",
    }

    update_parts = ["#updated_at = :updated_at", "#source_key = :source_key"]
    attr_names = {
        "#updated_at": "updated_at",
        "#source_key": "source_email_s3_key",
    }
    attr_values = {
        ":updated_at": now,
        ":source_key": s3_key,
    }

    for src_field, dynamo_field in field_map.items():
        value = parsed.get(src_field)
        if value is not None:
            placeholder = f":{dynamo_field}"
            name_placeholder = f"#{dynamo_field}"
            update_parts.append(f"{name_placeholder} = {placeholder}")
            attr_names[name_placeholder] = dynamo_field
            attr_values[placeholder] = value

    # For new items, set created_at
    update_parts.append("#created_at = if_not_exists(#created_at, :created_at)")
    attr_names["#created_at"] = "created_at"
    attr_values[":created_at"] = now

    # Customer is always AMAZON for now
    update_parts.append("#customer = :customer")
    attr_names["#customer"] = "customer"
    attr_values[":customer"] = "AMAZON"

    # Track the record type (new_work_order, update, comment)
    email_type = parsed.get("email_type")
    if email_type:
        update_parts.append("#record_type = :record_type")
        attr_names["#record_type"] = "record_type"
        attr_values[":record_type"] = email_type

    table.update_item(
        Key={"work_order_id": work_order_id},
        UpdateExpression="SET " + ", ".join(update_parts),
        ExpressionAttributeNames=attr_names,
        ExpressionAttributeValues=attr_values,
    )

    logger.info(f"Saved work order {work_order_id}")


def save_event(parsed: dict, s3_key: str):
    """Save an event to the events table. Every email creates an event entry."""
    table = dynamodb.Table(COMMENTS_TABLE)

    work_order_id = parsed["work_order_id"]
    email_type = parsed.get("email_type", "unknown")
    event_time = parsed.get("comment_time") or datetime.utcnow().isoformat()
    event_id = f"{work_order_id}#{event_time}"

    item = {
        "work_order_id": work_order_id,
        "comment_id": event_id,  # keeping key name for table compatibility
        "record_type": email_type,
        "commenter": parsed.get("commenter") or "",
        "text": parsed.get("comment_text") or "",
        "created_at": event_time,
        "source_email_s3_key": s3_key,
        "ingested_at": datetime.utcnow().isoformat(),
    }

    table.put_item(Item=item)
    logger.info(f"Saved event {event_id} (type={email_type})")


def handler(event, context):
    """Lambda entry point. Triggered by S3 ObjectCreated events."""
    for record in event.get("Records", []):
        bucket = record["s3"]["bucket"]["name"]
        key = record["s3"]["object"]["key"]

        logger.info(f"Processing email: s3://{bucket}/{key}")

        # Fetch raw email from S3
        response = s3.get_object(Bucket=bucket, Key=key)
        raw_email = response["Body"].read()

        # Parse the raw email
        email_data = parse_raw_email(raw_email)
        logger.info(f"Subject: {email_data['subject']}")

        # Extract structured data with Claude
        parsed = extract_with_claude(email_data)
        logger.info(
            f"Parsed: type={parsed.get('email_type')}, wo={parsed.get('work_order_id')}"
        )

        if not parsed.get("work_order_id"):
            logger.warning(f"No work order ID found in email, skipping: {key}")
            continue

        s3_key = f"s3://{bucket}/{key}"

        # Always upsert the work order with any new info
        save_work_order(parsed, s3_key)

        # Save every email as an event for history tracking
        save_event(parsed, s3_key)

    return {"statusCode": 200, "body": "OK"}