"""
PO email processor Lambda.

Triggered by S3 events when SES delivers a Coupa PO email.
Parses the raw email, sends it to Claude for structured extraction,
then writes the result to the purchase-orders DynamoDB table.
"""

import email
import email.utils
import json
import logging
import os
import re
from datetime import datetime
from decimal import Decimal
from email import policy

import anthropic
import boto3

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

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

PO_TABLE = os.environ.get("PO_TABLE", "purchase-orders")
ANTHROPIC_API_KEY_SECRET_ARN = os.environ.get("ANTHROPIC_API_KEY_SECRET_ARN")

# Allowlist of sender domains permitted to create/modify POs. Coupa sends Amazon
# procurement notifications from the coupahost.com family; the leading dot means
# "this domain or any subdomain". Override via the ALLOWED_SENDER_DOMAINS env var
# (comma-separated) without a redeploy of code. An attacker who can email
# amazon_po@int.seahaven.com but cannot forge a verified sender in this list is
# rejected before any DynamoDB write.
DEFAULT_ALLOWED_SENDER_DOMAINS = "coupahost.com,amazon.com"
ALLOWED_SENDER_DOMAINS = [
    d.strip().lower().lstrip("@")
    for d in os.environ.get(
        "ALLOWED_SENDER_DOMAINS", DEFAULT_ALLOWED_SENDER_DOMAINS
    ).split(",")
    if d.strip()
]

EXTRACTION_PROMPT = """\
You are an email parser for a purchase order ingest pipeline.
The emails are Coupa procurement platform notifications containing purchase order
data from Amazon.

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

{
  "email_type": "new_po" | "revision" | "cancellation",
  "po_number": "string or null",
  "po_status": "string or null",
  "source_system": "coupa",
  "submitted_by": "string or null",
  "on_behalf_of": "string or null",
  "order_date": "string or null",
  "revision_date": "string or null",
  "last_opened": "string or null",
  "acknowledged_at": "string or null",
  "payment_terms": "string or null",
  "requisition_number": "string or null",
  "department": "string or null",
  "view_order_url": "URL string or null",
  "supplier": {
    "name": "string or null"
  },
  "site_code": "string or null",
  "ship_to": {
    "name": "string or null",
    "address": "string or null",
    "street": "string or null",
    "city": "string or null",
    "state": "string or null",
    "zip": "string or null",
    "location_code": "string or null",
    "attn": "string or null"
  },
  "total_amount": 0.0,
  "currency": "USD",
  "fiscal_year": "string or null",
  "trade": "string or null",
  "coupa_category": "string or null",
  "line_items": [
    {
      "description": "string",
      "amount": 0.0,
      "currency": "USD",
      "need_by": "date string or null",
      "category": "string or null",
      "account_code": "string or null",
      "period": "string or null",
      "quantity": "string or null",
      "unit": "string or null",
      "price": "string or null"
    }
  ]
}

## email_type detection

- "new_po": email announces a new purchase order being issued
- "revision": email announces a revised/updated purchase order (look for "revised" in subject or body)
- "cancellation": email announces a PO has been cancelled

## PO number

Extract from the email subject or body. Format is a prefix + hyphen + digits:
- "2D-18206023", "FK-21088051", "B187-17955555"

## site_code extraction

The site code is the Amazon facility code — a 3-5 character alphanumeric code identifying
the delivery site. Check these locations in order:

1. Ship-to name in parentheses: "Amazon.com Services LLC (KLAL)" → KLAL
2. Ship-to name after dash: "Amazon.com Services LLC - SNY5" → SNY5
3. Ship-to ATTN line with dash or en-dash: "ATTN: Wagon Wheel DS Station –WKY3" → WKY3
4. Ship-to ATTN line directly: "Attn: HJX1" → HJX1
5. Ship-to name IS the code: if the name is just "DBU2" or similar, use it
6. Line item description prefix: "DYO1 - Sea Haven Ind - Plumbing Repairs" → DYO1
7. Line item description in brackets: "[HMK4] Assemble 3 Wire Security Cages" → HMK4

**Not site codes — do not extract these as site_code:**
- RME (Amazon Reliability Maintenance Engineering department)
- BBM (Coupa description format tag)
- JLL (Jones Lang LaSalle — facilities management vendor)
- PARAG, ERIK (vendor/person names)
- Industry acronyms: HVAC, LED, PVC, ADA, OSHA, EMR, BMS, DDC, MRO, NTE, EST

If the only candidate matches this skip list, set site_code to null.

## Ship-to address parsing

Parse the full address into separate fields. Be aware of these common issues:
- State abbreviation may be missing entirely (e.g., "Tucson, 85704" with no state)
- Zip codes may lack leading zeros (e.g., "MA 2149" should be zip "02149", "NJ 7001" should be "07001")
- City names may be misspelled (e.g., "Charoltte" for Charlotte) — extract as-is, do not correct
- Format varies: "City, ST - ZIP", "City, ST ZIP", "City, ZIP" (no state)

If state cannot be determined from the address, set ship_to.state to null.

## fiscal_year

The calendar year the work covers. Determine from:
1. The order_date year (primary source)
2. Need-by dates on line items
3. Year in line item descriptions (e.g., "HVB2 - 2025 - Plumbing PM" → "2025")

Use the 4-digit year string (e.g., "2025").

## trade classification

Classify the primary trade from line item descriptions. Use the FIRST match in priority order:

**Plumbing - PM**: "plumbing pm", "plumbing preventative", "plumbing maintenance",
  or BBM format: "Plumbing - Backflow", "Plumbing - Water Heater - Install/Repair"

**Plumbing - Reactive**: "plumbing" with: "reactive", "emergency", "repair", "clog",
  "unclog", "leak", "flood", "sewer", "drain", "grease trap", "jetter", "water line",
  "toilet", "faucet", "urinal", "pipe"

**Electrical**: "electrical", "lighting", "ballast", "outlet", "circuit", "panel",
  "generator", "transformer", "conduit" (but NOT if "dock door" context)

**HVAC**: "hvac", "heating", "cooling", "air conditioning", "RTU", "AHU", "VAV",
  "refrigerant", "thermostat", "ductwork"

**Dock Doors**: "dock door", "dock leveler", "dock plate", "dock seal", "dock bumper"

**Doors**: "door", "overhead door", "roll-up", "automatic door", "access door"
  (only if not matched by Dock Doors above)

**Signage**: "sign", "banner", "wayfinding", "marquee", "directional"

**Carpentry**: "carpentry", "cabinet", "millwork", "trim", "shelving", "framing"

**Fencing/Gates**: "fence", "fencing", "gate", "bollard" (not "dock gate")

**Conveyance/MHE**: "conveyor", "MHE", "material handling", "sortation"

**Painting**: "paint", "painting", "primer", "coating", "touch-up"

**Flooring**: "floor", "tile", "carpet", "epoxy", "polishing"

**Janitorial**: "janitorial", "cleaning", "custodial", "pressure wash", "power wash"

**Fire/Life Safety**: "fire", "sprinkler", "extinguisher", "fire alarm", "suppression"

**Landscaping/Yard**: "landscape", "lawn", "tree", "yard", "mowing", "irrigation"

**Roofing**: "roof", "roofing", "gutter", "downspout"

**Security/Locksmith**: "lock", "key", "access control", "camera", "security", "CCTV"

**Snow Removal**: "snow", "ice", "salt", "de-ice", "plow"

**PO Uplift**: description is exactly or primarily "PO Uplift"

**General Building - Emergency**: "EMER" prefix, or "emergency" in a general building context

**General Building - Handyman**: BBM format "General Building - General Building Technician"

**General Building - Project**: BBM format "General Building - General Building Project"

**General Building**: any remaining facility maintenance work

If a PO has multiple line items with different trades, set "trade" to the primary
(non-uplift, non-materials) trade. If genuinely mixed, use the trade of the highest-value line item.

## coupa_category

The Coupa commodity/category field if present in the email (e.g., "Maintenance - Facilities",
"Plumbing Equipment & Materials"). This is Coupa's own classification, not the trade field.

## General rules

- Extract all line items with descriptions, amounts, and metadata
- "quantity", "unit" (e.g., "EACH", "HR"), and "price" (unit price) should be extracted when present
- total_amount should be the numeric total in USD
- 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 extract_sender_domain(sender: str) -> str | None:
    """Extract the lowercased domain from a From header value.

    Handles "Name <user@domain>" and bare "user@domain" forms.
    """
    if not sender:
        return None
    _, addr = email.utils.parseaddr(sender)
    if "@" not in addr:
        return None
    return addr.rsplit("@", 1)[1].strip().lower()


def is_sender_allowed(sender: str) -> bool:
    """Return True if the sender domain is in the configured allowlist.

    A domain matches if it equals an allowlist entry or is a subdomain of one
    (e.g. "notifications.coupahost.com" matches "coupahost.com").
    """
    domain = extract_sender_domain(sender)
    if not domain:
        return False
    for allowed in ALLOWED_SENDER_DOMAINS:
        if domain == allowed or domain.endswith("." + allowed):
            return True
    return False


def ses_auth_failed(email_data: dict) -> bool:
    """Return True if SES recorded a hard SPF or DKIM failure for this email.

    SES (when receipt-rule spam/virus/auth scanning is enabled) stamps the stored
    object with X-SES-Spam-Verdict / X-SES-Virus-Verdict and an
    Authentication-Results header carrying spf=/dkim= results. We only block on an
    explicit "fail" so that mails delivered before scanning is enabled (no header)
    are not silently dropped; the domain allowlist remains the primary gate.
    """
    spam = (email_data.get("ses_spam_verdict") or "").upper()
    virus = (email_data.get("ses_virus_verdict") or "").upper()
    if spam == "FAIL" or virus == "FAIL":
        return True
    auth = (email_data.get("authentication_results") or "").lower()
    if "spf=fail" in auth or "dkim=fail" in auth:
        return True
    return False


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

    subject = msg.get("Subject", "")
    sender = msg.get("From", "")
    to = msg.get("To", "")
    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,
        "date": date,
        "body": body,
        # SES stamps these on the stored object when receipt-rule scanning is on.
        "ses_spam_verdict": msg.get("X-SES-Spam-Verdict", ""),
        "ses_virus_verdict": msg.get("X-SES-Virus-Verdict", ""),
        "authentication_results": msg.get("Authentication-Results", ""),
    }


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"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=2048,
        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(), parse_float=Decimal)


def pad_zip(zip_code: str | None) -> str | None:
    if not zip_code:
        return zip_code
    clean = zip_code.strip().split("-")[0]
    if clean.isdigit() and len(clean) < 5:
        return clean.zfill(5) + zip_code.strip()[len(clean) :]
    return zip_code


def enrich_parsed(parsed: dict, s3_key: str, email_subject: str):
    """Add metadata and promote nested fields to top level."""
    now = datetime.utcnow().isoformat()
    parsed["raw_s3_key"] = s3_key
    parsed["processed_at"] = now
    parsed["data_source"] = "email"
    parsed["email_subject"] = email_subject

    ship_to = parsed.get("ship_to") or {}
    if ship_to.get("address"):
        parsed["ship_to_raw"] = ship_to["address"]
    if ship_to.get("state"):
        parsed["state"] = ship_to["state"]

    if ship_to.get("zip"):
        ship_to["zip"] = pad_zip(ship_to["zip"])
    return parsed


def save_new_po(parsed: dict):
    """Insert a new PO into DynamoDB. Skips if po_number already exists."""
    table = dynamodb.Table(PO_TABLE)
    item = {k: v for k, v in parsed.items() if v is not None}

    try:
        table.put_item(
            Item=item,
            ConditionExpression="attribute_not_exists(po_number)",
        )
        logger.info(f"Created PO {parsed['po_number']}")
    except dynamodb.meta.client.exceptions.ConditionalCheckFailedException:
        logger.info(f"PO {parsed['po_number']} already exists, skipping insert")


def save_revision(parsed: dict):
    """Update an existing PO with revised data, or insert if it doesn't exist yet."""
    table = dynamodb.Table(PO_TABLE)
    item = {k: v for k, v in parsed.items() if v is not None}

    table.put_item(Item=item)
    logger.info(f"Revised PO {parsed['po_number']}")


def save_cancellation(parsed: dict):
    """Update an existing PO's status to Cancelled."""
    table = dynamodb.Table(PO_TABLE)

    table.update_item(
        Key={"po_number": parsed["po_number"]},
        UpdateExpression="SET po_status = :status, cancelled_at = :cancelled_at, raw_s3_key = :s3_key",
        ExpressionAttributeValues={
            ":status": "Cancelled",
            ":cancelled_at": parsed.get("processed_at", datetime.utcnow().isoformat()),
            ":s3_key": parsed.get("raw_s3_key", ""),
        },
    )
    logger.info(f"Cancelled PO {parsed['po_number']}")


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

        logger.info(f"Processing email: {s3_key}")

        response = s3.get_object(Bucket=bucket, Key=key)
        raw_email = response["Body"].read()

        email_data = parse_raw_email(raw_email)
        logger.info(f"Subject: {email_data['subject']}")

        # Authz: only act on email from an allowlisted sender domain that passed
        # SES auth checks. Anyone can email amazon_po@int.seahaven.com, but only
        # legitimate Coupa/Amazon senders may create or mutate POs.
        sender = email_data.get("sender", "")
        if not is_sender_allowed(sender):
            logger.warning(
                f"Rejecting email from disallowed sender '{sender}' "
                f"(domain not in allowlist): {key}"
            )
            continue
        if ses_auth_failed(email_data):
            logger.warning(
                f"Rejecting email from '{sender}' due to SES SPF/DKIM/spam "
                f"failure: {key}"
            )
            continue

        parsed = extract_with_claude(email_data)
        logger.info(
            f"Parsed: type={parsed.get('email_type')}, po={parsed.get('po_number')}"
        )

        if not parsed.get("po_number"):
            logger.warning(f"No PO number found in email, skipping: {key}")
            continue

        parsed = enrich_parsed(parsed, s3_key, email_data["subject"])

        email_type = parsed.get("email_type")
        if email_type == "cancellation":
            save_cancellation(parsed)
        elif email_type == "revision":
            save_revision(parsed)
        else:
            save_new_po(parsed)

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