"""Explicit purchase-mail linking, without changing purchase fulfilment or running workflows."""
import json
from fastapi import HTTPException
from app.core.database import atomic_transaction, execute_query_single, execute_update


def link_purchase_mail(email_id, purchase_id, kind, tracking_number=None, user_id=None):
    if kind not in {'order_confirmation', 'freight_note'}:
        raise HTTPException(400, 'Ukendt indkøbsmailtype')
    tracking = str(tracking_number or '').strip() or None
    if tracking and (kind != 'freight_note' or len(tracking) > 100):
        raise HTTPException(400, 'Trackingnummer må højst være 100 tegn og bruges kun ved levering')
    with atomic_transaction():
        mail = execute_query_single(
            'SELECT id, linked_case_id FROM email_messages WHERE id = %s AND deleted_at IS NULL FOR UPDATE',
            (email_id,))
        if not mail:
            raise HTTPException(404, 'Mailen blev ikke fundet')
        purchase = execute_query_single("""
            SELECT p.id, p.sag_id, p.description, s.titel AS case_title
            FROM sag_salgsvarer p JOIN sag_sager s ON s.id = p.sag_id
            WHERE p.id = %s AND p.type = 'purchase' AND p.status <> 'cancelled'
              AND s.deleted_at IS NULL FOR UPDATE OF p, s
        """, (purchase_id,))
        if not purchase:
            raise HTTPException(404, 'Bestillingen findes ikke eller er annulleret')
        if mail.get('linked_case_id') and mail['linked_case_id'] != purchase['sag_id']:
            raise HTTPException(409, 'Mailen er allerede knyttet til en anden sag. Ret sagstilknytningen først.')
        metadata = {'purchase_id': purchase_id, 'sag_id': purchase['sag_id'], 'kind': kind,
                    'tracking_number': tracking}
        previous = execute_query_single("""SELECT metadata FROM email_activity_log
            WHERE email_id = %s AND event_type = 'purchase_mail_link'
            ORDER BY id DESC LIMIT 1""", (email_id,))
        if previous:
            if previous['metadata'] != metadata:
                raise HTTPException(409, 'Mailen er allerede behandlet som indkøbsmail med andre oplysninger.')
            return {'success': True, 'sag_id': purchase['sag_id'], 'idempotent': True,
                    'message': 'Mailen er allerede knyttet til bestillingen'}
        execute_update('''INSERT INTO sag_emails (sag_id, email_id) VALUES (%s, %s)
            ON CONFLICT (sag_id, email_id) DO NOTHING''', (purchase['sag_id'], email_id))
        execute_update("""UPDATE email_messages SET linked_case_id = %s,
            classification = %s, confidence_score = 1.0,
            extracted_tracking_number = COALESCE(%s, extracted_tracking_number),
            status = 'processed', folder = 'Processed', processed_at = CURRENT_TIMESTAMP,
            updated_at = CURRENT_TIMESTAMP WHERE id = %s""",
            (purchase['sag_id'], kind, tracking, email_id))
        execute_update("""INSERT INTO email_activity_log
            (email_id, event_type, event_category, description, metadata, user_id, created_by)
            VALUES (%s, 'purchase_mail_link', 'user', %s, %s::jsonb, %s, 'mailindbakke')""",
            (email_id, ('Ordrebekræftelse' if kind == 'order_confirmation' else 'Levering / tracking')
             + ': ' + purchase['description'], json.dumps(metadata), user_id))
        return {'success': True, 'sag_id': purchase['sag_id'], 'message': 'Mailen er knyttet til bestillingen og sagen'}