"""BNPL Engine: Buy Now Pay Later integration stub.

Supports APLAZO, Kueski, Clip as providers.
This is an architecture stub — actual API integrations require:
  - APLAZO: merchant account + API credentials
  - Kueski: merchant account + API credentials  
  - Clip: merchant account + API credentials

The tables (bnpl_transactions) are created in v2.6 migration.
"""

import json
from datetime import datetime

# Provider configuration stubs
PROVIDER_CONFIGS = {
    'aplazo': {
        'api_base': 'https://api.aplazo.mx/v1',
        'auth_type': 'bearer',  # OAuth2 client credentials
        'webhook_path': '/pos/api/bnpl/webhook/aplazo',
    },
    'kueski': {
        'api_base': 'https://api.kueskipay.io/v1',
        'auth_type': 'api_key',
        'webhook_path': '/pos/api/bnpl/webhook/kueski',
    },
    'clip': {
        'api_base': 'https://api.clip.mx/v1',
        'auth_type': 'bearer',
        'webhook_path': '/pos/api/bnpl/webhook/clip',
    },
}


def get_provider_config(provider):
    return PROVIDER_CONFIGS.get(provider)


def create_bnpl_transaction(conn, sale_id, customer_id, amount, provider='aplazo',
                            installment_count=4, employee_id=None):
    """Record a BNPL transaction in pending state.

    In production, this would:
    1. Call the provider's API to create a checkout/session
    2. Store the provider's transaction ID
    3. Return a redirect URL for the customer to complete approval
    """
    cur = conn.cursor()
    cur.execute("""
        INSERT INTO bnpl_transactions
            (tenant_id, customer_id, sale_id, provider, amount,
             installment_count, status)
        VALUES (%s, %s, %s, %s, %s, %s, 'pending')
        RETURNING id
    """, (None, customer_id, sale_id, provider, amount, installment_count))
    txn_id = cur.fetchone()[0]
    conn.commit()
    cur.close()

    return {
        'transaction_id': txn_id,
        'provider': provider,
        'status': 'pending',
        'amount': amount,
        'installment_count': installment_count,
        'checkout_url': None,  # Would come from provider API
        'message': 'BNPL transaction recorded. Provider integration required for live checkout.',
    }


def get_bnpl_transaction(conn, txn_id):
    cur = conn.cursor()
    cur.execute("""
        SELECT id, customer_id, sale_id, provider, provider_transaction_id,
               amount, status, installment_count, installment_amount,
               customer_fee, merchant_fee, provider_response, created_at, updated_at
        FROM bnpl_transactions WHERE id = %s
    """, (txn_id,))
    row = cur.fetchone()
    cur.close()
    if not row:
        return None
    return {
        'id': row[0], 'customer_id': row[1], 'sale_id': row[2],
        'provider': row[3], 'provider_transaction_id': row[4],
        'amount': float(row[5]) if row[5] else 0,
        'status': row[6], 'installment_count': row[7],
        'installment_amount': float(row[8]) if row[8] else None,
        'customer_fee': float(row[9]) if row[9] else 0,
        'merchant_fee': float(row[10]) if row[10] else 0,
        'provider_response': row[11],
        'created_at': str(row[12]), 'updated_at': str(row[13]),
    }


def update_bnpl_status(conn, txn_id, new_status, provider_response=None,
                       webhook_payload=None):
    """Update BNPL transaction status (called by webhook or polling)."""
    cur = conn.cursor()
    cur.execute("""
        UPDATE bnpl_transactions
        SET status = %s,
            provider_response = COALESCE(provider_response, '{}'::jsonb) || COALESCE(%s, '{}'::jsonb),
            webhook_payload = COALESCE(webhook_payload, '{}'::jsonb) || COALESCE(%s, '{}'::jsonb),
            updated_at = NOW()
        WHERE id = %s
    """, (new_status, json.dumps(provider_response) if provider_response else None,
          json.dumps(webhook_payload) if webhook_payload else None, txn_id))
    conn.commit()
    cur.close()
    return True


def list_bnpl_transactions(conn, status=None, customer_id=None, provider=None,
                           page=1, per_page=50):
    cur = conn.cursor()
    where_clauses = []
    params = []
    if status:
        where_clauses.append("status = %s")
        params.append(status)
    if customer_id:
        where_clauses.append("customer_id = %s")
        params.append(customer_id)
    if provider:
        where_clauses.append("provider = %s")
        params.append(provider)

    where = " AND ".join(where_clauses) if where_clauses else "true"

    cur.execute(f"SELECT count(*) FROM bnpl_transactions WHERE {where}", params)
    total = cur.fetchone()[0]

    cur.execute(f"""
        SELECT id, customer_id, sale_id, provider, amount, status,
               installment_count, created_at
        FROM bnpl_transactions
        WHERE {where}
        ORDER BY created_at DESC
        LIMIT %s OFFSET %s
    """, params + [per_page, (page - 1) * per_page])

    txns = []
    for r in cur.fetchall():
        txns.append({
            'id': r[0], 'customer_id': r[1], 'sale_id': r[2],
            'provider': r[3], 'amount': float(r[4]) if r[4] else 0,
            'status': r[5], 'installment_count': r[6],
            'created_at': str(r[7]),
        })
    cur.close()
    return {
        'data': txns,
        'pagination': {'page': page, 'per_page': per_page, 'total': total}
    }


# ─── APLAZO API Stub ─────────────────────────────

def aplazo_create_checkout(amount, customer_email, customer_phone, order_id,
                           api_key=None, api_secret=None):
    """Stub for APLAZO checkout creation.

    Production implementation requires:
    1. OAuth2 token exchange: POST /oauth/token
    2. Create checkout: POST /checkouts
       Body: {amount, merchantOrderId, customer: {email, phone}, callbacks: {onSuccess, onCancel, onReject}}
    3. Return checkout URL for customer redirect
    """
    return {
        'checkout_url': None,
        'aplazo_order_id': None,
        'status': 'not_implemented',
        'message': 'APLAZO integration requires merchant credentials. Contact APLAZO to activate.',
    }


def aplazo_webhook_handler(payload):
    """Stub for APLAZO webhook handler.

    Expected events: checkout.approved, checkout.rejected, checkout.cancelled,
                     installment.paid, installment.failed
    """
    return {
        'event_type': payload.get('event'),
        'handled': False,
        'message': 'APLAZO webhook handler stub. Implement when APLAZO credentials are available.',
    }