"""Read-only customer order browsing; scope comes exclusively from verified sessions."""

import sqlite3
from contextlib import contextmanager

from .customer_service import effective_tenants
from .db import connect
from .order_data import OrderDataUnavailable, build_card
from .visitor_service import customer_tenant_ids

PAGE_SIZE = 20
SUMMARY_FIELDS = ('id', 'order_no', 'inbound_code', 'status', 'country_code',
                  'warehouse_code', 'transport_mode')
STATUS_GROUPS = {
    'pending': ('DRAFT', 'SUBMITTED', 'APPROVED', 'ACCEPTED'),
    'processing': ('PROCESSING',), 'completed': ('COMPLETED',), 'cancelled': ('CANCELLED',),
}
FILTERS = ('all', *STATUS_GROUPS, 'other')


@contextmanager
def order_connection():
    connection = None
    try:
        connection = connect()
        connection.row_factory = sqlite3.Row
        # Summary and list must describe the same snapshot, including during imports.
        connection.execute('BEGIN')
        yield connection
    except sqlite3.Error:
        raise OrderDataUnavailable from None
    finally:
        if connection is not None:
            connection.close()


def scoped_rows(connection, columns, suffix='', values=()):
    tenants = effective_tenants(customer_tenant_ids())
    if not tenants:
        return []
    placeholders = ','.join('?' for _ in tenants)
    return [dict(row) for row in connection.execute(
        f'SELECT {columns} FROM order_test_data WHERE tenant_id IN ({placeholders}) '+suffix,
        (*tenants, *values))]


def list_orders(before=None, status='all'):
    if status not in FILTERS:
        raise ValueError('Invalid order status filter')
    summary = dict.fromkeys(('total', *STATUS_GROUPS, 'other'), 0)
    suffix, values = '', ()
    if status in STATUS_GROUPS or status == 'other':
        codes = STATUS_GROUPS.get(status, tuple(code for codes in STATUS_GROUPS.values() for code in codes))
        suffix = 'AND status '+('NOT IN' if status == 'other' else 'IN')+' ('+','.join('?' for _ in codes)+') '
        values = codes
    if before is not None:
        suffix += 'AND id<? '
        values += (before,)
    with order_connection() as connection:
        for row in scoped_rows(connection, 'status,COUNT(*) AS count', 'GROUP BY status'):
            group = next((key for key, codes in STATUS_GROUPS.items() if row['status'] in codes), 'other')
            summary[group] += row['count']
            summary['total'] += row['count']
        rows = scoped_rows(connection, ','.join(SUMMARY_FIELDS), suffix+'ORDER BY id DESC LIMIT ?', values+(PAGE_SIZE+1,))
    return {'ok': True, 'orders': rows[:PAGE_SIZE], 'summary': summary,
            'next_before': rows[PAGE_SIZE-1]['id'] if len(rows) > PAGE_SIZE else None}


def order_detail(order_id):
    if not 0 < order_id <= 9223372036854775807:
        return None
    with order_connection() as connection:
        rows = scoped_rows(connection, '*', 'AND id=? LIMIT 1', (order_id,))
    return build_card(rows[0]) if rows else None