"""Single-field usage lookup against Apollo GraphOS."""

import argparse
import json
import os
import sys
import urllib.request
from datetime import datetime, timedelta, timezone

from src.config import DEFAULT_VARIANT, FIELD_USAGE_QUERY, GRAPH_ID, GRAPHOS_API


def lookup_field(parent_type: str, field_name: str, months: int, graph_id: str) -> None:
    """Query GraphOS for usage of a single Type.field and print results."""
    api_key = os.environ.get('APOLLO_KEY')
    if not api_key:
        print('Error: APOLLO_KEY environment variable not set', file=sys.stderr)
        sys.exit(1)

    since = datetime.now(timezone.utc) - timedelta(days=months * 30)
    since_str = since.strftime('%Y-%m-%dT00:00:00Z')

    query = FIELD_USAGE_QUERY % (graph_id, since_str, parent_type, field_name)
    payload = json.dumps({'query': query}).encode()

    req = urllib.request.Request(
        GRAPHOS_API,
        data=payload,
        headers={
            'Content-Type': 'application/json',
            'x-api-key': api_key,
        },
    )

    with urllib.request.urlopen(req) as resp:
        data = json.loads(resp.read())

    if 'errors' in data:
        for err in data['errors']:
            print(f'GraphQL error: {err["message"]}', file=sys.stderr)
        sys.exit(1)

    records = data['data']['service']['statsWindow']['fieldUsage']

    if not records:
        print(f'\n  {parent_type}.{field_name} — NO USAGE in the last {months} months\n')
        return

    total_executions = 0
    total_operations = 0
    by_query: dict[str, dict[str, int]] = {}

    for record in records:
        query_name = record['groupBy']['queryName'] or '(anonymous)'
        executions = record['metrics']['estimatedExecutionCount']
        operations = record['metrics']['referencingOperationCount']
        total_executions += executions
        total_operations += operations
        if query_name in by_query:
            by_query[query_name]['executions'] += executions
            by_query[query_name]['operations'] += operations
        else:
            by_query[query_name] = {'executions': executions, 'operations': operations}

    print(f'\n  {parent_type}.{field_name} — last {months} months (since {since_str})')
    print(f'  Total executions: {total_executions:,}')
    print(f'  Total referencing operations: {total_operations:,}')
    print('\n  Breakdown by operation:')
    print(f'  {"Operation":<50} {"Executions":>15} {"Operations":>15}')
    print(f'  {"─" * 80}')

    for name, counts in sorted(by_query.items(), key=lambda x: x[1]['executions'], reverse=True):
        print(f'  {name:<50} {counts["executions"]:>15,} {counts["operations"]:>15,}')

    print()


def main() -> None:
    parser = argparse.ArgumentParser(description='Check field usage in Apollo GraphOS')
    parser.add_argument('field', help='Type.fieldName (e.g. Query.product, Vendor.subaccountId)')
    parser.add_argument('--months', type=int, default=3, help='Lookback period in months (default: 3)')
    parser.add_argument('--graph-id', default=GRAPH_ID, help=f'Graph ID (default: {GRAPH_ID})')
    parser.add_argument('--variant', default=DEFAULT_VARIANT, help=f'Graph variant (default: {DEFAULT_VARIANT})')
    args = parser.parse_args()

    parts = args.field.split('.', 1)
    if len(parts) != 2:
        print(f"Error: expected Type.fieldName, got '{args.field}'", file=sys.stderr)
        sys.exit(1)

    parent_type, field_name = parts
    lookup_field(parent_type, field_name, args.months, args.graph_id)


if __name__ == '__main__':
    main()