#!/usr/bin/env python3
"""Render a validated S3 report as Prometheus text; no listener or delivery."""
import argparse
from datetime import datetime, timezone
import json
from pathlib import Path
import sys

from platform_event import translate
from receiver import STATES, contract_check, instant, read_json


def labels(values):
    def escape(value):
        return value.replace('\\', '\\\\').replace('\n', '\\n').replace('"', '\\"')
    return '{' + ','.join(f'{key}="{escape(value)}"' for key, value in values.items()) + '}'


def render(report, contract, now):
    contract_check(contract)
    event = translate(report, contract)
    observed = instant(event['observed_at']).timestamp()
    if not 0 <= now.timestamp() - observed <= contract['max_event_age_seconds']:
        raise ValueError('stale or future report')
    identity = dict(stream=contract['stream'], producer=contract['producer'])
    lines = ['# HELP railiance_assurance_state Producer classification, one hot per signal.',
             '# TYPE railiance_assurance_state gauge']
    for signal, state in sorted(event['states'].items()):
        for candidate in sorted(STATES):
            key = labels(dict(identity, signal=signal, state=candidate))
            lines.append(f'railiance_assurance_state{key} {int(state == candidate)}')
    lines.extend([
        '# HELP railiance_assurance_observed_timestamp_seconds Original producer evaluation time.',
        '# TYPE railiance_assurance_observed_timestamp_seconds gauge',
        f'railiance_assurance_observed_timestamp_seconds{labels(identity)} {observed}',
    ])
    return '\n'.join(lines) + '\n'


def main():
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument('--contract', required=True, type=Path)
    parser.add_argument('report', type=Path)
    args = parser.parse_args()
    try:
        output = render(read_json(args.report), read_json(args.contract), datetime.now(timezone.utc))
    except (OSError, ValueError, KeyError, TypeError, AttributeError):
        print(json.dumps({'status': 'rejected', 'error': 'invalid-or-expired-report'}), file=sys.stderr)
        return 2
    sys.stdout.write(output)
    return 0


if __name__ == '__main__':
    sys.exit(main())