"""Load and record Windows runner metadata for the benchmark dashboard."""

from __future__ import annotations

import csv
import json
from pathlib import Path
from typing import Dict, Optional

import pandas as pd

RUN_ENVIRONMENT_FIELDS = ('hostname', 'windows_version', 'os_build', 'cpu', 'ram_gb')
RUN_ENVIRONMENT_CSV = 'run_environment.csv'


def parse_machine_info(machine_info_file: Optional[Path]) -> Dict[str, str]:
    """Read system metadata from JSON (see machine_info.example.json)."""
    if machine_info_file is None or not machine_info_file.exists():
        return {}
    try:
        data = json.loads(machine_info_file.read_text(encoding='utf-8-sig'))
    except json.JSONDecodeError as error:
        print(f'Warning: Failed to parse machine info JSON {machine_info_file}: {error}')
        return {}
    if not isinstance(data, dict):
        return {}
    return {
        field: str(data[field]).strip()
        for field in RUN_ENVIRONMENT_FIELDS
        if data.get(field) is not None and str(data[field]).strip()
    }


def load_run_environment(data_dir: Path) -> pd.DataFrame:
    path = data_dir / RUN_ENVIRONMENT_CSV
    if not path.exists():
        return pd.DataFrame()
    return pd.read_csv(
        path,
        parse_dates=['date'],
        dtype={field: str for field in RUN_ENVIRONMENT_FIELDS},
    ).sort_values('date')


def record_run_environment(
    data_dir: Path,
    commit_hash: str,
    date: str,
    *,
    run_id: str = '',
    build_label: str = '',
    machine_info_file: Optional[Path] = None,
) -> bool:
    """Append one row to data/run_environment.csv when machine info is available."""
    machine_info = parse_machine_info(machine_info_file)
    if not machine_info:
        return False

    data_dir.mkdir(parents=True, exist_ok=True)
    csv_path = data_dir / RUN_ENVIRONMENT_CSV
    fieldnames = ['run_id', 'commit_hash', 'date', 'build_label', *RUN_ENVIRONMENT_FIELDS]
    if csv_path.exists():
        with open(csv_path, newline='', encoding='utf-8') as handle:
            reader = csv.DictReader(handle)
            current = list(reader.fieldnames or [])
            rows = list(reader)
        if current != fieldnames:
            unknown = [field for field in current if field not in fieldnames]
            if unknown:
                raise ValueError(f'Cannot migrate {csv_path}: unexpected columns {unknown}')
            with open(csv_path, 'w', newline='', encoding='utf-8') as handle:
                writer = csv.DictWriter(handle, fieldnames=fieldnames)
                writer.writeheader()
                writer.writerows(rows)
    file_exists = csv_path.exists()
    row = {
        'run_id': run_id or commit_hash,
        'commit_hash': commit_hash,
        'date': date,
        'build_label': build_label,
        **{field: machine_info.get(field, '') for field in RUN_ENVIRONMENT_FIELDS},
    }

    with open(csv_path, 'a', newline='', encoding='utf-8') as handle:
        writer = csv.DictWriter(handle, fieldnames=fieldnames)
        if not file_exists:
            writer.writeheader()
        writer.writerow(row)

    print('Recorded machine info for this run')
    return True