#!/usr/bin/env python3
"""
Audit each guide URL in guides.csv for WCAG 2.1 AA accessibility issues
(using pa11y).  Writes a report that omits issues appearing in *every*
guide.

Output file: output2.txt
Usage:
    python check_wcag_unique.py
Prerequisite:
    npm install -g pa11y            # or have pa11y available via npx
"""
from __future__ import annotations

import csv
import json
import shutil
import subprocess
import sys
from pathlib import Path
from typing import Dict, List, Set

GUIDES_CSV = Path(__file__).with_name("guides.csv")
OUTPUT_FILE = Path("output2.txt")


def run_pa11y(url: str) -> List[dict]:
    """Run pa11y on the URL and return its JSON‐parsed list of issues."""
    cmd_base = ["pa11y"] if shutil.which("pa11y") else ["npx", "pa11y"]
    result = subprocess.run(
        [*cmd_base, url, "--standard", "WCAG2AA", "--reporter", "json"],
        capture_output=True,
        text=True,
        check=False,
    )

    # pa11y exits 0 (no issues) or 1 (issues found). Treat both as success.
    if result.returncode not in (0, 1):
        print(f"[ERROR] pa11y failed with code {result.returncode} for {url}", file=sys.stderr)
        return []

    try:
        return json.loads(result.stdout)
    except json.JSONDecodeError:
        print(f"[WARN] Could not parse pa11y JSON output for {url}", file=sys.stderr)
        return []


def read_guides(csv_path: Path) -> List[Dict[str, str]]:
    with csv_path.open(newline="", encoding="utf-8-sig") as fh:
        return list(csv.DictReader(fh))


def compute_common_codes(issues_by_guide: Dict[str, List[dict]]) -> Set[str]:
    """Return set of issue codes present in *every* guide."""
    common: Set[str] | None = None
    for issues in issues_by_guide.values():
        codes = {i["code"] for i in issues}
        common = codes if common is None else common & codes
    return common or set()


def format_issue(issue: dict) -> str:
    selector = (issue.get("selector") or "").strip() or "N/A"
    return f"[{issue['type']}] {issue['code']}: {issue['message']}  (selector: {selector})"


def main() -> None:
    guides = read_guides(GUIDES_CSV)
    issues_by_guide: Dict[str, List[dict]] = {}

    print("Auditing guides with pa11y…\n")
    for guide in guides:
        name, url = guide["Name"], guide["URL"]
        print(f"• {name} — {url}")
        issues_by_guide[name] = run_pa11y(url)

    common_codes = compute_common_codes(issues_by_guide)

    lines: List[str] = []
    lines.append("Accessibility report (WCAG 2.1 AA — unique issues only)")
    lines.append("=" * 50)

    for name, issues in issues_by_guide.items():
        unique = [i for i in issues if i["code"] not in common_codes]
        lines.append(f"\nGuide: {name}")
        if not unique:
            lines.append("  ✔ No unique issues found.")
            continue
        for issue in unique:
            lines.append(f"  • {format_issue(issue)}")

    report = "\n".join(lines)
    print("\n" + report)
    OUTPUT_FILE.write_text(report, encoding="utf-8")
    print(f"\nReport written to {OUTPUT_FILE.resolve()}")


if __name__ == "__main__":
    main()