#!/usr/bin/env python3
"""gen_status.py — generate STATUS.md deterministically from frontmatter.

Writes STATUS.md (no timestamps — output depends only on repo content, so
reruns are diff-clean). With --check, regenerates in memory and fails if
the committed STATUS.md is stale; CI uses this mode.

Usage:
  python scripts/gen_status.py [repo-root]          # write STATUS.md
  python scripts/gen_status.py --check [repo-root]  # verify, exit 1 if stale
"""
from __future__ import annotations

import re
import sys
from pathlib import Path

try:
    import yaml
except ImportError:  # pragma: no cover
    sys.exit("gen_status.py needs PyYAML: pip install pyyaml")

H1_RE = re.compile(r"^#\s+(.*)$", re.M)


def parse(path: Path):
    lines = path.read_text(encoding="utf-8").splitlines()
    if not lines or lines[0].strip() != "---":
        return None, ""
    for j in range(1, len(lines)):
        if lines[j].strip() == "---":
            meta = yaml.safe_load("\n".join(lines[1:j])) or {}
            body = "\n".join(lines[j + 1:])
            return meta, body
    return None, ""


def title(body: str, fallback: str) -> str:
    match = H1_RE.search(body)
    return match.group(1).strip() if match else fallback


def collect(root: Path, subdir: str, wanted_type: str):
    items = []
    base = root / subdir
    if not base.is_dir():
        return items
    for path in sorted(base.rglob("*.md")):
        if path.name == "template.md":
            continue
        meta, body = parse(path)
        if not isinstance(meta, dict) or meta.get("type") != wanted_type:
            continue
        rel = path.relative_to(root).as_posix()
        items.append((rel, meta, title(body, path.stem)))
    return items


def render(root: Path) -> str:
    issues = collect(root, "docs/issues", "issue")
    designs = collect(root, "docs/design", "design")
    adrs = collect(root, "docs/adr", "adr")
    aars = collect(root, "docs/aar", "aar")

    out: list[str] = []
    out.append("# STATUS")
    out.append("")
    out.append("<!-- Generated by scripts/gen_status.py — do not edit. -->")
    out.append("")

    open_issues = [i for i in issues
                   if i[1].get("status") in ("open", "in-progress")]
    closed = len(issues) - len(open_issues)
    out.append(f"## Issues ({len(open_issues)} open, {closed} closed)")
    out.append("")
    if open_issues:
        out.append("| Issue | Status | Title |")
        out.append("|---|---|---|")
        for rel, meta, name in open_issues:
            out.append(f"| [{meta.get('id', '?')}]({rel}) "
                       f"| {meta.get('status')} | {name} |")
    else:
        out.append("_none open_")
    out.append("")

    active = [d for d in designs if d[1].get("status") != "done"]
    out.append(f"## Active design docs ({len(active)})")
    out.append("")
    if active:
        out.append("| Design | Gate | Title |")
        out.append("|---|---|---|")
        for rel, meta, name in active:
            out.append(f"| [{Path(rel).stem}]({rel}) "
                       f"| {meta.get('status')} | {name} |")
    else:
        out.append("_none active_")
    out.append("")

    out.append(f"## ADRs ({len(adrs)})")
    out.append("")
    if adrs:
        out.append("| ADR | Status | Title |")
        out.append("|---|---|---|")
        for rel, meta, name in adrs:
            out.append(f"| [{meta.get('id', '?')}]({rel}) "
                       f"| {meta.get('status')} | {name} |")
    else:
        out.append("_none_")
    out.append("")

    open_aars = [a for a in aars if a[1].get("status") == "open"]
    out.append(f"## Open AARs ({len(open_aars)})")
    out.append("")
    if open_aars:
        for rel, _meta, name in open_aars:
            out.append(f"- [{name}]({rel})")
    else:
        out.append("_none — nothing awaiting harvest_")
    out.append("")
    return "\n".join(out)


def main() -> int:
    args = [a for a in sys.argv[1:] if a != "--check"]
    check = "--check" in sys.argv[1:]
    root = Path(args[0]) if args else Path.cwd()
    content = render(root)
    status = root / "STATUS.md"
    if check:
        current = status.read_text(encoding="utf-8") if status.is_file() else ""
        if current != content:
            print("gen_status --check: STATUS.md is stale — "
                  "run scripts/gen_status.py and commit the result")
            return 1
        print("gen_status --check: STATUS.md is current")
        return 0
    status.write_text(content, encoding="utf-8", newline="\n")
    print(f"wrote {status}")
    return 0


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