#!/usr/bin/env python
"""Build hand-authored documentation folders from their markdown sources.

Companion to collect.py. While collect.py pulls *finished* HTML and MCP bundles
out of source repos, build.py compiles folders that keep their sources in this
hub. Any top-level folder with ``src/mkdocs.*.yml`` gets, for each config:

1. a MkDocs HTML build into the target dir the config declares
   (e.g. ``standards/src/mkdocs.wiki.yml`` -> ``standards/wiki/``), and
2. a doc-forge-shaped MCP bundle under ``<name>/mcp/``
   (``index.json``, ``nav.json``, ``modules/*.json``), regenerated from the
   lib pages (``src/lib/*.md``) so the bundle mirrors the lib site.

Each MkDocs config owns a dedicated site dir (declared via ``site_dir``), so
builds never touch ``src/`` or any other kind's output.

Usage:
    python build.py                # build every folder with src/mkdocs.*.yml
    python build.py --name standards
    python build.py --dry-run
"""
from __future__ import annotations

import argparse
import json
import re
import shutil
import subprocess
import sys
from pathlib import Path

ROOT = Path(__file__).resolve().parent

NUM_PREFIX = re.compile(r"^\d+[_-]?")


def find_src_dirs(root: Path = ROOT) -> list[Path]:
    """Return top-level folders containing ``src/mkdocs.*.yml``.

    Skips hidden directories, the mcp bundle container, and the generated
    portal index.
    """
    found: list[Path] = []
    for child in sorted(root.iterdir()):
        if not child.is_dir() or child.name.startswith("."):
            continue
        if child.name in ("mcp", "_index"):
            continue
        src = child / "src"
        if src.is_dir() and list(src.glob("mkdocs.*.yml")):
            found.append(child)
    return found


def build_html(folder: Path, dry_run: bool = False) -> None:
    """Compile each ``src/mkdocs.*.yml`` config of ``folder`` into HTML.

    Each config declares its own ``docs_dir`` and ``site_dir``, mirroring
    doc-forge (``mkdocs.wiki.yml`` -> ``<name>/wiki/``, ``mkdocs.lib.yml`` ->
    ``<name>/lib/``).

    Args:
        folder (Path): The hub folder owning ``src/mkdocs.*.yml``.
        dry_run (bool): Print the plan without executing.
    """
    name = folder.name
    for cfg in sorted((folder / "src").glob("mkdocs.*.yml")):
        site = cfg.name.removeprefix("mkdocs.").removesuffix(".yml")
        if dry_run:
            print(f"[BLD]  {name}  mkdocs build -f {cfg.relative_to(ROOT)} "
                  f"(-> {name}/{site}/)")
            continue

        result = subprocess.run(
            [sys.executable, "-m", "mkdocs", "build", "-f", str(cfg)],
            capture_output=True,
            text=True,
        )
        if result.returncode != 0:
            print(f"[ERR]  {name}  mkdocs failed:\n{result.stdout}\n{result.stderr}",
                  file=sys.stderr)
            raise SystemExit(1)
        print(f"[BLD]  {name}  {site} site built into {folder.relative_to(ROOT)}/{site}/")


# ── MCP bundle ───────────────────────────────────────────────────────────────


def _module_name(stem: str) -> str:
    """Map a markdown filename to a module name (strip the NN_ prefix)."""
    return NUM_PREFIX.sub("", stem) or stem


def _read_title(path: Path) -> str:
    """Return the first markdown H1 title, or a prettified fallback."""
    for line in path.read_text(encoding="utf-8").splitlines():
        if line.startswith("# "):
            return line[2:].strip()
    return _module_name(path.stem).replace("_", " ").title()


def build_bundle(folder: Path, dry_run: bool = False) -> None:
    """Regenerate ``<name>/mcp`` from ``folder/src/lib`` markdown.

    The bundle mirrors the lib site (in the same way doc-forge's MCP output
    mirrors its lib documentation). Writes ``index.json``, ``nav.json`` and
    ``modules/*.json`` in the doc-forge MCP bundle shape. Hand-authored extras
    (e.g. ``libraries.json``) are left untouched.

    Args:
        folder (Path): The hub folder owning a ``src/lib``.
        dry_run (bool): Print the plan without executing.
    """
    name = folder.name
    lib = folder / "src" / "lib"
    if not lib.is_dir():
        return
    out_dir = folder / "mcp"
    modules_dir = out_dir / "modules"
    if dry_run:
        print(f"[MCP]  {name}  {lib.relative_to(ROOT)}/*.md "
              f"-> {out_dir.relative_to(ROOT)}/")
        return

    if modules_dir.exists():
        shutil.rmtree(modules_dir)
    modules_dir.mkdir(parents=True, exist_ok=True)

    def write_module(module: str, body: str) -> None:
        payload = {
            "module": module,
            "content": {
                "path": module,
                "docstring": body.strip() + "\n",
                "objects": {},
            },
        }
        (modules_dir / f"{module}.json").write_text(
            json.dumps(payload, indent=2, ensure_ascii=False), encoding="utf-8"
        )

    nav = []
    for path in sorted(lib.glob("*.md")):
        module = _module_name(path.stem)
        write_module(module, path.read_text(encoding="utf-8"))
        nav.append({
            "module": module,
            "resource": f"doc://modules/{module}",
            "title": _read_title(path),
        })

    (out_dir / "nav.json").write_text(
        json.dumps(nav, indent=2, ensure_ascii=False), encoding="utf-8"
    )
    (out_dir / "index.json").write_text(
        json.dumps(
            {
                "project": name,
                "type": name,
                "modules_count": len(nav),
                "source": "hand-authored",
            },
            indent=2,
            ensure_ascii=False,
        ),
        encoding="utf-8",
    )
    print(f"[MCP]  {name}  bundle written to {out_dir.relative_to(ROOT)}/ ({len(nav)} modules)")


# ── CLI ──────────────────────────────────────────────────────────────────────


def main() -> None:
    parser = argparse.ArgumentParser(
        description="Build hub-authored doc folders (src/ -> HTML + MCP bundle)"
    )
    parser.add_argument("--name", help="Only build a single folder")
    parser.add_argument("--dry-run", action="store_true", help="Show the plan without writing")
    args = parser.parse_args()

    folders = [f for f in find_src_dirs() if not args.name or f.name == args.name]
    if not folders:
        print("No src/ doc folders found. Run build.py from the hub root.")
        return

    for folder in folders:
        build_bundle(folder, dry_run=args.dry_run)
        build_html(folder, dry_run=args.dry_run)


if __name__ == "__main__":
    main()