#!/usr/bin/env python3
"""Export Markdown API docs for packages listed in requirements.txt.

Creates docs/<import-module>/api.md under the current working directory using a
temporary virtualenv in /tmp (does not install into the system Python).

Supported requirements lines: PEP 508 name specs and ``-r`` includes (must stay
under the directory of the top-level requirements file). Lines like ``-e``,
direct URLs, and other pip options are installed by pip but not exported.

Example:
    ./scripts/export-api-docs.py requirements.txt
    ./scripts/export-api-docs.py /path/to/requirements.txt --recreate-venv
    ./scripts/export-api-docs.py requirements.txt --strict
"""

from __future__ import annotations

import argparse
import hashlib
import importlib.metadata as im
import os
import re
import shutil
import subprocess
import sys
from pathlib import Path

# Pin for reproducible exports (pydoc-markdown 4.x API).
PYDOC_MARKDOWN_SPEC = "pydoc-markdown>=4.0,<5"

# PyPI distribution name (normalized) -> import roots when metadata is missing.
PACKAGE_MODULE_FALLBACKS: dict[str, list[str]] = {
    "python-gitlab": ["gitlab"],
    "python-redmine": ["redminelib"],
    "pyyaml": ["yaml"],
    "pillow": ["PIL"],
}

MODULE_RE = re.compile(r"^[A-Za-z_][A-Za-z0-9_]*$")
REQUIREMENTS_HASH_FILE = ".requirements.sha256"


def parse_args() -> argparse.Namespace:
    parser = argparse.ArgumentParser(
        description="Export Markdown API docs for requirements.txt packages.",
    )
    parser.add_argument(
        "requirements",
        type=Path,
        help="Path to requirements.txt",
    )
    parser.add_argument(
        "--venv-dir",
        type=Path,
        default=None,
        help="Virtualenv location (default: /tmp/export-api-docs-<uid>-<hash>)",
    )
    parser.add_argument(
        "--recreate-venv",
        action="store_true",
        help="Remove and recreate the temporary virtualenv",
    )
    parser.add_argument(
        "--strict",
        action="store_true",
        help="Exit with failure if any package or module export fails",
    )
    return parser.parse_args()


def normalize_dist_name(name: str) -> str:
    return re.sub(r"[-_.]+", "-", name).lower()


def parse_requirements_file(
    path: Path,
    seen: set[Path] | None = None,
    anchor_dir: Path | None = None,
) -> list[str]:
    """Return normalized PyPI distribution names from a requirements file."""
    path = path.resolve()
    if seen is None:
        seen = set()
    if anchor_dir is None:
        anchor_dir = path.parent.resolve()
    if path in seen:
        return []
    seen.add(path)

    names: list[str] = []
    for raw in path.read_text(encoding="utf-8").splitlines():
        line = raw.split("#", 1)[0].strip()
        if not line:
            continue
        if line.startswith("-r"):
            parts = line.split(maxsplit=1)
            if len(parts) != 2:
                continue
            include = (path.parent / parts[1]).resolve()
            try:
                include.relative_to(anchor_dir)
            except ValueError:
                print(
                    f"warning: skipping -r outside requirements tree: {include}",
                    file=sys.stderr,
                )
                continue
            if not include.is_file():
                print(f"warning: requirements include not found: {include}", file=sys.stderr)
                continue
            names.extend(parse_requirements_file(include, seen, anchor_dir))
            continue
        if line.startswith("-"):
            continue

        line = re.split(r"[;@]", line, maxsplit=1)[0].strip()
        line = re.sub(r"\[.*\]", "", line).strip()
        match = re.match(r"^([A-Za-z0-9][A-Za-z0-9._-]*)", line)
        if match:
            names.append(normalize_dist_name(match.group(1)))
    return names


def default_venv_dir() -> Path:
    digest = hashlib.sha256(str(Path.cwd().resolve()).encode()).hexdigest()[:12]
    return Path("/tmp") / f"export-api-docs-{os.getuid()}-{digest}"


def venv_python(venv: Path) -> Path:
    if os.name == "nt":
        return venv / "Scripts" / "python.exe"
    return venv / "bin" / "python"


def venv_executable(venv: Path, name: str) -> Path:
    if os.name == "nt":
        return venv / "Scripts" / f"{name}.exe"
    return venv / "bin" / name


def run(cmd: list[str], **kwargs) -> None:
    subprocess.run(cmd, check=True, **kwargs)


def check_venv_module() -> None:
    try:
        subprocess.run(
            [sys.executable, "-m", "venv", "--help"],
            check=True,
            capture_output=True,
        )
    except (subprocess.CalledProcessError, FileNotFoundError) as exc:
        print(
            "error: python venv module unavailable "
            f"(install python3-venv): {exc}",
            file=sys.stderr,
        )
        sys.exit(1)


def collect_requirements_files(
    path: Path,
    seen: set[Path] | None = None,
    anchor_dir: Path | None = None,
) -> list[Path]:
    """Return all requirements files reachable via -r from path (in stable order)."""
    path = path.resolve()
    if seen is None:
        seen = set()
    if anchor_dir is None:
        anchor_dir = path.parent.resolve()
    if path in seen:
        return []
    seen.add(path)

    files = [path]
    for raw in path.read_text(encoding="utf-8").splitlines():
        line = raw.split("#", 1)[0].strip()
        if not line.startswith("-r"):
            continue
        parts = line.split(maxsplit=1)
        if len(parts) != 2:
            continue
        include = (path.parent / parts[1]).resolve()
        try:
            include.relative_to(anchor_dir)
        except ValueError:
            continue
        if include.is_file():
            files.extend(collect_requirements_files(include, seen, anchor_dir))
    return files


def requirements_tree_digest(root: Path) -> str:
    digest = hashlib.sha256()
    anchor = root.parent.resolve()
    for req_file in sorted(collect_requirements_files(root, anchor_dir=anchor)):
        digest.update(str(req_file).encode())
        digest.update(req_file.read_bytes())
    return digest.hexdigest()


def venv_needs_install(venv: Path, requirements: Path, recreate: bool) -> bool:
    if recreate or not venv.is_dir():
        return True
    stamp = venv / REQUIREMENTS_HASH_FILE
    if not stamp.is_file():
        return True
    return stamp.read_text(encoding="utf-8").strip() != requirements_tree_digest(requirements)


def ensure_venv(venv: Path, requirements: Path, recreate: bool) -> Path:
    check_venv_module()
    py = venv_python(venv)
    if recreate and venv.exists():
        shutil.rmtree(venv)

    if not venv.exists():
        print(f"Creating virtualenv: {venv}", file=sys.stderr)
        run([sys.executable, "-m", "venv", str(venv)])

    if venv_needs_install(venv, requirements, recreate=False):
        print("Installing packages into temporary virtualenv…", file=sys.stderr)
        run([str(py), "-m", "pip", "install", "-q", "-U", "pip", "setuptools", "wheel"])
        run(
            [
                str(py),
                "-m",
                "pip",
                "install",
                "-q",
                PYDOC_MARKDOWN_SPEC,
                "-r",
                str(requirements.resolve()),
            ],
        )
        (venv / REQUIREMENTS_HASH_FILE).write_text(
            requirements_tree_digest(requirements),
            encoding="utf-8",
        )
    elif not venv_executable(venv, "pydoc-markdown").is_file():
        print("Installing pydoc-markdown into virtualenv…", file=sys.stderr)
        run([str(py), "-m", "pip", "install", "-q", PYDOC_MARKDOWN_SPEC])

    return py


def site_packages(py: Path) -> Path:
    code = """
import site
import sys
from pathlib import Path

paths = site.getsitepackages()
if not paths:
    for entry in sys.path:
        if entry.endswith("site-packages"):
            paths.append(entry)
if not paths:
    ver = f"{sys.version_info.major}.{sys.version_info.minor}"
    guess = Path(sys.prefix) / "lib" / f"python{ver}" / "site-packages"
    if guess.is_dir():
        paths.append(str(guess))
if not paths:
    raise SystemExit("no site-packages directory found")
print(paths[0])
"""
    out = subprocess.check_output([str(py), "-c", code], text=True).strip()
    return Path(out)


def is_safe_module_name(module: str) -> bool:
    return MODULE_RE.fullmatch(module) is not None


def safe_output_dir(docs_root: Path, module: str) -> Path | None:
    if not is_safe_module_name(module):
        return None
    docs_resolved = docs_root.resolve()
    out_dir = (docs_root / module).resolve()
    try:
        out_dir.relative_to(docs_resolved)
    except ValueError:
        return None
    return out_dir


def import_modules_for_distribution(dist: im.Distribution) -> list[str]:
    modules: list[str] = []
    try:
        text = dist.read_text("top_level.txt")
    except (FileNotFoundError, OSError, TypeError):
        text = None
    if text:
        modules = [
            line.strip()
            for line in text.splitlines()
            if line.strip() and not line.strip().startswith("_")
        ]
    if modules:
        return sorted({m for m in modules if is_safe_module_name(m)})

    key = normalize_dist_name(dist.metadata.get("Name", ""))
    if key in PACKAGE_MODULE_FALLBACKS:
        return PACKAGE_MODULE_FALLBACKS[key]

    guess = key.replace("-", "_")
    if is_safe_module_name(guess):
        print(
            f"warning: guessing import module {guess!r} for {key!r} "
            "(no top_level.txt); may be wrong",
            file=sys.stderr,
        )
        return [guess]
    return []


def export_module(
    pydoc_markdown: Path,
    site_pkgs: Path,
    module: str,
    out_dir: Path,
) -> Path:
    out_dir.mkdir(parents=True, exist_ok=True)
    api_md = out_dir / "api.md"
    with api_md.open("w", encoding="utf-8") as handle:
        run(
            [
                str(pydoc_markdown),
                "-p",
                module,
                "-I",
                str(site_pkgs),
                "-q",
            ],
            stdout=handle,
        )
    if not api_md.is_file() or api_md.stat().st_size == 0:
        raise FileNotFoundError(f"Expected non-empty output file: {api_md}")
    return api_md


def write_docs_index(docs_root: Path, exports: list[tuple[str, Path]]) -> None:
    lines = [
        "# API documentation (exported)",
        "",
        "Generated from `requirements.txt` via `scripts/export-api-docs.py`.",
        "",
        "| Module | File |",
        "|--------|------|",
    ]
    for module, api_md in sorted(exports):
        rel = api_md.relative_to(docs_root)
        lines.append(f"| `{module}` | [{rel}]({rel}) |")
    (docs_root / "README.md").write_text("\n".join(lines) + "\n", encoding="utf-8")


def distribution_for_requirement_in_venv(
    name: str,
    site_pkgs: Path,
) -> im.Distribution | None:
    for dist in im.distributions(path=[str(site_pkgs)]):
        meta_name = dist.metadata.get("Name", "")
        if normalize_dist_name(meta_name) == name:
            return dist
    return None


def main() -> int:
    args = parse_args()
    requirements = args.requirements.resolve()
    if not requirements.is_file():
        print(f"error: requirements file not found: {requirements}", file=sys.stderr)
        return 1

    venv = args.venv_dir or default_venv_dir()
    docs_root = Path.cwd() / "docs"
    docs_root.mkdir(parents=True, exist_ok=True)

    py = ensure_venv(venv, requirements, args.recreate_venv)
    pydoc_markdown = venv_executable(venv, "pydoc-markdown")
    if not pydoc_markdown.is_file():
        print(f"error: pydoc-markdown not found in {venv}", file=sys.stderr)
        return 1

    site_pkgs = site_packages(py)
    anchor_dir = requirements.parent.resolve()
    req_names = list(dict.fromkeys(parse_requirements_file(requirements, anchor_dir=anchor_dir)))
    if not req_names:
        print(
            "error: no package names found in requirements file "
            "(only name-based specs and -r includes are parsed)",
            file=sys.stderr,
        )
        return 1

    exports: list[tuple[str, Path]] = []
    seen_modules: set[str] = set()
    failures = 0

    for req_name in req_names:
        dist = distribution_for_requirement_in_venv(req_name, site_pkgs)
        if dist is None:
            print(f"warning: package not installed in venv, skipping: {req_name}", file=sys.stderr)
            failures += 1
            continue

        display_name = dist.metadata.get("Name", req_name)
        modules = import_modules_for_distribution(dist)
        if not modules:
            print(
                f"warning: no safe import modules for {display_name}, skipping",
                file=sys.stderr,
            )
            failures += 1
            continue

        print(f"{display_name} -> {', '.join(modules)}", file=sys.stderr)

        for module in modules:
            if module in seen_modules:
                continue
            seen_modules.add(module)

            out_dir = safe_output_dir(docs_root, module)
            if out_dir is None:
                print(f"warning: unsafe module name, skipping: {module!r}", file=sys.stderr)
                failures += 1
                continue

            try:
                api_md = export_module(pydoc_markdown, site_pkgs, module, out_dir)
            except subprocess.CalledProcessError as exc:
                print(f"warning: failed to export {module}: {exc}", file=sys.stderr)
                failures += 1
                continue
            except OSError as exc:
                print(f"warning: failed to export {module}: {exc}", file=sys.stderr)
                failures += 1
                continue

            size_kb = api_md.stat().st_size // 1024
            print(f"  wrote {api_md} ({size_kb} KiB)", file=sys.stderr)
            exports.append((module, api_md))

    if exports:
        write_docs_index(docs_root, exports)
        print(f"Done. Documentation in {docs_root.resolve()}", file=sys.stderr)

    if not exports:
        print("error: no documentation was exported", file=sys.stderr)
        return 1

    if args.strict and failures:
        print(f"error: {failures} package/module export failure(s) (--strict)", file=sys.stderr)
        return 1

    if failures:
        print(f"warning: {failures} package/module export failure(s)", file=sys.stderr)

    return 0


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