"""Canonical FDS build version, shared by Cargo, images and package builders."""
from pathlib import Path
import re
import subprocess

ROOT = Path(__file__).resolve().parents[1]
RELEASE = re.compile(r'v?([0-9]+(?:\.[0-9]+){1,2})\Z')
VALID = re.compile(r'[0-9][A-Za-z0-9.]{0,31}\Z')


def validate(value):
    if not isinstance(value, str) or not VALID.fullmatch(value):
        raise ValueError(f'Invalid FDS version: {value!r}')
    return value


def git(root, *args):
    return subprocess.check_output(['git', '-C', str(root), *args], text=True, stderr=subprocess.DEVNULL).strip()


def version(root=ROOT):
    root = Path(root).resolve()
    # Source exports carry the value resolved when the export was created.
    # Never accidentally describe a containing repository during offline builds.
    if not (root / '.git').exists():
        return validate((root / 'FDS_VERSION').read_text().strip())
    revision = git(root, 'rev-parse', '--short=12', 'HEAD')
    tags = [tag for tag in git(root, 'tag', '--merged', 'HEAD').splitlines() if RELEASE.fullmatch(tag)]
    if tags:
        description = git(root, 'describe', '--tags', '--long', '--abbrev=12', *[f'--match={tag}' for tag in tags], 'HEAD')
        tag, distance, commit = description.rsplit('-', 2)
        value = RELEASE.fullmatch(tag)[1]
        if int(distance):
            value += f'.r{distance}.{commit}'
    else:
        value = f'0.dev.g{revision}'
    if git(root, 'status', '--porcelain', '--untracked-files=no'):
        value += '.dirty'
    return validate(value)


def cargo(root=ROOT):
    print(f'cargo:rustc-env=FDS_BUILD_VERSION={version(root)}')
    for path in [root / 'tools/fds_version.py', root / 'tools/version', root / 'tools/version-build.rs']:
        print(f'cargo:rerun-if-changed={path}')
    if not (root / '.git').exists():
        print(f'cargo:rerun-if-changed={root / "FDS_VERSION"}')
        return
    # Tag creation, ref changes, staging and edits must invalidate cached binaries.
    for name in ['HEAD', 'index', 'packed-refs', 'refs']:
        path = git(root, 'rev-parse', '--path-format=absolute', '--git-path', name)
        print(f'cargo:rerun-if-changed={path}')
    head = subprocess.run(['git', '-C', str(root), 'symbolic-ref', '-q', 'HEAD'], capture_output=True, text=True)
    if head.returncode == 0:
        print('cargo:rerun-if-changed=' + git(root, 'rev-parse', '--path-format=absolute', '--git-path', head.stdout.strip()))
    paths = git(root, 'ls-files', '--cached', '--others', '--exclude-standard').splitlines()
    for name in paths:
        if name != 'vendor/void-packages':
            print(f'cargo:rerun-if-changed={root / name}')