from __future__ import annotations

import pathlib
import re
import sys
from collections.abc import Iterable, Mapping, Sequence
from dataclasses import dataclass

import yaml

REPO_ROOT = pathlib.Path(__file__).resolve().parents[2]
WORKFLOW_DIR = REPO_ROOT / ".github" / "workflows"
CIRCLECI_CONFIG = REPO_ROOT / ".circleci" / "config.yml"
ALLOWLIST_FILE = REPO_ROOT / ".github" / "ci-coverage-allowlist.yml"
TESTS_ROOT = REPO_ROOT / "tests"

ALLOWLIST_KEYS = frozenset({"description", "test_paths", "dockerfiles"})
PATH_FILTER_KEYS = frozenset({"paths", "paths-ignore"})
TEST_PATH_KEYS = frozenset({"test-path", "test-paths"})
DOCKERFILE_INPUT_KEYS = frozenset({"file", "dockerfile"})
TEST_RUNNER_RE = re.compile(r"\bpytest\b|\bcircleci tests\b|\bhelm unittest\b|\bplaywright test\b|\bpython[0-9.]*\s")
IMAGE_BUILD_RE = re.compile(r"\bdocker\s+(?:buildx\s+)?build\b")
TEST_TOKEN_RE = re.compile(r"tests/[A-Za-z0-9_./*?-]+")
DOCKERFILE_TOKEN_RE = re.compile(r"[A-Za-z0-9_./-]*Dockerfile[A-Za-z0-9_.-]*")
COMMENT_RE = re.compile(r"^\s*#.*$", re.MULTILINE)
GLOB_CHARS = frozenset("*?")


@dataclass(frozen=True, slots=True)
class AllowEntry:
    paths: tuple[str, ...]
    reason: str


@dataclass(frozen=True, slots=True)
class Allowlist:
    test_paths: tuple[AllowEntry, ...]
    dockerfiles: tuple[AllowEntry, ...]

    def covers_test(self, relative_path: str) -> bool:
        return any(_token_covers(path, relative_path) for entry in self.test_paths for path in entry.paths)

    def covers_dockerfile(self, relative_path: str) -> bool:
        return any(relative_path == path for entry in self.dockerfiles for path in entry.paths)


@dataclass(frozen=True, slots=True)
class Scalar:
    key: str
    value: str


@dataclass(frozen=True, slots=True)
class Finding:
    subject: str
    detail: str


def _scalars(node: object, key: str) -> tuple[Scalar, ...]:
    if isinstance(node, str):
        return (Scalar(key=key, value=node),)
    if isinstance(node, Mapping):
        return tuple(
            scalar
            for child_key, value in node.items()
            if child_key not in PATH_FILTER_KEYS
            for scalar in _scalars(value, str(child_key))
        )
    if isinstance(node, Sequence):
        return tuple(scalar for item in node for scalar in _scalars(item, key))
    return ()


def _config_files() -> tuple[pathlib.Path, ...]:
    workflows = tuple(sorted(path for path in WORKFLOW_DIR.iterdir() if path.suffix in (".yml", ".yaml")))
    circleci = (CIRCLECI_CONFIG,) if CIRCLECI_CONFIG.is_file() else ()
    return workflows + circleci


def _all_scalars() -> tuple[Scalar, ...]:
    return tuple(
        scalar
        for path in _config_files()
        for scalar in _scalars(yaml.safe_load(path.read_text(encoding="utf-8")), path.name)
    )


def _uncommented(value: str) -> str:
    return COMMENT_RE.sub("", value)


def _invoked_test_tokens(scalars: Iterable[Scalar]) -> frozenset[str]:
    return frozenset(
        match.group(0).rstrip("/")
        for scalar in scalars
        if scalar.key in TEST_PATH_KEYS or TEST_RUNNER_RE.search(scalar.value)
        for match in TEST_TOKEN_RE.finditer(_uncommented(scalar.value))
    )


def _built_dockerfile_tokens(scalars: Iterable[Scalar]) -> frozenset[str]:
    return frozenset(
        match.group(0)
        for scalar in scalars
        if scalar.key in DOCKERFILE_INPUT_KEYS or IMAGE_BUILD_RE.search(scalar.value)
        for match in DOCKERFILE_TOKEN_RE.finditer(_uncommented(scalar.value))
    )


def _glob_to_regex(token: str) -> re.Pattern[str]:
    parts = re.split(r"(\*\*/|\*\*|\*|\?)", token)
    translated = "".join(
        {"**/": r"(?:.*/)?", "**": r".*", "*": r"[^/]*", "?": r"[^/]"}.get(part, re.escape(part)) for part in parts
    )
    return re.compile(rf"{translated}(?:/.*)?$")


def _token_covers(token: str, relative_path: str) -> bool:
    if GLOB_CHARS & set(token):
        return _glob_to_regex(token).match(relative_path) is not None
    return relative_path == token or relative_path.startswith(f"{token}/")


def _test_files() -> tuple[str, ...]:
    return tuple(
        sorted(
            path.relative_to(REPO_ROOT).as_posix()
            for path in TESTS_ROOT.rglob("test_*.py")
            if path.is_file() and "node_modules" not in path.parts
        )
    )


def _dockerfiles() -> tuple[str, ...]:
    return tuple(
        sorted(
            path.relative_to(REPO_ROOT).as_posix()
            for path in REPO_ROOT.rglob("Dockerfile*")
            if path.is_file()
            and ".git" not in path.parts
            and "node_modules" not in path.parts
            and not path.name.endswith(".dockerignore")
        )
    )


def _uncovered_tests(allowlist: Allowlist, tokens: frozenset[str]) -> tuple[Finding, ...]:
    uncovered = tuple(
        relative_path
        for relative_path in _test_files()
        if not any(_token_covers(token, relative_path) for token in tokens) and not allowlist.covers_test(relative_path)
    )
    directories = tuple(dict.fromkeys(path.rsplit("/", 1)[0] for path in uncovered))
    return tuple(
        Finding(
            subject=directory,
            detail=_describe(tuple(p for p in uncovered if p.rsplit("/", 1)[0] == directory)),
        )
        for directory in directories
    )


def _describe(paths: tuple[str, ...]) -> str:
    names = ", ".join(path.rsplit("/", 1)[1] for path in paths[:3])
    suffix = f", +{len(paths) - 3} more" if len(paths) > 3 else ""
    return f"{len(paths)} test file(s) invoked by no job: {names}{suffix}"


def _uncovered_dockerfiles(allowlist: Allowlist, tokens: frozenset[str]) -> tuple[Finding, ...]:
    return tuple(
        Finding(subject=relative_path, detail="built by no job")
        for relative_path in _dockerfiles()
        if relative_path not in tokens and not allowlist.covers_dockerfile(relative_path)
    )


def _parse_entry(item: object, section: str) -> AllowEntry:
    if not isinstance(item, dict):
        raise SystemExit(f"{ALLOWLIST_FILE.name}: '{section}' entries must be mappings")
    paths = item.get("paths")
    reason = item.get("reason")
    if (
        not isinstance(paths, list)
        or not paths
        or not all(isinstance(path, str) for path in paths)
        or not isinstance(reason, str)
        or not reason.strip()
    ):
        raise SystemExit(
            f"{ALLOWLIST_FILE.name}: every '{section}' entry needs a non-empty 'paths' "
            "list of strings and a non-empty 'reason'"
        )
    return AllowEntry(paths=tuple(paths), reason=reason)


def _parse_entries(raw: object, section: str) -> tuple[AllowEntry, ...]:
    if not isinstance(raw, list):
        raise SystemExit(f"{ALLOWLIST_FILE.name}: '{section}' must be a list")
    return tuple(_parse_entry(item, section) for item in raw)


def _load_allowlist() -> Allowlist:
    if not ALLOWLIST_FILE.is_file():
        return Allowlist(test_paths=(), dockerfiles=())
    raw = yaml.safe_load(ALLOWLIST_FILE.read_text(encoding="utf-8")) or {}
    if not isinstance(raw, dict):
        raise SystemExit(f"{ALLOWLIST_FILE.name}: top level must be a mapping")
    unknown = sorted(str(key) for key in raw if key not in ALLOWLIST_KEYS)
    if unknown:
        raise SystemExit(
            f"{ALLOWLIST_FILE.name}: unknown top-level key(s) {unknown}; expected only {sorted(ALLOWLIST_KEYS)}"
        )
    return Allowlist(
        test_paths=_parse_entries(raw.get("test_paths", []), "test_paths"),
        dockerfiles=_parse_entries(raw.get("dockerfiles", []), "dockerfiles"),
    )


def _write(message: str) -> None:
    sys.stdout.write(f"{message}\n")


def _report(title: str, findings: tuple[Finding, ...], remedy: str) -> None:
    _write(f"ERROR: {title}")
    for finding in findings:
        _write(f"  - {finding.subject}: {finding.detail}")
    _write("")
    _write(remedy)
    _write("")


def main() -> int:
    allowlist = _load_allowlist()
    scalars = _all_scalars()

    test_findings = _uncovered_tests(allowlist, _invoked_test_tokens(scalars))
    dockerfile_findings = _uncovered_dockerfiles(allowlist, _built_dockerfile_tokens(scalars))

    if test_findings:
        _report(
            "test files that no CI job invokes",
            test_findings,
            "Add each to a job's test path, or list it in .github/ci-coverage-allowlist.yml with a reason.",
        )
    if dockerfile_findings:
        _report(
            "Dockerfiles that no CI job builds",
            dockerfile_findings,
            "Build each in a workflow, or list it in .github/ci-coverage-allowlist.yml with a reason.",
        )
    if test_findings or dockerfile_findings:
        return 1

    _write(
        f"OK: {len(_test_files())} test files and {len(_dockerfiles())} Dockerfiles are each "
        "invoked by at least one job or carry an explicit allowlist entry."
    )
    return 0


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