"""Detect the language of a changed file from its path."""
from __future__ import annotations

from pathlib import PurePosixPath


SOURCE_EXTENSIONS: dict[str, str] = {
    ".py":  "python",
    ".js":  "javascript",
    ".jsx": "javascript",
    ".mjs": "javascript",
    ".cjs": "javascript",
    ".ts":  "typescript",
    ".tsx": "typescript",
    ".cs":  "csharp",
    ".lua": "lua",
    ".ps1":  "powershell",
    ".psm1": "powershell",
    ".psd1": "powershell",
}


DEP_MANIFESTS: set[str] = {
    "requirements.txt", "pyproject.toml", "poetry.lock", "Pipfile.lock",
    "Pipfile", "setup.py", "setup.cfg",
    "package.json", "package-lock.json", "yarn.lock", "pnpm-lock.yaml",
    "packages.config",
}

DEP_MANIFEST_PREFIXES: tuple[str, ...] = ("requirements",)
DEP_MANIFEST_EXTENSIONS: tuple[str, ...] = (".csproj", ".sln")


KNOWN_UNSUPPORTED_LANGUAGES: dict[str, str] = {
    ".go":     "Go",
    ".rb":     "Ruby",
    ".java":   "Java",
    ".kt":     "Kotlin",
    ".kts":    "Kotlin",
    ".rs":     "Rust",
    ".swift":  "Swift",
    ".php":    "PHP",
    ".scala":  "Scala",
    ".sc":     "Scala",
    ".clj":    "Clojure",
    ".cljs":   "ClojureScript",
    ".ex":     "Elixir",
    ".exs":    "Elixir",
    ".erl":    "Erlang",
    ".hrl":    "Erlang",
    ".dart":   "Dart",
    ".r":      "R",
    ".jl":     "Julia",
    ".zig":    "Zig",
    ".nim":    "Nim",
    ".hs":     "Haskell",
    ".ml":     "OCaml",
    ".mli":    "OCaml",
    ".fs":     "F#",
    ".fsi":    "F#",
    ".fsx":    "F#",
    ".vb":     "Visual Basic",
    ".pl":     "Perl",
    ".pm":     "Perl",
    ".c":      "C",
    ".h":      "C/C++ header",
    ".cpp":    "C++",
    ".cc":     "C++",
    ".cxx":    "C++",
    ".hpp":    "C++",
    ".m":      "Objective-C",
    ".mm":     "Objective-C++",
    ".groovy": "Groovy",
}

_GHA_YAML_EXTS: frozenset[str] = frozenset((".yml", ".yaml"))
_GHA_PATH_PREFIXES: tuple[str, ...] = (".github/workflows/", ".github/actions/")


def detect_language(path: str) -> str | None:
    suffix = PurePosixPath(path).suffix
    return SOURCE_EXTENSIONS.get(suffix)


def is_supported_source(path: str) -> bool:
    return detect_language(path) is not None


def is_gha_file(path: str) -> bool:
    """Return True if path is a GitHub Actions workflow or action definition."""
    normalized = path.replace("\\", "/")
    if PurePosixPath(normalized).suffix.lower() not in _GHA_YAML_EXTS:
        return False
    return normalized.startswith(_GHA_PATH_PREFIXES)


def known_unsupported_language(path: str) -> str | None:
    """Return the display name of a recognized-but-unsupported source language,
    or None if the path isn't one we recognize as source code.
    """
    suffix = PurePosixPath(path).suffix.lower()
    return KNOWN_UNSUPPORTED_LANGUAGES.get(suffix)


def is_dep_manifest(path: str) -> bool:
    name = PurePosixPath(path).name
    if name in DEP_MANIFESTS:
        return True
    if any(name.startswith(p) and name.endswith(".txt") for p in DEP_MANIFEST_PREFIXES):
        return True
    return any(name.endswith(ext) for ext in DEP_MANIFEST_EXTENSIONS)