import ast
import os
from argparse import Namespace
from os import PathLike
from pathlib import Path
from typing import Any, Dict, List, Mapping, Optional, Tuple, cast

from pdm.compat import tomllib
from pdm.formats.base import (
    MetaConverter,
    Unset,
    array_of_inline_tables,
    convert_from,
    make_array,
    make_inline_table,
)
from pdm.project import Project
from pdm.utils import cd


def check_fingerprint(project: Optional[Project], filename: PathLike) -> bool:
    with open(filename, "rb") as fp:
        try:
            data = tomllib.load(fp)
        except tomllib.TOMLDecodeError:
            return False

    return "tool" in data and "flit" in data["tool"]


def _get_author(metadata: Dict[str, Any], type_: str = "author") -> List[str]:
    name = metadata.pop(type_)
    email = metadata.pop(f"{type_}-email", None)
    return cast(List[str], array_of_inline_tables([{"name": name, "email": email}]))


def get_docstring_and_version_via_ast(
    target: Path,
) -> Tuple[Optional[str], Optional[str]]:
    """
    This function is borrowed from flit's implementation, but does not attempt to import
    that file. If docstring or version can't be retrieved by this function,
    they are just left empty.
    """
    # read as bytes to enable custom encodings
    node = ast.parse(target.read_bytes())
    for child in node.body:
        # Only use the version from the given module if it's a simple
        # string assignment to __version__
        is_version_str = (
            isinstance(child, ast.Assign)
            and len(child.targets) == 1
            and isinstance(child.targets[0], ast.Name)
            and child.targets[0].id == "__version__"
            and isinstance(child.value, ast.Str)
        )
        if is_version_str:
            version: Optional[str] = cast(ast.Str, cast(ast.Assign, child).value).s
            break
    else:
        version = None
    return ast.get_docstring(node), version


class FlitMetaConverter(MetaConverter):
    def warn_against_dynamic_version_or_docstring(
        self, source: Path, version: str, description: str
    ) -> None:
        if not self._ui:
            return
        dynamic_fields = []
        if not version:
            dynamic_fields.append("version")
        if not description:
            dynamic_fields.append("description")
        if not dynamic_fields:
            return
        fields = " and ".join(dynamic_fields)
        message = (
            f"Can't retrieve {fields} from pyproject.toml or parsing {source}. "
            "They are probably imported from other files which is not supported by PDM."
            " You may need to supply their values in pyproject.toml manually."
        )
        self._ui.echo(message, err=True, style="yellow")

    @convert_from("metadata")
    def name(self, metadata: Dict[str, Any]) -> str:
        # name
        module = metadata.pop("module")
        self._data["name"] = metadata.pop("dist-name", module)
        # version and description
        if (Path(module) / "__init__.py").exists():
            source = Path(module) / "__init__.py"
        else:
            source = Path(f"{module}.py")

        version = self._data.get("version")
        description = self._data.get("description")
        description_in_ast, version_in_ast = get_docstring_and_version_via_ast(source)
        self._data["version"] = version or version_in_ast or ""
        self._data["description"] = description or description_in_ast or ""
        self.warn_against_dynamic_version_or_docstring(
            source, self._data["version"], self._data["description"]
        )
        # author and maintainer
        if "author" in metadata:
            self._data["authors"] = _get_author(metadata)
        if "maintainer" in metadata:
            self._data["maintainers"] = _get_author(metadata, "maintainer")
        if "license" in metadata:
            self._data["license"] = make_inline_table({"text": metadata.pop("license")})
            self._data["dynamic"] = ["classifiers"]
        if "urls" in metadata:
            self._data["urls"] = metadata.pop("urls")
        if "home-page" in metadata:
            self._data.setdefault("urls", {})["homepage"] = metadata.pop("home-page")
        if "description-file" in metadata:
            self._data["readme"] = metadata.pop("description-file")
        if "requires-python" in metadata:
            self._data["requires-python"] = metadata.pop("requires-python")
            self._data["dynamic"] = ["classifiers"]
        # requirements
        self._data["dependencies"] = make_array(metadata.pop("requires", []), True)
        self._data["optional-dependencies"] = metadata.pop("requires-extra", {})
        # Add remaining metadata as the same key
        self._data.update(metadata)
        return self._data["name"]

    @convert_from("entrypoints", name="entry-points")
    def entry_points(
        self, value: Dict[str, Dict[str, str]]
    ) -> Dict[str, Dict[str, str]]:
        return value

    @convert_from("sdist")
    def includes(self, value: Dict[str, List[str]]) -> None:
        self.settings.setdefault("build", {}).update(
            {"excludes": value.get("exclude"), "includes": value.get("include")}
        )
        raise Unset()


def convert(
    project: Optional[Project], filename: PathLike, options: Optional[Namespace]
) -> Tuple[Mapping, Mapping]:
    with open(filename, "rb") as fp, cd(os.path.dirname(os.path.abspath(filename))):
        converter = FlitMetaConverter(
            tomllib.load(fp)["tool"]["flit"], project.core.ui if project else None
        )
        return converter.convert()


def export(project: Project, candidates: List, options: Optional[Namespace]) -> None:
    raise NotImplementedError()
