from __future__ import annotations

from typing import TYPE_CHECKING, Any

if TYPE_CHECKING:
    from collections.abc import Callable

    from hatchling.metadata.core import ProjectMetadata

DEFAULT_METADATA_VERSION = "2.4"
LATEST_METADATA_VERSION = "2.5"
CORE_METADATA_PROJECT_FIELDS = {
    "Author": ("authors",),
    "Author-email": ("authors",),
    "Classifier": ("classifiers",),
    "Description": ("readme",),
    "Description-Content-Type": ("readme",),
    "Dynamic": ("dynamic",),
    "Keywords": ("keywords",),
    "License": ("license",),
    "License-Expression": ("license",),
    "License-Files": ("license-files",),
    "Maintainer": ("maintainers",),
    "Maintainer-email": ("maintainers",),
    "Name": ("name",),
    "Provides-Extra": ("dependencies", "optional-dependencies"),
    "Requires-Dist": ("dependencies",),
    "Requires-Python": ("requires-python",),
    "Summary": ("description",),
    "Project-URL": ("urls",),
    "Version": ("version",),
    "Import-Name": ("import-names",),
    "Import-Namespace": ("import-namespaces",),
}
PROJECT_CORE_METADATA_FIELDS = {
    "authors": ("Author", "Author-email"),
    "classifiers": ("Classifier",),
    "dependencies": ("Requires-Dist",),
    "dynamic": ("Dynamic",),
    "keywords": ("Keywords",),
    "license": ("License", "License-Expression"),
    "license-files": ("License-Files",),
    "maintainers": ("Maintainer", "Maintainer-email"),
    "name": ("Name",),
    "optional-dependencies": ("Requires-Dist", "Provides-Extra"),
    "readme": ("Description", "Description-Content-Type"),
    "requires-python": ("Requires-Python",),
    "description": ("Summary",),
    "urls": ("Project-URL",),
    "version": ("Version",),
    "import-names": ("Import-Name",),
    "import-namespaces": ("Import-Namespace",),
}


def get_core_metadata_constructors() -> dict[str, Callable]:
    """
    https://packaging.python.org/specifications/core-metadata/
    """
    return {
        "1.2": construct_metadata_file_1_2,
        "2.1": construct_metadata_file_2_1,
        "2.2": construct_metadata_file_2_2,
        "2.3": construct_metadata_file_2_3,
        "2.4": construct_metadata_file_2_4,
        "2.5": construct_metadata_file_2_5,
    }


def project_metadata_from_core_metadata(core_metadata: str) -> dict[str, Any]:
    # https://packaging.python.org/en/latest/specifications/core-metadata/
    import email
    from email.headerregistry import HeaderRegistry

    header_registry = HeaderRegistry()

    message = email.message_from_string(core_metadata)
    metadata: dict[str, Any] = {}

    if name := message.get("Name"):
        metadata["name"] = name
    else:
        error_message = "Missing required core metadata: Name"
        raise ValueError(error_message)

    if version := message.get("Version"):
        metadata["version"] = version
    else:
        error_message = "Missing required core metadata: Version"
        raise ValueError(error_message)

    if (dynamic_fields := message.get_all("Dynamic")) is not None:
        # Use as an ordered set to retain bidirectional formatting.
        # This likely doesn't matter but we try hard around here.
        metadata["dynamic"] = list({
            project_field: None
            for core_metadata_field in dynamic_fields
            for project_field in CORE_METADATA_PROJECT_FIELDS.get(core_metadata_field, ())
        })

    if description := message.get_payload():
        metadata["readme"] = {
            "content-type": message.get("Description-Content-Type", "text/plain"),
            "text": description,
        }

    if (license_expression := message.get("License-Expression")) is not None:
        metadata["license"] = license_expression
    elif (license_text := message.get("License")) is not None:
        metadata["license"] = {"text": license_text}

    if (license_files := message.get_all("License-File")) is not None:
        metadata["license-files"] = license_files

    if (summary := message.get("Summary")) is not None:
        metadata["description"] = summary

    if (keywords := message.get("Keywords")) is not None:
        metadata["keywords"] = keywords.split(",")

    if (classifiers := message.get_all("Classifier")) is not None:
        metadata["classifiers"] = classifiers

    if (project_urls := message.get_all("Project-URL")) is not None:
        urls = {}
        for project_url in project_urls:
            label, url = project_url.split(",", maxsplit=1)
            urls[label.strip()] = url.strip()
        metadata["urls"] = urls

    authors = []
    if (author := message.get("Author")) is not None:
        authors.append({"name": author})

    if (author_email := message.get("Author-email")) is not None:
        address_header = header_registry("resent-from", author_email)
        for address in address_header.addresses:  # type: ignore[attr-defined]
            data = {"email": address.addr_spec}
            if name := address.display_name:
                data["name"] = name
            authors.append(data)

    if authors:
        metadata["authors"] = authors

    maintainers = []
    if (maintainer := message.get("Maintainer")) is not None:
        maintainers.append({"name": maintainer})

    if (maintainer_email := message.get("Maintainer-email")) is not None:
        address_header = header_registry("resent-from", maintainer_email)
        for address in address_header.addresses:  # type: ignore[attr-defined]
            data = {"email": address.addr_spec}
            if name := address.display_name:
                data["name"] = name
            maintainers.append(data)

    if maintainers:
        metadata["maintainers"] = maintainers

    if (requires_python := message.get("Requires-Python")) is not None:
        metadata["requires-python"] = requires_python

    optional_dependencies: dict[str, list[str]] = {}
    if (extras := message.get_all("Provides-Extra")) is not None:
        for extra in extras:
            optional_dependencies[extra] = []

    if (requirements := message.get_all("Requires-Dist")) is not None:
        from packaging.requirements import Requirement

        dependencies = []
        for requirement in requirements:
            req = Requirement(requirement)
            if req.marker is None:
                dependencies.append(str(req))
                continue

            markers = req.marker._markers  # noqa: SLF001
            for i, marker in enumerate(markers):
                if isinstance(marker, tuple):
                    left, _, right = marker
                    if left.value == "extra":
                        extra = right.value
                        del markers[i]  # noqa: B909
                        # If there was only one marker then there will be an unnecessary
                        # trailing semicolon in the string representation
                        if not markers:
                            req.marker = None
                        # Otherwise we need to remove the preceding `and` operation
                        else:
                            del markers[i - 1]

                        optional_dependencies.setdefault(extra, []).append(str(req))
                        break
            else:
                dependencies.append(str(req))

        metadata["dependencies"] = dependencies

    if optional_dependencies:
        metadata["optional-dependencies"] = optional_dependencies

    if (import_names := message.get_all("Import-Name")) is not None:
        metadata["import-names"] = import_names

    if (import_namespaces := message.get_all("Import-Namespace")) is not None:
        metadata["import-namespaces"] = import_namespaces

    if set(metadata.get("import-names", [])) & set(metadata.get("import-namespaces", [])):
        error_message = "Import-Name and Import-Namespace fields cannot contain the same name"
        raise ValueError(error_message)

    return metadata


def construct_metadata_file_1_2(metadata: ProjectMetadata, extra_dependencies: tuple[str] | None = None) -> str:
    """
    https://peps.python.org/pep-0345/
    """
    metadata_file = "Metadata-Version: 1.2\n"
    metadata_file += f"Name: {metadata.core.raw_name}\n"
    metadata_file += f"Version: {metadata.version}\n"

    if metadata.core.description:
        metadata_file += f"Summary: {metadata.core.description}\n"

    if metadata.core.urls:
        for label, url in metadata.core.urls.items():
            metadata_file += f"Project-URL: {label}, {url}\n"

    authors_data = metadata.core.authors_data
    if authors_data["name"]:
        metadata_file += f"Author: {', '.join(authors_data['name'])}\n"
    if authors_data["email"]:
        metadata_file += f"Author-email: {', '.join(authors_data['email'])}\n"

    maintainers_data = metadata.core.maintainers_data
    if maintainers_data["name"]:
        metadata_file += f"Maintainer: {', '.join(maintainers_data['name'])}\n"
    if maintainers_data["email"]:
        metadata_file += f"Maintainer-email: {', '.join(maintainers_data['email'])}\n"

    if metadata.core.license:
        license_start = "License: "
        indent = " " * (len(license_start) - 1)
        metadata_file += license_start

        for i, line in enumerate(metadata.core.license.splitlines()):
            if i == 0:
                metadata_file += f"{line}\n"
            else:
                metadata_file += f"{indent}{line}\n"
    elif metadata.core.license_expression:
        metadata_file += f"License: {metadata.core.license_expression}\n"

    if metadata.core.keywords:
        metadata_file += f"Keywords: {','.join(metadata.core.keywords)}\n"

    if metadata.core.classifiers:
        for classifier in metadata.core.classifiers:
            metadata_file += f"Classifier: {classifier}\n"

    if metadata.core.requires_python:
        metadata_file += f"Requires-Python: {metadata.core.requires_python}\n"

    if metadata.core.dependencies:
        for dependency in metadata.core.dependencies:
            metadata_file += f"Requires-Dist: {dependency}\n"

    if extra_dependencies:
        for dependency in extra_dependencies:
            metadata_file += f"Requires-Dist: {dependency}\n"

    return metadata_file


def construct_metadata_file_2_1(metadata: ProjectMetadata, extra_dependencies: tuple[str] | None = None) -> str:
    """
    https://peps.python.org/pep-0566/
    """
    metadata_file = "Metadata-Version: 2.1\n"
    metadata_file += f"Name: {metadata.core.raw_name}\n"
    metadata_file += f"Version: {metadata.version}\n"

    if metadata.core.description:
        metadata_file += f"Summary: {metadata.core.description}\n"

    if metadata.core.urls:
        for label, url in metadata.core.urls.items():
            metadata_file += f"Project-URL: {label}, {url}\n"

    authors_data = metadata.core.authors_data
    if authors_data["name"]:
        metadata_file += f"Author: {', '.join(authors_data['name'])}\n"
    if authors_data["email"]:
        metadata_file += f"Author-email: {', '.join(authors_data['email'])}\n"

    maintainers_data = metadata.core.maintainers_data
    if maintainers_data["name"]:
        metadata_file += f"Maintainer: {', '.join(maintainers_data['name'])}\n"
    if maintainers_data["email"]:
        metadata_file += f"Maintainer-email: {', '.join(maintainers_data['email'])}\n"

    if metadata.core.license:
        license_start = "License: "
        indent = " " * (len(license_start) - 1)
        metadata_file += license_start

        for i, line in enumerate(metadata.core.license.splitlines()):
            if i == 0:
                metadata_file += f"{line}\n"
            else:
                metadata_file += f"{indent}{line}\n"
    elif metadata.core.license_expression:
        metadata_file += f"License: {metadata.core.license_expression}\n"

    if metadata.core.keywords:
        metadata_file += f"Keywords: {','.join(metadata.core.keywords)}\n"

    if metadata.core.classifiers:
        for classifier in metadata.core.classifiers:
            metadata_file += f"Classifier: {classifier}\n"

    if metadata.core.requires_python:
        metadata_file += f"Requires-Python: {metadata.core.requires_python}\n"

    if metadata.core.dependencies:
        for dependency in metadata.core.dependencies:
            metadata_file += f"Requires-Dist: {dependency}\n"

    if extra_dependencies:
        for dependency in extra_dependencies:
            metadata_file += f"Requires-Dist: {dependency}\n"

    if metadata.core.optional_dependencies:
        for option, dependencies in metadata.core.optional_dependencies.items():
            metadata_file += f"Provides-Extra: {option}\n"
            for dependency in dependencies:
                if ";" in dependency:
                    dep_name, dep_env_marker = dependency.split(";", maxsplit=1)
                    metadata_file += f"Requires-Dist: {dep_name}; ({dep_env_marker.strip()}) and extra == {option!r}\n"
                elif "@ " in dependency:
                    metadata_file += f"Requires-Dist: {dependency} ; extra == {option!r}\n"
                else:
                    metadata_file += f"Requires-Dist: {dependency}; extra == {option!r}\n"

    if metadata.core.readme:
        metadata_file += f"Description-Content-Type: {metadata.core.readme_content_type}\n"
        metadata_file += f"\n{metadata.core.readme}"

    return metadata_file


def construct_metadata_file_2_2(metadata: ProjectMetadata, extra_dependencies: tuple[str] | None = None) -> str:
    """
    https://peps.python.org/pep-0643/
    """
    metadata_file = "Metadata-Version: 2.2\n"
    metadata_file += f"Name: {metadata.core.raw_name}\n"
    metadata_file += f"Version: {metadata.version}\n"

    if metadata.core.dynamic:
        # Ordered set
        for field in {
            core_metadata_field: None
            for project_field in metadata.core.dynamic
            for core_metadata_field in PROJECT_CORE_METADATA_FIELDS.get(project_field, ())
        }:
            metadata_file += f"Dynamic: {field}\n"

    if metadata.core.description:
        metadata_file += f"Summary: {metadata.core.description}\n"

    if metadata.core.urls:
        for label, url in metadata.core.urls.items():
            metadata_file += f"Project-URL: {label}, {url}\n"

    authors_data = metadata.core.authors_data
    if authors_data["name"]:
        metadata_file += f"Author: {', '.join(authors_data['name'])}\n"
    if authors_data["email"]:
        metadata_file += f"Author-email: {', '.join(authors_data['email'])}\n"

    maintainers_data = metadata.core.maintainers_data
    if maintainers_data["name"]:
        metadata_file += f"Maintainer: {', '.join(maintainers_data['name'])}\n"
    if maintainers_data["email"]:
        metadata_file += f"Maintainer-email: {', '.join(maintainers_data['email'])}\n"

    if metadata.core.license:
        license_start = "License: "
        indent = " " * (len(license_start) - 1)
        metadata_file += license_start

        for i, line in enumerate(metadata.core.license.splitlines()):
            if i == 0:
                metadata_file += f"{line}\n"
            else:
                metadata_file += f"{indent}{line}\n"
    elif metadata.core.license_expression:
        metadata_file += f"License: {metadata.core.license_expression}\n"

    if metadata.core.keywords:
        metadata_file += f"Keywords: {','.join(metadata.core.keywords)}\n"

    if metadata.core.classifiers:
        for classifier in metadata.core.classifiers:
            metadata_file += f"Classifier: {classifier}\n"

    if metadata.core.requires_python:
        metadata_file += f"Requires-Python: {metadata.core.requires_python}\n"

    if metadata.core.dependencies:
        for dependency in metadata.core.dependencies:
            metadata_file += f"Requires-Dist: {dependency}\n"

    if extra_dependencies:
        for dependency in extra_dependencies:
            metadata_file += f"Requires-Dist: {dependency}\n"

    if metadata.core.optional_dependencies:
        for option, dependencies in metadata.core.optional_dependencies.items():
            metadata_file += f"Provides-Extra: {option}\n"
            for dependency in dependencies:
                if ";" in dependency:
                    dep_name, dep_env_marker = dependency.split(";", maxsplit=1)
                    metadata_file += f"Requires-Dist: {dep_name}; ({dep_env_marker.strip()}) and extra == {option!r}\n"
                elif "@ " in dependency:
                    metadata_file += f"Requires-Dist: {dependency} ; extra == {option!r}\n"
                else:
                    metadata_file += f"Requires-Dist: {dependency}; extra == {option!r}\n"

    if metadata.core.readme:
        metadata_file += f"Description-Content-Type: {metadata.core.readme_content_type}\n"
        metadata_file += f"\n{metadata.core.readme}"

    return metadata_file


def construct_metadata_file_2_3(metadata: ProjectMetadata, extra_dependencies: tuple[str] | None = None) -> str:
    """
    https://peps.python.org/pep-0685/
    """
    metadata_file = "Metadata-Version: 2.3\n"
    metadata_file += f"Name: {metadata.core.raw_name}\n"
    metadata_file += f"Version: {metadata.version}\n"

    if metadata.core.dynamic:
        # Ordered set
        for field in {
            core_metadata_field: None
            for project_field in metadata.core.dynamic
            for core_metadata_field in PROJECT_CORE_METADATA_FIELDS.get(project_field, ())
        }:
            metadata_file += f"Dynamic: {field}\n"

    if metadata.core.description:
        metadata_file += f"Summary: {metadata.core.description}\n"

    if metadata.core.urls:
        for label, url in metadata.core.urls.items():
            metadata_file += f"Project-URL: {label}, {url}\n"

    authors_data = metadata.core.authors_data
    if authors_data["name"]:
        metadata_file += f"Author: {', '.join(authors_data['name'])}\n"
    if authors_data["email"]:
        metadata_file += f"Author-email: {', '.join(authors_data['email'])}\n"

    maintainers_data = metadata.core.maintainers_data
    if maintainers_data["name"]:
        metadata_file += f"Maintainer: {', '.join(maintainers_data['name'])}\n"
    if maintainers_data["email"]:
        metadata_file += f"Maintainer-email: {', '.join(maintainers_data['email'])}\n"

    if metadata.core.license:
        license_start = "License: "
        indent = " " * (len(license_start) - 1)
        metadata_file += license_start

        for i, line in enumerate(metadata.core.license.splitlines()):
            if i == 0:
                metadata_file += f"{line}\n"
            else:
                metadata_file += f"{indent}{line}\n"
    elif metadata.core.license_expression:
        metadata_file += f"License: {metadata.core.license_expression}\n"

    if metadata.core.keywords:
        metadata_file += f"Keywords: {','.join(metadata.core.keywords)}\n"

    if metadata.core.classifiers:
        for classifier in metadata.core.classifiers:
            metadata_file += f"Classifier: {classifier}\n"

    if metadata.core.requires_python:
        metadata_file += f"Requires-Python: {metadata.core.requires_python}\n"

    if metadata.core.dependencies:
        for dependency in metadata.core.dependencies:
            metadata_file += f"Requires-Dist: {dependency}\n"

    if extra_dependencies:
        for dependency in extra_dependencies:
            metadata_file += f"Requires-Dist: {dependency}\n"

    if metadata.core.optional_dependencies:
        for option, dependencies in metadata.core.optional_dependencies.items():
            metadata_file += f"Provides-Extra: {option}\n"
            for dependency in dependencies:
                if ";" in dependency:
                    dep_name, dep_env_marker = dependency.split(";", maxsplit=1)
                    metadata_file += f"Requires-Dist: {dep_name}; ({dep_env_marker.strip()}) and extra == {option!r}\n"
                elif "@ " in dependency:
                    metadata_file += f"Requires-Dist: {dependency} ; extra == {option!r}\n"
                else:
                    metadata_file += f"Requires-Dist: {dependency}; extra == {option!r}\n"

    if metadata.core.readme:
        metadata_file += f"Description-Content-Type: {metadata.core.readme_content_type}\n"
        metadata_file += f"\n{metadata.core.readme}"

    return metadata_file


def construct_metadata_file_2_4(metadata: ProjectMetadata, extra_dependencies: tuple[str] | None = None) -> str:
    """
    https://peps.python.org/pep-0639/
    """
    metadata_file = "Metadata-Version: 2.4\n"
    metadata_file += f"Name: {metadata.core.raw_name}\n"
    metadata_file += f"Version: {metadata.version}\n"

    if metadata.core.dynamic:
        # Ordered set
        for field in {
            core_metadata_field: None
            for project_field in metadata.core.dynamic
            for core_metadata_field in PROJECT_CORE_METADATA_FIELDS.get(project_field, ())
        }:
            metadata_file += f"Dynamic: {field}\n"

    if metadata.core.description:
        metadata_file += f"Summary: {metadata.core.description}\n"

    if metadata.core.urls:
        for label, url in metadata.core.urls.items():
            metadata_file += f"Project-URL: {label}, {url}\n"

    authors_data = metadata.core.authors_data
    if authors_data["name"]:
        metadata_file += f"Author: {', '.join(authors_data['name'])}\n"
    if authors_data["email"]:
        metadata_file += f"Author-email: {', '.join(authors_data['email'])}\n"

    maintainers_data = metadata.core.maintainers_data
    if maintainers_data["name"]:
        metadata_file += f"Maintainer: {', '.join(maintainers_data['name'])}\n"
    if maintainers_data["email"]:
        metadata_file += f"Maintainer-email: {', '.join(maintainers_data['email'])}\n"

    if metadata.core.license:
        license_start = "License: "
        indent = " " * (len(license_start) - 1)
        metadata_file += license_start

        for i, line in enumerate(metadata.core.license.splitlines()):
            if i == 0:
                metadata_file += f"{line}\n"
            else:
                metadata_file += f"{indent}{line}\n"

    if metadata.core.license_expression:
        metadata_file += f"License-Expression: {metadata.core.license_expression}\n"

    if metadata.core.license_files:
        for license_file in metadata.core.license_files:
            metadata_file += f"License-File: {license_file}\n"

    if metadata.core.keywords:
        metadata_file += f"Keywords: {','.join(metadata.core.keywords)}\n"

    if metadata.core.classifiers:
        for classifier in metadata.core.classifiers:
            metadata_file += f"Classifier: {classifier}\n"

    if metadata.core.requires_python:
        metadata_file += f"Requires-Python: {metadata.core.requires_python}\n"

    if metadata.core.dependencies:
        for dependency in metadata.core.dependencies:
            metadata_file += f"Requires-Dist: {dependency}\n"

    if extra_dependencies:
        for dependency in extra_dependencies:
            metadata_file += f"Requires-Dist: {dependency}\n"

    if metadata.core.optional_dependencies:
        for option, dependencies in metadata.core.optional_dependencies.items():
            metadata_file += f"Provides-Extra: {option}\n"
            for dependency in dependencies:
                if ";" in dependency:
                    dep_name, dep_env_marker = dependency.split(";", maxsplit=1)
                    metadata_file += f"Requires-Dist: {dep_name}; ({dep_env_marker.strip()}) and extra == {option!r}\n"
                elif "@ " in dependency:
                    metadata_file += f"Requires-Dist: {dependency} ; extra == {option!r}\n"
                else:
                    metadata_file += f"Requires-Dist: {dependency}; extra == {option!r}\n"

    if metadata.core.readme:
        metadata_file += f"Description-Content-Type: {metadata.core.readme_content_type}\n"
        metadata_file += f"\n{metadata.core.readme}"

    return metadata_file


def construct_metadata_file_2_5(metadata: ProjectMetadata, extra_dependencies: tuple[str] | None = None) -> str:
    """
    https://peps.python.org/pep-0794/
    """
    metadata_file = "Metadata-Version: 2.5\n"
    metadata_file += f"Name: {metadata.core.raw_name}\n"
    metadata_file += f"Version: {metadata.version}\n"

    if metadata.core.import_names is not None:
        if not metadata.core.import_names and not metadata.core.import_namespaces:
            # Projects MAY set `import-names` an empty array and not set `import-namespaces`
            # at all in a `pyproject.toml` file (e.g. `import-names = []`). To match this,
            # projects MAY have an empty `Import-Name` field in their metadata. This represents
            # a project with NO import names, public or private (i.e. there are no Python modules
            # of any kind in the distribution file).
            metadata_file += "Import-Name\n"

        for import_name in metadata.core.import_names:
            _name = f"{import_name}; private" if import_name.startswith("_") else import_name
            metadata_file += f"Import-Name: {_name}\n"

    if metadata.core.import_namespaces:
        for import_namespace in metadata.core.import_namespaces:
            _name = f"{import_namespace}; private" if import_namespace.startswith("_") else import_namespace
            metadata_file += f"Import-Namespace: {_name}\n"

    if metadata.core.dynamic:
        # Ordered set
        for field in {
            core_metadata_field: None
            for project_field in metadata.core.dynamic
            for core_metadata_field in PROJECT_CORE_METADATA_FIELDS.get(project_field, ())
        }:
            metadata_file += f"Dynamic: {field}\n"

    if metadata.core.description:
        metadata_file += f"Summary: {metadata.core.description}\n"

    if metadata.core.urls:
        for label, url in metadata.core.urls.items():
            metadata_file += f"Project-URL: {label}, {url}\n"

    authors_data = metadata.core.authors_data
    if authors_data["name"]:
        metadata_file += f"Author: {', '.join(authors_data['name'])}\n"
    if authors_data["email"]:
        metadata_file += f"Author-email: {', '.join(authors_data['email'])}\n"

    maintainers_data = metadata.core.maintainers_data
    if maintainers_data["name"]:
        metadata_file += f"Maintainer: {', '.join(maintainers_data['name'])}\n"
    if maintainers_data["email"]:
        metadata_file += f"Maintainer-email: {', '.join(maintainers_data['email'])}\n"

    if metadata.core.license:
        license_start = "License: "
        indent = " " * (len(license_start) - 1)
        metadata_file += license_start

        for i, line in enumerate(metadata.core.license.splitlines()):
            if i == 0:
                metadata_file += f"{line}\n"
            else:
                metadata_file += f"{indent}{line}\n"

    if metadata.core.license_expression:
        metadata_file += f"License-Expression: {metadata.core.license_expression}\n"

    if metadata.core.license_files:
        for license_file in metadata.core.license_files:
            metadata_file += f"License-File: {license_file}\n"

    if metadata.core.keywords:
        metadata_file += f"Keywords: {','.join(metadata.core.keywords)}\n"

    if metadata.core.classifiers:
        for classifier in metadata.core.classifiers:
            metadata_file += f"Classifier: {classifier}\n"

    if metadata.core.requires_python:
        metadata_file += f"Requires-Python: {metadata.core.requires_python}\n"

    if metadata.core.dependencies:
        for dependency in metadata.core.dependencies:
            metadata_file += f"Requires-Dist: {dependency}\n"

    if extra_dependencies:
        for dependency in extra_dependencies:
            metadata_file += f"Requires-Dist: {dependency}\n"

    if metadata.core.optional_dependencies:
        for option, dependencies in metadata.core.optional_dependencies.items():
            metadata_file += f"Provides-Extra: {option}\n"
            for dependency in dependencies:
                if ";" in dependency:
                    dep_name, dep_env_marker = dependency.split(";", maxsplit=1)
                    metadata_file += f"Requires-Dist: {dep_name}; ({dep_env_marker.strip()}) and extra == {option!r}\n"
                elif "@ " in dependency:
                    metadata_file += f"Requires-Dist: {dependency} ; extra == {option!r}\n"
                else:
                    metadata_file += f"Requires-Dist: {dependency}; extra == {option!r}\n"

    if metadata.core.readme:
        metadata_file += f"Description-Content-Type: {metadata.core.readme_content_type}\n"
        metadata_file += f"\n{metadata.core.readme}"

    return metadata_file
