"""
MkDocsRenderer

Generates Markdown source files compatible with MkDocs Material
and mkdocstrings, ensuring:

- Root index.md always exists
- Parent package indexes are created automatically
- Child modules are linked in parent index files
- README.md can be generated from the root package docstring
"""

from pathlib import Path
from docforge.models import Project, Module


class MkDocsRenderer:
    """
    Renderer that generates Markdown source files formatted for the MkDocs
    'mkdocstrings' plugin.
    """

    name = "mkdocs"

    # -------------------------
    # Public API
    # -------------------------
    def generate_sources(
        self,
        project: Project,
        out_dir: Path,
        module_is_source: bool | None = None,
    ) -> None:
        """
        Produce a set of Markdown files in the output directory based on the
        provided Project models.

        Args:
            project:
                The project model to render.

            out_dir:
                Target directory for generated Markdown.

            module_is_source:
                If True, treat the module as the root folder.
        """
        out_dir.mkdir(parents=True, exist_ok=True)
        self._ensure_root_index(project, out_dir)

        modules = list(project.get_all_modules())
        paths = {m.path for m in modules}

        # Package detection (level-agnostic)
        packages = {
            p for p in paths
            if any(other.startswith(p + ".") for other in paths)
        }

        for module in modules:
            self._write_module(
                module,
                packages,
                out_dir,
                module_is_source,
            )

    def generate_readme(
        self,
        project: Project,
        docs_dir: Path,
        module_is_source: bool | None = None,
    ) -> None:
        """
        Generate README.md from the root package docstring.

        Behavior:

        - If module_is_source is True:
            README.md is generated at project root (docs_dir.parent)

        - If module_is_source is False:
            TODO: generate README.md inside respective module folders
        """

        # -------------------------
        # Only implement source-root mode
        # -------------------------
        if not module_is_source:
            # TODO: support per-module README generation
            return

        readme_path = docs_dir.parent / "README.md"

        root_module = None
        for module in project.get_all_modules():
            if module.path == project.name:
                root_module = module
                break

        if root_module is None:
            return

        doc = ""

        if root_module.docstring:
            doc = getattr(
                root_module.docstring,
                "value",
                str(root_module.docstring),
            )

        content = (
            f"# {project.name}\n\n"
            f"{doc.strip()}\n"
        )

        if not readme_path.exists() or readme_path.read_text(encoding="utf-8") != content:
            readme_path.write_text(
                content,
                encoding="utf-8",
            )

    # -------------------------
    # Internal helpers
    # -------------------------

    def _find_root_module(self, project: Project) -> Module | None:
        """
        Find the root module matching the project name.
        """
        for module in project.get_all_modules():
            if module.path == project.name:
                return module
        return None

    def _write_module(
        self,
        module: Module,
        packages: set[str],
        out_dir: Path,
        module_is_source: bool | None = None,
    ) -> None:
        """
        Write a single module's documentation file. Packages are written as
        'index.md' inside their respective directories.

        Args:
            module: The module to write.
            packages: A set of module paths that are identified as packages.
            out_dir: The base output directory.
            module_is_source: Module is the source folder and to be treated as the root folder.
        """

        parts = module.path.split(".")

        if module_is_source:
            module_name, parts = parts[0], parts[1:]
        else:
            module_name, parts = parts[0], parts

        if module.path in packages:
            # Package → directory/index.md
            dir_path = out_dir.joinpath(*parts)
            dir_path.mkdir(parents=True, exist_ok=True)

            md_path = dir_path / "index.md"
            link_target = f"{parts[-1]}/" if parts else None

        else:
            # Leaf module → parent_dir/<name>.md
            dir_path = out_dir.joinpath(*parts[:-1])
            dir_path.mkdir(parents=True, exist_ok=True)

            md_path = dir_path / f"{parts[-1]}.md"
            link_target = f"{parts[-1]}.md" if parts else None

        title = parts[-1].replace("_", " ").title() if parts else module_name
        content = self._render_markdown(title, module.path)

        if not md_path.exists() or md_path.read_text(encoding="utf-8") != content:
            md_path.write_text(content, encoding="utf-8")

        if not module_is_source:
            self._ensure_parent_index(parts, out_dir, link_target, title)

    def _render_markdown(self, title: str, module_path: str) -> str:
        """
        Generate the Markdown content for a module file.

        Args:
            title: The display title for the page.
            module_path: The dotted path of the module to document.

        Returns:
            A string containing the Markdown source.
        """
        return (
            f"# {title}\n\n"
            f"::: {module_path}\n"
        )

    def _ensure_root_index(
        self,
        project: Project,
        out_dir: Path,
    ) -> None:
        root_index = out_dir / "index.md"

        if not root_index.exists():
            root_index.write_text(
                f"# {project.name}\n\n"
                "## Modules\n\n",
                encoding="utf-8",
            )

    def _ensure_parent_index(
        self,
        parts: list[str],
        out_dir: Path,
        link_target: str,
        title: str,
    ) -> None:
        if len(parts) == 1:
            parent_index = out_dir / "index.md"
        else:
            parent_dir = out_dir.joinpath(*parts[:-1])
            parent_dir.mkdir(parents=True, exist_ok=True)
            parent_index = parent_dir / "index.md"

            if not parent_index.exists():
                parent_title = parts[-2].replace("_", " ").title()
                parent_index.write_text(
                    f"# {parent_title}\n\n",
                    encoding="utf-8",
                )

        content = parent_index.read_text(encoding="utf-8")

        link = f"- [{title}]({link_target})\n"
        if link not in content:
            parent_index.write_text(content + link, encoding="utf-8")