"""
This module provides the MkDocsNavEmitter, which converts a ResolvedNav instance
into the specific YAML-ready list structure expected by the MkDocs 'nav'
configuration.
"""

from pathlib import Path
from typing import List, Dict, Any

from docforge.nav.resolver import ResolvedNav


class MkDocsNavEmitter:
    """
    Emitter responsible for transforming a ResolvedNav into an MkDocs-compatible
    navigation structure.
    """

    def emit(self, nav: ResolvedNav) -> List[Dict[str, Any]]:
        """
        Generate a list of navigation entries for mkdocs.yml.

        Args:
            nav: The resolved navigation data.

        Returns:
            A list of dictionary mappings representing the MkDocs navigation.
        """
        result: List[Dict[str, Any]] = []

        # Home entry (semantic path)
        if nav.home:
            result.append({"Home": nav.home})

        # Group entries
        for group, paths in nav.groups.items():
            entries: List[str] = []
            for p in paths:
                # Convert filesystem path back to docs-relative path
                rel_path = self._to_relative(p, nav._docs_root)
                entries.append(rel_path)
            result.append({group: entries})

        return result

    def _to_relative(self, path: Path, docs_root: Path | None) -> str:
        """
        Convert a filesystem path to a path relative to the documentation root.
        This handles both absolute and relative filesystem paths, ensuring the
        output is compatible with MkDocs navigation requirements.

        Args:
            path: The path to convert.
            docs_root: The root directory for documentation.

        Returns:
            A string representing the relative POSIX-style path.
        """
        if docs_root and path.is_absolute():
            try:
                path = path.relative_to(docs_root.resolve())
            except ValueError:
                pass
        elif docs_root:
            # Handle relative paths (e.g. starting with 'docs/')
            path_str = path.as_posix()
            docs_root_str = docs_root.as_posix()
            if path_str.startswith(docs_root_str + "/"):
                return path_str[len(docs_root_str) + 1:]
        
        # Fallback for other cases
        return path.as_posix().split("/docs/", 1)[-1]