"""
This module contains the 'mkdocs' CLI command, which orchestrates the generation
of the main mkdocs.yml configuration file.
"""

from pathlib import Path
from importlib import resources

import click
import yaml

from docforge.nav import load_nav_spec
from docforge.nav import resolve_nav
from docforge.nav import MkDocsNavEmitter


def _load_template(template: Path | None) -> dict:
    """
    Load a YAML template for mkdocs.yml. If no template is provided,
    loads the built-in sample template.

    Args:
        template: Path to the template file, or None.

    Returns:
        The loaded template data as a dictionary.
    """
    if template is not None:
        if not template.exists():
            raise click.FileError(str(template), hint="Template not found")
        return yaml.safe_load(template.read_text(encoding="utf-8"))

    # Load built-in default
    text = (
        resources.files("docforge.templates")
        .joinpath("mkdocs.sample.yml")
        .read_text(encoding="utf-8")
    )
    return yaml.safe_load(text)


@click.command("mkdocs")
@click.option(
    "--site-name",
    required=True,
    help="MkDocs site_name (required)",
)
@click.option(
    "--docs-dir",
    type=click.Path(path_type=Path),
    default=Path("docs"),
)
@click.option(
    "--nav",
    "nav_file",
    type=click.Path(path_type=Path),
    default=Path("docforge.nav.yml"),
)
@click.option(
    "--template",
    type=click.Path(path_type=Path),
    default=None,
    help="Override the built-in mkdocs template",
)
@click.option(
    "--out",
    type=click.Path(path_type=Path),
    default=Path("mkdocs.yml"),
)
def mkdocs_cmd(
    docs_dir: Path,
    nav_file: Path,
    template: Path | None,
    out: Path,
    site_name: str,
) -> None:
    """
    Generate an mkdocs.yml configuration file by combining a template with
    the navigation structure resolved from a docforge.nav.yml file.

    Args:
        docs_dir: Path to the directory containing documentation Markdown files.
        nav_file: Path to the docforge.nav.yml specification.
        template: Optional path to an mkdocs.yml template.
        out: Path where the final mkdocs.yml will be written.
        site_name: The name of the documentation site.
    """

    if not nav_file.exists():
        raise click.FileError(str(nav_file), hint="Nav spec not found")

    # Load nav spec
    spec = load_nav_spec(nav_file)

    # Resolve nav
    resolved = resolve_nav(spec, docs_dir)

    # Emit mkdocs nav
    nav_block = MkDocsNavEmitter().emit(resolved)

    # Load template (user or built-in)
    data = _load_template(template)

    # Inject site_name
    data["site_name"] = site_name

    # Inject nav
    data["nav"] = nav_block

    # Write output
    out.write_text(
        yaml.safe_dump(data, sort_keys=False),
        encoding="utf-8",
    )

    click.echo(f"mkdocs.yml written to {out}")