import argparse
import json
from pathlib import Path
from jinja2 import Environment, FileSystemLoader

from schema import DocumentInput


def parse_args() -> argparse.Namespace:
    # keep cli parsing separate so main stays about workflow
    parser = argparse.ArgumentParser(description="Render document from JSON + Jinja2 template")

    parser.add_argument(
        "--input",
        "-i",
        type=Path,
        required=True,
        help="Path to input JSON file (e.g. examples/input.json)"
    )
    parser.add_argument(
        "--template",
        "-t",
        default="doc.md.j2",
        help="Template file (e.g. doc.md.j2)"
    )
    parser.add_argument(
        "--output",
        "-o",
        type=Path,
        required=True,
        help="Path to write rendered output (e.g. out.md)"
    )

    return parser.parse_args()


def render_template(template_name: str, data: dict) -> str:
    # Jinja env points at templates/
    env = Environment(loader=FileSystemLoader("templates"),
                      trim_blocks=True,
                      lstrip_blocks=True)
    template = env.get_template(template_name)
    return template.render(data)


def main():
    args = parse_args()

    # load input data
    # path() over hardcoding str
    data = json.loads(args.input.read_text(encoding="utf-8"))

    # validate + normalise input
    doc_input = DocumentInput(**data)

    # load template to render
    out = render_template(args.template, doc_input.model_dump())

    # write output - render md to file
    args.output.write_text(out, encoding="utf-8")
    print(f"wrote {args.output}")


if __name__ == "__main__":
    main()