"""Document generation service via docxtpl (.docx + Jinja2)."""

from __future__ import annotations

import io
from datetime import datetime
from pathlib import Path

from docxtpl import DocxTemplate
from loguru import logger

from app.models.tech_stack import DocumentRequest

TEMPLATES_DIR = Path(__file__).resolve().parents[2] / "templates"


class DocumentEngine:
    """Render .docx templates with supplied context."""

    SUPPORTED = {
        "act_hidden_works": "act_hidden_works.docx",
        "act_osmotr_responsibility": "act_osmotr_responsibility.docx",
        "general_work_log": "general_work_log.docx",
        "material_certificate": "material_certificate.docx",
    }

    def render(self, request: DocumentRequest) -> bytes:
        template_file = self.SUPPORTED.get(request.template_name)
        if template_file is None:
            raise ValueError(
                f"Unknown template: {request.template_name}. "
                f"Supported: {list(self.SUPPORTED)}"
            )

        template_path = TEMPLATES_DIR / template_file
        if not template_path.exists():
            raise FileNotFoundError(
                f"Template file not found: {template_path}"
            )

        logger.info(f"Rendering document: {request.template_name}")
        tpl = DocxTemplate(str(template_path))

        context = {
            "generated_at": datetime.utcnow().strftime("%d.%m.%Y %H:%M"),
            "project_id": request.project_id,
            **request.context,
        }
        tpl.render(context)

        buf = io.BytesIO()
        tpl.save(buf)
        buf.seek(0)
        return buf.read()


def get_document_engine() -> DocumentEngine:
    return DocumentEngine()