"""Template engine using Jinja2 for project scaffolding."""

import os
from pathlib import Path
from typing import Any, Dict, Optional

from jinja2 import (
    BaseLoader,
    Environment,
    FileSystemLoader,
    TemplateSyntaxError,
)

from .config import Config


class TemplateEngine:
    """Jinja2 template rendering engine for project scaffolding."""

    SUPPORTED_LANGUAGES = ["python", "nodejs", "go", "rust"]

    def __init__(self, template_path: Optional[str] = None, config: Optional[Config] = None):
        self.template_path = template_path
        self.config = config or Config()
        self._env: Optional[Environment] = None

    def _get_environment(self) -> Environment:
        """Get or create the Jinja2 environment."""
        if self._env is not None:
            return self._env

        if self.template_path and not os.path.isabs(self.template_path):
            search_dirs = self.config.get_template_dirs()
            search_dirs.insert(0, str(Path.cwd()))
            self._env = Environment(
                loader=FileSystemLoader(search_dirs),
                trim_blocks=True,
                lstrip_blocks=True,
            )
        elif self.template_path:
            template_dir = Path(self.template_path).parent
            self._env = Environment(
                loader=FileSystemLoader([str(template_dir)]),
                trim_blocks=True,
                lstrip_blocks=True,
            )
        else:
            project_root = self._get_project_root()
            self._env = Environment(
                loader=FileSystemLoader(str(project_root)),
                trim_blocks=True,
                lstrip_blocks=True,
            )

        return self._env

    def _get_project_root(self) -> Path:
        """Get the project root directory for built-in templates."""
        return Path(__file__).parent / "templates"

    def _validate_template(self, template_name: str) -> bool:
        """Validate that a template exists."""
        env = self._get_environment()
        try:
            env.get_template(template_name)
            return True
        except Exception:
            return False

    def _render_template(
        self, template_name: str, context: Dict[str, Any]
    ) -> str:
        """Render a single template with context."""
        env = self._get_environment()
        template = env.get_template(template_name)
        return template.render(**context)

    def render_language_template(
        self, language: str, context: Dict[str, Any], output_dir: Path
    ) -> None:
        """Render all templates for a language."""
        if language not in self.SUPPORTED_LANGUAGES:
            raise ValueError(
                f"Unsupported language: {language}. "
                f"Supported: {', '.join(self.SUPPORTED_LANGUAGES)}"
            )

        env = self._get_environment()
        language_dir = language

        try:
            project_root = self._get_project_root() / language_dir
            for root, dirs, files in os.walk(project_root):
                rel_path = Path(root).relative_to(project_root)

                rel_path_str = rel_path.as_posix()
                rel_path_str = rel_path_str.replace("{{project_slug}}", context.get("project_slug", ""))
                rel_path_str = rel_path_str.replace("{{ project_name }}", context.get("project_name", ""))

                dest_dir = output_dir / rel_path_str
                dest_dir.mkdir(parents=True, exist_ok=True)

                for file in files:
                    if file.endswith((".j2", ".jinja2")):
                        template_path = (
                            Path(root) / file
                        ).relative_to(project_root).as_posix()
                        dest_file = Path(dest_dir) / file[:-3]

                        try:
                            content = self._render_template(
                                language_dir + "/" + template_path, context
                            )
                            dest_file.write_text(content)
                        except TemplateSyntaxError as e:
                            raise ValueError(
                                f"Template syntax error in {template_path}: {e}"
                            )
                    else:
                        src_file = Path(root) / file
                        dest_file = Path(dest_dir) / file
                        dest_file.write_bytes(src_file.read_bytes())

        except Exception as e:
            raise RuntimeError(f"Error rendering language template: {e}")

    def render_project(
        self,
        context: Dict[str, Any],
        output_dir: Path,
        template: str,
    ) -> None:
        """Render a custom project template."""
        if not self._validate_template(template):
            raise ValueError(f"Template not found: {template}")

        try:
            for root, dirs, files in os.walk(
                self._get_environment().loader.searchpath[0]
            ):
                for pattern in self._get_environment().loader.get_files(
                    template
                ):
                    pass

            env = self._get_environment()
            base_template = env.get_template(template)

            for item in base_template.list_templates():
                pass

        except Exception as e:
            raise ValueError(f"Error rendering project template: {e}")

    def render_ci_template(
        self,
        ci_provider: str,
        context: Dict[str, Any],
        output_dir: Path,
    ) -> None:
        """Render CI/CD template for a provider."""
        ci_templates = {
            "github": "ci/.github/workflows/ci.yml.j2",
            "gitlab": "ci/.gitlab-ci.yml.j2",
        }

        if ci_provider not in ci_templates:
            raise ValueError(
                f"Unsupported CI provider: {ci_provider}. "
                f"Supported: {', '.join(ci_templates.keys())}"
            )

        env = self._get_environment()
        template_name = ci_templates[ci_provider]

        try:
            content = self._render_template(template_name, context)

            if ci_provider == "github":
                workflow_dir = output_dir / ".github" / "workflows"
                workflow_dir.mkdir(parents=True, exist_ok=True)
                output_file = workflow_dir / "ci.yml"
            else:
                output_file = output_dir / ".gitlab-ci.yml"

            output_file.write_text(content)

        except Exception as e:
            raise RuntimeError(f"Error rendering CI template: {e}")

    def get_template_list(self) -> list[str]:
        """Get list of available templates."""
        env = self._get_environment()
        return env.list_templates()

    def validate_context(self, context: Dict[str, Any]) -> list[str]:
        """Validate that all required context variables are provided."""
        required = ["project_name", "author"]
        missing = [var for var in required if var not in context or not context[var]]
        return missing