"""Template management for env-pro."""

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


class TemplateError(Exception):
    """Base exception for template errors."""
    pass


BUILTIN_TEMPLATES = {
    "fastapi": {
        "description": "FastAPI Python application",
        "variables": {
            "APP_NAME": {"default": "MyFastAPIApp", "description": "Application name"},
            "DEBUG": {"default": "false", "description": "Enable debug mode"},
            "DATABASE_URL": {"default": "postgresql://localhost:5432/app", "description": "Database URL"},
            "SECRET_KEY": {"default": "", "description": "Secret key for JWT", "encrypt": True},
            "ALLOWED_HOSTS": {"default": "*", "description": "Allowed hosts"},
        }
    },
    "django": {
        "description": "Django Python application",
        "variables": {
            "APP_NAME": {"default": "MyDjangoApp", "description": "Application name"},
            "DEBUG": {"default": "false", "description": "Enable debug mode"},
            "DATABASE_URL": {"default": "postgresql://localhost:5432/app", "description": "Database URL"},
            "SECRET_KEY": {"default": "", "description": "Secret key", "encrypt": True},
            "ALLOWED_HOSTS": {"default": "localhost,127.0.0.1", "description": "Allowed hosts"},
        }
    },
    "nodejs": {
        "description": "Node.js application",
        "variables": {
            "NODE_ENV": {"default": "development", "description": "Environment"},
            "PORT": {"default": "3000", "description": "Port number"},
            "DATABASE_URL": {"default": "mongodb://localhost:27017/app", "description": "Database URL"},
            "JWT_SECRET": {"default": "", "description": "JWT secret", "encrypt": True},
        }
    },
    "python": {
        "description": "Generic Python application",
        "variables": {
            "ENVIRONMENT": {"default": "development", "description": "Environment"},
            "LOG_LEVEL": {"default": "INFO", "description": "Logging level"},
            "DATABASE_URL": {"default": "", "description": "Database URL"},
            "API_KEY": {"default": "", "description": "API key", "encrypt": True},
        }
    },
    "golang": {
        "description": "Go application",
        "variables": {
            "GO_ENV": {"default": "development", "description": "Environment"},
            "PORT": {"default": "8080", "description": "Port number"},
            "DATABASE_URL": {"default": "postgresql://localhost:5432/app", "description": "Database URL"},
            "API_KEY": {"default": "", "description": "API key", "encrypt": True},
        }
    },
    "minimal": {
        "description": "Minimal .env template",
        "variables": {
            "ENVIRONMENT": {"default": "development", "description": "Environment"},
            "DEBUG": {"default": "false", "description": "Enable debug mode"},
        }
    },
}


class TemplateManager:
    """Manages environment variable templates."""

    def __init__(self, custom_templates_dir: Optional[Path] = None):
        """Initialize template manager."""
        self.custom_templates_dir = custom_templates_dir

    def list_templates(self) -> List[Dict[str, str]]:
        """List all available templates."""
        templates = []

        for name, config in BUILTIN_TEMPLATES.items():
            templates.append({
                "name": name,
                "description": config["description"],
                "builtin": True
            })

        if self.custom_templates_dir and self.custom_templates_dir.exists():
            for template_dir in self.custom_templates_dir.iterdir():
                if template_dir.is_dir():
                    templates.append({
                        "name": template_dir.name,
                        "description": f"Custom template from {template_dir}",
                        "builtin": False
                    })

        return templates

    def get_template(self, name: str) -> Optional[Dict]:
        """Get a specific template."""
        if name in BUILTIN_TEMPLATES:
            return BUILTIN_TEMPLATES[name]

        if self.custom_templates_dir:
            template_file = self.custom_templates_dir / name / "template.yaml"
            if template_file.exists():
                import yaml
                with open(template_file, 'r') as f:
                    return yaml.safe_load(f)

        return None

    def apply_template(self, name: str, variables: Dict[str, str] = None, output_file: Optional[Path] = None):
        """Apply a template and generate .env content."""
        template = self.get_template(name)

        if template is None:
            raise TemplateError(f"Template '{name}' not found")

        if variables is None:
            variables = {}

        content_lines = ["# Generated by env-pro", f"# Template: {name}", ""]

        for var_name, var_config in template["variables"].items():
            value = variables.get(var_name, var_config.get("default", ""))
            comment = var_config.get("description", "")

            if comment:
                content_lines.append(f"# {comment}")

            content_lines.append(f"{var_name}={value}")
            content_lines.append("")

        content = "\n".join(content_lines)

        if output_file:
            output_file.write_text(content)

        return content

    def create_custom_template(self, name: str, variables: Dict, description: str = ""):
        """Create a custom template."""
        if self.custom_templates_dir is None:
            raise TemplateError("Custom templates directory not configured")

        template_dir = self.custom_templates_dir / name
        template_dir.mkdir(parents=True, exist_ok=True)

        import yaml
        template_file = template_dir / "template.yaml"
        template_file.write_text(yaml.dump({
            "description": description,
            "variables": variables
        }))

        return template_dir