"""Parse and validate OpenAPI specifications."""

import yaml
from pathlib import Path
from typing import Any, Dict, List, Optional, Tuple
from openapi_spec_validator import validate
from openapi_spec_validator.versions import consts as validator_consts


class OpenAPISpecError(Exception):
    """Base exception for OpenAPI spec errors."""
    pass


class SpecValidationError(OpenAPISpecError):
    """Raised when OpenAPI spec validation fails."""
    pass


class SpecNotFoundError(OpenAPISpecError):
    """Raised when OpenAPI spec file is not found."""
    pass


def load_spec(spec_path: str) -> Dict[str, Any]:
    """Load and parse an OpenAPI specification from a YAML or JSON file.

    Args:
        spec_path: Path to the OpenAPI specification file.

    Returns:
        Parsed OpenAPI specification as a dictionary.

    Raises:
        SpecNotFoundError: If the spec file does not exist.
        SpecValidationError: If the spec is invalid.
    """
    path = Path(spec_path)
    if not path.exists():
        raise SpecNotFoundError(f"OpenAPI spec file not found: {spec_path}")

    try:
        with open(path, 'r', encoding='utf-8') as f:
            spec = yaml.safe_load(f)
    except yaml.YAMLError as e:
        raise OpenAPISpecError(f"Invalid YAML syntax in {spec_path}: {e}")
    except IOError as e:
        raise OpenAPISpecError(f"Error reading {spec_path}: {e}")

    if spec is None:
        raise OpenAPISpecError(f"Empty specification file: {spec_path}")

    try:
        validate(spec)
    except Exception as e:
        raise SpecValidationError(f"OpenAPI spec validation failed: {e}")

    return spec


def extract_paths(spec: Dict[str, Any]) -> Dict[str, Dict[str, Any]]:
    """Extract all paths and their operations from an OpenAPI spec.

    Args:
        spec: Parsed OpenAPI specification.

    Returns:
        Dictionary mapping path strings to operation dictionaries.
    """
    return spec.get('paths', {})


def extract_schemas(spec: Dict[str, Any]) -> Dict[str, Any]:
    """Extract all schemas from an OpenAPI spec.

    Args:
        spec: Parsed OpenAPI specification.

    Returns:
        Dictionary mapping schema names to schema definitions.
    """
    components = spec.get('components', {})
    schemas = components.get('schemas', {})

    if not schemas and 'definitions' in spec:
        schemas = spec.get('definitions', {})

    return schemas


def extract_path_params(path: str) -> List[str]:
    """Extract parameter names from a path string.

    Args:
        path: API path string like '/users/{id}/posts/{post_id}'.

    Returns:
        List of parameter names without braces.
    """
    import re
    params = re.findall(r'\{([^}]+)\}', path)
    return params


def get_operation_id(path: str, method: str) -> str:
    """Generate an operation ID for a path/method combination.

    Args:
        path: API path string.
        method: HTTP method (get, post, put, delete, etc.).

    Returns:
        Generated operation ID string.
    """
    import re
    clean_path = path.lstrip('/').replace('/', '_').replace('-', '_')
    params = re.findall(r'\{([^}]+)\}', clean_path)
    for param in params:
        clean_path = clean_path.replace(f'{{{param}}}', f'_{param}_')
    method = method.lower()
    return f"{method}_{clean_path}"


def extract_security_schemes(spec: Dict[str, Any]) -> Dict[str, Any]:
    """Extract security schemes from an OpenAPI spec.

    Args:
        spec: Parsed OpenAPI specification.

    Returns:
        Dictionary mapping security scheme names to scheme definitions.
    """
    components = spec.get('components', {})
    return components.get('securitySchemes', {})


def extract_global_security(spec: Dict[str, Any]) -> List[Dict[str, List[str]]]:
    """Extract global security requirements from an OpenAPI spec.

    Args:
        spec: Parsed OpenAPI specification.

    Returns:
        List of security requirement dictionaries.
    """
    return spec.get('security', [])


def get_response_schema(
    spec: Dict[str, Any],
    path: str,
    method: str,
    status_code: str = '200'
) -> Optional[Dict[str, Any]]:
    """Get the response schema for a specific path/method/status_code.

    Args:
        spec: Parsed OpenAPI specification.
        path: API path string.
        method: HTTP method.
        status_code: Response status code.

    Returns:
        Response schema definition or None if not found.
    """
    paths = spec.get('paths', {})
    path_item = paths.get(path, {})
    operation = path_item.get(method.lower(), {})

    responses = operation.get('responses', {})
    response = responses.get(status_code, responses.get('default', {}))

    content = response.get('content', {})
    if 'application/json' in content:
        media_type = content['application/json']
        return media_type.get('schema')

    return None


def get_spec_version(spec: Dict[str, Any]) -> str:
    """Get the OpenAPI version from the spec.

    Args:
        spec: Parsed OpenAPI specification.

    Returns:
        OpenAPI version string (e.g., "3.0.3", "2.0").
    """
    return spec.get('openapi', spec.get('swagger', 'unknown'))


def is_openapi_3(spec: Dict[str, Any]) -> bool:
    """Check if the spec is OpenAPI 3.x.

    Args:
        spec: Parsed OpenAPI specification.

    Returns:
        True if OpenAPI 3.x, False if Swagger 2.0.
    """
    openapi_version = spec.get('openapi', '')
    return openapi_version.startswith('3.')