"""Dependency parsing utilities for PyPI packages."""

import re
from typing import Any, Dict, List, Optional, Set, Tuple
from packaging.requirements import Requirement
from packaging.specifiers import SpecifierSet
from packaging.version import Version
import logging

logger = logging.getLogger(__name__)


class DependencyParser:
    """Parser for Python package dependencies."""
    
    def __init__(self):
        self.parsed_cache: Dict[str, List[Requirement]] = {}
    
    def parse_requirements(self, requires_dist: List[str]) -> List[Requirement]:
        """Parse requirements from requires_dist list.
        
        Args:
            requires_dist: List of requirement strings from PyPI metadata
            
        Returns:
            List of parsed Requirement objects
        """
        requirements = []
        
        for req_str in requires_dist or []:
            if not req_str or not req_str.strip():
                continue
                
            try:
                req = Requirement(req_str)
                requirements.append(req)
            except Exception as e:
                logger.warning(f"Failed to parse requirement '{req_str}': {e}")
                continue
                
        return requirements
    
    def filter_requirements_by_python_version(
        self, 
        requirements: List[Requirement], 
        python_version: str
    ) -> List[Requirement]:
        """Filter requirements based on Python version.
        
        Args:
            requirements: List of Requirement objects
            python_version: Target Python version (e.g., "3.10")
            
        Returns:
            Filtered list of requirements applicable to the Python version
        """
        filtered = []
        
        try:
            target_version = Version(python_version)
        except Exception as e:
            logger.warning(f"Invalid Python version '{python_version}': {e}")
            return requirements
        
        for req in requirements:
            if self._is_requirement_applicable(req, target_version):
                filtered.append(req)
                
        return filtered
    
    def _is_requirement_applicable(self, req: Requirement, python_version: Version) -> bool:
        """Check if a requirement is applicable for the given Python version.
        
        Args:
            req: Requirement object
            python_version: Target Python version
            
        Returns:
            True if requirement applies to the Python version
        """
        if not req.marker:
            return True
            
        # Create environment for marker evaluation
        env = {
            'python_version': str(python_version),
            'python_full_version': str(python_version),
            'platform_system': 'Linux',  # Default assumption
            'platform_machine': 'x86_64',  # Default assumption
            'implementation_name': 'cpython',
            'implementation_version': str(python_version),
        }
        
        try:
            return req.marker.evaluate(env)
        except Exception as e:
            logger.warning(f"Failed to evaluate marker for {req}: {e}")
            return True  # Include by default if evaluation fails
    
    def categorize_dependencies(
        self, 
        requirements: List[Requirement]
    ) -> Dict[str, List[Requirement]]:
        """Categorize dependencies into runtime, development, and optional groups.
        
        Args:
            requirements: List of Requirement objects
            
        Returns:
            Dictionary with categorized dependencies
        """
        categories = {
            'runtime': [],
            'development': [],
            'optional': {},
            'extras': {}
        }
        
        for req in requirements:
            if not req.marker:
                # No marker means it's a runtime dependency
                categories['runtime'].append(req)
                continue
                
            marker_str = str(req.marker)
            
            # Check for extra dependencies
            if 'extra ==' in marker_str:
                extra_match = re.search(r'extra\s*==\s*["\']([^"\']+)["\']', marker_str)
                if extra_match:
                    extra_name = extra_match.group(1)
                    if extra_name not in categories['extras']:
                        categories['extras'][extra_name] = []
                    categories['extras'][extra_name].append(req)
                    continue
            
            # Check for development dependencies
            if any(keyword in marker_str.lower() for keyword in ['dev', 'test', 'lint', 'doc']):
                categories['development'].append(req)
            else:
                categories['runtime'].append(req)
                
        return categories
    
    def extract_package_names(self, requirements: List[Requirement]) -> Set[str]:
        """Extract package names from requirements.
        
        Args:
            requirements: List of Requirement objects
            
        Returns:
            Set of package names
        """
        return {req.name.lower() for req in requirements}
    
    def get_version_constraints(self, req: Requirement) -> Dict[str, Any]:
        """Get version constraints from a requirement.
        
        Args:
            req: Requirement object
            
        Returns:
            Dictionary with version constraint information
        """
        if not req.specifier:
            return {'constraints': [], 'allows_any': True}
            
        constraints = []
        for spec in req.specifier:
            constraints.append({
                'operator': spec.operator,
                'version': str(spec.version)
            })
            
        return {
            'constraints': constraints,
            'allows_any': len(constraints) == 0,
            'specifier_str': str(req.specifier)
        }