#!/usr/bin/env python3
"""
Common utility functions for MCP servers
Provide shared utilities for path handling, file validation, and request processing
"""

import json
import os
import sys
import asyncio
from typing import Any, Dict, List, Optional, Union
import re

def get_allowed_directory():
    """Get the allowed directory"""
    # Prefer dataset_dir passed in through command-line arguments
    if len(sys.argv) > 1:
        dataset_dir = sys.argv[1]
        return os.path.abspath(dataset_dir)

    # Read the project data directory from the environment variable
    project_dir = os.getenv("PROJECT_DATA_DIR", "./projects/data")
    return os.path.abspath(project_dir)


def resolve_file_path(file_path: str, default_subfolder: str = "default") -> str:
    """
    Resolve file paths, supporting both folder/document.txt and document.txt formats
    
    Args:
        file_path: input file path
        default_subfolder: default subfolder name used when only a file name is provided
    
    Returns:
        resolved full file path
    """
    # If the path contains a folder separator, use it directly
    if '/' in file_path or '\\' in file_path:
        clean_path = file_path.replace('\\', '/')
        
        # Remove the projects/ prefix if present
        if clean_path.startswith('projects/'):
            clean_path = clean_path[9:]  # Remove the 'projects/' prefix
        elif clean_path.startswith('./projects/'):
            clean_path = clean_path[11:]  # Remove the './projects/' prefix
    else:
        # If only the file name is provided, prepend the default subfolder
        clean_path = f"{default_subfolder}/{file_path}"
    
    # Get the allowed directory
    project_data_dir = get_allowed_directory()
    
    # Try to locate the file in the project directory
    full_path = os.path.join(project_data_dir, clean_path.lstrip('./'))
    if os.path.exists(full_path):
        return full_path
    
    # If the direct path does not exist, try a recursive search
    found = find_file_in_project(clean_path, project_data_dir)
    if found:
        return found
    
    # If this is a bare file name and it is not found in the default subfolder, try the root directory
    if '/' not in file_path and '\\' not in file_path:
        root_path = os.path.join(project_data_dir, file_path)
        if os.path.exists(root_path):
            return root_path
    
    raise FileNotFoundError(f"File not found: {file_path} (searched in {project_data_dir})")


def find_file_in_project(filename: str, project_dir: str) -> Optional[str]:
    """Recursively search for a file in the project directory"""
    # If filename includes a path, search only that path
    if '/' in filename:
        parts = filename.split('/')
        target_file = parts[-1]
        search_dir = os.path.join(project_dir, *parts[:-1])
        
        if os.path.exists(search_dir):
            target_path = os.path.join(search_dir, target_file)
            if os.path.exists(target_path):
                return target_path
    else:
        # If this is a bare file name, recursively search the entire project directory
        for root, dirs, files in os.walk(project_dir):
            if filename in files:
                return os.path.join(root, filename)
    return None


def load_tools_from_json(tools_file_name: str) -> List[Dict[str, Any]]:
    """Load tool definitions from a JSON file"""
    try:
        tools_file = os.path.join(os.path.dirname(__file__), "tools", tools_file_name)
        if os.path.exists(tools_file):
            with open(tools_file, 'r', encoding='utf-8') as f:
                return json.load(f)
        else:
            # If the JSON file does not exist, use the default definition
            return []
    except Exception as e:
        print(f"Warning: Unable to load tool definition JSON file: {str(e)}")
        return []


def create_error_response(request_id: Any, code: int, message: str) -> Dict[str, Any]:
    """Create a standardized error response"""
    return {
        "jsonrpc": "2.0",
        "id": request_id,
        "error": {
            "code": code,
            "message": message
        }
    }


def create_success_response(request_id: Any, result: Any) -> Dict[str, Any]:
    """Create a standardized success response"""
    return {
        "jsonrpc": "2.0",
        "id": request_id,
        "result": result
    }


def create_initialize_response(request_id: Any, server_name: str, server_version: str = "1.0.0") -> Dict[str, Any]:
    """Create a standardized initialize response"""
    return {
        "jsonrpc": "2.0",
        "id": request_id,
        "result": {
            "protocolVersion": "2024-11-05",
            "capabilities": {
                "tools": {}
            },
            "serverInfo": {
                "name": server_name,
                "version": server_version
            }
        }
    }


def create_ping_response(request_id: Any) -> Dict[str, Any]:
    """Create a standardized ping response"""
    return {
        "jsonrpc": "2.0",
        "id": request_id,
        "result": {
            "pong": True
        }
    }


def create_tools_list_response(request_id: Any, tools: List[Dict[str, Any]]) -> Dict[str, Any]:
    """Create a standardized tool list response"""
    return {
        "jsonrpc": "2.0",
        "id": request_id,
        "result": {
            "tools": tools
        }
    }


def is_regex_pattern(pattern: str) -> bool:
    """Detect whether a string is a regular expression pattern"""
    # Check /pattern/ format
    if pattern.startswith('/') and pattern.endswith('/') and len(pattern) > 2:
        return True
    
    # Check r"pattern" or r'pattern' format
    if pattern.startswith(('r"', "r'")) and pattern.endswith(('"', "'")) and len(pattern) > 3:
        return True
    
    # Check whether it contains regex metacharacters
    regex_chars = {'*', '+', '?', '|', '(', ')', '[', ']', '{', '}', '^', '$', '\\', '.'}
    return any(char in pattern for char in regex_chars)


def compile_pattern(pattern: str) -> Union[re.Pattern, str, None]:
    """Compile a regex pattern, or return the original string if it is not regex"""
    if not is_regex_pattern(pattern):
        return pattern
    
    try:
        # Handle /pattern/ format
        if pattern.startswith('/') and pattern.endswith('/'):
            regex_body = pattern[1:-1]
            return re.compile(regex_body)
        
        # Handle r"pattern" or r'pattern' format
        if pattern.startswith(('r"', "r'")) and pattern.endswith(('"', "'")):
            regex_body = pattern[2:-1]
            return re.compile(regex_body)
        
        # Directly compile strings containing regex characters
        return re.compile(pattern)
    except re.error as e:
        # If compilation fails, return None to indicate an invalid regex
        print(f"Warning: Regular expression '{pattern}' compilation failed: {e}")
        return None


async def handle_mcp_streaming(request_handler):
    """Handle the standard main loop for MCP requests"""
    try:
        while True:
            # Read from stdin
            line = await asyncio.get_event_loop().run_in_executor(None, sys.stdin.readline)
            if not line:
                break
            
            line = line.strip()
            if not line:
                continue
            
            try:
                request = json.loads(line)
                response = await request_handler(request)
                
                # Write to stdout
                sys.stdout.write(json.dumps(response, ensure_ascii=False) + "\n")
                sys.stdout.flush()
            
            except json.JSONDecodeError:
                error_response = {
                    "jsonrpc": "2.0",
                    "error": {
                        "code": -32700,
                        "message": "Parse error"
                    }
                }
                sys.stdout.write(json.dumps(error_response, ensure_ascii=False) + "\n")
                sys.stdout.flush()
            
            except Exception as e:
                error_response = {
                    "jsonrpc": "2.0",
                    "error": {
                        "code": -32603,
                        "message": f"Internal error: {str(e)}"
                    }
                }
                sys.stdout.write(json.dumps(error_response, ensure_ascii=False) + "\n")
                sys.stdout.flush()
    
    except KeyboardInterrupt:
        pass