import os
from dotenv import load_dotenv

class ConfigManager:
    """Safely manages multi-line .env files without corrupting other content."""
    
    @staticmethod
    def get_root_env_path():
        # backend/config_manager.py -> backend/ -> /
        base_dir = os.path.dirname(os.path.abspath(__file__))
        project_root = os.path.dirname(base_dir)
        return os.path.join(project_root, "inventory.env")

    @staticmethod
    def update_keys(updates: dict):
        """
        Updates specific keys in inventory.env.
        Preserves comments and order where possible.
        Appends new keys at the end if not found.
        """
        env_path = ConfigManager.get_root_env_path()
        
        if not os.path.exists(env_path):
            # Create a basic file if it doesn't exist (unlikely in this project)
            with open(env_path, 'w', encoding='utf-8') as f:
                f.write("# TFM aInventory — Generated Configuration\n")

        with open(env_path, 'r', encoding='utf-8') as f:
            lines = f.readlines()

        new_lines = []
        keys_to_process = set(updates.keys())
        processed_keys = set()

        for line in lines:
            trimmed = line.strip()
            # Skip empty lines or comments when matching
            if not trimmed or trimmed.startswith('#'):
                new_lines.append(line)
                continue

            # Check if this line is a key assignment we want to update
            found_match = False
            for key in keys_to_process:
                if trimmed.startswith(f"{key}="):
                    new_lines.append(f"{key}={updates[key]}\n")
                    processed_keys.add(key)
                    found_match = True
                    break
            
            if not found_match:
                new_lines.append(line)

        # Append keys that weren't found in the file
        missing_keys = keys_to_process - processed_keys
        if missing_keys:
            if new_lines and not new_lines[-1].endswith('\n'):
                new_lines.append('\n')
            if new_lines and not new_lines[-1].strip() == '':
                new_lines.append('\n')
            
            new_lines.append("# --- Automatically Added Keys ---\n")
            for key in missing_keys:
                new_lines.append(f"{key}={updates[key]}\n")

        with open(env_path, 'w', encoding='utf-8') as f:
            f.writelines(new_lines)

        # Force reload environment variables for the current process
        load_dotenv(env_path, override=True)
        return True

    @staticmethod
    def get_masked_key(key_name: str):
        """Returns a masked version of the environment variable."""
        val = os.environ.get(key_name)
        if not val:
            return None
        
        # Determine prefix based on key type
        prefix = ""
        if key_name == "GEMINI_API_KEY":
            prefix = "G-"
        elif key_name == "CLAUDE_API_KEY":
            prefix = "sk-"
            
        if len(val) <= 8:
            return f"{prefix}****"
        
        return f"{prefix}****{val[-4:]}"