import uuid
import hmac
import hashlib
import json
import sys
import os
from datetime import datetime
from pathlib import Path

# This MUST match the key in your generator exactly.
# Because this file is compiled via Cython to a .so/.pyd file, 
# This MUST match the key in your generator exactly.
_SECRET_KEY = b"mxPIC_Super_Secret_Master_Key_2026!"
_ENV_VAR_NAME = "LIC_MXPIC_OPTIHK_DIR"

def _get_local_mac() -> str:
    """Retrieves the physical MAC address of the current machine."""
    mac = uuid.getnode()
    return ':'.join(("%012X" % mac)[i:i+2] for i in range(0, 12, 2))

def _locate_license_file() -> Path:
    """Intelligently resolves the path to the license file."""
    env_path_str = os.getenv(_ENV_VAR_NAME)
    
    if env_path_str:
        path_obj = Path(env_path_str)
        # If the user pointed to a directory, append the default filename
        if path_obj.is_dir():
            return path_obj / "mxpic.lic"
        # Otherwise, assume they pointed directly to the file itself
        return path_obj
    else:
        # Fallback: Look in the current working directory where the script is run
        return Path("mxpic.lic")

def verify_license() -> None:
    """Verifies the license file. Halts execution if invalid."""
    
    lic_file = _locate_license_file()
    
    if not lic_file.exists():
        print(f"\n❌ mxPIC FATAL ERROR: License file not found.")
        print(f"Searched at: {lic_file.resolve()}")
        print(f"Please set the '{_ENV_VAR_NAME}' environment variable to point to your license file.")
        sys.exit(1)
        
    try:
        with open(lic_file, "r", encoding="utf-8") as f:
            lic = json.load(f)
            
        local_mac = _get_local_mac()
        
        # 1. Check MAC match
        if lic["mac_address"] != local_mac:
            print(f"\n❌ mxPIC FATAL ERROR: License registered to different machine.")
            print(f"Registered: {lic['mac_address']} | Local: {local_mac}")
            sys.exit(1)
            
        # 2. Check Expiration
        exp_date = datetime.strptime(lic["expiration"], "%Y-%m-%d")
        if datetime.now() > exp_date:
            print(f"\n❌ mxPIC FATAL ERROR: License expired on {lic['expiration']}.")
            sys.exit(1)
            
        # 3. Verify Signature
        message = f"{lic['mac_address']}|{lic['expiration']}".encode('utf-8')
        expected_sig = hmac.new(_SECRET_KEY, message, hashlib.sha256).hexdigest()
        
        if not hmac.compare_digest(expected_sig, lic["signature"]):
            print("\n❌ mxPIC FATAL ERROR: License signature is corrupted or forged.")
            sys.exit(1)
            
    except json.JSONDecodeError:
        print(f"\n❌ mxPIC FATAL ERROR: License file is corrupted (invalid JSON).")
        sys.exit(1)
    except KeyError as e:
        print(f"\n❌ mxPIC FATAL ERROR: License file is missing required data: {e}")
        sys.exit(1)
    except Exception as e:
        print(f"\n❌ mxPIC FATAL ERROR: Failed to read license. {e}")
        sys.exit(1)