import sys
from importlib.metadata import distribution, PackageNotFoundError, version
from packaging.requirements import Requirement

def main(req_file):
    with open(req_file) as f:
        requirements = [line.strip() for line in f if line.strip() and not line.startswith('#')]

    missing = []
    mismatch = []
    for req_line in requirements:
        try:
            req = Requirement(req_line)
            pkg_name = req.name
            spec = req.specifier
            try:
                installed_ver = version(pkg_name)
                if not spec.contains(installed_ver):
                    mismatch.append(f"{pkg_name} (requires {spec}, but {installed_ver} installed)")
            except PackageNotFoundError:
                missing.append(f"{pkg_name} (requires {spec if spec else 'any version'})")
        except Exception as e:
            print(f"Failed to parse: {req_line} - {e}")

    if missing:
        print("Missing packages:")
        for m in missing:
            print(f"  {m}")
    if mismatch:
        print("\nVersion mismatches:")
        for m in mismatch:
            print(f"  {m}")
    if not missing and not mismatch:
        print("All dependencies are correctly installed.")

if __name__ == "__main__":
    if len(sys.argv) != 2:
        print("Usage: python check_reqs_improved.py requirements.txt")
        sys.exit(1)
    main(sys.argv[1])