import subprocess
import sys
from pathlib import Path


class DependencyManager:
    def __init__(self, requirements_path: Path) -> None:
        self.requirements_path = requirements_path

    @staticmethod
    def _normalize_requirement_name(requirement_line: str) -> str:
        line = requirement_line.split(";", 1)[0].strip()
        for sep in ["==", ">=", "<=", "!=", "~=", ">", "<"]:
            if sep in line:
                line = line.split(sep, 1)[0].strip()
                break
        if "[" in line:
            line = line.split("[", 1)[0].strip()
        return line

    def parse_requirements(self) -> list[str]:
        if not self.requirements_path.exists():
            return []

        requirements: list[str] = []
        for raw in self.requirements_path.read_text(encoding="utf-8").splitlines():
            line = raw.strip()
            if not line or line.startswith("#"):
                continue
            requirements.append(line)
        return requirements

    def _is_installed(self, requirement: str) -> bool:
        package_name = self._normalize_requirement_name(requirement)
        if not package_name:
            return True

        result = subprocess.run(
            [sys.executable, "-m", "pip", "show", package_name],
            stdout=subprocess.DEVNULL,
            stderr=subprocess.DEVNULL,
            check=False,
        )
        return result.returncode == 0

    def install_missing(self) -> list[str]:
        requirements = self.parse_requirements()
        missing = [req for req in requirements if not self._is_installed(req)]

        if missing:
            subprocess.check_call([sys.executable, "-m", "pip", "install", *missing])

        return missing