import sys
from pprint import pformat


def read_pip_freeze_file(file_path):
    try:
        with open(file_path, 'r') as f:
            return [l.strip() for l in f.readlines()]
    except Exception as e:
        print("Error while reading pip freeze file: {}".format(e))


def parse_line(line):
    if "===" in line:
        pkg, version = line.split("===")
    elif "==" in line:
        pkg, version = line.split("==")
    elif line.startswith("-e"):
        pkg = line.split("=")[-1]
        version = "egg"
    else:
        pkg, version = None, None
        print("Couldn't understand line: {}".format(line))
    return pkg, version


def get_package_dict(file_path):
    lines = read_pip_freeze_file(file_path)
    return dict([parse_line(line) for line in lines])


def compare_envs(d1, d2):
    pkg1 = set(list(d1.keys()))
    pkg2 = set(list(d2.keys()))
    in_both = pkg1.intersection(pkg2)
    only_in_1 = list(pkg1 - in_both)
    only_in_2 = list(pkg2 - in_both)

    # compare versions
    diff_version = []
    same_version = []

    for pkg in in_both:
        assert pkg not in only_in_1
        assert pkg not in only_in_2

        v1, v2 = d1.get(pkg), d2.get(pkg)
        if v1 != v2:
            diff_version.append("{} ({} vs {})".format(pkg, v1, v2))
        else:
            same_version.append("{}=={}".format(pkg, v1))

    return only_in_1, only_in_2, diff_version, same_version


if __name__ == "__main__":
    try:
        env1 = sys.argv[1]
        env2 = sys.argv[2]
    except IndexError:
        print("you need to pass the name of two environments at the commmand line")

    e1 = get_package_dict(env1)
    e2 = get_package_dict(env2)
    in_one, in_two, diff_version, same_version = compare_envs(e1, e2)

    print("\n", "-" * 20, "only in {}".format(env1), "-" * 20)
    print(pformat(in_one))
    print("-" * 20, "only in {}".format(env2), "-" * 20)
    print(pformat(in_two))
    print("\n", "-" * 20, "Common same version", "-" * 20)
    print(pformat(same_version))
    print("\n", "-" * 20, "Common different version", "-" * 20)
    print(pformat(diff_version))