main.py

import os
import requests  # noqa We are just importing this to prove the dependency installed correctly
import semver
import re
from github_action_utils import set_output


def main():
    # cut initial v from input
    current_tag = os.environ["INPUT_CURRENTTAG"][1:]
    # optional parameter
    previous_full_tag = os.environ.get("INPUT_PREVFULLTAG")

    major, minor, patch, prerelease, _ = semver.VersionInfo.parse(current_tag)
    if previous_full_tag:
        pft_ver = list(semver.VersionInfo.parse(previous_full_tag[1:]))
    else:
        pft_ver = list(semver.VersionInfo.parse(current_tag))
        pft_ver[1] -= 1
        pft_ver[2] = 0
    if prerelease:
        type, number = re.match('(?P<type>alpha|beta|rc)(?P<number>\d+)', prerelease).groups(['type', 'number'])
        if type in ['alpha', 'beta'] and number == '1':
            # compare 3.3.0-beta1 with 3.2.0
            # but if it's patch compare with last released patch
            if not patch:
                previous_tag = semver.format_version(pft_ver[0], pft_ver[1], 0)
            else:
                previous_tag = semver.format_version(major, minor, patch - 1)
        elif type == 'rc' and number == '1':
            # compare 3.3.0-rc1 with 3.3.0-beta1
            previous_tag = semver.format_version(major, minor, patch, 'beta1')
        else:
            previous_tag = semver.format_version(major, minor, patch, f"{type}{int(number) - 1}")
    elif not patch and not minor:
        previous_tag = semver.format_version(major - 1, 0, 0)
    elif not patch:
        previous_tag = semver.format_version(major, minor - 1, 0)
    else:
        previous_tag = semver.format_version(major, minor, patch - 1)

    set_output("previousTag", f"v{previous_tag}")


if __name__ == "__main__":
    main()