import re


_SEMVER_RE = re.compile(
    r"(0|[1-9][0-9]*)\."
    r"(0|[1-9][0-9]*)\."
    r"(0|[1-9][0-9]*)"
    r"(?:-([0-9A-Za-z-]+(?:\.[0-9A-Za-z-]+)*))?"
    r"(?:\+([0-9A-Za-z-]+(?:\.[0-9A-Za-z-]+)*))?"
)


def parse_semver(s):
    if not isinstance(s, str):
        return None

    match = _SEMVER_RE.fullmatch(s)
    if match is None:
        return None

    prerelease = match.group(4)
    if prerelease is not None:
        for identifier in prerelease.split("."):
            if len(identifier) > 1 and identifier[0] == "0" and identifier.isdigit():
                return None

    numbers = []
    for text in match.group(1, 2, 3):
        value = 0
        for digit in text:
            value = value * 10 + ord(digit) - ord("0")
        numbers.append(value)

    return {
        "major": numbers[0],
        "minor": numbers[1],
        "patch": numbers[2],
        "prerelease": prerelease,
        "build": match.group(5),
    }