import re

def parse_stages(content: str) -> list:
    # Try inline format: stages: a, b, c
    match = re.search(r"^stages:\s*(.+)$", content, re.MULTILINE)
    if match and "," in match.group(1) and "\n" not in match.group(1):
        return [s.strip() for s in match.group(1).split(",")]

    lines = content.splitlines()
    stages = []
    in_stages_block = False

    for line in lines:
        if line.strip().startswith("stages:"):
            in_stages_block = True
            continue

        if in_stages_block:
            if line.strip().startswith("-"):
                stages.append(line.strip().lstrip("- ").strip())
            elif line.strip() == "":
                continue
            else:
                break

    return stages

def validate_ci_stages(ci_content: str):
    stages = parse_stages(ci_content)

    if not stages:
        raise ValueError("ci.yml has no valid stages defined.")

    if "install" not in stages or "test" not in stages:
        raise ValueError("ci.yml must define both 'install' and 'test' stages.")

    # Only check 'build' if it exists
    if "build" in stages:
        if stages.index("test") < stages.index("install") or stages.index("test") < stages.index("build"):
            raise ValueError("ci.yml stage ordering is invalid.")
    else:
        if stages.index("test") < stages.index("install"):
            raise ValueError("ci.yml stage ordering is invalid.")