get-github-default-branch-name/src/index.ts

get github default branch name

import { Octokit } from "@octokit/rest";
import * as st from "scripting-tools";

export const previousResults: Record<string, string> = {};

const getOctokit = (() => {
    let octokit: Octokit | undefined = undefined;

    return function(): Octokit {
        if (octokit !== undefined) {
            return octokit;
        }

        const auth = process.env["GITHUB_TOKEN"];
        octokit = new Octokit(auth ? { auth } : undefined);

        return getOctokit();
    };
})();

export async function getGithubDefaultBranchName(params: {
    owner: string;
    repo: string;
}): Promise<string> {
    const { owner, repo } = params;

    const key = `${owner}/${repo}`;

    if (key in previousResults) {
        return previousResults[key];
    }

    const octokit = getOctokit();

    const resp = await octokit.repos
        .get({
            owner,
            repo,
        })
        .catch(error => error);

    if (resp instanceof Error) {
        throw new Error(
            `Can't get default branch name for ${key}: ${resp.message}`,
        );
    }

    previousResults[key] = resp.data.default_branch;

    return getGithubDefaultBranchName(params);
}

export function getGithubDefaultBranchNameSync(params: {
    owner: string;
    repo: string;
}): string {
    const { owner, repo } = params;

    const key = `${owner}/${repo}`;

    if (key in previousResults) {
        return previousResults[key];
    }

    previousResults[key] = st.execSync(`${process.argv[0]} ${__filename}`, {
        "env": {
            "OWNER": owner,
            "REPO": repo,
        },
    });

    return getGithubDefaultBranchNameSync(params);
}

if (require.main === module) {
    (async () => {
        const defaultBranchName = await getGithubDefaultBranchName({
            "owner": process.env["OWNER"] as string,
            "repo": process.env["REPO"] as string,
        }).catch(error => error);

        if (defaultBranchName instanceof Error) {
            console.error(defaultBranchName.message);
            process.exit(1);
        }

        process.stdout.write(defaultBranchName);

        process.exit(0);
    })();
}