index.js

const titleRegex = /(\w*)(?:\((\w*)\))?: (.*)/;

module.exports = (app) => {
  app.on(
    [`pull_request.opened`, `pull_request.edited`, `pull_request.synchronize`],
    async (context) => {
      const config = await context.config(`badge.yml`);
      const { owner, repo } = context.repo();
      if (!config || config === null) {
        context.log(`${owner}/${repo}`, `No config found, skipping`);
        return;
      }
      const {
        payload: {
          pull_request: { title, labels },
        },
      } = context;
      if (titleRegex.test(title)) {
        const [, type, scope, message] = titleRegex.exec(title);
        let label = null;
        if (config && config.types[type]) {
          if (typeof config.types[type] === `string`) {
            label = config.types[type];
          } else if (typeof config.types[type] === `object`) {
            if (scope && config.types[type][scope]) {
              label = config.types[type][scope];
            } else if (config.types[type].default) {
              label = config.types[type].default;
            }
          }
        } else if (config.default) {
          label = config.default;
        }
        if (label !== null) {
          context.log(`${owner}/${repo}`, `Using label:`, label);
          const oldLabels = labels.map((lab) => lab.name);
          const newLabels = Array.from(new Set([...oldLabels, label]));
          const params = context.issue({ labels: newLabels });
          context.github.issues.addLabels(params);
        }
      }
    }
  );
};