#!/usr/bin/env node

// Output some `export` commands with a few extra environment variables. They'll be evaluated
// into the build environment and available for use in later steps.

const github = require('@octokit/rest')();
const {execSync} = require('child_process');

let environment = module.exports = async function() {
    const head = process.env['CIRCLE_SHA1'] || 'HEAD';

    if (process.env['CIRCLE_TARGET_BRANCH'] && process.env['CIRCLE_MERGE_BASE']) {
        return {
            head,
            base: process.env['CIRCLE_TARGET_BRANCH'],
            mergeBase: process.env['CIRCLE_MERGE_BASE']
        };
    }

    const pr = process.env['CIRCLE_PULL_REQUEST'];
    if (pr) {
        const number = +pr.match(/\/(\d+)\/?$/)[1];
        const data = (await github.pullRequests.get({ owner: 'mapbox', repo: 'mapbox-gl-native', number })).data;
        const base = data.base.ref;
        const mergeBase = execSync(`git merge-base origin/${base} ${head}`).toString().trim();
        return { head, base, mergeBase };
    } else {
        for (const sha of execSync(`git rev-list --max-count=10 ${head}`).toString().trim().split('\n')) {
            const base = execSync(`git branch -r --contains ${sha} origin/master origin/release-*`).toString().split('\n')[0].trim().replace(/^origin\//, '');
            if (base.match(/^(master|release-[a-z]+)$/)) {
                const mergeBase = execSync(`git merge-base origin/${base} ${head}`).toString().trim();
                return { head, base, mergeBase };
            }
        }
        return { head, base: null, mergeBase: null };
    }
}

async function main() {
    const env = await environment();
    console.log(`export CIRCLE_TARGET_BRANCH=${env.base}`);
    console.log(`export CIRCLE_MERGE_BASE=${env.mergeBase}`);
}

if (require.main === module) {
    main();
}