// hardcoded global variable
def targetBranch = "master"

// then later in node before doing a checkout:
if(env.CHANGE_TARGET != null) {
    targetBranch = env.CHANGE_TARGET
}

node {
            if(env.BRANCH_NAME.startsWith("PR-")) {
                if(env.CHANGE_TARGET != null) {
                    targetBranch = env.CHANGE_TARGET
                }
                echo "Source branches: ${scm.branches[0].name}"

                def ffMode = 'FF_ONLY'
                if(nonFFBranches.contains(scm.branches[0].name)) {
                    ffMode = 'NO_FF'
                }
                // do a full clone with merge before build when building pull request
                checkout([
                    $class: 'GitSCM',
                    branches: scm.branches,
                    doGenerateSubmoduleConfigurations: scm.doGenerateSubmoduleConfigurations,
                    extensions: scm.extensions + [[$class: 'CloneOption', noTags: false, reference: '', shallow: false, depth: 0, timeout: 60], [$class: 'PruneStaleBranch'], [$class: 'CheckoutOption', timeout: 60], [$class: 'PreBuildMerge', options: [mergeRemote: 'origin', mergeTarget: targetBranch, fastForwardMode: ffMode]]],
                    submoduleCfg: [],
                    userRemoteConfigs: scm.userRemoteConfigs,
                    browser: [$class: 'BitbucketWeb', repoUrl: 'https://bitbucket.org/microblink/core']
                  ])
            } else {
                // do a shallow clone when building feature branch HEAD
                checkout([
                    $class: 'GitSCM',
                    branches: scm.branches,
                    doGenerateSubmoduleConfigurations: scm.doGenerateSubmoduleConfigurations,
                    extensions: scm.extensions + [[$class: 'CloneOption', noTags: false, reference: '', shallow: true, depth: 1, timeout: 60], [$class: 'PruneStaleBranch'], [$class: 'CheckoutOption', timeout: 60]],
                    submoduleCfg: [],
                    userRemoteConfigs: scm.userRemoteConfigs,
                    browser: [$class: 'BitbucketWeb', repoUrl: 'https://bitbucket.org/microblink/core']
                  ])
            }
}

def getPullRequestID() {
    return env.BRANCH_NAME.substring(3)
}

def obtainBitbucketToken() {
    try {
        echo "Obtaining BitBucket Access Token"
        sh "curl -s -X POST https://bitbucket.org/site/oauth2/access_token -u \"${getBitbucketOAuthKey()}:${getBitbucketOAuthSecret()}\" -d grant_type=client_credentials | jsawk 'return this.access_token' | tr -d \"\\n\" > accessToken.txt"

        def accessToken = readFile 'accessToken.txt'

        echo "BitBucket Token request response: ${accessToken}"

        return accessToken
    } catch (error) {
        echo "Failed to obtain BitBucket access token!"
        return null
    }
}

def getPullRequestTargetAndSourceCommit(String accessToken, String repository, String pullRequestID) {
    try {
        sh "curl -s -X GET https://api.bitbucket.org/2.0/repositories/microblink/${repository}/pullrequests/${pullRequestID} -H \"Authorization: Bearer ${accessToken}\" > pullRequestInfo.json"
        sh "cat pullRequestInfo.json | jsawk 'return this.source.commit.hash' | tr -d '\\n' > commitID.txt"
        sh "cat pullRequestInfo.json | jsawk 'return this.destination.branch.name' | tr -d '\\n' > destinationBranch.txt"
        return [commitHash: readFile('commitID.txt'), destinationBranch: readFile('destinationBranch.txt')]
    } catch (error) {
        echo "Failed to obtain pull request target and source commit. Reason: ${error}"
        return null
    }
}

def accessToken = obtainBitbucketToken()
def pullRequestID = getPullRequestID()
def prInfo = getPullRequestTargetAndSourceCommit(accessToken, repository, pullRequestID)

def targetBranch = 'master'
if (prInfo != null) {
    targetBranch = prInfo.destinationBranch
}