gcar-auth.gradle

import java.util.concurrent.TimeUnit

class GoogleArtifactRegistryCredentials {

    private final String username;
    private final String password;

    GoogleArtifactRegistryCredentials(String username, String password) {
        this.username = username
        this.password = password
    }

    String getUsername() {
        return this.username
    }

    String getPassword() {
        return this.password
    }

}

class ResolveGoogleArtifactRegistryCredentialsAction implements Action<Credentials> {

    def resolveGCARCredentials() {
        def serviceAccountKeyFile = new File("${System.getenv('HOME')}/gcp-service-account-key.json")
        if (serviceAccountKeyFile.exists()) {
            return resolveSAKeyCredentials(serviceAccountKeyFile)
        }

        //SA key is not present on path `$HOME/gcp-service-account-key.json`.
        //Fall back to using access token of any active account.
        return resolveUserCredentials()
    }

    def resolveSAKeyCredentials(serviceAccountKeyFile) {
        def username = "_json_key_base64"
        def password = serviceAccountKeyFile.text.bytes.encodeBase64().toString()

        return new GoogleArtifactRegistryCredentials(username, password)
    }

    def resolveUserCredentials() {
        def sout = new StringBuilder(), serr = new StringBuilder()

        try {
            def proc = ['gcloud', 'auth', 'print-access-token'].execute(null, new File('.'))
            proc.consumeProcessOutput(sout, serr)
            proc.waitFor(5, TimeUnit.SECONDS)
            if (!serr.allWhitespace) {
                println "Unable to retrieve access token: ${serr.toString()}"
            }
            return new GoogleArtifactRegistryCredentials("oauth2accesstoken", sout.toString())
        } catch (e) {
            println "Errors returned by `gcloud auth print-access-token`: $serr, result: $sout"
            throw new Exception('Unable to retrieve access token ', e)
        }
    }

    @Override
    void execute(Credentials credentials) {
        def gCARCredentials = resolveGCARCredentials()
        credentials.setUsername(gCARCredentials.getUsername())
        credentials.setPassword(gCARCredentials.getPassword())
    }
}

ext {
    resolveGCARCredentialsAction = { new ResolveGoogleArtifactRegistryCredentialsAction() }
}