Block commits for files containing content that doesn't match regex

import com.atlassian.bitbucket.commit.Commit
import com.atlassian.bitbucket.commit.CommitService
import com.atlassian.bitbucket.content.Change
import com.atlassian.bitbucket.content.ChangesRequest
import com.atlassian.bitbucket.content.ContentService
import com.atlassian.bitbucket.hook.repository.RepositoryHookResult
import com.atlassian.sal.api.component.ComponentLocator
import com.onresolve.scriptrunner.parameters.annotation.ShortTextInput

import java.util.regex.Pattern

@ShortTextInput(label = 'regex', description = 'Regex expression used to verify file content')
String regexValue
def pattern = Pattern.compile(regexValue)

def commitService = ComponentLocator.getComponent(CommitService)
def contentService = ComponentLocator.getComponent(ContentService)

def commits = refChanges.getCommits(repository) as List<Commit>

// filePaths to commit Id, if file was modified in multiple commits, take the last commit id
def filePaths = [:] as Map<String, String>
commits.reverseEach { commit ->
    def changesRequest = new ChangesRequest.Builder(repository, commit.id).build()
    commitService.streamChanges(changesRequest) { Change change ->
        if (change.path.extension == 'java') {
            filePaths[change.path.toString()] = commit.id
        }
        true
    }
}

def result = filePaths.keySet().collect { filePath ->
    def fileStream = new ByteArrayOutputStream()
    contentService.streamFile(repository, filePaths[filePath], filePath) {
        fileStream
    }
    fileStream.toString()
}.every {
    pattern.matcher(it).count > 0
}

result ? RepositoryHookResult.accepted() : RepositoryHookResult.rejected('Push blocked', 'Java files should match regex')