build-system/gradle-core/src/main/java/com/android/build/gradle/internal/tasks/MergeFileTask.kt


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/*
 * Copyright (C) 2013 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.android.build.gradle.internal.tasks

import com.android.build.gradle.internal.caching.DisabledCachingReason.SIMPLE_MERGING_TASK
import com.android.buildanalyzer.common.TaskCategory
import com.android.utils.FileUtils
import com.google.common.base.Charsets
import com.google.common.io.Files
import org.gradle.api.file.ConfigurableFileCollection
import org.gradle.api.file.RegularFileProperty
import org.gradle.api.tasks.InputFiles
import org.gradle.api.tasks.OutputFile
import org.gradle.api.tasks.PathSensitive
import org.gradle.api.tasks.PathSensitivity
import org.gradle.work.DisableCachingByDefault
import java.io.File
import java.io.IOException

/**
 * Task to merge files. This appends all the files together into an output file.
 */
@DisableCachingByDefault(because = SIMPLE_MERGING_TASK)
@BuildAnalyzer(primaryTaskCategory = TaskCategory.MISC, secondaryTaskCategories = [TaskCategory.MERGING])
abstract class MergeFileTask : NonIncrementalTask() {

    @get:InputFiles
    @get:PathSensitive(PathSensitivity.RELATIVE)
    abstract val inputFiles: ConfigurableFileCollection

    @get:OutputFile
    abstract val outputFile: RegularFileProperty

    @Throws(IOException::class)
    override fun doTaskAction() {
        mergeFiles(inputFiles.files, outputFile.get().asFile)
    }

    companion object {

        fun mergeFiles(inputFiles: Collection<File>, output: File) {
            // filter out any non-existent files
            val existingFiles = inputFiles.filter { it.isFile() }

            if (existingFiles.size == 1) {
                FileUtils.copyFile(existingFiles[0], output)
                return
            }

            // first delete the current file
            FileUtils.deleteIfExists(output)

            // no input? done.
            if (existingFiles.isEmpty()) {
                return
            }

            // otherwise put all the files together
            for (file in existingFiles) {
                val content = Files.toString(file, Charsets.UTF_8)
                Files.append("$content\n", output, Charsets.UTF_8)
            }
        }
    }
}