/*
 * 第 9 章 · build.gradle.kts
 * ------------------------------------------------------------
 * 演示：
 *   1) 给自定义 task 加 @CacheableTask 让它能进 Build Cache
 *   2) Worker API 的并行执行
 *   3) Configuration Cache 安全的 task 写法（用 Provider，不直接读 env）
 */

plugins {
    java
}

java {
    toolchain { languageVersion.set(JavaLanguageVersion.of(17)) }
}

repositories { mavenCentral() }

// ============================================================
// 示例 1：可缓存的"行数统计" task
// ============================================================
@CacheableTask
abstract class CountLinesTask : DefaultTask() {
    @get:InputDirectory
    @get:org.gradle.api.tasks.PathSensitive(org.gradle.api.tasks.PathSensitivity.RELATIVE)
    abstract val sourceDir: org.gradle.api.file.DirectoryProperty

    @get:Input
    abstract val fileExtension: org.gradle.api.provider.Property<String>

    @get:OutputFile
    abstract val report: org.gradle.api.file.RegularFileProperty

    @TaskAction
    fun count() {
        val ext = fileExtension.get()
        val total = sourceDir.asFileTree.matching {
            include("**/*." + ext)
        }.sumOf { it.readLines().size }
        report.get().asFile.writeText("总行数(*.$ext)=$total\n")
        logger.lifecycle("✅ 行数统计完成：$total（已写入缓存友好型 task）")
    }
}

tasks.register<CountLinesTask>("countLines") {
    group = "perf"
    description = "可缓存：第二次运行如果输入未变会 FROM-CACHE"
    sourceDir.set(layout.projectDirectory.dir("src"))
    fileExtension.set("java")
    report.set(layout.buildDirectory.file("reports/lines.txt"))
}

// ============================================================
// 示例 2：演示"Configuration Cache 友好"的写法
// ============================================================

// ❌ 错误示范（会被 Configuration Cache 警告）
// tasks.register("badEnv") {
//     val env = System.getenv("USER")          // 在配置阶段直接读，破坏可缓存性
//     doLast { println("Hello, $env") }
// }

// ✅ 正确示范：用 Provider 懒求值
val userEnv = providers.environmentVariable("USER")
tasks.register("greet") {
    group = "perf"
    description = "Configuration Cache 友好版"
    doLast {
        println("👋 Hello, ${userEnv.orNull ?: "anonymous"}")
    }
}

// ============================================================
// 示例 3：Worker API 并行处理多个文件
// ============================================================

interface MockWorkParameters : org.gradle.workers.WorkParameters {
    val index: org.gradle.api.provider.Property<Int>
}

abstract class MockWorkAction : org.gradle.workers.WorkAction<MockWorkParameters> {
    override fun execute() {
        val i = parameters.index.get()
        // 模拟一个耗时 600ms 的"压缩/转换"操作
        Thread.sleep(600)
        println("  worker-${Thread.currentThread().id} 完成任务 #$i")
    }
}

abstract class ParallelDemoTask : DefaultTask() {
    @get:javax.inject.Inject
    abstract val workerExecutor: org.gradle.workers.WorkerExecutor

    @TaskAction
    fun go() {
        val queue = workerExecutor.noIsolation()
        val total = 8
        logger.lifecycle("派发 $total 个 worker 任务...")
        repeat(total) { i ->
            queue.submit(MockWorkAction::class.java) {
                index.set(i)
            }
        }
        logger.lifecycle("派发完毕，等待 worker 收尾。")
    }
}

tasks.register<ParallelDemoTask>("parallelDemo") {
    group = "perf"
    description = "Worker API 并行示例：8 个任务，并行 4-8 个 worker，1s 内完成"
}

// ============================================================
// 示例 4：观察哪些 task 会跑 / 哪些会 UP-TO-DATE
// ============================================================
tasks.register("explainCache") {
    group = "perf"
    description = "提示如何观察缓存命中"
    doLast {
        println("""
            
        ▶ 试试以下命令观察输出：
          ./gradlew countLines                 # 第一次：真正执行
          ./gradlew countLines                 # 第二次：UP-TO-DATE
          ./gradlew clean countLines --build-cache
                                              # 第三次：FROM-CACHE
        
        ▶ 想看慢在哪儿？
          ./gradlew build --scan
          ./gradlew build --profile
          
        """.trimIndent())
    }
}