/*
 * Copyright 2026 the original author or authors.
 *
 * 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 gradlebuild

import com.google.gson.Gson
import org.gradle.api.DefaultTask
import org.gradle.api.file.ConfigurableFileCollection
import org.gradle.api.file.FileCollection
import org.gradle.api.file.RegularFileProperty
import org.gradle.api.model.ObjectFactory
import org.gradle.api.provider.Provider
import org.gradle.api.tasks.CacheableTask
import org.gradle.api.tasks.Input
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.api.tasks.TaskAction
import java.io.File

@CacheableTask
abstract class GeneratePackageInfoDataTask : DefaultTask() {

    companion object {
        val packageLineRegex = Regex("""package\s*([^;\s]+)\s*;""")

        fun findPackageInfoFiles(objects: ObjectFactory, projectBaseDirs: Provider<List<File>>): FileCollection {
            return objects.fileCollection().from(projectBaseDirs.map {
                it.flatMap { projectDir -> listOf(File(projectDir, "src/main/java"), File(projectDir, "src/main/groovy")) }
            }).asFileTree.matching {
                include("**/package-info.java")
            }.filter {
                it.isFile
            }
        }
    }

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

    @get:Input
    // Preserve the project path in the cache key, since packageInfoFiles are fingerprinted relative to each source root.
    val packageInfoFilePaths: List<String>
        get() = packageInfoFiles.files.map { it.relativeTo(baseDir).path.replace(File.separatorChar, '/') }.sorted()

    @get:OutputFile
    abstract val outputFile: RegularFileProperty

    private val baseDir = project.layout.settingsDirectory.asFile

    @TaskAction
    fun action() {
        val results = mutableListOf<Pair<String, String>>()

        for (packageInfoFile in packageInfoFiles.files) {
            val packageLine = packageInfoFile.useLines { lines -> lines.first { it.startsWith("package") } }
            val packageName = packageLineRegex.find(packageLine)!!.groupValues[1]
            results.add(packageName to packageInfoFile.relativeTo(baseDir).path)
        }

        val outputData = results.groupBy(keySelector = { it.first }, valueTransform = { it.second })
        outputFile.get().asFile.writeText(Gson().toJson(outputData))
    }

}
