/*
 * Copyright © 2024-2026 Apple Inc. and the Pkl project authors. All rights reserved.
 *
 * 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
 *
 *     https://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.
 */
import java.io.File
import java.util.regex.Matcher
import java.util.regex.Pattern
import org.gradle.api.DefaultTask
import org.gradle.api.file.ConfigurableFileCollection
import org.gradle.api.file.FileVisitDetails
import org.gradle.api.file.RegularFileProperty
import org.gradle.api.provider.ListProperty
import org.gradle.api.provider.MapProperty
import org.gradle.api.tasks.Input
import org.gradle.api.tasks.InputFiles
import org.gradle.api.tasks.OutputFile
import org.gradle.api.tasks.TaskAction
import org.gradle.kotlin.dsl.listProperty
import org.gradle.kotlin.dsl.mapProperty

open class MergeSourcesJars : DefaultTask() {
  @get:InputFiles val inputJars: ConfigurableFileCollection = project.objects.fileCollection()

  @get:InputFiles
  val mergedBinaryJars: ConfigurableFileCollection = project.objects.fileCollection()

  @get:Input val relocatedPackages: MapProperty<String, String> = project.objects.mapProperty()

  @get:Input
  var sourceFileExtensions: ListProperty<String> =
    project.objects.listProperty<String>().convention(listOf(".java", ".kt"))

  @get:OutputFile val outputJar: RegularFileProperty = project.objects.fileProperty()

  @TaskAction
  @Suppress("unused")
  fun merge() {
    val binaryPaths = collectBinaryPaths()

    val relocatedPkgs = relocatedPackages.get()

    val relocatedPaths =
      relocatedPkgs.entries.associate { (key, value) -> toPath(key) to toPath(value) }

    // use negative lookbehind to match any that don't precede with
    // a word or a period character. should catch most cases.
    val importPattern =
      Pattern.compile(
        "(?<!([\\w.]))(" + relocatedPkgs.keys.joinToString("|") { it.replace(".", "\\.") } + ")"
      )

    val sourceFileExts = sourceFileExtensions.get()

    val outDir = this.temporaryDir

    for (jar in inputJars) {
      // as of Gradle 2.4, doesn't visit dirs despite the claims
      project.zipTree(jar).visit {
        val details = this
        if (details.isDirectory) return@visit

        var path = details.relativePath.parent!!.pathString
        val relocatedPath = relocatedPaths.keys.find { path.startsWith(it) }
        if (relocatedPath != null) {
          path = path.replace(relocatedPath, relocatedPaths.getValue(relocatedPath))
        }
        // conservative shrinking
        if (!binaryPaths.contains(path)) return@visit

        val outFile = File("$outDir/$path/${details.file.name}")
        outFile.parentFile.mkdirs()

        if (sourceFileExts.any { details.file.name.endsWith(it) }) {
          val oldContents = details.file.readText(Charsets.UTF_8)
          val newContents = fixImports(relocatedPkgs, details, oldContents, importPattern)
          outFile.writeText(newContents, Charsets.UTF_8)
        } else {
          details.copyTo(outFile)
        }
      }
    }

    project.ant.invokeMethod("jar", mapOf("basedir" to outDir, "destfile" to outputJar.get()))
  }

  private fun collectBinaryPaths(): Set<String> {
    val result = mutableSetOf<String>()
    for (jar in mergedBinaryJars) {
      // as of Gradle 2.4 doesn't visit dirs despite the claims
      project.zipTree(jar).visit {
        val details = this
        if (details.isDirectory) return@visit // avoid adding empty dirs
        result.add(details.relativePath.parent!!.pathString)
      }
    }
    return result
  }

  private fun fixImports(
    relocatedPkgs: Map<String, String>,
    details: FileVisitDetails,
    sourceText: String,
    importPattern: Pattern,
  ): String {
    val matcher = importPattern.matcher(sourceText)
    val buffer = StringBuffer()
    logger.debug("Inspecting file: {}", details.relativePath)
    while (matcher.find()) {
      val newStat = relocatedPkgs[matcher.group(2)]
      logger.debug("Old: {}", matcher.group())
      logger.debug("New: {}", newStat)
      matcher.appendReplacement(buffer, Matcher.quoteReplacement(newStat))
    }
    matcher.appendTail(buffer)
    return buffer.toString()
  }

  private fun toPath(packageName: String): String = packageName.replace(".", "/")
}
