/*
 * Copyright 2020 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.buildutils.tasks

import org.gradle.api.DefaultTask
import org.gradle.api.file.RegularFileProperty
import org.gradle.api.provider.Property
import org.gradle.api.tasks.Internal
import org.gradle.api.tasks.TaskAction
import org.gradle.internal.util.PropertiesUtils
import org.w3c.dom.Element
import java.util.Properties
import javax.xml.parsers.DocumentBuilderFactory


/**
 * Fetch the latest AGP versions and write a properties file.
 * Never up-to-date, non-cacheable.
 */
abstract class UpdateAgpVersions : DefaultTask() {

    @get:Internal
    abstract val comment: Property<String>

    @get:Internal
    abstract val minimumSupportedMinor: Property<String>

    @get:Internal
    abstract val propertiesFile: RegularFileProperty

    @TaskAction
    fun fetch() {

        val dbf = DocumentBuilderFactory.newInstance()
        val latests = dbf.fetchLatests(minimumSupportedMinor.get())
        val nightly = dbf.fetchNightly()
        val properties = Properties().apply {
            setProperty("latests", latests.joinToString(","))
            setProperty("nightly", nightly)
        }
        properties.store(
            propertiesFile.get().asFile,
            comment.get()
        )
    }

    private
    fun DocumentBuilderFactory.fetchLatests(minimumSupported: String): List<String> {
        var latests = fetchVersionsFromMavenMetadata("https://dl.google.com/dl/android/maven2/com/android/tools/build/gradle/maven-metadata.xml")
            .groupBy { it.take(3) }
            .map { (_, versions) -> versions.first() }
        latests = (latests + minimumSupported).sorted()
        latests = latests.subList(latests.indexOf(minimumSupported) + 1, latests.size)
        return latests
    }

    private
    fun DocumentBuilderFactory.fetchNightly(): String =
        fetchVersionsFromMavenMetadata("https://repo.gradle.org/gradle/ext-snapshots-local/com/android/tools/build/gradle/maven-metadata.xml")
            .first()

    private
    fun DocumentBuilderFactory.fetchVersionsFromMavenMetadata(url: String): List<String> =
        newDocumentBuilder()
            .parse(url)
            .getElementsByTagName("version").let { versions ->
                (0 until versions.length)
                    .map { idx -> (versions.item(idx) as Element).textContent }
                    .reversed()
            }

    private
    fun Properties.store(file: java.io.File, comment: String? = null) {
        PropertiesUtils.store(this, file, comment, Charsets.ISO_8859_1, "\n")
    }
}
