/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

import java.io.File
import java.util.TreeSet
import okhttp3.OkHttpClient
import okhttp3.Request
import okio.ByteString
import okio.ByteString.Companion.encodeUtf8
import okio.buffer
import okio.sink
import org.gradle.api.Plugin
import org.gradle.api.Project

/**
 * Gradle plugin to update the public suffix list used by the `lib-publicsuffixlist` component.
 *
 * Base on PublicSuffixListGenerator from OkHttp:
 * https://github.com/square/okhttp/blob/master/okhttp/src/test/java/okhttp3/internal/publicsuffix/PublicSuffixListGenerator.java
 */
class PublicSuffixListPlugin : Plugin<Project> {
  override fun apply(project: Project) {
    project.tasks.register("updatePSL") {
      doLast {
        val filename = project.projectDir.absolutePath + "/src/main/assets/publicsuffixes"
        updatePublicSuffixList(filename)
      }
    }
  }

  private fun updatePublicSuffixList(destination: String) {
    val list = fetchPublicSuffixList()
    writeListToDisk(destination, list)
  }

  private fun writeListToDisk(destination: String, data: PublicSuffixListData) {
    val fileSink = File(destination).sink()

    fileSink.buffer().use { sink ->
      sink.writeInt(data.totalRuleBytes)

      for (domain in data.sortedRules) {
        sink.write(domain).writeByte('\n'.toInt())
      }

      sink.writeInt(data.totalExceptionRuleBytes)

      for (domain in data.sortedExceptionRules) {
        sink.write(domain).writeByte('\n'.toInt())
      }
    }
  }

  private fun fetchPublicSuffixList(): PublicSuffixListData {
    val client = OkHttpClient.Builder().build()

    val request =
      Request.Builder().url("https://publicsuffix.org/list/public_suffix_list.dat").build()

    client.newCall(request).execute().use { response ->
      val source = requireNotNull(response.body).source()

      val data = PublicSuffixListData()

      while (!source.exhausted()) {
        val line = source.readUtf8LineStrict()

        if (line.trim { it <= ' ' }.isEmpty() || line.startsWith("//")) {
          continue
        }

        if (line.contains(WILDCARD_CHAR)) {
          assertWildcardRule(line)
        }

        var rule = line.encodeUtf8()

        if (rule.startsWith(EXCEPTION_RULE_MARKER)) {
          rule = rule.substring(1)
          // We use '\n' for end of value.
          data.totalExceptionRuleBytes += rule.size + 1
          data.sortedExceptionRules.add(rule)
        } else {
          data.totalRuleBytes += rule.size + 1 // We use '\n' for end of value.
          data.sortedRules.add(rule)
        }
      }

      return data
    }
  }

  @Suppress("TooGenericExceptionThrown", "ThrowsCount")
  private fun assertWildcardRule(rule: String) {
    if (rule.indexOf(WILDCARD_CHAR) != 0) {
      throw RuntimeException("Wildcard is not not in leftmost position")
    }

    if (rule.indexOf(WILDCARD_CHAR, 1) != -1) {
      throw RuntimeException("Rule contains multiple wildcards")
    }

    if (rule.length == 1) {
      throw RuntimeException("Rule wildcards the first level")
    }
  }

  companion object {
    private const val WILDCARD_CHAR = "*"
    private val EXCEPTION_RULE_MARKER = "!".encodeUtf8()
  }
}

data class PublicSuffixListData(
  var totalRuleBytes: Int = 0,
  var totalExceptionRuleBytes: Int = 0,
  val sortedRules: TreeSet<ByteString> = TreeSet(),
  val sortedExceptionRules: TreeSet<ByteString> = TreeSet()
)