/*
 * Copyright (C) 2022 The Android Open Source Project
 *
 * 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 com.android.quicksearchbox.google

import android.content.Context
import android.content.SharedPreferences
import android.util.Log
import com.android.quicksearchbox.R
import com.android.quicksearchbox.SearchSettings
import com.android.quicksearchbox.SearchSettingsImpl
import com.android.quicksearchbox.util.HttpHelper
import java.util.Locale
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.async

/** Helper to build the base URL for all search requests. */
class SearchBaseUrlHelper(
  context: Context?,
  helper: HttpHelper,
  searchSettings: SearchSettings,
  prefs: SharedPreferences
) : SharedPreferences.OnSharedPreferenceChangeListener {
  private val mHttpHelper: HttpHelper
  private val mContext: Context?
  private val mSearchSettings: SearchSettings
  private val scope = CoroutineScope(Dispatchers.IO)

  /**
   * Update the base search url, either: (a) it has never been set (first run) (b) it has expired
   * (c) if the caller forces an update by setting the "force" parameter.
   *
   * @param force if true, then the URL is reset whether or not it has expired.
   */
  fun maybeUpdateBaseUrlSetting(force: Boolean) {
    val lastUpdateTime: Long = mSearchSettings.searchBaseDomainApplyTime
    val currentTime: Long = System.currentTimeMillis()
    if (
      force || lastUpdateTime == -1L || currentTime - lastUpdateTime >= SEARCH_BASE_URL_EXPIRY_MS
    ) {
      if (mSearchSettings.shouldUseGoogleCom()) {
        setSearchBaseDomain(defaultBaseDomain)
      } else {
        checkSearchDomain()
      }
    }
  }

  /** @return the base url for searches. */
  val searchBaseUrl: String?
    get() =
      mContext
        ?.getResources()
        ?.getString(
          R.string.google_search_base_pattern,
          searchDomain,
          GoogleSearch.getLanguage(Locale.getDefault())
        ) // This is required to deal with the case wherein getSearchDomain
  // is called before checkSearchDomain returns a valid URL. This will
  // happen *only* on the first run of the app when the "use google.com"
  // option is unchecked. In other cases, the previously set domain (or
  // the default) will be returned.
  //
  // We have no choice in this case but to use the default search domain.
  /**
   * @return the search domain. This is of the form "google.co.xx" or "google.com", used by UI code.
   */
  val searchDomain: String?
    get() {
      var domain: String? = mSearchSettings.searchBaseDomain
      if (domain == null) {
        if (DBG) {
          Log.w(
            TAG,
            "Search base domain was null, last apply time=" +
              mSearchSettings.searchBaseDomainApplyTime
          )
        }

        // This is required to deal with the case wherein getSearchDomain
        // is called before checkSearchDomain returns a valid URL. This will
        // happen *only* on the first run of the app when the "use google.com"
        // option is unchecked. In other cases, the previously set domain (or
        // the default) will be returned.
        //
        // We have no choice in this case but to use the default search domain.
        domain = defaultBaseDomain
      }
      if (domain?.startsWith(".") == true) {
        if (DBG) Log.d(TAG, "Prepending www to $domain")
        domain = "www$domain"
      }
      return domain
    }

  /**
   * Issue a request to google.com/searchdomaincheck to retrieve the base URL for search requests.
   */
  private fun checkSearchDomain() {
    val request = HttpHelper.GetRequest(DOMAIN_CHECK_URL)
    scope.async {
      if (DBG) Log.d(TAG, "Starting request to /searchdomaincheck")
      var domain: String?
      try {
        domain = mHttpHelper[request]
      } catch (e: Exception) {
        if (DBG) Log.d(TAG, "Request to /searchdomaincheck failed : $e")
        // Swallow any exceptions thrown by the HTTP helper, in
        // this rare case, we just use the default URL.
        domain = defaultBaseDomain
      }
      if (DBG) Log.d(TAG, "Request to /searchdomaincheck succeeded")
      setSearchBaseDomain(domain)
    }
  }

  private val defaultBaseDomain: String?
    get() = mContext?.getResources()?.getString(R.string.default_search_domain)

  private fun setSearchBaseDomain(domain: String?) {
    if (DBG) Log.d(TAG, "Setting search domain to : $domain")
    mSearchSettings.searchBaseDomain = domain
  }

  @Override
  override fun onSharedPreferenceChanged(pref: SharedPreferences?, key: String?) {
    // Listen for changes only to the SEARCH_BASE_URL preference.
    if (DBG) Log.d(TAG, "Handling changed preference : $key")
    if (SearchSettingsImpl.USE_GOOGLE_COM_PREF.equals(key)) {
      maybeUpdateBaseUrlSetting(true)
    }
  }

  companion object {
    private const val DBG = false
    private const val TAG = "QSB.SearchBaseUrlHelper"
    private const val DOMAIN_CHECK_URL = "https://www.google.com/searchdomaincheck?format=domain"
    private const val SEARCH_BASE_URL_EXPIRY_MS = 24 * 3600 * 1000L
  }

  /**
   * Note that this constructor will spawn a thread to issue a HTTP request if shouldUseGoogleCom is
   * false.
   */
  init {
    mHttpHelper = helper
    mContext = context
    mSearchSettings = searchSettings

    // Note: This earlier used an inner class, but that causes issues
    // because SharedPreferencesImpl uses a WeakHashMap< > and the listener
    // will be GC'ed unless we keep a reference to it here.
    prefs.registerOnSharedPreferenceChangeListener(this)
    maybeUpdateBaseUrlSetting(false)
  }
}