/*
 * Copyright © 2017-2021 Soren Stoutner <soren@stoutner.com>.
 *
 * This file is part of Privacy Browser <https://www.stoutner.com/privacy-browser>.
 *
 * Privacy Browser is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Privacy Browser is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Privacy Browser.  If not, see <http://www.gnu.org/licenses/>.
 */

package com.stoutner.privacybrowser.activities

import android.content.res.Configuration
import android.os.Build
import android.os.Bundle
import android.text.SpannableStringBuilder
import android.text.Spanned
import android.text.style.ForegroundColorSpan
import android.util.TypedValue
import android.view.KeyEvent
import android.view.Menu
import android.view.MenuItem
import android.view.View
import android.view.View.OnFocusChangeListener
import android.view.WindowManager
import android.view.inputmethod.InputMethodManager
import android.widget.EditText
import android.widget.ProgressBar
import android.widget.TextView

import androidx.appcompat.app.ActionBar
import androidx.appcompat.app.AppCompatActivity
import androidx.appcompat.widget.Toolbar
import androidx.core.app.NavUtils
import androidx.fragment.app.DialogFragment
import androidx.lifecycle.ViewModelProvider
import androidx.preference.PreferenceManager
import androidx.swiperefreshlayout.widget.SwipeRefreshLayout

import com.google.android.material.snackbar.Snackbar

import com.stoutner.privacybrowser.R
import com.stoutner.privacybrowser.dialogs.AboutViewSourceDialog
import com.stoutner.privacybrowser.dialogs.UntrustedSslCertificateDialog
import com.stoutner.privacybrowser.dialogs.UntrustedSslCertificateDialog.UntrustedSslCertificateListener
import com.stoutner.privacybrowser.helpers.ProxyHelper
import com.stoutner.privacybrowser.viewmodelfactories.WebViewSourceFactory
import com.stoutner.privacybrowser.viewmodels.WebViewSource

import java.util.Locale

// Declare the public constants.
const val CURRENT_URL = "current_url"
const val USER_AGENT = "user_agent"

class ViewSourceActivity: AppCompatActivity(), UntrustedSslCertificateListener {
    // Declare the class variables.
    private lateinit var initialGrayColorSpan: ForegroundColorSpan
    private lateinit var finalGrayColorSpan: ForegroundColorSpan
    private lateinit var redColorSpan: ForegroundColorSpan
    private lateinit var webViewSource: WebViewSource

    // Declare the class views.
    private lateinit var urlEditText: EditText
    private lateinit var requestHeadersTitleTextView: TextView
    private lateinit var requestHeadersTextView: TextView
    private lateinit var responseMessageTitleTextView: TextView
    private lateinit var responseMessageTextView: TextView
    private lateinit var responseHeadersTitleTextView: TextView
    private lateinit var responseBodyTitleTextView: TextView

    override fun onCreate(savedInstanceState: Bundle?) {
        // Get a handle for the shared preferences.
        val sharedPreferences = PreferenceManager.getDefaultSharedPreferences(applicationContext)

        // Get the preferences.
        val allowScreenshots = sharedPreferences.getBoolean(getString(R.string.allow_screenshots_key), false)
        val bottomAppBar = sharedPreferences.getBoolean(getString(R.string.bottom_app_bar_key), false)

        // Disable screenshots if not allowed.
        if (!allowScreenshots) {
            window.addFlags(WindowManager.LayoutParams.FLAG_SECURE)
        }

        // Set the theme.
        setTheme(R.style.PrivacyBrowser)

        // Run the default commands.
        super.onCreate(savedInstanceState)

        // Get the launching intent
        val intent = intent

        // Get the information from the intent.
        val currentUrl = intent.getStringExtra(CURRENT_URL)!!
        val userAgent = intent.getStringExtra(USER_AGENT)!!

        // Set the content view.
        if (bottomAppBar) {
            setContentView(R.layout.view_source_coordinatorlayout_bottom_appbar)
        } else {
            setContentView(R.layout.view_source_coordinatorlayout_top_appbar)
        }

        // Get a handle for the toolbar.
        val toolbar = findViewById<Toolbar>(R.id.view_source_toolbar)

        // Set the support action bar.
        setSupportActionBar(toolbar)

        // Get a handle for the action bar.
        val actionBar = supportActionBar!!

        // Add the custom layout to the action bar.
        actionBar.setCustomView(R.layout.view_source_app_bar)

        // Instruct the action bar to display a custom layout.
        actionBar.displayOptions = ActionBar.DISPLAY_SHOW_CUSTOM

        // Get handles for the views.
        urlEditText = findViewById(R.id.url_edittext)
        val progressBar = findViewById<ProgressBar>(R.id.progress_bar)
        val swipeRefreshLayout = findViewById<SwipeRefreshLayout>(R.id.view_source_swiperefreshlayout)
        requestHeadersTitleTextView = findViewById(R.id.request_headers_title_textview)
        requestHeadersTextView = findViewById(R.id.request_headers_textview)
        responseMessageTitleTextView = findViewById(R.id.response_message_title_textview)
        responseMessageTextView = findViewById(R.id.response_message_textview)
        responseHeadersTitleTextView = findViewById(R.id.response_headers_title_textivew)
        val responseHeadersTextView = findViewById<TextView>(R.id.response_headers_textview)
        responseBodyTitleTextView = findViewById(R.id.response_body_title_textview)
        val responseBodyTextView = findViewById<TextView>(R.id.response_body_textview)

        // Populate the URL text box.
        urlEditText.setText(currentUrl)

        // Initialize the gray foreground color spans for highlighting the URLs.  The deprecated `getColor()` must be used until the minimum API >= 23.
        @Suppress("DEPRECATION")
        initialGrayColorSpan = ForegroundColorSpan(resources.getColor(R.color.gray_500))
        @Suppress("DEPRECATION")
        finalGrayColorSpan = ForegroundColorSpan(resources.getColor(R.color.gray_500))

        // Get the current theme status.
        val currentThemeStatus = resources.configuration.uiMode and Configuration.UI_MODE_NIGHT_MASK

        // Set the red color span according to the theme.  The deprecated `getColor()` must be used until the minimum API >= 23.
        redColorSpan = if (currentThemeStatus == Configuration.UI_MODE_NIGHT_NO) {
            @Suppress("DEPRECATION")
            ForegroundColorSpan(resources.getColor(R.color.red_a700))
        } else {
            @Suppress("DEPRECATION")
            ForegroundColorSpan(resources.getColor(R.color.red_900))
        }

        // Apply text highlighting to the URL.
        highlightUrlText()

        // Get a handle for the input method manager, which is used to hide the keyboard.
        val inputMethodManager = (getSystemService(INPUT_METHOD_SERVICE) as InputMethodManager)

        // Remove the formatting from the URL when the user is editing the text.
        urlEditText.onFocusChangeListener = OnFocusChangeListener { _: View?, hasFocus: Boolean ->
            if (hasFocus) {  // The user is editing the URL text box.
                // Remove the highlighting.
                urlEditText.text.removeSpan(redColorSpan)
                urlEditText.text.removeSpan(initialGrayColorSpan)
                urlEditText.text.removeSpan(finalGrayColorSpan)
            } else {  // The user has stopped editing the URL text box.
                // Hide the soft keyboard.
                inputMethodManager.hideSoftInputFromWindow(urlEditText.windowToken, 0)

                // Move to the beginning of the string.
                urlEditText.setSelection(0)

                // Reapply the highlighting.
                highlightUrlText()
            }
        }

        // Set the refresh color scheme according to the theme.
        if (currentThemeStatus == Configuration.UI_MODE_NIGHT_NO) {
            swipeRefreshLayout.setColorSchemeResources(R.color.blue_700)
        } else {
            swipeRefreshLayout.setColorSchemeResources(R.color.violet_500)
        }

        // Initialize a color background typed value.
        val colorBackgroundTypedValue = TypedValue()

        // Get the color background from the theme.
        theme.resolveAttribute(android.R.attr.colorBackground, colorBackgroundTypedValue, true)

        // Get the color background int from the typed value.
        val colorBackgroundInt = colorBackgroundTypedValue.data

        // Set the swipe refresh background color.
        swipeRefreshLayout.setProgressBackgroundColorSchemeColor(colorBackgroundInt)

        // Populate the locale string.
        val localeString = if (Build.VERSION.SDK_INT >= 24) {  // SDK >= 24 has a list of locales.
            // Get the list of locales.
            val localeList = resources.configuration.locales

            // Initialize a string builder to extract the locales from the list.
            val localesStringBuilder = StringBuilder()

            // Initialize a `q` value, which is used by `WebView` to indicate the order of importance of the languages.
            var q = 10

            // Populate the string builder with the contents of the locales list.
            for (i in 0 until localeList.size()) {
                // Append a comma if there is already an item in the string builder.
                if (i > 0) {
                    localesStringBuilder.append(",")
                }

                // Get the locale from the list.
                val locale = localeList[i]

                // Add the locale to the string.  `locale` by default displays as `en_US`, but WebView uses the `en-US` format.
                localesStringBuilder.append(locale.language)
                localesStringBuilder.append("-")
                localesStringBuilder.append(locale.country)

                // If not the first locale, append `;q=0.x`, which drops by .1 for each removal from the main locale until q=0.1.
                if (q < 10) {
                    localesStringBuilder.append(";q=0.")
                    localesStringBuilder.append(q)
                }

                // Decrement `q` if it is greater than 1.
                if (q > 1) {
                    q--
                }

                // Add a second entry for the language only portion of the locale.
                localesStringBuilder.append(",")
                localesStringBuilder.append(locale.language)

                // Append `1;q=0.x`, which drops by .1 for each removal form the main locale until q=0.1.
                localesStringBuilder.append(";q=0.")
                localesStringBuilder.append(q)

                // Decrement `q` if it is greater than 1.
                if (q > 1) {
                    q--
                }
            }

            // Store the populated string builder in the locale string.
            localesStringBuilder.toString()
        } else {  // SDK < 24 only has a primary locale.
            // Store the locale in the locale string.
            Locale.getDefault().toString()
        }

        // Instantiate the proxy helper.
        val proxyHelper = ProxyHelper()

        // Get the current proxy.
        val proxy = proxyHelper.getCurrentProxy(this)

        // Make the progress bar visible.
        progressBar.visibility = View.VISIBLE

        // Set the progress bar to be indeterminate.
        progressBar.isIndeterminate = true

        // Update the layout.
        updateLayout(currentUrl)

        // Instantiate the WebView source factory.
        val webViewSourceFactory: ViewModelProvider.Factory = WebViewSourceFactory(currentUrl, userAgent, localeString, proxy, contentResolver, MainWebViewActivity.executorService)

        // Instantiate the WebView source view model class.
        webViewSource = ViewModelProvider(this, webViewSourceFactory).get(WebViewSource::class.java)

        // Create a source observer.
        webViewSource.observeSource().observe(this, { sourceStringArray: Array<SpannableStringBuilder> ->
            // Populate the text views.  This can take a long time, and freezes the user interface, if the response body is particularly large.
            requestHeadersTextView.text = sourceStringArray[0]
            responseMessageTextView.text = sourceStringArray[1]
            responseHeadersTextView.text = sourceStringArray[2]
            responseBodyTextView.text = sourceStringArray[3]

            // Hide the progress bar.
            progressBar.isIndeterminate = false
            progressBar.visibility = View.GONE

            //Stop the swipe to refresh indicator if it is running
            swipeRefreshLayout.isRefreshing = false
        })

        // Create an error observer.
        webViewSource.observeErrors().observe(this, { errorString: String ->
            // Display an error snackbar if the string is not `""`.
            if (errorString != "") {
                if (errorString.startsWith("javax.net.ssl.SSLHandshakeException")) {
                    // Instantiate the untrusted SSL certificate dialog.
                    val untrustedSslCertificateDialog = UntrustedSslCertificateDialog()

                    // Show the untrusted SSL certificate dialog.
                    untrustedSslCertificateDialog.show(supportFragmentManager, getString(R.string.invalid_certificate))
                } else {
                    // Display a snackbar with the error message.
                    Snackbar.make(swipeRefreshLayout, errorString, Snackbar.LENGTH_LONG).show()
                }
            }
        })

        // Implement swipe to refresh.
        swipeRefreshLayout.setOnRefreshListener {
            // Make the progress bar visible.
            progressBar.visibility = View.VISIBLE

            // Set the progress bar to be indeterminate.
            progressBar.isIndeterminate = true

            // Get the URL.
            val urlString = urlEditText.text.toString()

            // Update the layout.
            updateLayout(urlString)

            // Get the updated source.
            webViewSource.updateSource(urlString, false)
        }

        // Set the go button on the keyboard to request new source data.
        urlEditText.setOnKeyListener { _: View?, keyCode: Int, event: KeyEvent ->
            // Request new source data if the enter key was pressed.
            if (event.action == KeyEvent.ACTION_DOWN && keyCode == KeyEvent.KEYCODE_ENTER) {
                // Hide the soft keyboard.
                inputMethodManager.hideSoftInputFromWindow(urlEditText.windowToken, 0)

                // Remove the focus from the URL box.
                urlEditText.clearFocus()

                // Make the progress bar visible.
                progressBar.visibility = View.VISIBLE

                // Set the progress bar to be indeterminate.
                progressBar.isIndeterminate = true

                // Get the URL.
                val urlString = urlEditText.text.toString()

                // Update the layout.
                updateLayout(urlString)

                // Get the updated source.
                webViewSource.updateSource(urlString, false)

                // Consume the key press.
                return@setOnKeyListener true
            } else {
                // Do not consume the key press.
                return@setOnKeyListener false
            }
        }
    }

    override fun onCreateOptionsMenu(menu: Menu): Boolean {
        // Inflate the menu.
        menuInflater.inflate(R.menu.view_source_options_menu, menu)

        // Display the menu.
        return true
    }

    override fun onOptionsItemSelected(menuItem: MenuItem): Boolean {
        // Instantiate the about dialog fragment.
        val aboutDialogFragment: DialogFragment = AboutViewSourceDialog()

        // Show the about alert dialog.
        aboutDialogFragment.show(supportFragmentManager, getString(R.string.about))

        // Consume the event.
        return true
    }

    // This method must be named `goBack()` and must have a View argument to match the default back arrow in the app bar.
    fun goBack(@Suppress("UNUSED_PARAMETER") view: View) {
        // Go home.
        NavUtils.navigateUpFromSameTask(this)
    }

    override fun loadAnyway() {
        // Load the URL anyway.
        webViewSource.updateSource(urlEditText.text.toString(), true)
    }

    private fun highlightUrlText() {
        // Get a handle for the URL edit text.
        val urlEditText = findViewById<EditText>(R.id.url_edittext)

        // Get the URL string.
        val urlString = urlEditText.text.toString()

        // Highlight the URL according to the protocol.
        if (urlString.startsWith("file://")) {  // This is a file URL.
            // De-emphasize only the protocol.
            urlEditText.text.setSpan(initialGrayColorSpan, 0, 7, Spanned.SPAN_INCLUSIVE_INCLUSIVE)
        } else if (urlString.startsWith("content://")) {
            // De-emphasize only the protocol.
            urlEditText.text.setSpan(initialGrayColorSpan, 0, 10, Spanned.SPAN_INCLUSIVE_INCLUSIVE)
        } else {  // This is a web URL.
            // Get the index of the `/` immediately after the domain name.
            val endOfDomainName = urlString.indexOf("/", urlString.indexOf("//") + 2)

            // Get the base URL.
            val baseUrl = if (endOfDomainName > 0) {  // There is at least one character after the base URL.
                // Get the base URL.
                urlString.substring(0, endOfDomainName)
            } else {  // There are no characters after the base URL.
                // Set the base URL to be the entire URL string.
                urlString
            }

            // Get the index of the last `.` in the domain.
            val lastDotIndex = baseUrl.lastIndexOf(".")

            // Get the index of the penultimate `.` in the domain.
            val penultimateDotIndex = baseUrl.lastIndexOf(".", lastDotIndex - 1)

            // Markup the beginning of the URL.
            if (urlString.startsWith("http://")) {  // Highlight the protocol of connections that are not encrypted.
                urlEditText.text.setSpan(redColorSpan, 0, 7, Spanned.SPAN_INCLUSIVE_INCLUSIVE)

                // De-emphasize subdomains.
                if (penultimateDotIndex > 0) {  // There is more than one subdomain in the domain name.
                    urlEditText.text.setSpan(initialGrayColorSpan, 7, penultimateDotIndex + 1, Spanned.SPAN_INCLUSIVE_INCLUSIVE)
                }
            } else if (urlString.startsWith("https://")) {  // De-emphasize the protocol of connections that are encrypted.
                if (penultimateDotIndex > 0) {  // There is more than one subdomain in the domain name.
                    // De-emphasize the protocol and the additional subdomains.
                    urlEditText.text.setSpan(initialGrayColorSpan, 0, penultimateDotIndex + 1, Spanned.SPAN_INCLUSIVE_INCLUSIVE)
                } else {  // There is only one subdomain in the domain name.
                    // De-emphasize only the protocol.
                    urlEditText.text.setSpan(initialGrayColorSpan, 0, 8, Spanned.SPAN_INCLUSIVE_INCLUSIVE)
                }
            }

            // De-emphasize the text after the domain name.
            if (endOfDomainName > 0) {
                urlEditText.text.setSpan(finalGrayColorSpan, endOfDomainName, urlString.length, Spanned.SPAN_INCLUSIVE_INCLUSIVE)
            }
        }
    }

    private fun updateLayout(urlString: String) {
        if (urlString.startsWith("content://")) {  // This is a content URL.
            // Hide the unused text views.
            requestHeadersTitleTextView.visibility = View.GONE
            requestHeadersTextView.visibility = View.GONE
            responseMessageTitleTextView.visibility = View.GONE
            responseMessageTextView.visibility = View.GONE

            // Change the text of the remaining title text views.
            responseHeadersTitleTextView.setText(R.string.content_metadata)
            responseBodyTitleTextView.setText(R.string.content_data)
        } else {  // This is not a content URL.
            // Show the views.
            requestHeadersTitleTextView.visibility = View.VISIBLE
            requestHeadersTextView.visibility = View.VISIBLE
            responseMessageTitleTextView.visibility = View.VISIBLE
            responseMessageTextView.visibility = View.VISIBLE

            // Restore the text of the other title text views.
            responseHeadersTitleTextView.setText(R.string.response_headers)
            responseBodyTitleTextView.setText(R.string.response_body)
        }
    }
}