weserplaner/app/src/main/java/com/denizk0461/studip/activity/FetcherActivity.kt

package com.denizk0461.studip.activity

import android.annotation.SuppressLint
import android.os.Bundle
import android.webkit.WebResourceRequest
import android.webkit.WebView
import android.webkit.WebViewClient
import androidx.fragment.app.FragmentActivity
import androidx.lifecycle.ViewModelProvider
import com.denizk0461.studip.R
import com.denizk0461.studip.data.showErrorSnackBar
import com.denizk0461.studip.data.showToast
import com.denizk0461.studip.databinding.ActivityFetcherBinding
import com.denizk0461.studip.sheet.TextSheet
import com.denizk0461.studip.viewmodel.FetcherViewModel
import java.io.IOException
import java.net.URLDecoder

/**
 * Activity for allowing the user to log in to access and fetch their schedule from their Stud.IP
 * profile. Launched through a button in the app's settings.
 */
class FetcherActivity : FragmentActivity() {

    // View binding
    private lateinit var binding: ActivityFetcherBinding
    // View model
    private lateinit var viewModel: FetcherViewModel

    /**
     * Enabling JavaScript is necessary to get the HTML source in this context. As the HTML can only
     * be accessed once the user has logged in, a simple HTML request would not suffice here.
     */
    @SuppressLint("SetJavaScriptEnabled")
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        // Instantiate view model
        viewModel = ViewModelProvider.AndroidViewModelFactory(this.application).create(FetcherViewModel::class.java)
        // Inflate view binding and bind to this activity
        binding = ActivityFetcherBinding.inflate(layoutInflater)
        setContentView(binding.root)

        // Enabling JavaScript. See comment above lint suppression for reason why this is done.
        binding.webview.settings.apply {
            javaScriptEnabled = true
        }
        binding.webview.webViewClient = object : WebViewClient() {
            // Disallow redirecting to prevent the app from launching Chrome after the user logs in
            override fun shouldOverrideUrlLoading(
                view: WebView,
                request: WebResourceRequest
            ): Boolean {
                return false
            }
        }

        // Set up bottom app bar for various actions
        binding.bottomAppBar.setOnMenuItemClickListener { item ->
            when (item.itemId) {
                R.id.close -> {
                    // Close the activity
                    finish()
                    true
                }
                R.id.refresh -> {
                    // Refresh the currently opened page
                    binding.webview.reload()
                    true
                }
                R.id.help -> {
                    // Present the user with a small tutorial on how to fetch their timetable
                    TextSheet().also { sheet ->
                        val bundle = Bundle()
                        bundle.putString("header", getString(R.string.fetch_bar_help_sheet_title))
                        bundle.putString("content", getString(R.string.fetch_bar_help_sheet_content))
                        sheet.arguments = bundle
                    }.show(supportFragmentManager, TextSheet::class.java.simpleName)
                    true
                }
                else -> false
            }
        }

        /*
         * Attempt to load the user-set Stud.IP front page. Redirects to login page if user is
         * not logged in.
         */
        binding.webview.loadUrl("https://elearning.uni-bremen.de/index.php?again=yes")

        binding.fab.setOnClickListener {

            if (binding.webview.url?.contains(
                    "https://elearning.uni-bremen.de/dispatch.php/calendar/schedule"
                ) == true) {
                /*
                 * Retrieve encoded HTML via JavaScript function. Encoding is done as otherwise not all
                 * symbols will be accurately fetched.
                 */
                binding.webview.evaluateJavascript(
                    "(function(){return encodeURI(document.getElementsByTagName('html')[0].innerHTML)})();"
                ) { p0 ->
                    try {
                        // Decode HTML and parse it into a list of StudIPEvent.kt
                        // TODO add a tutorial for the user to know what to do
                        viewModel.parse(URLDecoder.decode(p0, "UTF-8"))

                        // Notify the user that the fetch was successful
                        showToast(this, getString(R.string.toast_fetch_finished))

                        // Close the activity
                        finish()

                    } catch (e: IOException) {
                        // Let the user know that an error occurred
                        theme.showErrorSnackBar(binding.rootView, getString(R.string.fetch_error_snack), binding.bottomAppBar)
                    }
                }
            } else {
                // Tell the user that they must navigate to their timetable
                theme.showErrorSnackBar(binding.rootView, getString(R.string.fetch_error_webpage_snack), binding.bottomAppBar)
            }
        }
    }
}