PixelDroid-App-Android/app/src/main/java/com/h/pixeldroid/LoginActivity.kt

package com.h.pixeldroid

import android.app.AlertDialog
import android.content.Context
import android.content.Intent
import android.content.SharedPreferences
import android.net.Uri
import android.os.Bundle
import android.view.View
import android.view.inputmethod.InputMethodManager
import androidx.lifecycle.lifecycleScope
import com.h.pixeldroid.databinding.ActivityLoginBinding
import com.h.pixeldroid.utils.*
import com.h.pixeldroid.utils.api.PixelfedAPI
import com.h.pixeldroid.utils.api.objects.*
import com.h.pixeldroid.utils.db.addUser
import com.h.pixeldroid.utils.db.storeInstance
import kotlinx.coroutines.*
import retrofit2.HttpException
import java.io.IOException
import java.lang.IllegalArgumentException

/**
Overview of the flow of the login process: (boxes are requests done in parallel,
since they do not depend on each other)

 _________________________________
|[PixelfedAPI.registerApplication]|
|[PixelfedAPI.wellKnownNodeInfo]  |
 ̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅
+----> [PixelfedAPI.nodeInfoSchema] (and then [PixelfedAPI.instance] if needed)
+----> [promptOAuth]
+----> [PixelfedAPI.obtainToken]
+----> [PixelfedAPI.verifyCredentials]

 */

class LoginActivity : BaseActivity() {

    companion object {
        private const val PACKAGE_ID = BuildConfig.APPLICATION_ID
        private const val SCOPE = "read write follow"
    }

    private lateinit var oauthScheme: String
    private lateinit var appName: String
    private lateinit var preferences: SharedPreferences

    private lateinit var pixelfedAPI: PixelfedAPI
    private var inputVisibility: Int = View.GONE

    private lateinit var binding: ActivityLoginBinding

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityLoginBinding.inflate(layoutInflater)
        setContentView(binding.root)

        loadingAnimation(true)
        appName = getString(R.string.app_name)
        oauthScheme = getString(R.string.auth_scheme)
        preferences = getSharedPreferences("$PACKAGE_ID.pref", Context.MODE_PRIVATE)

        if (hasInternet(applicationContext)) {
            binding.connectInstanceButton.setOnClickListener {
                registerAppToServer(normalizeDomain(binding.editText.text.toString()))
            }
            binding.whatsAnInstanceTextView.setOnClickListener{ whatsAnInstance() }
            inputVisibility = View.VISIBLE
        } else {
            binding.loginActivityConnectionRequired.visibility = View.VISIBLE
            binding.loginActivityConnectionRequiredButton.setOnClickListener {
                finish()
                startActivity(intent)
            }
        }
        loadingAnimation(false)
    }

    override fun onStart() {
        super.onStart()
        val url: Uri? = intent.data

        //Check if the activity was started after the authentication
        if (url == null || !url.toString().startsWith("$oauthScheme://$PACKAGE_ID")) return
        loadingAnimation(true)

        val code = url.getQueryParameter("code")
        authenticate(code)
    }

    override fun onStop() {
        super.onStop()
        loadingAnimation(false)
    }


    private fun whatsAnInstance() {
        val builder = AlertDialog.Builder(this)
        builder.apply {
            setView(layoutInflater.inflate(R.layout.whats_an_instance_explanation, null))
            setPositiveButton(android.R.string.ok) { _, _ -> }
        }
        // Create the AlertDialog
        builder.show()
    }

    private fun hideKeyboard() {
        val view = currentFocus
        if (view != null) {
            (getSystemService(Context.INPUT_METHOD_SERVICE) as InputMethodManager).hideSoftInputFromWindow(
                view.windowToken,
                InputMethodManager.HIDE_NOT_ALWAYS
            )
        }
    }

    private fun registerAppToServer(normalizedDomain: String) {

        if(!validDomain(normalizedDomain)) return failedRegistration(getString(R.string.invalid_domain))

        hideKeyboard()
        loadingAnimation(true)

        pixelfedAPI = PixelfedAPI.createFromUrl(normalizedDomain)

        lifecycleScope.launch {
            try {
                val credentialsDeferred: Deferred<Application?> = async {
                    try {
                        pixelfedAPI.registerApplication(
                                appName, "$oauthScheme://$PACKAGE_ID", SCOPE
                        )
                    } catch (exception: IOException) {
                        return@async null
                    } catch (exception: HttpException) {
                        return@async null
                    }
                }

                val nodeInfoJRD = pixelfedAPI.wellKnownNodeInfo()

                val credentials = credentialsDeferred.await()

                val clientId = credentials?.client_id ?: return@launch failedRegistration()
                preferences.edit()
                    .putString("clientID", clientId)
                    .putString("clientSecret", credentials.client_secret)
                    .apply()


                // c.f. https://nodeinfo.diaspora.software/protocol.html for more info
                val nodeInfoSchemaUrl = nodeInfoJRD.links.firstOrNull {
                    it.rel == "http://nodeinfo.diaspora.software/ns/schema/2.0"
                }?.href ?: return@launch failedRegistration(getString(R.string.instance_error))

                nodeInfoSchema(normalizedDomain, clientId, nodeInfoSchemaUrl)
            } catch (exception: IOException) {
                return@launch failedRegistration()
            } catch (exception: HttpException) {
                return@launch failedRegistration()
            }
        }
    }

    private suspend fun nodeInfoSchema(
        normalizedDomain: String,
        clientId: String,
        nodeInfoSchemaUrl: String
    ) = coroutineScope {

        val nodeInfo: NodeInfo = try {
            pixelfedAPI.nodeInfoSchema(nodeInfoSchemaUrl)
        } catch (exception: IOException) {
            return@coroutineScope failedRegistration(getString(R.string.instance_error))
        } catch (exception: HttpException) {
            return@coroutineScope failedRegistration(getString(R.string.instance_error))
        }

        val domain: String = try {
            if (nodeInfo.hasInstanceEndpointInfo()) {
                storeInstance(db, nodeInfo)
                nodeInfo.metadata?.config?.site?.url
            } else {
                val instance: Instance = try {
                    pixelfedAPI.instance()
                } catch (exception: IOException) {
                    return@coroutineScope failedRegistration(getString(R.string.instance_error))
                } catch (exception: HttpException) {
                    return@coroutineScope failedRegistration(getString(R.string.instance_error))
                }
                storeInstance(db, nodeInfo = null, instance = instance)
                instance.uri
            }
        } catch (e: IllegalArgumentException){ null }
                ?: return@coroutineScope failedRegistration(getString(R.string.instance_error))

        preferences.edit().putString("domain", normalizeDomain(domain)).apply()


        if (!nodeInfo.software?.name.orEmpty().contains("pixelfed")) {
            AlertDialog.Builder(this@LoginActivity).apply {
                setMessage(R.string.instance_not_pixelfed_warning)
                setPositiveButton(R.string.instance_not_pixelfed_continue) { _, _ ->
                    promptOAuth(normalizedDomain, clientId)
                }
                setNegativeButton(R.string.instance_not_pixelfed_cancel) { _, _ ->
                    loadingAnimation(false)
                    wipeSharedSettings()
                }
            }.show()
        } else if (nodeInfo.metadata?.config?.features?.mobile_apis != true) {
            AlertDialog.Builder(this@LoginActivity).apply {
                setMessage(R.string.api_not_enabled_dialog)
                setNegativeButton(android.R.string.ok) { _, _ ->
                    loadingAnimation(false)
                    wipeSharedSettings()
                }
            }.show()
        } else {
            promptOAuth(normalizedDomain, clientId)
        }
    }


    private fun promptOAuth(normalizedDomain: String, client_id: String) {

        val url = "$normalizedDomain/oauth/authorize?" +
                "client_id" + "=" + client_id + "&" +
                "redirect_uri" + "=" + "$oauthScheme://$PACKAGE_ID" + "&" +
                "response_type=code" + "&" +
                "scope=$SCOPE"

        if (!openUrl(url)) return failedRegistration(getString(R.string.browser_launch_failed))
    }

    private fun authenticate(code: String?) {

        // Get previous values from preferences
        val domain = preferences.getString("domain", "") as String
        val clientId = preferences.getString("clientID", "") as String
        val clientSecret = preferences.getString("clientSecret", "") as String

        if (code.isNullOrBlank() || domain.isBlank() || clientId.isBlank() || clientSecret.isBlank()) {
            return failedRegistration(getString(R.string.auth_failed))
        }

        //Successful authorization
        pixelfedAPI = PixelfedAPI.createFromUrl(domain)

        lifecycleScope.launch {
            try {
                val token = pixelfedAPI.obtainToken(
                    clientId, clientSecret, "$oauthScheme://$PACKAGE_ID", SCOPE, code,
                    "authorization_code"
                )
                if (token.access_token == null) {
                    return@launch failedRegistration(getString(R.string.token_error))
                }
                storeUser(
                    token.access_token,
                    token.refresh_token,
                    clientId,
                    clientSecret,
                    domain
                )
                wipeSharedSettings()
            } catch (exception: IOException) {
                return@launch failedRegistration(getString(R.string.token_error))

            } catch (exception: HttpException) {
                return@launch failedRegistration(getString(R.string.token_error))
            }
        }
    }

    private fun failedRegistration(message: String = getString(R.string.registration_failed)) {
        loadingAnimation(false)
        binding.editText.error = message
        wipeSharedSettings()
    }

    private fun wipeSharedSettings(){
        preferences.edit().remove("domain").remove("clientId").remove("clientSecret")
            .apply()
    }

    private fun loadingAnimation(on: Boolean){
        if(on) {
            binding.loginActivityInstanceInputLayout.visibility = View.GONE
            binding.progressLayout.visibility = View.VISIBLE
        }
        else {
            binding.loginActivityInstanceInputLayout.visibility = inputVisibility
            binding.progressLayout.visibility = View.GONE
        }
    }

    private suspend fun storeUser(accessToken: String, refreshToken: String?, clientId: String, clientSecret: String, instance: String) {
        try {
            val user = pixelfedAPI.verifyCredentials("Bearer $accessToken")
            db.userDao().deActivateActiveUsers()
            addUser(
                db,
                user,
                instance,
                activeUser = true,
                accessToken = accessToken,
                refreshToken = refreshToken,
                clientId = clientId,
                clientSecret = clientSecret
            )
            apiHolder.setToCurrentUser()
            val intent = Intent(this@LoginActivity, MainActivity::class.java)
            intent.flags = Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_CLEAR_TASK
            startActivity(intent)
        } catch (exception: IOException) {
            return failedRegistration(getString(R.string.verify_credentials))
        } catch (exception: HttpException) {
            return failedRegistration(getString(R.string.verify_credentials))
        }
    }

}