Let the Matrix SDK compute the Fallback urls

matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/auth/AuthenticationService.kt

@@ -46,6 +46,11 @@ interface AuthenticationService {
      */
     fun getSsoUrl(redirectUrl: String, deviceId: String?, providerId: String?): String?
 
+    /**
+     * Get the sign in or sign up fallback URL
+     */
+    fun getFallbackUrl(forSignIn: Boolean, deviceId: String?): String?
+
     /**
      * Return a LoginWizard, to login to the homeserver. The login flow has to be retrieved first.
      */

matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/auth/Constants.kt

@@ -20,13 +20,13 @@ package org.matrix.android.sdk.api.auth
  * Path to use when the client does not supported any or all login flows
  * Ref: https://matrix.org/docs/spec/client_server/latest#login-fallback
  */
-const val LOGIN_FALLBACK_PATH = "/_matrix/static/client/login/"
+internal const val LOGIN_FALLBACK_PATH = "/_matrix/static/client/login/"
 
 /**
  * Path to use when the client does not supported any or all registration flows
  * Not documented
  */
-const val REGISTER_FALLBACK_PATH = "/_matrix/static/client/register/"
+internal const val REGISTER_FALLBACK_PATH = "/_matrix/static/client/register/"
 
 /**
  * Path to use when the client want to connect using SSO

matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/auth/DefaultAuthenticationService.kt

@@ -23,7 +23,9 @@ import kotlinx.coroutines.withContext
 import okhttp3.OkHttpClient
 import org.matrix.android.sdk.api.MatrixCallback
 import org.matrix.android.sdk.api.auth.AuthenticationService
+import org.matrix.android.sdk.api.auth.LOGIN_FALLBACK_PATH
 import org.matrix.android.sdk.api.auth.MSC2858_SSO_REDIRECT_PATH
+import org.matrix.android.sdk.api.auth.REGISTER_FALLBACK_PATH
 import org.matrix.android.sdk.api.auth.SSO_REDIRECT_PATH
 import org.matrix.android.sdk.api.auth.SSO_REDIRECT_URL_PARAM
 import org.matrix.android.sdk.api.auth.data.Credentials
@@ -104,27 +106,51 @@ internal class DefaultAuthenticationService @Inject constructor(
     }
 
     override fun getSsoUrl(redirectUrl: String, deviceId: String?, providerId: String?): String? {
-        return pendingSessionData?.let { safePendingSessionData ->
+        val homeServerUrlBase = getHomeServerUrlBase() ?: return null
-            val homeServerUrl = safePendingSessionData.homeServerConnectionConfig.homeServerUri.toString()
 
-            buildString {
+        return buildString {
-                append(homeServerUrl.trim { it == '/' })
+            append(homeServerUrlBase)
-                if (providerId != null) {
+            if (providerId != null) {
-                    append(MSC2858_SSO_REDIRECT_PATH)
+                append(MSC2858_SSO_REDIRECT_PATH)
-                    append("/$providerId")
+                append("/$providerId")
-                } else {
+            } else {
-                    append(SSO_REDIRECT_PATH)
+                append(SSO_REDIRECT_PATH)
-                }
+            }
-                // Set a redirect url we will intercept later
+            // Set the redirect url
-                appendParamToUrl(SSO_REDIRECT_URL_PARAM, redirectUrl)
+            appendParamToUrl(SSO_REDIRECT_URL_PARAM, redirectUrl)
+            deviceId?.takeIf { it.isNotBlank() }?.let {
+                // But https://github.com/matrix-org/synapse/issues/5755
+                appendParamToUrl("device_id", it)
+            }
+        }
+    }
+
+    override fun getFallbackUrl(forSignIn: Boolean, deviceId: String?): String? {
+        val homeServerUrlBase = getHomeServerUrlBase() ?: return null
+
+        return buildString {
+            append(homeServerUrlBase)
+            if (forSignIn) {
+                append(LOGIN_FALLBACK_PATH)
                 deviceId?.takeIf { it.isNotBlank() }?.let {
                     // But https://github.com/matrix-org/synapse/issues/5755
                     appendParamToUrl("device_id", it)
                 }
+            } else {
+                // For sign up
+                append(REGISTER_FALLBACK_PATH)
             }
         }
     }
 
+    private fun getHomeServerUrlBase(): String? {
+        return pendingSessionData
+                ?.homeServerConnectionConfig
+                ?.homeServerUri
+                ?.toString()
+                ?.trim { it == '/' }
+    }
+
     override fun getLoginFlow(homeServerConnectionConfig: HomeServerConnectionConfig, callback: MatrixCallback<LoginFlowResult>): Cancelable {
         pendingSessionData = null
 

vector/src/main/java/im/vector/app/features/login/LoginViewModel.kt

@@ -822,4 +822,8 @@ class LoginViewModel @AssistedInject constructor(
     fun getSsoUrl(redirectUrl: String, deviceId: String?, providerId: String?): String? {
         return authenticationService.getSsoUrl(redirectUrl, deviceId, providerId)
     }
+
+    fun getFallbackUrl(forSignIn: Boolean, deviceId: String?): String? {
+        return authenticationService.getFallbackUrl(forSignIn, deviceId)
+    }
 }

vector/src/main/java/im/vector/app/features/login/LoginWebFragment.kt

@@ -38,10 +38,7 @@ import im.vector.app.databinding.FragmentLoginWebBinding
 import im.vector.app.features.signout.soft.SoftLogoutAction
 import im.vector.app.features.signout.soft.SoftLogoutViewModel
 
-import org.matrix.android.sdk.api.auth.LOGIN_FALLBACK_PATH
-import org.matrix.android.sdk.api.auth.REGISTER_FALLBACK_PATH
 import org.matrix.android.sdk.api.auth.data.Credentials
-import org.matrix.android.sdk.api.util.appendParamToUrl
 import org.matrix.android.sdk.internal.di.MoshiProvider
 import timber.log.Timber
 import java.net.URLDecoder
@@ -119,19 +116,7 @@ class LoginWebFragment @Inject constructor(
     }
 
     private fun launchWebView(state: LoginViewState) {
-        val url = buildString {
+        val url = loginViewModel.getFallbackUrl(state.signMode == SignMode.SignIn, state.deviceId) ?: return
-            append(state.homeServerUrl?.trim { it == '/' })
-            if (state.signMode == SignMode.SignIn) {
-                append(LOGIN_FALLBACK_PATH)
-                state.deviceId?.takeIf { it.isNotBlank() }?.let {
-                    // But https://github.com/matrix-org/synapse/issues/5755
-                    appendParamToUrl("device_id", it)
-                }
-            } else {
-                // MODE_REGISTER
-                append(REGISTER_FALLBACK_PATH)
-            }
-        }
 
         views.loginWebWebView.loadUrl(url)