Complete the chat page

app/src/main/java/eu/m724/chatapp/activity/chat/ChatActivity.kt

@@ -4,14 +4,20 @@ import android.os.Bundle
 import androidx.activity.ComponentActivity
 import androidx.activity.compose.setContent
 import androidx.activity.enableEdgeToEdge
+import androidx.compose.animation.animateColorAsState
+import androidx.compose.animation.core.animateDpAsState
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.imePadding
 import androidx.compose.foundation.layout.padding
-import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.items
+import androidx.compose.foundation.lazy.rememberLazyListState
 import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.automirrored.filled.Send
@@ -19,6 +25,8 @@ import androidx.compose.material3.ElevatedCard
 import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.material3.Icon
 import androidx.compose.material3.IconButton
+import androidx.compose.material3.IconButtonDefaults
+import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Scaffold
 import androidx.compose.material3.Text
 import androidx.compose.material3.TextField
@@ -37,11 +45,18 @@ import androidx.compose.ui.focus.focusRequester
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.tooling.preview.Preview
 import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.sp
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import androidx.lifecycle.viewmodel.compose.viewModel
+import dagger.hilt.android.AndroidEntryPoint
+import eu.m724.chatapp.activity.chat.compose.AnimatedChangingText
 import eu.m724.chatapp.activity.ui.theme.ChatAppTheme
 
+@AndroidEntryPoint
 class ChatActivity : ComponentActivity() {
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
+
         enableEdgeToEdge()
         setContent {
             Content()
@@ -50,18 +65,74 @@ class ChatActivity : ComponentActivity() {
 }
 
 @Composable
-fun Content() {
+fun Content(
+    viewModel: ChatActivityViewModel = viewModel()
+) {
+    val uiState by viewModel.uiState.collectAsStateWithLifecycle()
+
+    var composerValue by remember { mutableStateOf("") }
+
     ChatAppTheme {
         Scaffold(
             modifier = Modifier.fillMaxSize(),
-            topBar = { ChatTopAppBar() }
+            topBar = {
+                ChatTopAppBar(uiState.chatTitle ?: "Start a new conversation")
+            }
         ) { innerPadding ->
             Column(
-                modifier = Modifier.padding(innerPadding).imePadding()
+                modifier = Modifier.fillMaxSize().padding(innerPadding).imePadding(),
+                horizontalAlignment = Alignment.CenterHorizontally
             ) {
-                MessageComposer(
+                val lazyListState = rememberLazyListState()
-                    modifier = Modifier.padding(5.dp)
+
+                LazyColumn(
+                    modifier = Modifier.fillMaxSize().weight(1f),
+                    state = lazyListState
+                ) {
+                    items(uiState.messageHistory) { message ->
+                        MessageExchange(
+                            modifier = Modifier.padding(5.dp),
+                            isComposing = false,
+                            composerValue = message.prompt,
+                            responseValue = message.response
+                        )
+                    }
+
+                    item {
+                        MessageExchange(
+                            modifier = Modifier.padding(5.dp).fillParentMaxHeight(),
+                            isComposing = !uiState.requestInProgress,
+                            composerValue = composerValue,
+                            onComposerValueChange = { composerValue = it },
+                            responseValue = uiState.currentMessageResponse // TODO animate this
+                        )
+                    }
+                }
+
+                ComposerToolBar(
+                    modifier = Modifier.width(500.dp).padding(horizontal = 10.dp),
+                    canSend = composerValue.isNotBlank() && !uiState.requestInProgress,
+                    onSend = {
+                        viewModel.sendMessage(composerValue)
+                    }
                 )
+
+                Text(
+                    text = "AI can make mistakes, double-check.",
+                    modifier = Modifier.padding(vertical = 10.dp),
+                    color = MaterialTheme.colorScheme.secondary.copy(alpha = 0.6f),
+                    fontSize = 12.sp,
+                    lineHeight = 14.sp
+                )
+
+                LaunchedEffect(uiState.requestInProgress) { // TODO probably not the best way
+                    if (!uiState.requestInProgress) {
+                        composerValue = ""
+                        if (!uiState.messageHistory.isEmpty()) {
+                            lazyListState.animateScrollToItem(uiState.messageHistory.size - 1)
+                        }
+                    }
+                }
             }
         }
     }
@@ -69,57 +140,116 @@ fun Content() {
 
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
-fun ChatTopAppBar() {
+fun ChatTopAppBar(
+    title: String
+) {
     TopAppBar(
         title = {
-            Text(
+            AnimatedChangingText(title)
-                modifier = Modifier.fillMaxWidth(),
-                text = "Start a new conversation"
-            )
         }
     )
 }
 
 @Composable
-fun MessageComposer(
+fun MessageExchange(
-    modifier: Modifier = Modifier
+    modifier: Modifier = Modifier,
+    isComposing: Boolean,
+    composerValue: String,
+    onComposerValueChange: (String) -> Unit = {},
+    responseValue: String = "",
 ) {
-    var value by remember { mutableStateOf("Hello") }
-    val focusRequester = remember { FocusRequester() }
-
-    LaunchedEffect(Unit) {
-        focusRequester.requestFocus()
-    }
 
     Column(
-        modifier = modifier,
+        modifier = modifier.padding(horizontal = 10.dp)
     ) {
-        TextField(
+        MessageComposer(
-            value = value,
+            value = composerValue,
-            onValueChange = {
+            onValueChange = onComposerValueChange,
-                value = it
+            enabled = isComposing
-            },
-            modifier = Modifier.weight(1f).padding(horizontal = 10.dp).focusRequester(focusRequester),
-            placeholder = {
-                Text("Type something here...")
-            },
-            shape = RoundedCornerShape(16.dp),
-            colors = TextFieldDefaults.colors(
-                unfocusedContainerColor = Color.Transparent,
-                focusedContainerColor = Color.Transparent,
-                unfocusedIndicatorColor = Color.Transparent,
-                focusedIndicatorColor = Color.Transparent,
-            )
         )
 
-        ComposerToolBar()
+        if (!isComposing) {
+            Text(
+                text = responseValue,
+                modifier = Modifier
+                    .padding(horizontal = 16.dp)
+            )
+        }
+
     }
 }
 
 @Composable
-fun ComposerToolBar() {
+fun MessageComposer(
+    value: String,
+    onValueChange: (String) -> Unit,
+    enabled: Boolean,
+    modifier: Modifier = Modifier
+) {
+    val textFieldPadding by animateDpAsState(
+        targetValue = if (enabled) {
+            0.dp
+        } else {
+            16.dp
+        }
+    )
+
+    val textFieldTextColor by animateColorAsState(
+        targetValue = if (enabled) {
+            TextFieldDefaults.colors().focusedTextColor
+        } else {
+            TextFieldDefaults.colors().disabledTextColor
+        }
+    )
+
+    val focusRequester = remember { FocusRequester() }
+
+    LaunchedEffect(enabled) {
+        if (enabled) {
+            focusRequester.requestFocus()
+        }
+    }
+
+    TextField(
+        value = value,
+        onValueChange = onValueChange,
+        modifier = modifier
+            .fillMaxWidth()
+            .padding(horizontal = textFieldPadding)
+            .focusRequester(focusRequester),
+            // .animateContentSize()
+        placeholder = {
+            Text("Type your message...")
+        },
+        colors = TextFieldDefaults.colors(
+            unfocusedContainerColor = Color.Transparent,
+            focusedContainerColor = Color.Transparent,
+            disabledContainerColor = Color.Transparent,
+            unfocusedIndicatorColor = Color.Transparent,
+            focusedIndicatorColor = Color.Transparent,
+            disabledIndicatorColor = Color.Transparent,
+            disabledTextColor = textFieldTextColor
+        ),
+        enabled = enabled
+    )
+}
+
+@Composable
+fun ComposerToolBar(
+    modifier: Modifier = Modifier,
+    canSend: Boolean,
+    onSend: () -> Unit
+) {
+    val sendButtonColor by animateColorAsState(
+        targetValue = if (canSend) {
+            IconButtonDefaults.iconButtonColors().contentColor
+        } else {
+            IconButtonDefaults.iconButtonColors().disabledContentColor
+        }
+    )
+
     ElevatedCard(
-        modifier = Modifier.fillMaxWidth().padding(10.dp),
+        modifier = modifier,
         shape = RoundedCornerShape(100)
     ) {
         Row(
@@ -128,9 +258,14 @@ fun ComposerToolBar() {
         ) {
             IconButton(
                 onClick = {
-                    // TODO send
+                    onSend()
                 },
-                modifier = Modifier.size(48.dp)
+                modifier = Modifier.height(48.dp).padding(horizontal = 8.dp),
+                enabled = canSend,
+                colors = IconButtonDefaults.iconButtonColors(
+                    contentColor = sendButtonColor,
+                    disabledContentColor = sendButtonColor
+                )
             ) {
                 Column (
                     horizontalAlignment = Alignment.CenterHorizontally

app/src/main/java/eu/m724/chatapp/activity/chat/ChatActivityUiState.kt

@@ -1,5 +1,13 @@
 package eu.m724.chatapp.activity.chat
 
 data class ChatActivityUiState(
-    val requestInProgress: Boolean
+    val chatTitle: String? = null,
+    val requestInProgress: Boolean = false,
+    val currentMessageResponse: String = "",
+    val messageHistory: List<ChatMessageExchange> = listOf()
+)
+
+data class ChatMessageExchange(
+    val prompt: String,
+    var response: String
 )

app/src/main/java/eu/m724/chatapp/activity/chat/ChatActivityViewModel.kt

@@ -1,13 +1,67 @@
 package eu.m724.chatapp.activity.chat
 
 import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
 import dagger.hilt.android.lifecycle.HiltViewModel
 import eu.m724.chatapp.api.AiApiService
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.flow.update
+import kotlinx.coroutines.launch
 import javax.inject.Inject
 
 @HiltViewModel
 class ChatActivityViewModel @Inject constructor(
     private val aiApiService: AiApiService
 ) : ViewModel() {
+    private val _uiState = MutableStateFlow(ChatActivityUiState())
+    val uiState: StateFlow<ChatActivityUiState> = _uiState.asStateFlow()
 
+    val responses = arrayOf(
+        "Hello right back at you! How can I help you today?",
+        "I'm sorry, but I can't assist with that."
+    )
+
+    fun sendMessage(message: String) {
+
+        _uiState.update {
+            it.copy(
+                requestInProgress = true,
+                currentMessageResponse = ""
+            )
+        }
+
+        if (_uiState.value.chatTitle == null) {
+            _uiState.update {
+                it.copy(chatTitle = message) // TODO
+            }
+        }
+
+
+        viewModelScope.launch {
+            val response = responses.random()
+            val targetResponseParts = response.split(" ")
+
+            for (part in targetResponseParts) {
+                delay(50)
+
+                _uiState.update {
+                    it.copy(
+                        currentMessageResponse = it.currentMessageResponse.trim() + " $part"
+                    )
+                }
+            }
+
+            _uiState.update {
+                it.copy(
+                    requestInProgress = false,
+                    messageHistory = it.messageHistory.plus(
+                        ChatMessageExchange(message, response)
+                    )
+                )
+            }
+        }
+    }
 }

app/src/main/java/eu/m724/chatapp/activity/chat/compose/AnimatedChangingText.kt

@@ -0,0 +1,41 @@
+package eu.m724.chatapp.activity.chat.compose
+
+import androidx.compose.animation.AnimatedContent
+import androidx.compose.animation.core.tween
+import androidx.compose.animation.fadeIn
+import androidx.compose.animation.fadeOut
+import androidx.compose.animation.shrinkHorizontally
+import androidx.compose.animation.togetherWith
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Modifier
+
+@Composable
+fun AnimatedChangingText(
+    text: String,
+    modifier: Modifier = Modifier
+) {
+    Row(
+        modifier = modifier.fillMaxWidth(),
+        horizontalArrangement = Arrangement.Center
+    ) {
+        AnimatedContent(
+            targetState = text,
+            transitionSpec = {
+                val enter = fadeIn() //  + expandHorizontally()
+                val exit = fadeOut() + shrinkHorizontally(animationSpec = tween(800))
+
+                enter.togetherWith(exit)
+            },
+            label = "Animated horizontal text"
+        ) { targetText ->
+            Text(
+                text = targetText,
+                softWrap = false
+            )
+        }
+    }
+}