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Merged
ralyodio merged 1 commit into from
Sep 22, 2026
Merged

Make mobile chat requests cancellable and recoverable #110

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104 changes: 84 additions & 20 deletions apps/mobile/src/lib/ai.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -14,28 +14,92 @@ export interface ChatMessage {
text: string;
}

/** Endpoint override (e.g. from Expo config). Empty = offline echo mode. */
export const AI_ENDPOINT = process.env.EXPO_PUBLIC_AI_ENDPOINT ?? '';

export async function sendChat(history: ChatMessage[]): Promise<ChatMessage> {
const last = history[history.length - 1]?.text ?? '';
export const CHAT_TIMEOUT_MS = 30000;
export type ChatFailure =
| 'timeout'
| 'cancelled'
| 'network'
| 'http'
| 'invalid';
export class ChatError extends Error {
constructor(readonly kind: ChatFailure) {
super(kind);
this.name = 'ChatError';
}
}

if (!AI_ENDPOINT) {
// Offline placeholder until the provider is wired.
await new Promise((r) => setTimeout(r, 350));
return {
id: `a-${Date.now()}`,
role: 'assistant',
text: `You said: “${last}”. (Offline stub — set EXPO_PUBLIC_AI_ENDPOINT to reach a model.)`,
function offlineDelay(signal: AbortSignal): Promise<void> {
return new Promise((resolve, reject) => {
const abort = () => {
clearTimeout(timer);
reject(new ChatError('cancelled'));
};
}
const timer = setTimeout(() => {
signal.removeEventListener('abort', abort);
resolve();
}, 350);
signal.addEventListener('abort', abort, { once: true });
if (signal.aborted) abort();
});
}

const res = await fetch(`${AI_ENDPOINT}/chat`, {
method: 'POST',
headers: { 'content-type': 'application/json' },
body: JSON.stringify({ messages: history.map(({ role, text }) => ({ role, text })) }),
/** One attempt. Cancellation cannot guarantee that the remote service stopped. */
export async function sendChat(history: readonly ChatMessage[], options: {signal?: AbortSignal} = {}): Promise<string> {
if (options.signal?.aborted) throw new ChatError('cancelled');
const controller = new AbortController();
let timedOut = false;
const timer = setTimeout(() => { timedOut = true; controller.abort(); }, CHAT_TIMEOUT_MS);
const forwardAbort = () => controller.abort();
options.signal?.addEventListener('abort', forwardAbort, {once:true});
let rejectAbort: () => void = () => {};
const aborted = new Promise<never>((_, reject) => {
rejectAbort = () => reject(new ChatError(timedOut ? 'timeout' : 'cancelled'));
controller.signal.addEventListener('abort', rejectAbort, {once:true});
});
if (!res.ok) throw new Error(`AI request failed (${res.status})`);
const data = (await res.json()) as { text?: string };
return { id: `a-${Date.now()}`, role: 'assistant', text: data.text ?? '(empty response)' };
const work = async () => {
const endpoint = process.env.EXPO_PUBLIC_AI_ENDPOINT ?? '';
if (!endpoint) {
await offlineDelay(controller.signal);
const last = history[history.length - 1]?.text ?? '';
return `You said: “${last}”. (Offline stub — set EXPO_PUBLIC_AI_ENDPOINT to reach a model.)`;
}
const response = await fetch(`${endpoint.replace(/\/+$/, '')}/chat`, {
method: 'POST',
headers: { 'content-type': 'application/json' },
signal: controller.signal,
body: JSON.stringify({
messages: history.map(({ role, text }) => ({ role, text })),
}),
});
if (!response.ok) {
void response.body?.cancel().catch(() => {});
throw new ChatError('http');
}
let data: unknown;
try {
data = await response.json();
} catch {
throw new ChatError('invalid');
}
if (
!data ||
typeof data !== 'object' ||
!('text' in data) ||
typeof data.text !== 'string' ||
!data.text.trim()
)
throw new ChatError('invalid');
return data.text;
};
try {
return await Promise.race([work(), aborted]);
} catch (error) {
if (controller.signal.aborted)
throw new ChatError(timedOut ? 'timeout' : 'cancelled');
throw error instanceof ChatError ? error : new ChatError('network');
} finally {
clearTimeout(timer);
options.signal?.removeEventListener('abort', forwardAbort);
controller.signal.removeEventListener('abort', rejectAbort);
}
}
205 changes: 180 additions & 25 deletions apps/mobile/src/screens/ChatScreen.tsx
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Open in desktop
Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
import { useCallback, useRef, useState } from 'react';
import { useCallback, useEffect, useRef, useState } from 'react';
import {
FlatList,
KeyboardAvoidingView,
Expand All @@ -10,50 +10,164 @@ import {
View,
} from 'react-native';
import { theme } from '../theme';
import { sendChat, type ChatMessage } from '../lib/ai';
import {
CHAT_TIMEOUT_MS,
ChatError,
sendChat,
type ChatFailure,
type ChatMessage,
} from '../lib/ai';

const INITIAL: ChatMessage[] = [
{
id: 'sys-0',
role: 'assistant',
text: 'Hi — I’m your TronBrowser agent. Ask me anything.',
},
];
type Turn =
| { message: ChatMessage; state: 'pending' }
| { message: ChatMessage; state: 'failed'; reason: ChatFailure };
const FAILURE_COPY: Record<ChatFailure, string> = {
timeout: `No reply within ${CHAT_TIMEOUT_MS / 1000} seconds. The request may still have reached the service.`,
cancelled: 'Stopped. The request may still have reached the service.',
network: "Couldn't reach the assistant.",
http: 'The assistant service returned an error.',
invalid: "The assistant sent a reply this app couldn't read.",
};

/**
* AI chat tab (PRD §Mobile). Wired to `../lib/ai`, which is the single seam
* where the real model provider / `@tronbrowser/ai-core` gets plugged in.
*/
export function ChatScreen() {
const [messages, setMessages] = useState<ChatMessage[]>([
{ id: 'sys-0', role: 'assistant', text: 'Hi — I’m your TronBrowser agent. Ask me anything.' },
]);
const [messages, setMessages] = useState<ChatMessage[]>(INITIAL);
const [draft, setDraft] = useState('');
const [busy, setBusy] = useState(false);
const [turn, setTurn] = useState<Turn | null>(null);
const [confirmClear, setConfirmClear] = useState(false);
const history = useRef(INITIAL);
const generation = useRef(0);
const nextId = useRef(0);
const pending = useRef<{
controller: AbortController;
message: ChatMessage;
} | null>(null);
const busy = turn?.state === 'pending';
const listRef = useRef<FlatList<ChatMessage>>(null);

const submit = useCallback(async () => {
const text = draft.trim();
if (!text || busy) return;
const userMsg: ChatMessage = { id: `u-${Date.now()}`, role: 'user', text };
setMessages((m) => [...m, userMsg]);
setDraft('');
setBusy(true);
const run = useCallback(async (message: ChatMessage) => {
if (pending.current) return;
const controller = new AbortController();
const attempt = ++generation.current;
pending.current = { controller, message };
setTurn({ message, state: 'pending' });
try {
const reply = await sendChat([...messages, userMsg]);
setMessages((m) => [...m, reply]);
} catch (err) {
setMessages((m) => [
...m,
{ id: `e-${Date.now()}`, role: 'assistant', text: `Error: ${(err as Error).message}` },
]);
const text = await sendChat([...history.current, message], {
signal: controller.signal,
});
if (attempt !== generation.current) return;
history.current = [
...history.current,
message,
{ id: `a-${++nextId.current}`, role: 'assistant', text },
];
setMessages(history.current);
setTurn(null);
} catch (error) {
if (attempt !== generation.current) return;
setTurn({
message,
state: 'failed',
reason: error instanceof ChatError ? error.kind : 'network',
});
} finally {
setBusy(false);
requestAnimationFrame(() => listRef.current?.scrollToEnd({ animated: true }));
if (pending.current?.controller === controller) pending.current = null;
}
}, [draft, busy, messages]);
}, []);

const submit = () => {
const text = draft.trim();
if (!text || pending.current) return;
setDraft('');
void run({ id: `u-${++nextId.current}`, role: 'user', text });
};
const stop = () => {
const request = pending.current;
if (!request) {
setTurn((current) =>
current?.state === 'pending'
? { message: current.message, state: 'failed', reason: 'cancelled' }
: current,
);
return;
}
generation.current++;
pending.current = null;
request.controller.abort();
setTurn({ message: request.message, state: 'failed', reason: 'cancelled' });
};
const clear = () => {
generation.current++;
pending.current?.controller.abort();
pending.current = null;
history.current = INITIAL;
setMessages(INITIAL);
setTurn(null);
setConfirmClear(false);
};
useEffect(
() => () => {
generation.current++;
pending.current?.controller.abort();
pending.current = null;
},
[],
);

return (
<KeyboardAvoidingView
style={styles.container}
behavior={Platform.OS === 'ios' ? 'padding' : undefined}
keyboardVerticalOffset={90}
>
<View style={styles.actions}>
{confirmClear ? (
<>
<TouchableOpacity
accessibilityRole="button"
accessibilityLabel="Confirm clear conversation"
onPress={clear}
style={styles.action}
>
<Text style={styles.actionText}>Confirm clear</Text>
</TouchableOpacity>
<TouchableOpacity
accessibilityRole="button"
accessibilityLabel="Cancel clear conversation"
onPress={() => setConfirmClear(false)}
style={styles.action}
>
<Text style={styles.actionText}>Cancel</Text>
</TouchableOpacity>
</>
) : (
<TouchableOpacity
accessibilityRole="button"
accessibilityLabel="Clear conversation"
disabled={messages.length === 1 && !turn}
onPress={() => setConfirmClear(true)}
style={styles.action}
>
<Text style={styles.actionText}>Clear conversation</Text>
</TouchableOpacity>
)}
</View>
<FlatList
ref={listRef}
data={messages}
data={turn ? [...messages, turn.message] : messages}
onContentSizeChange={() =>
listRef.current?.scrollToEnd({ animated: true })
}
keyExtractor={(m) => m.id}
contentContainerStyle={styles.list}
renderItem={({ item }) => (
Expand All @@ -67,21 +181,47 @@ export function ChatScreen() {
</View>
)}
/>
{turn && (
<View style={styles.status}>
<Text accessibilityRole="alert" style={styles.statusText}>
{turn.state === 'pending'
? 'Waiting for reply...'
: FAILURE_COPY[turn.reason]}
</Text>
<TouchableOpacity
accessibilityRole="button"
accessibilityLabel={busy ? 'Stop response' : 'Retry message'}
accessibilityHint={busy ? undefined : 'Sends the message again.'}
style={styles.action}
onPress={
busy
? stop
: () => {
void run(turn.message);
}
}
>
<Text style={styles.actionText}>{busy ? 'Stop' : 'Retry'}</Text>
</TouchableOpacity>
</View>
)}
<View style={styles.composer}>
<TextInput
accessibilityLabel="Chat message"
style={styles.input}
value={draft}
onChangeText={setDraft}
onSubmitEditing={submit}
placeholder={busy ? 'Thinking…' : 'Message'}
placeholderTextColor={theme.textDim}
editable={!busy}
multiline
/>
<TouchableOpacity
style={[styles.send, (!draft.trim() || busy) && styles.sendDisabled]}
onPress={submit}
disabled={!draft.trim() || busy}
accessibilityRole="button"
accessibilityLabel="Send message"
>
<Text style={styles.sendText}>Send</Text>
</TouchableOpacity>
Expand All @@ -93,6 +233,21 @@ export function ChatScreen() {
const styles = StyleSheet.create({
container: { flex: 1, backgroundColor: theme.bg },
list: { padding: 12, gap: 8 },
actions: {
flexDirection: 'row',
flexWrap: 'wrap',
justifyContent: 'flex-end',
paddingHorizontal: 8,
},
action: { minHeight: 44, justifyContent: 'center', paddingHorizontal: 12 },
actionText: { color: theme.accent, fontWeight: '600' },
status: {
paddingHorizontal: 12,
flexDirection: 'row',
alignItems: 'center',
gap: 8,
},
statusText: { color: theme.textDim, flex: 1, flexShrink: 1 },
bubble: { maxWidth: '85%', padding: 10, borderRadius: 12 },
userBubble: { alignSelf: 'flex-end', backgroundColor: theme.accentDim },
aiBubble: { alignSelf: 'flex-start', backgroundColor: theme.surfaceAlt },
Expand Down
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