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//! UI-only reconstruction of compact assistant updates. This is not a lossless
//! replacement for provider messages: snapshots retain authority over metadata.
use std::collections::BTreeMap;
use serde_json::{json, Value};
use super::protocol::RemoteEvent;
#[derive(Debug, Clone, Default)]
pub(crate) struct MessageAccumulator {
message: Value,
blocks: BTreeMap<u64, Value>,
tool_json: BTreeMap<u64, String>,
}
impl MessageAccumulator {
fn reset(&mut self) {
*self = Self::default();
}
fn snapshot(&mut self, message: &Value) {
self.message = message.clone();
self.blocks = message
.get("content")
.and_then(Value::as_array)
.into_iter()
.flatten()
.enumerate()
.map(|(index, block)| (index as u64, block.clone()))
.collect();
}
fn projected_message(&self) -> Value {
let mut message = if self.message.is_object() {
self.message.clone()
} else {
json!({"role": "assistant"})
};
message["content"] = Value::Array(self.blocks.values().cloned().collect());
message
}
/// Normalize before UI projection; never append a delta to its own snapshot.
pub(crate) fn apply(&mut self, event: &RemoteEvent) -> RemoteEvent {
match event {
RemoteEvent::AgentStart
| RemoteEvent::AgentEnd { .. }
| RemoteEvent::RetryScheduled { .. }
| RemoteEvent::TurnStart
| RemoteEvent::TurnEnd { .. } => self.reset(),
RemoteEvent::MessageStart { message, .. } => {
self.reset();
self.snapshot(message);
}
RemoteEvent::MessageEnd { .. } => self.reset(),
RemoteEvent::MessageUpdate {
message,
assistant_message_event: nested,
event_type,
content_index,
delta,
..
} => {
let kind = if event_type.is_empty() {
nested.get("type").and_then(Value::as_str).unwrap_or("")
} else {
event_type.as_str()
};
let index =
content_index.or_else(|| nested.get("contentIndex").and_then(Value::as_u64));
let delta = delta
.as_deref()
.or_else(|| nested.get("delta").and_then(Value::as_str));
// Top-level messages can intentionally differ from nested partials.
let snapshot = if message.is_object() {
Some(message)
} else {
["partial", "message", "error"]
.iter()
.find_map(|key| nested.get(*key).filter(|value| value.is_object()))
};
if kind == "start" {
self.reset();
}
if let Some(index) = index {
if matches!(kind, "toolcall_start" | "tool_call_start") {
self.tool_json.remove(&index);
}
// Keep the raw argument stream even on snapshot events, so
// switching between snapshot and compact updates is safe.
if matches!(kind, "toolcall_delta" | "tool_call_delta") {
if let Some(delta) = delta {
self.tool_json.entry(index).or_default().push_str(delta);
}
}
}
if let Some(snapshot) = snapshot {
self.snapshot(snapshot);
} else if let Some(index) = index {
match kind {
"text_delta" | "thinking_delta" => {
let (ty, field) = if kind == "text_delta" {
("text", "text")
} else {
("thinking", "thinking")
};
let block = self
.blocks
.entry(index)
.or_insert_with(|| json!({"type": ty, (field): ""}));
let mut text = block
.get(field)
.and_then(Value::as_str)
.unwrap_or("")
.to_owned();
text.push_str(delta.unwrap_or(""));
block[field] = Value::String(text);
}
"toolcall_delta" | "tool_call_delta" => {
// Use only provider-supplied identity metadata;
// never invent an identity from the content index.
let block = self
.blocks
.entry(index)
.or_insert_with(|| json!({"type": "toolCall"}));
for (source, target) in [("id", "id"), ("toolName", "name")] {
if let Some(value) = nested.get(source).and_then(Value::as_str) {
block[target] = Value::String(value.to_owned());
}
}
block["arguments"] = rpi_ai::json_parse::parse_streaming_json(
self.tool_json.get(&index).map(String::as_str),
);
}
"text_end" | "thinking_end" => {
let (ty, field) = if kind == "text_end" {
("text", "text")
} else {
("thinking", "thinking")
};
if let Some(content) = nested.get("content").and_then(Value::as_str) {
self.blocks
.insert(index, json!({"type": ty, (field): content}));
}
}
_ => {}
}
}
// The explicit final payload is more precise than a streaming
// partial (including the tool's eventual id/name/arguments).
if matches!(kind, "toolcall_end" | "tool_call_end") {
if let (Some(index), Some(tool)) = (
index,
nested.get("toolCall").filter(|tool| tool.is_object()),
) {
let mut tool = tool.clone();
tool["type"] = json!("toolCall");
self.blocks.insert(index, tool);
self.tool_json.remove(&index);
}
}
let mut normalized = event.clone();
if let RemoteEvent::MessageUpdate { message, .. } = &mut normalized {
*message = self.projected_message();
}
if matches!(kind, "done" | "error") {
self.reset();
}
return normalized;
}
_ => {}
}
event.clone()
}
}