feat: add functions for parsing chat messages

CHANGELOG.md

@@ -6,6 +6,7 @@
 
 - fix: omit parallel_tool_calls in Go OpenAI SDK if it is set to true [#849](https://github.com/hypermodeinc/modus/pull/849)
 - feat: use embedded postgres on Windows [#851](https://github.com/hypermodeinc/modus/pull/851)
+- feat: add functions for parsing chat messages [#853](https://github.com/hypermodeinc/modus/pull/853)
 
 ## 2025-05-19 - Go SDK 0.18.0-alpha.2
 

sdk/assemblyscript/src/assembly/__tests__/openai.spec.ts

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2025 Hypermode Inc.
+ * Licensed under the terms of the Apache License, Version 2.0
+ * See the LICENSE file that accompanied this code for further details.
+ *
+ * SPDX-FileCopyrightText: 2025 Hypermode Inc. <[email protected]>
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { expect, it, log, run } from "as-test";
+import { JSON } from "json-as";
+
+import {
+  SystemMessage,
+  UserMessage,
+  AssistantMessage,
+  RequestMessage,
+  parseMessages,
+} from "../../models/openai/chat";
+
+it("should round-trip chat messages", () => {
+  const msgs: RequestMessage[] = [
+    new SystemMessage("You are a helpful assistant."),
+    new UserMessage("What is the capital of France?"),
+    new AssistantMessage("The capital of France is Paris."),
+  ];
+
+  const data = JSON.stringify(msgs);
+  const parsedMsgs = parseMessages(data);
+
+  expect(parsedMsgs.length).toBe(msgs.length);
+  for (let i = 0; i < msgs.length; i++) {
+    expect(msgs[i].role).toBe(parsedMsgs[i].role);
+  }
+
+  const roundTrip = JSON.stringify(parsedMsgs);
+
+  log(data);
+  log(roundTrip);
+  expect(roundTrip).toBe(data); // <-----    this currently fails
+});
+
+run();

sdk/assemblyscript/src/models/openai/chat.ts

@@ -1352,6 +1352,7 @@ export class AssistantMessage<T> extends RequestMessage {
   /**
    * Data about a previous audio response from the model.
    */
+  @omitnull()
   audio: AudioRef | null = null;
 
   /**
@@ -1538,3 +1539,51 @@ export class AudioOutput {
    */
   transcript!: string;
 }
+
+/**
+ * Represents a a raw message object, which is used when reconstructing messages from JSON.
+ * A raw message will round-trip all the JSON data, but does not expose the fields directly.
+ * (note, this type is not exported)
+ */
+class RawMessage extends RequestMessage {
+  constructor(data: string) {
+    const obj = JSON.parse<JSON.Obj>(data);
+    if (!obj.has("role")) {
+      throw new Error("Missing role field in message JSON.");
+    }
+
+    const role = obj.get("role")!.get<string>();
+    super(role);
+
+    this._data = data;
+  }
+
+  private _data: string;
+
+
+  @serializer
+  serialize(self: RawMessage): string {
+    return self._data;
+  }
+
+
+  @deserializer
+  deserialize(data: string): RawMessage {
+    return new RawMessage(data);
+  }
+}
+
+/**
+ * Parses a JSON-encoded request message into a list of RequestMessage objects.
+ * The resulting message objects are suitable for restoring a previous chat conversation.
+ * However, the original message types are not preserved.
+ */
+export function parseMessages(data: string): RequestMessage[] {
+  const messages = JSON.parse<JSON.Value[]>(data);
+  const results = new Array<RequestMessage>(messages.length);
+  for (let i = 0; i < messages.length; i++) {
+    const msg = messages[i].toString();
+    results[i] = new RawMessage(msg);
+  }
+  return results;
+}

sdk/assemblyscript/src/tests/openai.run.ts

@@ -0,0 +1,17 @@
+/*
+ * Copyright 2025 Hypermode Inc.
+ * Licensed under the terms of the Apache License, Version 2.0
+ * See the LICENSE file that accompanied this code for further details.
+ *
+ * SPDX-FileCopyrightText: 2025 Hypermode Inc. <[email protected]>
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { readFileSync } from "fs";
+import { instantiate } from "../build/openai.spec.js";
+const binary = readFileSync("./build/openai.spec.wasm");
+const module = new WebAssembly.Module(binary);
+instantiate(module, {
+  env: {},
+  modus_models: {},
+});

sdk/go/pkg/models/openai/chat.go

@@ -1234,3 +1234,49 @@ func (mi *ChatModelInput) MarshalJSON() ([]byte, error) {
 
 	return b, nil
 }
+
+// Represents a a raw message object, which is used when reconstructing messages from JSON.
+// A raw message will round-trip all the JSON data, but does not expose the fields directly.
+// (note, this type is not exported)
+type rawMessage struct {
+	role string
+	data json.RawMessage
+}
+
+func (m *rawMessage) Role() string {
+	return m.role
+}
+
+func (m *rawMessage) MarshalJSON() ([]byte, error) {
+	if len(m.data) == 0 {
+		return nil, fmt.Errorf("missing data in message")
+	}
+	return m.data, nil
+}
+
+func (m *rawMessage) UnmarshalJSON(data []byte) error {
+	r := gjson.GetBytes(data, "role")
+	if !r.Exists() {
+		return fmt.Errorf("missing role field in message JSON")
+	}
+	m.role = r.String()
+	m.data = data
+	return nil
+}
+
+// Parses a JSON-encoded request message into a list of RequestMessage objects.
+// The resulting message objects are suitable for restoring a previous chat conversation.
+// However, the original message types are not preserved.
+func ParseMessages(data []byte) ([]RequestMessage, error) {
+	var messages []rawMessage
+	if err := json.Unmarshal([]byte(data), &messages); err != nil {
+		return nil, err
+	}
+
+	results := make([]RequestMessage, len(messages))
+	for i := range messages {
+		results[i] = &messages[i]
+	}
+
+	return results, nil
+}

sdk/go/pkg/models/openai/chat_test.go

@@ -0,0 +1,53 @@
+/*
+ * Copyright 2025 Hypermode Inc.
+ * Licensed under the terms of the Apache License, Version 2.0
+ * See the LICENSE file that accompanied this code for further details.
+ *
+ * SPDX-FileCopyrightText: 2025 Hypermode Inc. <[email protected]>
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package openai_test
+
+import (
+	"bytes"
+	"encoding/json"
+	"testing"
+
+	"github.com/hypermodeinc/modus/sdk/go/pkg/models/openai"
+)
+
+func TestMessagesRoundTrip(t *testing.T) {
+	msgs := []openai.RequestMessage{
+		openai.NewSystemMessage("You are a helpful assistant."),
+		openai.NewUserMessage("What is the capital of France?"),
+		openai.NewAssistantMessage("The capital of France is Paris."),
+	}
+
+	data, err := json.Marshal(msgs)
+	if err != nil {
+		t.Fatalf("Failed to marshal messages: %v", err)
+	}
+
+	parsedMsgs, err := openai.ParseMessages(data)
+	if err != nil {
+		t.Fatalf("Failed to parse messages: %v", err)
+	}
+	if len(parsedMsgs) != len(msgs) {
+		t.Fatalf("Expected %d messages, but got %d", len(msgs), len(parsedMsgs))
+	}
+
+	for i, msg := range msgs {
+		if msg.Role() != parsedMsgs[i].Role() {
+			t.Errorf("Expected role %s for message %d, but got %s", msg.Role(), i, parsedMsgs[i].Role())
+		}
+	}
+
+	roundTrip, err := json.Marshal(parsedMsgs)
+	if err != nil {
+		t.Fatalf("Failed to marshal parsed messages: %v", err)
+	}
+	if !bytes.Equal(data, roundTrip) {
+		t.Fatalf("Expected original and parsed messages to have the same JSON representation, but they differ")
+	}
+}