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utils.ts
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utils.ts
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import {
BaseMessageLike,
BaseMessage,
isBaseMessage,
StoredMessage,
StoredMessageV1,
} from "./base.js";
import { HumanMessage, HumanMessageChunk } from "./human.js";
import { AIMessage, AIMessageChunk } from "./ai.js";
import { SystemMessage, SystemMessageChunk } from "./system.js";
import {
ChatMessage,
ChatMessageChunk,
ChatMessageFieldsWithRole,
} from "./chat.js";
import {
FunctionMessage,
FunctionMessageChunk,
FunctionMessageFieldsWithName,
} from "./function.js";
import { ToolMessage, ToolMessageFieldsWithToolCallId } from "./tool.js";
export function coerceMessageLikeToMessage(
messageLike: BaseMessageLike
): BaseMessage {
if (typeof messageLike === "string") {
return new HumanMessage(messageLike);
} else if (isBaseMessage(messageLike)) {
return messageLike;
}
const [type, content] = messageLike;
if (type === "human" || type === "user") {
return new HumanMessage({ content });
} else if (type === "ai" || type === "assistant") {
return new AIMessage({ content });
} else if (type === "system") {
return new SystemMessage({ content });
} else {
throw new Error(
`Unable to coerce message from array: only human, AI, or system message coercion is currently supported.`
);
}
}
/**
* This function is used by memory classes to get a string representation
* of the chat message history, based on the message content and role.
*/
export function getBufferString(
messages: BaseMessage[],
humanPrefix = "Human",
aiPrefix = "AI"
): string {
const string_messages: string[] = [];
for (const m of messages) {
let role: string;
if (m._getType() === "human") {
role = humanPrefix;
} else if (m._getType() === "ai") {
role = aiPrefix;
} else if (m._getType() === "system") {
role = "System";
} else if (m._getType() === "function") {
role = "Function";
} else if (m._getType() === "tool") {
role = "Tool";
} else if (m._getType() === "generic") {
role = (m as ChatMessage).role;
} else {
throw new Error(`Got unsupported message type: ${m._getType()}`);
}
const nameStr = m.name ? `${m.name}, ` : "";
string_messages.push(`${role}: ${nameStr}${m.content}`);
}
return string_messages.join("\n");
}
/**
* Maps messages from an older format (V1) to the current `StoredMessage`
* format. If the message is already in the `StoredMessage` format, it is
* returned as is. Otherwise, it transforms the V1 message into a
* `StoredMessage`. This function is important for maintaining
* compatibility with older message formats.
*/
function mapV1MessageToStoredMessage(
message: StoredMessage | StoredMessageV1
): StoredMessage {
// TODO: Remove this mapper when we deprecate the old message format.
if ((message as StoredMessage).data !== undefined) {
return message as StoredMessage;
} else {
const v1Message = message as StoredMessageV1;
return {
type: v1Message.type,
data: {
content: v1Message.text,
role: v1Message.role,
name: undefined,
tool_call_id: undefined,
},
};
}
}
export function mapStoredMessageToChatMessage(message: StoredMessage) {
const storedMessage = mapV1MessageToStoredMessage(message);
switch (storedMessage.type) {
case "human":
return new HumanMessage(storedMessage.data);
case "ai":
return new AIMessage(storedMessage.data);
case "system":
return new SystemMessage(storedMessage.data);
case "function":
if (storedMessage.data.name === undefined) {
throw new Error("Name must be defined for function messages");
}
return new FunctionMessage(
storedMessage.data as FunctionMessageFieldsWithName
);
case "tool":
if (storedMessage.data.tool_call_id === undefined) {
throw new Error("Tool call ID must be defined for tool messages");
}
return new ToolMessage(
storedMessage.data as ToolMessageFieldsWithToolCallId
);
case "chat": {
if (storedMessage.data.role === undefined) {
throw new Error("Role must be defined for chat messages");
}
return new ChatMessage(storedMessage.data as ChatMessageFieldsWithRole);
}
default:
throw new Error(`Got unexpected type: ${storedMessage.type}`);
}
}
/**
* Transforms an array of `StoredMessage` instances into an array of
* `BaseMessage` instances. It uses the `mapV1MessageToStoredMessage`
* function to ensure all messages are in the `StoredMessage` format, then
* creates new instances of the appropriate `BaseMessage` subclass based
* on the type of each message. This function is used to prepare stored
* messages for use in a chat context.
*/
export function mapStoredMessagesToChatMessages(
messages: StoredMessage[]
): BaseMessage[] {
return messages.map(mapStoredMessageToChatMessage);
}
/**
* Transforms an array of `BaseMessage` instances into an array of
* `StoredMessage` instances. It does this by calling the `toDict` method
* on each `BaseMessage`, which returns a `StoredMessage`. This function
* is used to prepare chat messages for storage.
*/
export function mapChatMessagesToStoredMessages(
messages: BaseMessage[]
): StoredMessage[] {
return messages.map((message) => message.toDict());
}
export function convertToChunk(message: BaseMessage) {
const type = message._getType();
if (type === "human") {
// eslint-disable-next-line @typescript-eslint/no-use-before-define
return new HumanMessageChunk({ ...message });
} else if (type === "ai") {
// eslint-disable-next-line @typescript-eslint/no-use-before-define
return new AIMessageChunk({ ...message });
} else if (type === "system") {
// eslint-disable-next-line @typescript-eslint/no-use-before-define
return new SystemMessageChunk({ ...message });
} else if (type === "function") {
// eslint-disable-next-line @typescript-eslint/no-use-before-define
return new FunctionMessageChunk({ ...message });
// eslint-disable-next-line @typescript-eslint/no-use-before-define
} else if (ChatMessage.isInstance(message)) {
// eslint-disable-next-line @typescript-eslint/no-use-before-define
return new ChatMessageChunk({ ...message });
} else {
throw new Error("Unknown message type.");
}
}