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response-handler.ts
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response-handler.ts
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import { APICallError, EmptyResponseBodyError } from '@ai-sdk/provider';
import {
EventSourceParserStream,
ParsedEvent,
} from 'eventsource-parser/stream';
import { ZodSchema } from 'zod';
import { extractResponseHeaders } from './extract-response-headers';
import { ParseResult, parseJSON, safeParseJSON } from './parse-json';
export type ResponseHandler<RETURN_TYPE> = (options: {
url: string;
requestBodyValues: unknown;
response: Response;
}) => PromiseLike<{
value: RETURN_TYPE;
responseHeaders?: Record<string, string>;
}>;
export const createJsonErrorResponseHandler =
<T>({
errorSchema,
errorToMessage,
isRetryable,
}: {
errorSchema: ZodSchema<T>;
errorToMessage: (error: T) => string;
isRetryable?: (response: Response, error?: T) => boolean;
}): ResponseHandler<APICallError> =>
async ({ response, url, requestBodyValues }) => {
const responseBody = await response.text();
const responseHeaders = extractResponseHeaders(response);
// Some providers return an empty response body for some errors:
if (responseBody.trim() === '') {
return {
responseHeaders,
value: new APICallError({
message: response.statusText,
url,
requestBodyValues,
statusCode: response.status,
responseHeaders,
responseBody,
isRetryable: isRetryable?.(response),
}),
};
}
// resilient parsing in case the response is not JSON or does not match the schema:
try {
const parsedError = parseJSON({
text: responseBody,
schema: errorSchema,
});
return {
responseHeaders,
value: new APICallError({
message: errorToMessage(parsedError),
url,
requestBodyValues,
statusCode: response.status,
responseHeaders,
responseBody,
data: parsedError,
isRetryable: isRetryable?.(response, parsedError),
}),
};
} catch (parseError) {
return {
responseHeaders,
value: new APICallError({
message: response.statusText,
url,
requestBodyValues,
statusCode: response.status,
responseHeaders,
responseBody,
isRetryable: isRetryable?.(response),
}),
};
}
};
export const createEventSourceResponseHandler =
<T>(
chunkSchema: ZodSchema<T>,
): ResponseHandler<ReadableStream<ParseResult<T>>> =>
async ({ response }: { response: Response }) => {
const responseHeaders = extractResponseHeaders(response);
if (response.body == null) {
throw new EmptyResponseBodyError({});
}
return {
responseHeaders,
value: response.body
.pipeThrough(new TextDecoderStream())
.pipeThrough(new EventSourceParserStream())
.pipeThrough(
new TransformStream<ParsedEvent, ParseResult<T>>({
transform({ data }, controller) {
// ignore the 'DONE' event that e.g. OpenAI sends:
if (data === '[DONE]') {
return;
}
controller.enqueue(
safeParseJSON({
text: data,
schema: chunkSchema,
}),
);
},
}),
),
};
};
export const createJsonResponseHandler =
<T>(responseSchema: ZodSchema<T>): ResponseHandler<T> =>
async ({ response, url, requestBodyValues }) => {
const responseBody = await response.text();
const parsedResult = safeParseJSON({
text: responseBody,
schema: responseSchema,
});
const responseHeaders = extractResponseHeaders(response);
if (!parsedResult.success) {
throw new APICallError({
message: 'Invalid JSON response',
cause: parsedResult.error,
statusCode: response.status,
responseHeaders,
responseBody,
url,
requestBodyValues,
});
}
return {
responseHeaders,
value: parsedResult.value,
};
};