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boilerplate/platform/relay/adapters/http.ts
2025-11-23 22:57:43 +01:00

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TypeScript

import {
assertServerErrorResponse,
type RelayAdapter,
type RelayInput,
type RelayResponse,
type ServerErrorResponse,
} from "../libraries/adapter.ts";
import { ServerError, type ServerErrorType } from "../libraries/errors.ts";
/**
* HttpAdapter provides a unified transport layer for Relay.
*
* It supports sending JSON objects, nested structures, arrays, and file uploads
* via FormData. The adapter automatically detects the payload type and formats
* the request accordingly. Responses are normalized into `RelayResponse`.
*
* @example
* ```ts
* const adapter = new HttpAdapter({ url: "https://api.example.com" });
*
* // Sending JSON data
* const jsonResponse = await adapter.send({
* method: "POST",
* endpoint: "/users",
* body: { name: "Alice", age: 30 },
* });
*
* // Sending files and nested objects
* const formResponse = await adapter.send({
* method: "POST",
* endpoint: "/upload",
* body: {
* user: { name: "Bob", avatar: fileInput.files[0] },
* documents: [fileInput.files[1], fileInput.files[2]],
* },
* });
* ```
*/
export class HttpAdapter implements RelayAdapter {
/**
* Instantiate a new HttpAdapter instance.
*
* @param options - Adapter options.
*/
constructor(readonly options: HttpAdapterOptions) {}
/**
* Override the initial url value set by instantiator.
*/
set url(value: string) {
this.options.url = value;
}
/**
* Retrieve the URL value from options object.
*/
get url() {
return this.options.url;
}
/**
* Return the full URL from given endpoint.
*
* @param endpoint - Endpoint to get url for.
*/
getUrl(endpoint: string): string {
return `${this.url}${endpoint}`;
}
async send({ method, endpoint, query, body, headers = new Headers() }: RelayInput): Promise<RelayResponse> {
const init: RequestInit = { method, headers };
// ### Before Request
// If any before request hooks has been defined, we run them here passing in the
// request headers for further modification.
await this.#beforeRequest(headers);
// ### Body
if (body !== undefined) {
const type = this.#getRequestFormat(body);
if (type === "form-data") {
headers.delete("content-type");
init.body = this.#getFormData(body);
}
if (type === "json") {
headers.set("content-type", "application/json");
init.body = JSON.stringify(body);
}
}
// ### Response
return this.request(`${endpoint}${query}`, init);
}
/**
* Send a fetch request using the given fetch options and returns
* a relay formatted response.
*
* @param endpoint - Which endpoint to submit request to.
* @param init - Request init details to submit with the request.
*/
async request(endpoint: string, init?: RequestInit): Promise<RelayResponse> {
return this.#toResponse(await fetch(this.getUrl(endpoint), init));
}
/**
* Run before request operations.
*
* @param headers - Headers to pass to hooks.
*/
async #beforeRequest(headers: Headers) {
if (this.options.hooks?.beforeRequest !== undefined) {
for (const hook of this.options.hooks.beforeRequest) {
await hook(headers);
}
}
}
/**
* Determine the parser method required for the request.
*
* @param body - Request body.
*/
#getRequestFormat(body: unknown): "form-data" | "json" {
if (body instanceof FormData) {
return "form-data";
}
if (containsFile(body) === true) {
return "form-data";
}
return "json";
}
/**
* Get FormData instance for the given body.
*
* @param body - Request body.
*/
#getFormData(data: Record<string, unknown>, formData = new FormData(), parentKey?: string): FormData {
for (const key in data) {
const value = data[key];
if (value === undefined || value === null) continue;
const formKey = parentKey ? `${parentKey}[${key}]` : key;
if (value instanceof File) {
formData.append(formKey, value, value.name);
} else if (Array.isArray(value)) {
value.forEach((item, index) => {
if (item instanceof File) {
formData.append(`${formKey}[${index}]`, item, item.name);
} else if (typeof item === "object") {
this.#getFormData(item as Record<string, unknown>, formData, `${formKey}[${index}]`);
} else {
formData.append(`${formKey}[${index}]`, String(item));
}
});
} else if (typeof value === "object") {
this.#getFormData(value as Record<string, unknown>, formData, formKey);
} else {
formData.append(formKey, String(value));
}
}
return formData;
}
/**
* Convert a fetch response to a compliant relay response.
*
* @param response - Fetch response to convert.
*/
async #toResponse(response: Response): Promise<RelayResponse> {
const type = response.headers.get("content-type");
// ### Content Type
// Ensure that the server responds with a 'content-type' definition. We should
// always expect the server to respond with a type.
if (type === null) {
return {
result: "error",
headers: response.headers,
error: {
code: "CONTENT_TYPE_MISSING",
status: response.status,
message: "Missing 'content-type' in header returned from server.",
},
};
}
// ### Empty Response
// If the response comes back with empty response status 204 we simply return a
// empty success.
if (response.status === 204) {
return {
result: "success",
headers: response.headers,
data: null,
};
}
// ### JSON
// If the 'content-type' contains 'json' we treat it as a 'json' compliant response
// and attempt to resolve it as such.
if (type.includes("json") === true) {
const parsed = await response.json();
if ("data" in parsed) {
return {
result: "success",
headers: response.headers,
data: parsed.data,
};
}
if ("error" in parsed) {
return {
result: "error",
headers: response.headers,
error: this.#toError(parsed),
};
}
return {
result: "error",
headers: response.headers,
error: {
code: "INVALID_SERVER_RESPONSE",
status: response.status,
message: "Unsupported 'json' body returned from server, missing 'data' or 'error' key.",
},
};
}
// ### Error
// If the 'content-type' is not a JSON response from the API then we check if the
// response status is an error code.
if (response.status >= 400) {
return {
result: "error",
headers: response.headers,
error: {
code: "SERVER_ERROR_RESPONSE",
status: response.status,
message: await response.text(),
},
};
}
// ### Success
// If the 'content-type' is not a JSON response from the API and the request is not
// an error we simply return the pure response in the data key.
return {
result: "success",
headers: response.headers,
data: response,
};
}
#toError(candidate: unknown, status: number = 500): ServerErrorType | ServerErrorResponse["error"] {
if (assertServerErrorResponse(candidate)) {
return ServerError.fromJSON(candidate.error);
}
if (typeof candidate === "string") {
return {
code: "ERROR",
status,
message: candidate,
};
}
return {
code: "UNSUPPORTED_SERVER_ERROR",
status,
message: "Unsupported 'error' returned from server.",
};
}
}
function containsFile(value: unknown): boolean {
if (value instanceof File) {
return true;
}
if (Array.isArray(value)) {
return value.some(containsFile);
}
if (typeof value === "object" && value !== null) {
return Object.values(value).some(containsFile);
}
return false;
}
export type HttpAdapterOptions = {
url: string;
hooks?: {
beforeRequest?: ((headers: Headers) => Promise<void>)[];
};
};