1 files changed, 102 insertions, 0 deletions
diff --git a/packages/misskey-js/src/api.ts b/packages/misskey-js/src/api.ts
new file mode 100644
index 0000000000..fcc9884465
--- /dev/null
+++ b/packages/misskey-js/src/api.ts
@@ -0,0 +1,102 @@
+import type { Endpoints } from './api.types';
+
+const MK_API_ERROR = Symbol();
+
+export type APIError = {
+	id: string;
+	code: string;
+	message: string;
+	kind: 'client' | 'server';
+	info: Record<string, any>;
+};
+
+export function isAPIError(reason: any): reason is APIError {
+	return reason[MK_API_ERROR] === true;
+}
+
+export type FetchLike = (input: string, init?: {
+		method?: string;
+		body?: string;
+		credentials?: RequestCredentials;
+		cache?: RequestCache;
+		headers: {[key in string]: string}
+	}) => Promise<{
+		status: number;
+		json(): Promise<any>;
+	}>;
+
+type IsNeverType<T> = [T] extends [never] ? true : false;
+
+type StrictExtract<Union, Cond> = Cond extends Union ? Union : never;
+
+type IsCaseMatched<E extends keyof Endpoints, P extends Endpoints[E]['req'], C extends number> =
+	IsNeverType<StrictExtract<Endpoints[E]['res']['$switch']['$cases'][C], [P, any]>> extends false ? true : false;
+
+type GetCaseResult<E extends keyof Endpoints, P extends Endpoints[E]['req'], C extends number> =
+	StrictExtract<Endpoints[E]['res']['$switch']['$cases'][C], [P, any]>[1];
+
+export class APIClient {
+	public origin: string;
+	public credential: string | null | undefined;
+	public fetch: FetchLike;
+
+	constructor(opts: {
+		origin: APIClient['origin'];
+		credential?: APIClient['credential'];
+		fetch?: APIClient['fetch'] | null | undefined;
+	}) {
+		this.origin = opts.origin;
+		this.credential = opts.credential;
+		// ネイティブ関数をそのまま変数に代入して使おうとするとChromiumではIllegal invocationエラーが発生するため、
+		// 環境で実装されているfetchを使う場合は無名関数でラップして使用する
+		this.fetch = opts.fetch || ((...args) => fetch(...args));
+	}
+
+	public request<E extends keyof Endpoints, P extends Endpoints[E]['req']>(
+		endpoint: E, params: P = {} as P, credential?: string | null | undefined,
+	): Promise<Endpoints[E]['res'] extends { $switch: { $cases: [any, any][]; $default: any; }; }
+		?
+			IsCaseMatched<E, P, 0> extends true ? GetCaseResult<E, P, 0> :
+			IsCaseMatched<E, P, 1> extends true ? GetCaseResult<E, P, 1> :
+			IsCaseMatched<E, P, 2> extends true ? GetCaseResult<E, P, 2> :
+			IsCaseMatched<E, P, 3> extends true ? GetCaseResult<E, P, 3> :
+			IsCaseMatched<E, P, 4> extends true ? GetCaseResult<E, P, 4> :
+			IsCaseMatched<E, P, 5> extends true ? GetCaseResult<E, P, 5> :
+			IsCaseMatched<E, P, 6> extends true ? GetCaseResult<E, P, 6> :
+			IsCaseMatched<E, P, 7> extends true ? GetCaseResult<E, P, 7> :
+			IsCaseMatched<E, P, 8> extends true ? GetCaseResult<E, P, 8> :
+			IsCaseMatched<E, P, 9> extends true ? GetCaseResult<E, P, 9> :
+			Endpoints[E]['res']['$switch']['$default']
+		: Endpoints[E]['res']>
+	{
+		const promise = new Promise((resolve, reject) => {
+			this.fetch(`${this.origin}/api/${endpoint}`, {
+				method: 'POST',
+				body: JSON.stringify({
+					...params,
+					i: credential !== undefined ? credential : this.credential,
+				}),
+				headers: {
+					'Content-Type': 'application/json',
+				},
+				credentials: 'omit',
+				cache: 'no-cache',
+			}).then(async (res) => {
+				const body = res.status === 204 ? null : await res.json();
+
+				if (res.status === 200) {
+					resolve(body);
+				} else if (res.status === 204) {
+					resolve(null);
+				} else {
+					reject({
+						[MK_API_ERROR]: true,
+						...body.error,
+					});
+				}
+			}).catch(reject);
+		});
+
+		return promise as any;
+	}
+}