From a1f2dd78465c1f6e5f1f7f928b025978dd094e25 Mon Sep 17 00:00:00 2001
From: syuilo <Syuilotan@yahoo.co.jp>
Date: Mon, 31 May 2021 23:00:48 +0900
Subject: [PATCH] Improve type

---
 src/api.ts       | 17 +++++++++++++----
 src/endpoints.ts | 13 +++++++++++--
 2 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/src/api.ts b/src/api.ts
index 1e622d372..8961fb7ba 100644
--- a/src/api.ts
+++ b/src/api.ts
@@ -24,6 +24,10 @@ export type FetchLike = (input: string, init?: {
 		json(): Promise<any>;
 	}>;
 
+type IsNeverType<T> = [T] extends [never] ? true : false;
+
+type StrictExtract<Union, Cond> = Cond extends Union ? Union : never;
+
 export class APIClient {
 	public origin: string;
 	public credential: string | null | undefined;
@@ -39,14 +43,19 @@ export class APIClient {
 		this.fetch = opts.fetch || fetch;
 	}
 
-	public request<E extends keyof Endpoints>(
-		endpoint: E, data: Endpoints[E]['req'] = {}, credential?: string | null | undefined,
-	): Promise<Endpoints[E]['res']> {
+	public request<E extends keyof Endpoints, P extends Endpoints[E]['req']>(
+		endpoint: E, params: P, credential?: string | null | undefined,
+	): Promise<Endpoints[E]['res'] extends { $switch: { $cases: [any, any][]; $default: any; }; }
+		? IsNeverType<StrictExtract<Endpoints[E]['res']['$switch']['$cases'][number], [P, any]>> extends true
+			? Endpoints[E]['res']['$switch']['$default']
+			: StrictExtract<Endpoints[E]['res']['$switch']['$cases'][number], [P, any]>[1]
+		: Endpoints[E]['res']>
+	{
 		const promise = new Promise<Endpoints[E]['res']>((resolve, reject) => {
 			this.fetch(`${this.origin}/api/${endpoint}`, {
 				method: 'POST',
 				body: JSON.stringify({
-					...data,
+					...params,
 					i: credential !== undefined ? credential : this.credential
 				}),
 				credentials: 'omit',
diff --git a/src/endpoints.ts b/src/endpoints.ts
index 9998fb622..99804e182 100644
--- a/src/endpoints.ts
+++ b/src/endpoints.ts
@@ -1,5 +1,6 @@
 import {
-	Ad, Announcement, Antenna, App, AuthSession, Clip, DriveFile, DriveFolder, GalleryPost, InstanceMetadata,
+	Ad, Announcement, Antenna, App, AuthSession, Clip, DetailedInstanceMetadata, DriveFile, DriveFolder, GalleryPost, InstanceMetadata,
+	LiteInstanceMetadata,
 	Note, OriginType, Page, ServerInfo, Stats, User, UserGroup, UserList, UserSorting
 } from './entities';
 
@@ -257,7 +258,15 @@ export type Endpoints = {
 	'messaging/messages/read': { req: TODO; res: TODO; };
 
 	// meta
-	'meta': { req: { detail?: boolean; }; res: InstanceMetadata; }; // TODO: 「detail が true なら DetailedInstanceMetadata を返す」のような型付けをしたい
+	'meta': { req: { detail?: boolean; }; res: {
+		$switch: {
+			$cases: [[
+				{ detail: true; },
+				DetailedInstanceMetadata,
+			]];
+			$default: LiteInstanceMetadata;
+		};
+	}; };
 
 	// miauth
 	'miauth/gen-token': { req: TODO; res: TODO; };