api library

front/src/api/index.ts

@@ -0,0 +1,76 @@
+export interface QueryParams {
+  [key: string]: (string | number)
+}
+
+export interface APIDef {
+  [key: string]: ({
+    kind: "POST",
+    query?: QueryParams,
+    request?: Object,
+    response: Object,
+  } | {
+    kind: "GET",
+    query?: QueryParams,
+    response: Object,
+  })
+}
+
+type A = {
+  "/api/blah": {
+    kind: "GET",
+    request: {
+      mjau: number
+      cat: string
+    }
+    response: {
+      status: number
+    }
+  }
+}
+
+export type ValidEndPointForMethod<T, U extends (keyof T & string), method extends "GET" | "POST"> 
+  = T[U] extends { kind: method } ? U : never
+
+export type QR = { query: Object, request: Object }
+
+export class API<T extends APIDef> {
+  base: string;
+
+  constructor(base: string) {
+    this.base = base;
+  }
+
+  private dispatch(method : "POST" | "GET", 
+                   endpoint : keyof T & string,
+                   req : T[typeof endpoint] & QR):
+                     Promise<T[typeof endpoint]["response"]> {
+    let url : URL = new URL(endpoint, this.base)
+    let opts : RequestInit = { method }
+    if (req.query != null) {
+      const params = new URLSearchParams()
+      for (const [key, value] of Object.entries(req.query)) {
+        params.set(key, typeof(value) == "string" ? value : value.toString())
+      }
+      url = new URL(params.toString(), url)
+    }
+    if (method == "POST" && req.request != null) {
+      opts.body = JSON.stringify(req.request)
+      opts.headers = { "Content-Type": "application/json" }
+    }
+    return fetch(url, opts)
+  }
+
+  get(endpoint : ValidEndPointForMethod<T, string, "GET">, 
+      req: T[typeof endpoint] & QR): 
+        Promise<T[typeof endpoint]["response"]> {
+    return this.dispatch("GET", endpoint, req)
+  }
+
+  post(endpoint : ValidEndPointForMethod<T, string, "POST">, 
+       req: T[typeof endpoint] & QR): 
+         Promise<T[typeof endpoint]["response"]> {
+    return this.dispatch("POST", endpoint, req)
+  }
+}
+
+const test = new API<A>("mjau")