feat(api:user:submissions): add endpoint `/api/users/[username]/submi…

…ssions`

  ## what
  - add endpoint `/api/users/[username]/submissions`

  ## how
  - check if username is valid (using zod schema)
  - if username doesn't exist, return 404
  - fetch all problems from `/api/problems`
    - used as a cache for `pnum`, `pTitle`
  - fetch user submissions
  - sort the submissions by submission time in descending order
  - take only the first 500 elements in the array
  - convert submission array into `UserSub` object
    - add properties
      - pnum
      - pTitle
      - verdict

  ## why
  - this will be used for fetching user submissions

  ## where
  - ./src/app/api/users/[username]/submissions/route.ts

  ## usage

src/app/api/users/[username]/submissions/route.ts

@@ -0,0 +1,118 @@
+import { NextResponse } from "next/server";
+import { z } from "zod";
+
+import { userSchema as schema } from "@/schema";
+import {
+  uhuntUserSubmissionsUrl,
+  uhuntUsername2UidUrl,
+} from "@/utils/constants";
+import {
+  Language,
+  Problem,
+  ProblemVerdictMap,
+  UserSub,
+  UserSubmission,
+} from "@/types";
+
+type getParamsType = {
+  params: z.infer<typeof schema>;
+};
+
+export const GET = async (_request: Request, { params }: getParamsType) => {
+  // validate params
+  const schemaResponse = await schema.safeParseAsync(params);
+  if (!schemaResponse.success) {
+    const message = {
+      message: schemaResponse.error.issues[0].message,
+    };
+
+    return NextResponse.json(message, {
+      status: 400,
+    });
+  }
+
+  //----------------------------------------------------------------------------------------------//
+
+  // fetch username ID
+  const { username } = params;
+
+  const usernameUrl = uhuntUsername2UidUrl(username);
+  const usernameResponse = await fetch(usernameUrl);
+  const usernameData: number = await usernameResponse.json();
+
+  // return 404 if problem doesn't exist
+  if (usernameData === 0) {
+    const message = {
+      message: `Username ${username} not found`,
+    };
+    return NextResponse.json(message, {
+      status: 404,
+    });
+  }
+
+  //----------------------------------------------------------------------------------------------//
+
+  // fetch all problems
+  // this is needed because later each submission will need problem number and problem title.
+  //    if repeatedly fetching from upstream api server, it will slow down.
+  const allProblemsUrl = `http://localhost:${process.env.PORT}/api/problems`;
+  const allProblemsResponse = await fetch(allProblemsUrl);
+  const allProblemsData: Problem[] = await allProblemsResponse.json();
+
+  // fetch submissions of the user
+  const userSubmissionsUrl = uhuntUserSubmissionsUrl(usernameData);
+  const userSubmissionResponse = await fetch(userSubmissionsUrl, {
+    cache: "no-cache",
+  });
+  const userSubmissionData =
+    (await userSubmissionResponse.json()) as UserSubmission;
+
+  // change userSubmissionData.sub[] into UserSub[]
+  // originally the upstream api would return `userSubmissionData.sub` as an array of array
+  // // ex:
+  // [
+  //   [
+  //     0: 5251911       // submission ID
+  //     1: 62            // problem ID
+  //     2: 10            // verdict ID
+  //     3: 0             // runtime
+  //     4: 1168359789    // submission time
+  //     5: 4             // language ID
+  //     6: -1            // rank
+  //   ]
+  // ]
+  const converted = (userSubmissionData.subs as unknown as number[][])
+    .sort((a, b) => b[4] - a[4]) // sort by submission time in descending order
+    .slice(0, 500) // take only the most recent 500 submissions
+    .map((submission: number[]) => {
+      const converted: Partial<UserSub> = {};
+      converted.sid = submission[0];
+      converted.pid = submission[1];
+      converted.ver = submission[2];
+      converted.run = submission[3];
+      converted.sbt = submission[4];
+      converted.lan = submission[5] as unknown as string;
+      converted.rank = submission[6];
+
+      const problemData = allProblemsData.find(
+        (problem) => problem.pid === converted.pid,
+      );
+
+      converted.pnum = (problemData as Problem).num;
+      converted.pTitle = (problemData as Problem).title;
+      converted.verdict = ProblemVerdictMap[converted.ver as number] || {
+        fgColor: "text-primary-foreground dark:text-secondary-foreground",
+        bgColor: "bg-gray-500",
+        title: "- In Queue -",
+        fgHex: "",
+        bgHex: "6b7280",
+      };
+      converted.lan = Language[converted.lan];
+
+      return converted;
+    });
+
+  userSubmissionData.subs = converted as unknown as UserSub[];
+
+  return Response.json(userSubmissionData);
+};