feat(api:problemNum:ranklist): add endpoint `/api/problems/ranklist/[…

…problemNum]`

  ## what
  - add endpoint `/api/problems/ranklist/[problemNum]`
    - get ranklist of a problem using problem number
      - if invalid `problem number` is given, a response of 400 will be returned
      - if the problem doesn't exist, a response of 404 will be returned
      - fetch problem ranklist
      - add extra properties
        - verdict object
          - fgColor
          - bgColor
          - title
          - fgHex
          - bgHex
        - language: convert language ID into a string
        - pnum: problem number
        - pTitle: name of the problem

  ## how

  ## why

  ## where
  - ./src/app/api/problems/ranklist/[problemNum]/route.ts

  ## usage

src/app/api/problems/ranklist/[problemNum]/route.ts

@@ -0,0 +1,68 @@
+import { NextResponse } from "next/server";
+import { z } from "zod";
+
+import { problemNumRanklistSchema as schema } from "@/schema";
+import { Language, Problem, ProblemVerdictMap, Submission } from "@/types";
+import { uhuntProblemNumUrl, uhuntProblemRankUrl } from "@/utils/constants";
+
+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 problem stats
+  const { problemNum } = params;
+
+  const problemUrl = uhuntProblemNumUrl(problemNum);
+  const problemResponse = await fetch(problemUrl);
+  const problemData: Problem = await problemResponse.json();
+
+  // return 404 if problem doesn't exist
+  if (Object.entries(problemData).length === 0) {
+    const message = {
+      message: `Problem number ${problemNum} not found`,
+    };
+    return NextResponse.json(message, {
+      status: 404,
+    });
+  }
+
+  //----------------------------------------------------------------------------------------------//
+
+  // fetch problem ranklist
+  const ranklistUrl = uhuntProblemRankUrl(problemData.pid, 1, 10);
+  const ranklistResponse = await fetch(ranklistUrl);
+  const ranklistData: Submission["msg"][] = await ranklistResponse.json();
+
+  // add properties to the ranklist array
+  const converted = ranklistData.map((rank: Submission["msg"]) => {
+    rank.verdict = ProblemVerdictMap[rank.ver] || {
+      fgColor: "text-primary-foreground dark:text-secondary-foreground",
+      bgColor: "bg-gray-500",
+      title: "- In Queue -",
+      fgHex: "",
+      bgHex: "6b7280",
+    };
+    rank.lan = Language[rank.lan] || "--";
+    rank.pnum = problemData.num;
+    rank.pTitle = problemData.title;
+
+    return rank;
+  });
+
+  return Response.json(converted);
+};