feat: add AI Cover Letter Generator from Resume (#411)

app/api/generate/cover-letter-from-resume/route.ts

@@ -0,0 +1,75 @@
+import { NextResponse } from "next/server";
+
+type Body = {
+  resume?: string;
+  jobDescription?: string;
+  tone?: string;
+};
+
+function buildPrompt(resume: string, jobDescription: string, tone?: string) {
+  const t = tone && tone.trim().length > 0 ? tone.trim() : "professional";
+  return [
+    "Write a tailored cover letter using the following resume and job description.",
+    "Goals:",
+    "- Mirror the resume’s tone, keywords, and achievements.",
+    "- Align with the job description’s requirements and terminology.",
+    "- Keep it concise, one page, clear sections, and easy to scan.",
+    "- Use the same voice and tense as the resume.",
+    "- Avoid repeating the resume verbatim; synthesize and contextualize.",
+    `Tone: ${t}`,
+    "",
+    "Resume:",
+    "-----",
+    resume,
+    "-----",
+    "",
+    "Job Description:",
+    "-----",
+    jobDescription,
+    "-----",
+    "",
+    "Return only the final cover letter text."
+  ].join("\n");
+}
+
+async function callGemini(prompt: string): Promise<string> {
+  const gemini: any = await import("../../../../lib/gemini").catch(() => ({}));
+  let output = "";
+  try {
+    if (typeof gemini.generateText === "function") {
+      const r = await gemini.generateText(prompt);
+      if (typeof r === "string" && r.trim().length > 0) return r;
+      if (r && typeof r.text === "function") return r.text();
+      if (r && typeof r.text === "string") return r.text;
+    }
+  } catch {}
+  try {
+    const model = gemini.model || gemini.gemini || gemini.client || gemini.default || gemini;
+    if (model && typeof model.generateContent === "function") {
+      const r = await model.generateContent(prompt as any);
+      if (r?.response?.text && typeof r.response.text === "function") return r.response.text();
+      if (r?.response?.candidates?.[0]?.content?.parts?.[0]?.text) return r.response.candidates[0].content.parts[0].text;
+      if (typeof r?.text === "function") return r.text();
+      if (typeof r?.text === "string") return r.text;
+    }
+  } catch {}
+  throw new Error("Gemini client unavailable or incompatible");
+}
+
+export async function POST(req: Request) {
+  try {
+    const body: Body = await req.json().catch(() => ({}));
+    const resume = typeof body.resume === "string" ? body.resume.trim() : "";
+    const jobDescription = typeof body.jobDescription === "string" ? body.jobDescription.trim() : "";
+    const tone = typeof body.tone === "string" ? body.tone : undefined;
+    if (!resume || !jobDescription) {
+      return NextResponse.json({ error: "Missing resume or jobDescription" }, { status: 400 });
+    }
+    const prompt = buildPrompt(resume, jobDescription, tone);
+    const text = await callGemini(prompt);
+    return NextResponse.json({ text });
+  } catch (e: any) {
+    return NextResponse.json({ error: e?.message || "Unexpected error" }, { status: 500 });
+  }
+}
+

app/letter/cover-letter-from-resume/page.tsx

@@ -0,0 +1,11 @@
+import CoverLetterFromResume from "../../../components/letter/CoverLetterFromResume";
+
+export default function Page() {
+  return (
+    <main style={{ maxWidth: 880, margin: "0 auto", padding: 24 }}>
+      <h1>Cover Letter from Resume</h1>
+      <p>Create a tailored cover letter using your resume and a job description.</p>
+      <CoverLetterFromResume />
+    </main>
+  );
+}

components/letter/CoverLetterFromResume.tsx

@@ -0,0 +1,88 @@
+\"use client\";
+
+import { useState } from "react";
+
+export default function CoverLetterFromResume() {
+  const [resume, setResume] = useState(\"\"");
+  const [jobDescription, setJobDescription] = useState(\"\"");
+  const [tone, setTone] = useState(\"professional\");
+  const [output, setOutput] = useState(\"\"");
+  const [loading, setLoading] = useState(false);
+  const [error, setError] = useState(\"\"");
+
+  async function generate() {
+    setError(\"\");
+    setOutput(\"\"");
+    if (!resume.trim() || !jobDescription.trim()) {
+      setError(\"Please provide both resume and job description\");
+      return;
+    }
+    setLoading(true);
+    try {
+      const res = await fetch(\"/api/generate/cover-letter-from-resume\", {
+        method: \"POST\",
+        headers: { \"Content-Type\": \"application/json\" },
+        body: JSON.stringify({ resume, jobDescription, tone }),
+      });
+      const data = await res.json();
+      if (!res.ok) {
+        setError(data?.error || \"Failed to generate cover letter\");
+      } else {
+        setOutput(data?.text || \"\");
+      }
+    } catch (e: any) {
+      setError(e?.message || \"Failed to generate cover letter\");
+    } finally {
+      setLoading(false);
+    }
+  }
+
+  return (
+    <div style={{ display: \"grid\", gap: 16 }}>
+      <div style={{ display: \"grid\", gap: 8 }}>
+        <label>Resume</label>
+        <textarea
+          value={resume}
+          onChange={(e) => setResume(e.target.value)}
+          rows={10}
+          placeholder=\"Paste your resume content\"
+          style={{ width: \"100%\" }}
+        />
+      </div>
+      <div style={{ display: \"grid\", gap: 8 }}>
+        <label>Job Description</label>
+        <textarea
+          value={jobDescription}
+          onChange={(e) => setJobDescription(e.target.value)}
+          rows={10}
+          placeholder=\"Paste the job description\"
+          style={{ width: \"100%\" }}
+        />
+      </div>
+      <div style={{ display: \"grid\", gap: 8 }}>
+        <label>Tone</label>
+        <input
+          value={tone}
+          onChange={(e) => setTone(e.target.value)}
+          placeholder=\"e.g., professional, friendly\"
+          style={{ width: \"100%\" }}
+        />
+      </div>
+      <button onClick={generate} disabled={loading} style={{ padding: 10 }}>
+        {loading ? \"Generating...\" : \"Generate Cover Letter\"}
+      </button>
+      {error ? <div style={{ color: \"red\" }}>{error}</div> : null}
+      <div style={{ display: \"grid\", gap: 8 }}>
+        <label>Output</label>
+        <textarea
+          value={output}
+          readOnly
+          rows={16}
+          placeholder=\"The generated cover letter will appear here\"
+          style={{ width: \"100%\" }}
+        />
+      </div>
+    </div>
+  );
+}
+