feat: initialize asin-check project with Bun

- Add README.md with installation and usage instructions.
- Create bun.lock for dependency management.
- Add package.json to define project metadata and dependencies.
- Implement caching with Redis in cache.ts for ASIN data.
- Configure environment variables in config.ts for API keys and Redis URL.
- Develop main application logic in index.ts to read products, fetch data, and analyze results.
- Integrate Keepa API for product data retrieval in keepa.ts.
- Create LLM analysis functionality in llm.ts for product viability assessment.
- Implement product reading from Excel files in reader.ts.
- Stub SP-API integration in sp-api.ts for future implementation.
- Define TypeScript types in types.ts for product and analysis data structures.
- Write results to console and CSV in writer.ts.
- Configure TypeScript settings in tsconfig.json for project compilation.

src/writer.ts

@@ -0,0 +1,67 @@
+import * as XLSX from "xlsx";
+import type { AnalysisResult } from "./types.ts";
+
+function buildRow(r: AnalysisResult) {
+  const price = r.product.keepa?.currentPrice ?? r.product.spApi.estimatedSalePrice;
+  const rank = r.product.keepa?.salesRank ?? r.product.record.amazonRank;
+
+  return {
+    ASIN: r.product.record.asin,
+    Name: r.product.record.name,
+    Brand: r.product.record.brand ?? "",
+    Category: r.product.record.category ?? r.product.keepa?.categoryTree?.join(" > ") ?? "",
+    "Unit Cost": r.product.record.unitCost,
+    "Current Price": price ?? "",
+    "Avg Price 90d": r.product.keepa?.avgPrice90 ?? "",
+    "Sales Rank": rank ?? "",
+    "Rank Avg 90d": r.product.keepa?.salesRankAvg90 ?? "",
+    Sellers: r.product.keepa?.sellerCount ?? "",
+    "Monthly Sold": r.product.keepa?.monthlySold ?? "",
+    "Rank Drops 30d": r.product.keepa?.salesRankDrops30 ?? "",
+    "Rank Drops 90d": r.product.keepa?.salesRankDrops90 ?? "",
+    "FBA Net (sheet)": r.product.record.fbaNet ?? "",
+    "Gross Profit $": r.product.record.grossProfit ?? "",
+    "Gross Profit %": r.product.record.grossProfitPct ?? "",
+    MOQ: r.product.record.moq ?? "",
+    "MOQ Cost": r.product.record.moqCost ?? "",
+    "Qty Available": r.product.record.totalQtyAvail ?? "",
+    "FBA Fee": r.product.spApi.fbaFee,
+    "FBM Fee": r.product.spApi.fbmFee,
+    "Referral %": r.product.spApi.referralFeePercent,
+    Verdict: r.verdict.verdict,
+    Confidence: r.verdict.confidence,
+    Reasoning: r.verdict.reasoning,
+  };
+}
+
+export function printResults(results: AnalysisResult[]): void {
+  const rows = results.map((r) => {
+    const row = buildRow(r);
+    return {
+      ...row,
+      Name: row.Name.slice(0, 40),
+      Category: String(row.Category).slice(0, 20),
+      Reasoning: row.Reasoning.slice(0, 60),
+    };
+  });
+
+  console.log("\n=== Analysis Results ===\n");
+  console.table(rows);
+
+  const summary = {
+    FBA: results.filter((r) => r.verdict.verdict === "FBA").length,
+    FBM: results.filter((r) => r.verdict.verdict === "FBM").length,
+    SKIP: results.filter((r) => r.verdict.verdict === "SKIP").length,
+  };
+  console.log(`\nSummary: ${summary.FBA} FBA | ${summary.FBM} FBM | ${summary.SKIP} SKIP out of ${results.length} products\n`);
+}
+
+export function writeResultsCsv(results: AnalysisResult[], outputPath: string): void {
+  const rows = results.map(buildRow);
+
+  const ws = XLSX.utils.json_to_sheet(rows);
+  const wb = XLSX.utils.book_new();
+  XLSX.utils.book_append_sheet(wb, ws, "Results");
+  XLSX.writeFile(wb, outputPath);
+  console.log(`Results written to ${outputPath}`);
+}