feat(upload): preview API route with schema detection

Author: William-Hill

codebenders-dashboard/app/api/admin/upload/preview/route.ts

@@ -0,0 +1,71 @@
+import { NextRequest, NextResponse } from "next/server"
+import { parseFileBuffer, getFileType, validateFileSize } from "@/lib/upload-parser"
+import { detectSchema, mapColumns } from "@/lib/upload-schemas"
+
+export async function POST(request: NextRequest) {
+  try {
+    const formData = await request.formData()
+    const file = formData.get("file") as File | null
+
+    if (!file) {
+      return NextResponse.json({ error: "No file provided" }, { status: 400 })
+    }
+
+    if (!validateFileSize(file.size)) {
+      return NextResponse.json(
+        { error: "File exceeds 50 MB limit" },
+        { status: 413 }
+      )
+    }
+
+    const fileType = getFileType(file.name)
+    if (!fileType) {
+      return NextResponse.json(
+        { error: "Unsupported file type. Please upload a .csv or .xlsx file." },
+        { status: 400 }
+      )
+    }
+
+    const buffer = Buffer.from(await file.arrayBuffer())
+    const { headers, rows, totalRows } = await parseFileBuffer(buffer, fileType, 50)
+
+    const detection = detectSchema(headers)
+
+    const columns = detection.schema
+      ? mapColumns(headers, detection.schema)
+      : headers.map((h) => ({ header: h, mappedTo: null, status: "unmapped" as const }))
+
+    const missingRequired = detection.schema
+      ? detection.schema.columns
+          .filter((c) => c.required)
+          .filter((c) => !columns.some((col) => col.mappedTo === c.name))
+          .map((c) => `Missing required column: ${c.name}`)
+      : []
+
+    const warnings = detection.schema
+      ? detection.schema.columns
+          .filter((c) => !c.required)
+          .filter((c) => !columns.some((col) => col.mappedTo === c.name))
+          .slice(0, 5)
+          .map((c) => `Missing optional column: ${c.name}`)
+      : []
+
+    return NextResponse.json({
+      detectedSchema: detection.schema?.id ?? null,
+      detectedSchemaLabel: detection.schema?.label ?? null,
+      confidence: Math.round(detection.confidence * 100) / 100,
+      scores: detection.scores,
+      columns,
+      sampleRows: rows.slice(0, 10),
+      totalRows,
+      warnings,
+      errors: missingRequired,
+    })
+  } catch (err) {
+    console.error("Upload preview error:", err)
+    return NextResponse.json(
+      { error: `Failed to parse file: ${(err as Error).message}` },
+      { status: 500 }
+    )
+  }
+}