clicktrack/app/api/generate/route.ts

import { NextRequest, NextResponse } from "next/server";
import { z } from "zod";
import { query } from "@/lib/db/client";
import { validateCTP } from "@/lib/ctp/validate";
import { renderCTP } from "@/lib/ctp/render";
import type { TempoMapRow } from "@/lib/db/client";

const ParamsSchema = z.object({
  id: z.string().uuid("tempo map id must be a UUID"),
  count_in: z
    .enum(["true", "false"])
    .transform((v) => v === "true")
    .optional(),
});

/**
 * GET /api/generate?id=<tempo-map-uuid>[&count_in=true]
 *
 * Renders the requested tempo map to a WAV file and streams it back.
 * The response is cached for 1 hour since tempo maps are immutable once created.
 */
export async function GET(req: NextRequest) {
  const raw = Object.fromEntries(req.nextUrl.searchParams);
  const parsed = ParamsSchema.safeParse(raw);

  if (!parsed.success) {
    return NextResponse.json(
      { error: "Invalid parameters", details: parsed.error.flatten() },
      { status: 400 }
    );
  }

  const { id, count_in } = parsed.data;

  // Load tempo map from DB
  const { rows } = await query<TempoMapRow>(
    "SELECT * FROM tempo_maps WHERE id = $1",
    [id]
  );

  if (rows.length === 0) {
    return NextResponse.json({ error: "Tempo map not found" }, { status: 404 });
  }

  const map = rows[0];
  const validation = validateCTP(map.ctp_data);

  if (!validation.success) {
    return NextResponse.json(
      { error: "Stored CTP document is invalid", details: validation.errors.flatten() },
      { status: 500 }
    );
  }

  const doc = validation.data;

  // Render WAV
  let wav: Buffer;
  try {
    wav = renderCTP(doc, { countIn: count_in });
  } catch (err) {
    console.error("[generate] Render error:", err);
    return NextResponse.json(
      { error: "Failed to render click track", detail: String(err) },
      { status: 500 }
    );
  }

  // Build a clean filename
  const safeName = `${doc.metadata.artist} - ${doc.metadata.title}`
    .replace(/[^\w\s\-]/g, "")
    .replace(/\s+/g, "_")
    .slice(0, 80);

  const filename = `${safeName}_click.wav`;

  return new NextResponse(new Uint8Array(wav), {
    status: 200,
    headers: {
      "Content-Type": "audio/wav",
      "Content-Disposition": `attachment; filename="${filename}"`,
      "Content-Length": String(wav.byteLength),
      "Cache-Control": "public, max-age=3600, immutable",
    },
  });
}