implementing cava for real time visualization

tests/cavacore-smoke.ts

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+/**
+ * Smoke test: load libcavacore.dylib via bun:ffi, init → execute → destroy.
+ * Run: bun tests/cavacore-smoke.ts
+ */
+import { dlopen, FFIType, ptr } from "bun:ffi"
+import { join } from "path"
+
+const libPath = join(import.meta.dir, "..", "src", "native", "libcavacore.dylib")
+
+const lib = dlopen(libPath, {
+  cava_init: {
+    args: [FFIType.i32, FFIType.u32, FFIType.i32, FFIType.i32, FFIType.double, FFIType.i32, FFIType.i32],
+    returns: FFIType.ptr,
+  },
+  cava_execute: {
+    args: [FFIType.ptr, FFIType.i32, FFIType.ptr, FFIType.ptr],
+    returns: FFIType.void,
+  },
+  cava_destroy: {
+    args: [FFIType.ptr],
+    returns: FFIType.void,
+  },
+})
+
+const bars = 10
+const rate = 44100
+const channels = 1
+
+// Init
+const plan = lib.symbols.cava_init(bars, rate, channels, 1, 0.77, 50, 10000)
+if (!plan) {
+  console.error("FAIL: cava_init returned null")
+  process.exit(1)
+}
+console.log("cava_init OK, plan pointer:", plan)
+
+// Generate a 200Hz sine wave test signal
+const bufferSize = 512
+const cavaIn = new Float64Array(bufferSize)
+const cavaOut = new Float64Array(bars * channels)
+
+for (let k = 0; k < 100; k++) {
+  for (let n = 0; n < bufferSize; n++) {
+    cavaIn[n] = Math.sin(2 * Math.PI * 200 / rate * (n + k * bufferSize)) * 20000
+  }
+  lib.symbols.cava_execute(ptr(cavaIn), bufferSize, ptr(cavaOut), plan)
+}
+
+console.log("cava_execute OK, output:", Array.from(cavaOut).map(v => v.toFixed(3)))
+
+// Check that bar 2 (200Hz) has the peak
+const maxIdx = cavaOut.indexOf(Math.max(...cavaOut))
+console.log(`Peak at bar ${maxIdx} (expected ~2 for 200Hz)`)
+
+// Destroy
+lib.symbols.cava_destroy(plan)
+console.log("cava_destroy OK")
+console.log("\nSMOKE TEST PASSED")