From 11a2b2a9421ddf3bb397603120db3222d9eef142 Mon Sep 17 00:00:00 2001
From: Damian Tarnawski <gthetarnav@gmail.com>
Date: Fri, 27 Oct 2023 00:05:38 +0200
Subject: [PATCH] Add system_random and random_bytes for js target

---
 core/crypto/rand_generic.odin |  4 ++--
 core/crypto/rand_js.odin      | 20 ++++++++++++++++++++
 core/math/rand/system_js.odin | 11 +++++++++++
 vendor/wasm/js/runtime.js     |  6 ++++++
 4 files changed, 39 insertions(+), 2 deletions(-)
 create mode 100644 core/crypto/rand_js.odin
 create mode 100644 core/math/rand/system_js.odin

diff --git a/core/crypto/rand_generic.odin b/core/crypto/rand_generic.odin
index 52abfe4d7..fde91f85a 100644
--- a/core/crypto/rand_generic.odin
+++ b/core/crypto/rand_generic.odin
@@ -1,7 +1,7 @@
 package crypto
 
-when ODIN_OS != .Linux && ODIN_OS != .OpenBSD && ODIN_OS != .Windows {
-	_rand_bytes :: proc (dst: []byte) {
+when ODIN_OS != .Linux && ODIN_OS != .OpenBSD && ODIN_OS != .Windows && ODIN_OS != .JS {
+	_rand_bytes :: proc(dst: []byte) {
 		unimplemented("crypto: rand_bytes not supported on this OS")
 	}
 }
diff --git a/core/crypto/rand_js.odin b/core/crypto/rand_js.odin
new file mode 100644
index 000000000..99a5bbcbc
--- /dev/null
+++ b/core/crypto/rand_js.odin
@@ -0,0 +1,20 @@
+package crypto
+
+foreign import "odin_env"
+foreign odin_env {
+	@(link_name = "rand_bytes")
+	env_rand_bytes :: proc "contextless" (buf: []byte) ---
+}
+
+_MAX_PER_CALL_BYTES :: 65536
+
+_rand_bytes :: proc(dst: []byte) {
+	dst := dst
+
+	for len(dst) > 0 {
+		to_read := min(len(dst), _MAX_PER_CALL_BYTES)
+		env_rand_bytes(dst[:to_read])
+
+		dst = dst[to_read:]
+	}
+}
diff --git a/core/math/rand/system_js.odin b/core/math/rand/system_js.odin
new file mode 100644
index 000000000..11e1385a2
--- /dev/null
+++ b/core/math/rand/system_js.odin
@@ -0,0 +1,11 @@
+package rand
+
+foreign import "odin_env"
+foreign odin_env {
+	rand :: proc "contextless" () -> f64 ---
+}
+
+@(require_results)
+_system_random :: proc() -> u64 {
+	return u64(rand() * 0x1fffffffffffff)
+}
diff --git a/vendor/wasm/js/runtime.js b/vendor/wasm/js/runtime.js
index d5ab383f0..33ce9640e 100644
--- a/vendor/wasm/js/runtime.js
+++ b/vendor/wasm/js/runtime.js
@@ -1349,6 +1349,12 @@ function odinSetupDefaultImports(wasmMemoryInterface, consoleElement) {
 			ln:      Math.log,
 			exp:     Math.exp,
 			ldexp:   (x, exp) => x * Math.pow(2, exp),
+
+			rand: Math.random,
+			rand_bytes: (ptr, len) => {
+				const view = new Uint8Array(wasm_memory.buffer, ptr, len)
+				crypto.getRandomValues(view)
+			},
 		},
 		"odin_dom": {
 			init_event_raw: (ep) => {