Migrate bigint module to use shared web declarations

Author: whyoleg

cryptography-bigint/build.gradle.kts

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2023-2024 Oleg Yukhnevich. Use of this source code is governed by the Apache 2.0 license.
+ * Copyright (c) 2023-2025 Oleg Yukhnevich. Use of this source code is governed by the Apache 2.0 license.
  */
 
 import ckbuild.*
@@ -23,11 +23,7 @@ kotlin {
     applyDefaultHierarchyTemplate {
         common {
             group("nonJvm") {
-                // js and wasmJs
-                group("jsAndWasmJs") {
-                    withJs()
-                    withWasmJs()
-                }
+                group("web")
                 // all native targets + wasmWasi
                 group("nativeAndWasmWasi") {
                     group("native")

cryptography-bigint/src/jsAndWasmJsMain/kotlin/JsBigInt.kt

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2024-2025 Oleg Yukhnevich. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+@file:OptIn(ExperimentalWasmJsInterop::class)
+
+package dev.whyoleg.cryptography.bigint
+
+import kotlin.js.*
+
+internal external interface JsBigInt : JsAny {
+    @JsName("toString")
+    fun convertToString(): String
+
+    @JsName("toString")
+    fun convertToString(radix: Int): String
+}
+
+@JsName("BigInt")
+internal external fun jsBigInt(value: Int): JsBigInt
+
+@JsName("BigInt")
+internal external fun jsBigInt(value: String): JsBigInt
+
+internal fun jsBigIntNegate(value: JsBigInt): JsBigInt = js("-value")
+
+internal fun jsBigIntSign(value: JsBigInt): Int = js("value == 0 ? 0 : (value < 0 ? -1 : 1)")
+
+internal fun jsBigIntCompareTo(a: JsBigInt, b: JsBigInt): Int = js("a < b ? -1 : a > b ? 1 : 0")
+
+internal fun jsBigIntEquals(a: JsBigInt, b: JsBigInt): Boolean = js("a === b")
+
+internal fun jsBigIntAsInt(value: JsBigInt, bits: Int): JsBigInt = js("BigInt.asIntN(bits, value)")