slight refactor and basic test

circuits/http/interpreter.circom

@@ -0,0 +1,34 @@
+pragma circom 2.1.9;
+
+include "parser/language.circom";
+include "../utils/array.circom";
+
+/* TODO: 
+Notes --
+- This is a pretty efficient way to simply check what the method used in a request is by checking
+the first `DATA_LENGTH` number of bytes. 
+- Certainly this could be more modular.
+*/
+template YieldMethod(DATA_LENGTH) {
+    signal input bytes[DATA_LENGTH];
+    signal output MethodTag;
+
+    component RequestMethod = RequestMethod();
+    component RequestMethodTag = RequestMethodTag();
+
+    component IsGet = IsEqualArray(3);
+    for(var byte_idx = 0; byte_idx < 3; byte_idx++) {
+        IsGet.in[0][byte_idx] <== bytes[byte_idx];
+        IsGet.in[1][byte_idx] <== RequestMethod.GET[byte_idx];
+    }
+    signal TagGet <== IsGet.out * RequestMethodTag.GET;
+
+    component IsPost = IsEqualArray(4);
+    for(var byte_idx = 0; byte_idx < 4; byte_idx++) {
+        IsPost.in[0][byte_idx] <== bytes[byte_idx];
+        IsPost.in[1][byte_idx] <== RequestMethod.POST[byte_idx];
+    }
+    signal TagPost <== IsPost.out * RequestMethodTag.POST;
+
+    MethodTag <== TagGet + TagPost;
+}

circuits/test/http/interpreter.test.ts

@@ -0,0 +1,25 @@
+import { circomkit, WitnessTester, generateDescription } from "../common";
+
+describe("HTTP :: Interpreter", async () => {
+    describe("YieldMethod", async () => {
+        let circuit: WitnessTester<["bytes"], ["MethodTag"]>;
+
+        function generatePassCase(input: any, expected: any, depth: number, desc: string) {
+            const description = generateDescription(input);
+
+            it(`(valid) witness: ${description} ${desc}`, async () => {
+                circuit = await circomkit.WitnessTester(`YieldMethod`, {
+                    file: "circuits/http/interpreter",
+                    template: "YieldMethod",
+                    params: [4],
+                });
+                console.log("#constraints:", await circuit.getConstraintCount());
+
+                await circuit.expectPass(input, expected);
+            });
+        }
+
+        // The string `"GET "`
+        generatePassCase({ bytes: [71, 69, 84, 32] }, { MethodTag: 1 }, 0, "");
+    });
+});