Flesh out functionality

package.json

@@ -23,5 +23,8 @@
     "coveralls": "^3.0.8",
     "nyc": "^14.1.1",
     "xo": "^0.25.3"
+  },
+  "dependencies": {
+    "bip39": "^3.0.2"
   }
 }

src/index.js

@@ -1,3 +1,43 @@
-const bip39 = () => {};
+const bip39 = require('bip39');
 
-module.exports = bip39;
+const P2PKH = 0x00;
+const P2WPKHP2SH = 0x01;
+const P2WPKH = 0x02;
+
+const bip39v = {
+	versions: {P2PKH, P2WPKHP2SH, P2WPKH}
+};
+
+const getEntropyBuffer = mnemonic => Buffer.from(
+	bip39.mnemonicToEntropy(mnemonic),
+	'hex'
+);
+
+bip39v.generateMnemonic = (length, versionByte = P2PKH) => {
+	const entropy = getEntropyBuffer(bip39.generateMnemonic(length));
+	entropy[0] = versionByte;
+
+	return bip39.entropyToMnemonic(entropy);
+};
+
+bip39v.mnemonicToVersionByte = mnemonic => {
+	const entropy = getEntropyBuffer(mnemonic);
+
+	return entropy[0];
+};
+
+bip39v.mnemonicToVersionByte = mnemonic => getEntropyBuffer(mnemonic)[0];
+
+bip39v.mnemonicToVersion = mnemonic => {
+	const versionByte = bip39v.mnemonicToVersionByte(mnemonic);
+
+	for (const [name, byte] of Object.entries(bip39v.versions)) {
+		if (versionByte === byte) {
+			return name;
+		}
+	}
+
+	return 'UNKNOWN';
+};
+
+module.exports = bip39v;

test/unit.js

@@ -1,6 +1,6 @@
 import test from 'ava';
-import bip39 from '..';
+import bip39v from '..';
 
-test('bip39 is exported', t => {
-	t.not(bip39, undefined);
+test('bip39v is exported', t => {
+	t.not(bip39v, undefined);
 });