Add getKeyAndLanguageFromWords() method to Mnemonics class.

- The getKeyAndLanguageFromWords() method receives a list of words and validates that they correspond to an actual Dero seed, and obtains the corresponding Key and language.
- Added tests to verify that the getKeyAndLanguageFromWords() method works as expected in different scenarios.

shared/stargate/src/commonMain/kotlin/net/agorise/shared/stargate/mnemonics/Mnemonics.kt

@@ -1,7 +1,7 @@
 package net.agorise.shared.stargate.mnemonics
 
 import dev.whyoleg.cryptography.bigint.BigInt
-import dev.whyoleg.cryptography.bigint.toBigInt
+import dev.whyoleg.cryptography.bigint.decodeToBigInt
 import io.ktor.utils.io.core.toByteArray
 import net.agorise.shared.crypto.crc.Crc32
 
@@ -40,28 +40,53 @@ class Mnemonics {
     /**
      * Given a list of words, returns the associated key if the words are valid or an exception otherwise
      */
-    fun getKeyFromWords(words: List<String>): Result<BigInt> {
+    fun getKeyAndLanguageFromWords(words: List<String>): Result<Pair<BigInt, String>> {
         // The list must contain SEED_LENGTH + 1 words. The SEED_LENGTH + 1 word is the checksum
         if (words.size != (SEED_LENGTH + 1)) {
             return Result.failure(Exception("Invalid seed"))
         }
 
-        val wordsLanguageAndIndices = getWordsLanguageAndIndices(words)
+        val (languageIndex, indices) = getWordsLanguageAndIndices(words)
             ?: return Result.failure(Exception("Seed not found in any language"))
 
-        val languageName = languages[wordsLanguageAndIndices.languageIndex].name
+        val prefixLen = languages[languageIndex].uniquePrefixLength
+        if (verifyChecksum(words, prefixLen).not()) {
+            return Result.failure(Exception("Seed checksum verification failed"))
+        }
 
+        // Map 3 words to 4 bytes each, so 24 words = 32 bytes
+        val key = ByteArray(32)
+        val wordsSize = WORDS_SIZE.toULong()
+        for (i in 0 until SEED_LENGTH / 3) {
+            val w1 = indices[i * 3]
+            val w2 = indices[i * 3 + 1]
+            val w3 = indices[i * 3 + 2]
 
-        val key = byteArrayOf()
+            val value = w1 + wordsSize * ((wordsSize - w1 + w2) % wordsSize) +
+                wordsSize * wordsSize * ((wordsSize - w2 + w3) % wordsSize)
 
-        return Result.success("".toBigInt()) // TODO Remove hardcoded value
+            // Sanity check, this can never occur
+            if (value % wordsSize != w1) {
+                return Result.failure(Exception("Word list error"))
+            }
+
+            val value32bit = value.toUInt()
+            key[i * 4 + 0] = (value32bit and 0xFFu).toByte()
+            key[i * 4 + 1] = ((value32bit shr 8) and 0xFFu).toByte()
+            key[i * 4 + 2] = ((value32bit shr 16) and 0xFFu).toByte()
+            key[i * 4 + 3] = ((value32bit shr 24) and 0xFFu).toByte()
+        }
+
+        val languageName = languages[languageIndex].name
+
+        return Result.success(Pair(key.decodeToBigInt(), languageName))
     }
 
     /**
      * Returns the words language and the indices where each word was found. All words must be
      * from the same language.
      */
-    private fun getWordsLanguageAndIndices(words: List<String>): WordsLanguageAndIndices? {
+    private fun getWordsLanguageAndIndices(words: List<String>): Pair<Int, List<ULong>>? {
         for (i in languages.indices) {
             val indices = mutableListOf<ULong>()
 
@@ -84,20 +109,13 @@ class Mnemonics {
             }
 
             if (foundAllWords) {
-                val wordsListCount = languages[i].words.size.toULong()
-                return WordsLanguageAndIndices(indices, i, wordsListCount)
+                return Pair(i, indices)
             }
         }
 
         return null
     }
 
-    private data class WordsLanguageAndIndices(
-        val indices: List<ULong>,
-        val languageIndex: Int,
-        val wordListCount: ULong,
-    )
-
     /**
      * Obtains that the checksum index and verifies it corresponds to the checksum word.
      */

shared/stargate/src/commonTest/kotlin/net/agorise/shared/stargate/mnemonics/MnemonicsDataProvider.kt

@@ -6,6 +6,10 @@ object MnemonicsDataProvider {
         ("sequence atlas unveil summon pebbles tuesday beer rudely snake rockets different " +
             "fuselage woven tagged bested dented vegan hover rapid fawns obvious muppet " +
             "randomly seasons summon").split(" ")
+    val invalidWordsSeed =
+        ("sequence atlas unveil summon pebbles tuesday beer rudely snake rockets different " +
+            "fuselage woven tagged bested dented vegan hover rapid fawns obvious muppet " +
+            "randomly seasons paella").split(" ")
     val validEnglishSeed =
         ("sequence atlas unveil summon pebbles tuesday beer rudely snake rockets different " +
             "fuselage woven tagged bested dented vegan hover rapid fawns obvious muppet " +

shared/stargate/src/commonTest/kotlin/net/agorise/shared/stargate/mnemonics/MnemonicsTest.kt

@@ -1,5 +1,6 @@
 package net.agorise.shared.stargate.mnemonics
 
+import dev.whyoleg.cryptography.bigint.toHexString
 import kotlin.test.Test
 import kotlin.test.assertEquals
 import kotlin.test.assertFalse
@@ -74,4 +75,59 @@ class MnemonicsTest {
 
         assertTrue(result)
     }
+
+    @Test
+    fun `given an invalid size seed - when getKeyAndLanguageFromWords is called - then result is failure`() {
+        val invalidSizeSeed = MnemonicsDataProvider.invalidSizeSeed
+
+        val result = mnemonics.getKeyAndLanguageFromWords(invalidSizeSeed)
+
+        assertTrue(result.isFailure)
+    }
+
+    @Test
+    fun `given an invalid words seed - when getKeyAndLanguageFromWords is called - then result is failure`() {
+        val invalidWordsSeed = MnemonicsDataProvider.invalidWordsSeed
+
+        val result = mnemonics.getKeyAndLanguageFromWords(invalidWordsSeed)
+
+        assertTrue(result.isFailure)
+    }
+
+    @Test
+    fun `given an invalid checksum seed - when getKeyAndLanguageFromWords is called - then result is failure`() {
+        val invalidChecksumSeed = MnemonicsDataProvider.invalidChecksumSeed
+
+        val result = mnemonics.getKeyAndLanguageFromWords(invalidChecksumSeed)
+
+        assertTrue(result.isFailure)
+    }
+
+    @OptIn(ExperimentalStdlibApi::class)
+    @Test
+    fun `given a valid english seed - when getKeyAndLanguageFromWords is called - then result is correct`() {
+        val expectedKey = "b0ef6bd527b9b23b9ceef70dc8b4cd1ee83ca14541964e764ad23f5151204f0f"
+        val expectedLanguage = "English"
+        val validEnglishSeed = MnemonicsDataProvider.validEnglishSeed
+
+        val result = mnemonics.getKeyAndLanguageFromWords(validEnglishSeed)
+        val (actualKey, actualLanguage) = result.getOrThrow()
+
+        assertEquals(expectedKey, actualKey.toHexString())
+        assertEquals(expectedLanguage, actualLanguage)
+    }
+
+    @OptIn(ExperimentalStdlibApi::class)
+    @Test
+    fun `given a valid spanish seed - when getKeyAndLanguageFromWords is called - then result is correct`() {
+        val expectedKey = "4f1101c4cc6adc6e6a63acde4e71fd76dc4471fa54769866d5e80a0a3d53d00c"
+        val expectedLanguage = "Español"
+        val validSpanishSeed = MnemonicsDataProvider.validSpanishSeed
+
+        val result = mnemonics.getKeyAndLanguageFromWords(validSpanishSeed)
+        val (actualKey, actualLanguage) = result.getOrThrow()
+
+        assertEquals(expectedKey, actualKey.toHexString())
+        assertEquals(expectedLanguage, actualLanguage)
+    }
 }