accept decimal and bitcoin exchanges

3 files changed, 339 insertions, 0 deletions

diff --git a/taler-kotlin-android/src/main/java/net/taler/common/Amount.kt b/taler-kotlin-android/src/main/java/net/taler/common/Amount.kt
index a36c0ab..18fb6cb 100644
--- a/taler-kotlin-android/src/main/java/net/taler/common/Amount.kt
+++ b/taler-kotlin-android/src/main/java/net/taler/common/Amount.kt
@@ -56,12 +56,19 @@ public data class Amount(
     public companion object {
 
         private const val FRACTIONAL_BASE: Int = 100000000 // 1e8
+        public val SEGWIT_MIN = Amount("BTC", 0, 294)
 
         private val REGEX_CURRENCY = Regex("""^[-_*A-Za-z0-9]{1,12}$""")
         public val MAX_VALUE: Long = 2.0.pow(52).toLong()
         private const val MAX_FRACTION_LENGTH = 8
         public const val MAX_FRACTION: Int = 99_999_999
 
+        public fun fromDouble(currency: String, value: Double): Amount {
+            val intPart = Math.floor(value).toLong()
+            val fraPart = Math.floor((value - intPart) *  FRACTIONAL_BASE).toInt()
+            return Amount(currency, intPart, fraPart)
+        }
+
         public fun zero(currency: String): Amount {
             return Amount(checkCurrency(currency), 0, 0)
         }
@@ -141,6 +148,10 @@ public data class Amount(
         return result
     }
 
+    public fun withCurrency(currency: String): Amount {
+        return Amount(checkCurrency(currency), this.value, this.fraction)
+    }
+
     public operator fun minus(other: Amount): Amount {
         check(currency == other.currency) { "Can only subtract from same currency" }
         var resultValue = value
diff --git a/taler-kotlin-android/src/main/java/net/taler/common/Bech32.kt b/taler-kotlin-android/src/main/java/net/taler/common/Bech32.kt
new file mode 100644
index 0000000..32885df
--- /dev/null
+++ b/taler-kotlin-android/src/main/java/net/taler/common/Bech32.kt
@@ -0,0 +1,257 @@
+/*
+ * This file is part of GNU Taler
+ * (C) 2020 Taler Systems S.A.
+ *
+ * GNU Taler is free software; you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 3, or (at your option) any later version.
+ *
+ * GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ * A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+// Copyright (c) 2020 Figure Technologies Inc.
+// The contents of this file were derived from an implementation
+// by the btcsuite developers https://github.com/btcsuite/btcutil.
+
+// Copyright (c) 2017 The btcsuite developers
+// Use of this source code is governed by an ISC
+// license that can be found in the LICENSE file.
+
+// modified version of https://gist.github.com/iramiller/4ebfcdfbc332a9722c4a4abeb4e16454
+
+import net.taler.common.CyptoUtils
+import kotlin.experimental.and
+import kotlin.experimental.or
+
+
+infix fun Int.min(b: Int): Int = b.takeIf { this > b } ?: this
+infix fun UByte.shl(bitCount: Int) = ((this.toInt() shl bitCount) and 0xff).toUByte()
+infix fun UByte.shr(bitCount: Int) = (this.toInt() shr bitCount).toUByte()
+
+/**
+ * Given an array of bytes, associate an HRP and return a Bech32Data instance.
+ */
+fun ByteArray.toBech32Data(hrp: String) =
+    Bech32Data(hrp, Bech32.convertBits(this, 8, 5, true))
+
+/**
+ * Using a string in bech32 encoded address format, parses out and returns a Bech32Data instance
+ */
+fun String.toBech32Data() = Bech32.decode(this)
+
+/**
+ * Bech32 Data encoding instance containing data for encoding as well as a human readable prefix
+ */
+data class Bech32Data(val hrp: String, val fiveBitData: ByteArray) {
+
+    /**
+     * The encapsulated data as typical 8bit bytes.
+     */
+    val data = Bech32.convertBits(fiveBitData, 5, 8, false)
+
+    /**
+     * Address is the Bech32 encoded value of the data prefixed with the human readable portion and
+     * protected by an appended checksum.
+     */
+    val address = Bech32.encode(hrp, fiveBitData)
+
+    /**
+     * Checksum for encapsulated data + hrp
+     */
+    val checksum = Bech32.checksum(this.hrp, this.fiveBitData.toTypedArray())
+
+    /**
+     * The Bech32 Address toString prints state information for debugging purposes.
+     * @see address() for the bech32 encoded address string output.
+     */
+    override fun toString(): String {
+        return "bech32 : ${this.address}\nhuman: ${this.hrp} \nbytes"
+    }
+}
+
+/**
+ * BIP173 compliant processing functions for handling Bech32 encoding for addresses
+ */
+class Bech32 {
+
+    companion object {
+        const val CHECKSUM_SIZE = 6
+        const val MIN_VALID_LENGTH = 8
+        const val MAX_VALID_LENGTH = 90
+        const val MIN_VALID_CODEPOINT = 33
+        const val MAX_VALID_CODEPOINT = 126
+
+        const val charset = "qpzry9x8gf2tvdw0s3jn54khce6mua7l"
+        val gen = intArrayOf(0x3b6a57b2, 0x26508e6d, 0x1ea119fa, 0x3d4233dd, 0x2a1462b3)
+
+        fun generateFakeSegwitAddress(reservePub: String?, addr: String): List<String> {
+            if (reservePub == null || reservePub.isEmpty()) return listOf<String>()
+            val pub = CyptoUtils.decodeCrock(reservePub)
+            if (pub.size != 32) return listOf()
+
+            val first_rnd = pub.copyOfRange(0,4)
+            val second_rnd = pub.copyOfRange(0,4)
+
+            first_rnd[0] = first_rnd[0].and(0b0111_1111);
+            second_rnd[0] = second_rnd[0].or(0b1000_0000.toByte());
+
+            val first_part = ByteArray(20);
+            first_rnd.copyInto( first_part, 0, 0, 4)
+            pub.copyInto( first_part, 4, 0, 16)
+
+            val second_part = ByteArray(20);
+            second_rnd.copyInto( second_part, 0, 0, 4)
+            pub.copyInto( second_part, 4, 16, 32)
+
+            val zero = ByteArray(1)
+            zero[0] = 0
+            val hrp = when {
+                addr[0] == 'b' && addr[1] == 'c' && addr[2] == 'r' && addr[3] == 't' -> "bcrt"
+                addr[0] == 't' && addr[1] == 'b' -> "tb"
+                addr[0] == 'b' && addr[1] == 'c' -> "bc"
+                else -> throw Error("unknown bitcoin net")
+            }
+
+            return listOf(
+                Bech32Data(hrp, zero + convertBits(first_part, 8, 5, true)).address,
+                Bech32Data(hrp, zero + convertBits(second_part, 8, 5, true)).address,
+            )
+        }
+
+        /**
+         * Decodes a Bech32 String
+         */
+        fun decode(bech32: String): Bech32Data {
+            require(bech32.length >= MIN_VALID_LENGTH && bech32.length <= MAX_VALID_LENGTH) { "invalid bech32 string length" }
+            require(bech32.toCharArray().none { c -> c.toInt() < MIN_VALID_CODEPOINT || c.toInt() > MAX_VALID_CODEPOINT })
+            { "invalid character in bech32: ${bech32.toCharArray().map { c -> c.toInt() }
+                .filter { c -> c.toInt() < MIN_VALID_CODEPOINT || c.toInt() > MAX_VALID_CODEPOINT }}" }
+
+            require(bech32.equals(bech32.toLowerCase()) || bech32.equals(bech32.toUpperCase()))
+            { "bech32 must be either all upper or lower case" }
+            require(bech32.substring(1).dropLast(CHECKSUM_SIZE).contains('1')) { "invalid index of '1'" }
+
+            val hrp = bech32.substringBeforeLast('1').toLowerCase()
+            val dataString = bech32.substringAfterLast('1').toLowerCase()
+
+            require(dataString.toCharArray().all { c -> charset.contains(c) }) { "invalid data encoding character in bech32"}
+
+            val dataBytes = dataString.map { c -> charset.indexOf(c).toByte() }.toByteArray()
+            val checkBytes = dataString.takeLast(CHECKSUM_SIZE).map { c -> charset.indexOf(c).toByte() }.toByteArray()
+
+            val actualSum = checksum(hrp, dataBytes.dropLast(CHECKSUM_SIZE).toTypedArray())
+            require(1 == polymod(expandHrp(hrp).plus(dataBytes.map { d -> d.toInt() }))) { "checksum failed: $checkBytes != $actualSum" }
+
+            return Bech32Data(hrp, dataBytes.dropLast(CHECKSUM_SIZE).toByteArray())
+        }
+
+        /**
+         * ConvertBits regroups bytes with toBits set based on reading groups of bits as a continuous stream group by fromBits.
+         * This process is used to convert from base64 (from 8) to base32 (to 5) or the inverse.
+         */
+        fun convertBits(data: ByteArray, fromBits: Int, toBits: Int, pad: Boolean): ByteArray {
+            require (fromBits in 1..8 && toBits in 1..8) { "only bit groups between 1 and 8 are supported"}
+
+            // resulting bytes with each containing the toBits bits from the input set.
+            var regrouped = arrayListOf<Byte>()
+
+            var nextByte = 0.toUByte()
+            var filledBits = 0
+
+            data.forEach { d ->
+                // discard unused bits.
+                var b = (d.toUByte() shl (8 - fromBits))
+
+                // How many bits remain to extract from input data.
+                var remainFromBits = fromBits
+
+                while (remainFromBits > 0) {
+                    // How many bits remain to be copied in
+                    val remainToBits = toBits - filledBits
+
+                    // we extract the remaining bits unless that is more than we need.
+                    val toExtract = remainFromBits.takeUnless { remainToBits < remainFromBits } ?: remainToBits
+                    check(toExtract >= 0) { "extract should be positive"}
+
+                    // move existing bits to the left to make room for bits toExtract, copy in bits to extract
+                    nextByte = (nextByte shl toExtract) or (b shr (8 - toExtract))
+
+                    // discard extracted bits and update position counters
+                    b = b shl toExtract
+                    remainFromBits -= toExtract
+                    filledBits += toExtract
+
+                    // if we have a complete group then reset.
+                    if (filledBits == toBits) {
+                        regrouped.add(nextByte.toByte())
+                        filledBits = 0
+                        nextByte = 0.toUByte()
+                    }
+                }
+            }
+
+            // pad any unfinished groups as required
+            if (pad && filledBits > 0) {
+                nextByte = nextByte shl (toBits - filledBits)
+                regrouped.add(nextByte.toByte())
+                filledBits = 0
+                nextByte = 0.toUByte()
+            }
+
+            return regrouped.toByteArray()
+        }
+
+        /**
+         * Encodes data 5-bit bytes (data) with a given human readable portion (hrp) into a bech32 string.
+         * @see convertBits for conversion or ideally use the Bech32Data extension functions
+         */
+        fun encode(hrp: String, fiveBitData: ByteArray): String {
+            return (fiveBitData.plus(checksum(hrp, fiveBitData.toTypedArray()))
+                .map { b -> charset[b.toInt()] }).joinToString("", hrp + "1")
+        }
+
+        /**
+         * Calculates a bech32 checksum based on BIP 173 specification
+         */
+        fun checksum(hrp: String, data: Array<Byte>): ByteArray {
+            var values = expandHrp(hrp)
+                .plus(data.map { d -> d.toInt() })
+                .plus(Array<Int>(6){ _ -> 0}.toIntArray())
+
+            var poly = polymod(values) xor 1
+
+            return (0..5).map {
+                ((poly shr (5 * (5-it))) and 31).toByte()
+            }.toByteArray()
+        }
+
+        /**
+         * Expands the human readable prefix per BIP173 for Checksum encoding
+         */
+        fun expandHrp(hrp: String) =
+            hrp.map { c -> c.toInt() shr 5 }
+                .plus(0)
+                .plus(hrp.map { c -> c.toInt() and 31 })
+                .toIntArray()
+
+        /**
+         * Polynomial division function for checksum calculation.  For details see BIP173
+         */
+        fun polymod(values: IntArray): Int {
+            var chk = 1
+            return values.map {
+                var b = chk shr 25
+                chk = ((chk and 0x1ffffff) shl 5) xor it
+                (0..4).map {
+                    if (((b shr it) and 1) == 1) {
+                        chk = chk xor gen[it]
+                    }
+                }
+            }.let { chk }
+        }
+    }
+}
\ No newline at end of file
diff --git a/taler-kotlin-android/src/main/java/net/taler/common/CyptoUtils.kt b/taler-kotlin-android/src/main/java/net/taler/common/CyptoUtils.kt
new file mode 100644
index 0000000..c1fbe8c
--- /dev/null
+++ b/taler-kotlin-android/src/main/java/net/taler/common/CyptoUtils.kt
@@ -0,0 +1,71 @@
+/*
+ * This file is part of GNU Taler
+ * (C) 2022 Taler Systems S.A.
+ *
+ * GNU Taler is free software; you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 3, or (at your option) any later version.
+ *
+ * GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ * A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+
+package net.taler.common
+
+import kotlin.math.floor
+
+object CyptoUtils {
+    internal fun getValue(c: Char): Int {
+        val a = when (c) {
+            'o','O' -> '0'
+            'i','I','l','L' -> '1'
+            'u','U' -> 'V'
+            else -> c
+        }
+        if (a in '0'..'9') {
+            return a - '0'
+        }
+        val A = if (a in 'a'..'z') a.uppercaseChar() else a
+        var dec = 0
+        if (A in 'A'..'Z') {
+            if ('I' < A) dec++
+            if ('L' < A) dec++
+            if ('O' < A) dec++
+            if ('U' < A) dec++
+            return A - 'A' + 10 - dec
+        }
+        throw Error("encoding error")
+    }
+
+    fun decodeCrock(e: String): ByteArray {
+        val size = e.length
+        var bitpos = 0
+        var bitbuf = 0
+        var readPosition = 0
+        val outLen = floor((size * 5f) / 8).toInt()
+        val out = ByteArray(outLen)
+        var outPos = 0
+        while (readPosition < size || bitpos > 0) {
+            if (readPosition < size) {
+                val v = getValue(e[readPosition++])
+                bitbuf = bitbuf.shl(5).or(v)
+                bitpos += 5
+            }
+            while (bitpos >= 8) {
+                val d = bitbuf.shr(bitpos -8).and(0xff).toByte()
+                out[outPos++] = d
+                bitpos -= 8
+            }
+            if (readPosition == size && bitpos > 0) {
+                bitbuf = bitbuf.shl( 8 - bitpos).and(0xff)
+                bitpos = if (bitbuf == 0) 0 else 8
+            }
+        }
+        return out
+    }
+
+}
\ No newline at end of file