From f06a9c18c457b77ce756e52b0d311140f38a0992 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mihael=20=C5=A0inkec?= <sinkec.mihael@gmail.com>
Date: Tue, 5 Sep 2023 16:13:10 +0200
Subject: [PATCH] Add BSV20Mint contract.

---
 src/contracts/bsv20Mint.ts | 168 +++++++++++++++++++++++++++++++++++++
 1 file changed, 168 insertions(+)
 create mode 100644 src/contracts/bsv20Mint.ts

diff --git a/src/contracts/bsv20Mint.ts b/src/contracts/bsv20Mint.ts
new file mode 100644
index 00000000..3e0526c7
--- /dev/null
+++ b/src/contracts/bsv20Mint.ts
@@ -0,0 +1,168 @@
+import { assert } from 'console'
+import {
+    ByteString,
+    FixedArray,
+    OpCode,
+    PubKeyHash,
+    SmartContract,
+    Utils,
+    byteString2Int,
+    hash256,
+    int2ByteString,
+    len,
+    lshift,
+    method,
+    prop,
+    slice,
+    toByteString,
+} from 'scrypt-ts'
+import { Shift10 } from 'scrypt-ts-lib'
+
+export class BSV20Mint extends SmartContract {
+    @prop()
+    totalSupply: bigint
+
+    @prop(true)
+    alreadyMinted: bigint
+
+    @prop(true)
+    isFirstMint: boolean
+
+    @prop(true)
+    tokenId: ByteString
+
+    @prop()
+    static readonly hexAsciiTable: FixedArray<ByteString, 16> = [
+        toByteString('0', true),
+        toByteString('1', true),
+        toByteString('2', true),
+        toByteString('3', true),
+        toByteString('4', true),
+        toByteString('5', true),
+        toByteString('6', true),
+        toByteString('7', true),
+        toByteString('8', true),
+        toByteString('9', true),
+        toByteString('a', true),
+        toByteString('b', true),
+        toByteString('c', true),
+        toByteString('d', true),
+        toByteString('e', true),
+        toByteString('f', true),
+    ]
+
+    constructor(totalSupply: bigint) {
+        super(...arguments)
+        this.totalSupply = totalSupply
+        this.alreadyMinted = 0n
+        this.isFirstMint = false
+        this.tokenId = toByteString('')
+    }
+
+    @method()
+    public mint(dest: PubKeyHash, amount: bigint) {
+        // If first mint, parse token id and store it in a state var
+        if (this.isFirstMint) {
+            this.tokenId =
+                BSV20Mint.txId2Ascii(this.ctx.utxo.outpoint.txid) +
+                toByteString('_', true) +
+                BSV20Mint.int2Ascii(this.ctx.utxo.outpoint.outputIndex)
+            this.isFirstMint = false
+        }
+
+        // Check if tokens still available.
+        assert(
+            this.totalSupply - this.alreadyMinted >= amount,
+            'not enough tokens left to mint'
+        )
+
+        // Update already minted amount.
+        this.alreadyMinted += amount
+
+        // Build state output inscribed with leftover tokens.
+        const leftover = this.totalSupply - this.alreadyMinted
+        const script0 =
+            BSV20Mint.getTransferInsciption(this.tokenId, leftover) +
+            this.getStateScript()
+        let outputs = Utils.buildOutput(script0, 1n)
+
+        // Build P2PKH output to dest paying specified amount of tokens.
+        const script1 =
+            BSV20Mint.getTransferInsciption(this.tokenId, leftover) +
+            Utils.buildPublicKeyHashScript(dest)
+        outputs += Utils.buildOutput(script1, 1n)
+
+        // Build change output.
+        outputs += this.buildChangeOutput()
+
+        assert(hash256(outputs) == this.ctx.hashOutputs, 'hashOutputs mismatch')
+    }
+
+    // OP_FALSE OP_IF OP_DATA3 "ord" OP_1 OP_DATA18 "application/bsv-20" OP_FALSE <transfer-json> OP_ENDIF
+    // Transfer JSON example:
+    //{
+    //  "p": "bsv-20",
+    //  "op": "transfer",
+    //  "id": "3b313338fa0555aebeaf91d8db1ffebd74773c67c8ad5181ff3d3f51e21e0000_1"
+    //  "amt": "10000"
+    //}
+    @method()
+    static getTransferInsciption(tokenId: ByteString, amt: bigint): ByteString {
+        const transferJson =
+            toByteString('{"p":"bsv-20","op":"transfer","id":"', true) +
+            toByteString('","amt":"', true) +
+            BSV20Mint.int2Ascii(amt) +
+            toByteString('"}', true)
+
+        return (
+            toByteString(
+                '0063036f726451126170706c69636174696f6e2f6273762d323000'
+            ) +
+            int2ByteString(len(transferJson)) +
+            transferJson +
+            OpCode.OP_ENDIF
+        )
+    }
+
+    // Converts integer to hex-encoded ASCII.
+    // 1000 -> '31303030'
+    // Input cannot be larger than 2^64-1.
+    @method()
+    static int2Ascii(n: bigint): ByteString {
+        // Max 2^64-1
+        assert(n < lshift(1n, 64n), 'n is larger than 2^64-1')
+
+        let res = toByteString('')
+        let done = false
+
+        for (let i = 0; i < 20; i++) {
+            if (!done) {
+                // Get ith digit: n // 10^i % 10
+                const denominator = Shift10.pow(BigInt(i))
+
+                if (n < denominator) {
+                    done = true
+                } else {
+                    const ithDigit = (n / denominator) % 10n
+
+                    // Transform digit to ASCII (hex encoded) and prepend to result.
+                    res = int2ByteString(48n + ithDigit, 1n) + res
+                }
+            }
+        }
+
+        return res
+    }
+
+    @method()
+    static txId2Ascii(txId: ByteString): ByteString {
+        let res = toByteString('')
+
+        for (let i = 0; i < 64; i++) {
+            const char = slice(txId, BigInt(i), BigInt(i + 1))
+            const charInt = byteString2Int(char)
+            res += BSV20Mint.hexAsciiTable[Number(charInt)]
+        }
+        return res
+    }
+}