279 lines
8.4 KiB
Go
279 lines
8.4 KiB
Go
/*
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Package nft contains non-divisible non-fungible NEP-11-compatible token
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implementation. This token can be minted with GAS transfer to contract address,
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it will hash some data (including data provided in transfer) and produce
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base64-encoded string that is your NFT. Since it's based on hashing and basically
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you own a hash it's HASHY.
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*/
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package nft
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import (
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"github.com/nspcc-dev/neo-go/pkg/interop"
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"github.com/nspcc-dev/neo-go/pkg/interop/contract"
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"github.com/nspcc-dev/neo-go/pkg/interop/iterator"
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"github.com/nspcc-dev/neo-go/pkg/interop/native/crypto"
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"github.com/nspcc-dev/neo-go/pkg/interop/native/gas"
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"github.com/nspcc-dev/neo-go/pkg/interop/native/management"
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"github.com/nspcc-dev/neo-go/pkg/interop/native/std"
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"github.com/nspcc-dev/neo-go/pkg/interop/runtime"
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"github.com/nspcc-dev/neo-go/pkg/interop/storage"
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"github.com/nspcc-dev/neo-go/pkg/interop/util"
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)
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// Prefixes used for contract data storage.
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const (
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totalSupplyPrefix = "s"
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// balancePrefix contains map from addresses to balances.
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balancePrefix = "b"
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// accountPrefix contains map from address + token id to tokens
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accountPrefix = "a"
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// tokenPrefix contains map from token id to it's owner.
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tokenPrefix = "t"
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)
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var (
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// contractOwner is a special address that can perform some management
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// functions on this contract like updating/destroying it and can also
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// be used for contract address verification.
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contractOwner = util.FromAddress("NbrUYaZgyhSkNoRo9ugRyEMdUZxrhkNaWB")
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)
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// Symbol returns token symbol, it's HASHY.
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func Symbol() string {
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return "HASHY"
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}
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// Decimals returns token decimals, this NFT is non-divisible, so it's 0.
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func Decimals() int {
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return 0
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}
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// TotalSupply is a contract method that returns the number of tokens minted.
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func TotalSupply() int {
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return totalSupply(storage.GetReadOnlyContext())
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}
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// totalSupply is an internal implementation of TotalSupply operating with
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// given context. The number itself is stored raw in the DB with totalSupplyPrefix
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// key.
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func totalSupply(ctx storage.Context) int {
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var res int
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val := storage.Get(ctx, []byte(totalSupplyPrefix))
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if val != nil {
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res = val.(int)
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}
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return res
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}
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// mkAccountPrefix creates DB key-prefix for account tokens specified
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// by concatenating accountPrefix and account address.
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func mkAccountPrefix(holder interop.Hash160) []byte {
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res := []byte(accountPrefix)
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return append(res, holder...)
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}
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// mkBalanceKey creates DB key for account specified by concatenating balancePrefix
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// and account address.
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func mkBalanceKey(holder interop.Hash160) []byte {
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res := []byte(balancePrefix)
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return append(res, holder...)
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}
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// mkTokenKey creates DB key for token specified by concatenating tokenPrefix
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// and token ID.
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func mkTokenKey(tokenID []byte) []byte {
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res := []byte(tokenPrefix)
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return append(res, tokenID...)
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}
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// BalanceOf returns the number of tokens owned by specified address.
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func BalanceOf(holder interop.Hash160) int {
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if len(holder) != 20 {
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panic("bad owner address")
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}
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ctx := storage.GetReadOnlyContext()
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return getBalanceOf(ctx, mkBalanceKey(holder))
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}
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// getBalanceOf returns balance of the account using database key.
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func getBalanceOf(ctx storage.Context, balanceKey []byte) int {
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val := storage.Get(ctx, balanceKey)
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if val != nil {
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return val.(int)
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}
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return 0
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}
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// addToBalance adds amount to the account balance. Amount can be negative.
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func addToBalance(ctx storage.Context, holder interop.Hash160, amount int) {
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key := mkBalanceKey(holder)
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old := getBalanceOf(ctx, key)
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old += amount
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if old > 0 {
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storage.Put(ctx, key, old)
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} else {
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storage.Delete(ctx, key)
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}
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}
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// addToken adds token to the account.
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func addToken(ctx storage.Context, holder interop.Hash160, token []byte) {
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key := mkAccountPrefix(holder)
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storage.Put(ctx, append(key, token...), token)
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}
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// removeToken removes token from the account.
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func removeToken(ctx storage.Context, holder interop.Hash160, token []byte) {
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key := mkAccountPrefix(holder)
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storage.Delete(ctx, append(key, token...))
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}
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// Tokens returns an iterator that contains all of the tokens minted by the contract.
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func Tokens() iterator.Iterator {
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ctx := storage.GetReadOnlyContext()
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key := []byte(tokenPrefix)
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iter := storage.Find(ctx, key, storage.RemovePrefix|storage.KeysOnly)
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return iter
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}
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// TokensOf returns an iterator with all tokens held by specified address.
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func TokensOf(holder interop.Hash160) iterator.Iterator {
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if len(holder) != 20 {
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panic("bad owner address")
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}
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ctx := storage.GetReadOnlyContext()
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key := mkAccountPrefix(holder)
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iter := storage.Find(ctx, key, storage.ValuesOnly)
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return iter
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}
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// getOwnerOf returns current owner of the specified token or panics if token
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// ID is invalid. Owner is stored as value of the token key (prefix + token ID).
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func getOwnerOf(ctx storage.Context, token []byte) interop.Hash160 {
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key := mkTokenKey(token)
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val := storage.Get(ctx, key)
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if val == nil {
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panic("no token found")
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}
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return val.(interop.Hash160)
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}
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// setOwnerOf writes current owner of the specified token into the DB.
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func setOwnerOf(ctx storage.Context, token []byte, holder interop.Hash160) {
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key := mkTokenKey(token)
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storage.Put(ctx, key, holder)
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}
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// OwnerOf returns owner of specified token.
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func OwnerOf(token []byte) interop.Hash160 {
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ctx := storage.GetReadOnlyContext()
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return getOwnerOf(ctx, token)
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}
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// Transfer token from its owner to another user, notice that it only has three
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// parameters because token owner can be deduced from token ID itself.
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func Transfer(to interop.Hash160, token []byte, data interface{}) bool {
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if len(to) != 20 {
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panic("invalid 'to' address")
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}
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ctx := storage.GetContext()
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owner := getOwnerOf(ctx, token)
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// Note that although calling script hash is not checked explicitly in
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// this contract it is in fact checked for in `CheckWitness` itself.
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if !runtime.CheckWitness(owner) {
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return false
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}
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if string(owner) != string(to) {
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addToBalance(ctx, owner, -1)
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removeToken(ctx, owner, token)
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addToBalance(ctx, to, 1)
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addToken(ctx, to, token)
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setOwnerOf(ctx, token, to)
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}
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postTransfer(owner, to, token, data)
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return true
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}
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// postTransfer emits Transfer event and calls onNEP11Payment if needed.
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func postTransfer(from interop.Hash160, to interop.Hash160, token []byte, data interface{}) {
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runtime.Notify("Transfer", from, to, 1, token)
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if management.GetContract(to) != nil {
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contract.Call(to, "onNEP11Payment", contract.All, from, 1, token, data)
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}
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}
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// OnNEP17Payment mints tokens if at least 10 GAS is provided. You don't call
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// this method directly, instead it's called by GAS contract when you transfer
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// GAS from your address to the address of this NFT contract.
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func OnNEP17Payment(from interop.Hash160, amount int, data interface{}) {
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if string(runtime.GetCallingScriptHash()) != gas.Hash {
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panic("only GAS is accepted")
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}
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if amount < 10_00000000 {
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panic("minting HASHY costs at least 10 GAS")
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}
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var tokIn = []byte{}
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var ctx = storage.GetContext()
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total := totalSupply(ctx)
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tokIn = append(tokIn, []byte(std.Itoa(total, 10))...)
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tokIn = append(tokIn, []byte(std.Itoa(amount, 10))...)
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tokIn = append(tokIn, from...)
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tx := runtime.GetScriptContainer()
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tokIn = append(tokIn, tx.Hash...)
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if data != nil {
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tokIn = append(tokIn, std.Serialize(data)...)
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}
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tokenHash := crypto.Ripemd160(tokIn)
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token := std.Base64Encode(tokenHash)
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addToken(ctx, from, []byte(token))
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setOwnerOf(ctx, []byte(token), from)
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addToBalance(ctx, from, 1)
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total++
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storage.Put(ctx, []byte(totalSupplyPrefix), total)
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postTransfer(nil, from, []byte(token), nil) // no `data` during minting
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}
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// Verify allows owner to manage contract's address, including earned GAS
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// transfer from contract's address to somewhere else. It just checks for transaction
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// to also be signed by contract owner, so contract's witness should be empty.
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func Verify() bool {
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return runtime.CheckWitness(contractOwner)
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}
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// Destroy destroys the contract, only owner can do that.
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func Destroy() {
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if !Verify() {
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panic("only owner can destroy")
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}
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management.Destroy()
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}
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// Update updates the contract, only owner can do that.
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func Update(nef, manifest []byte) {
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if !Verify() {
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panic("only owner can update")
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}
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management.Update(nef, manifest)
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}
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// Properties returns properties of the given NFT.
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func Properties(id []byte) map[string]string {
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ctx := storage.GetReadOnlyContext()
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owner := storage.Get(ctx, mkTokenKey(id)).(interop.Hash160)
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if owner == nil {
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panic("unknown token")
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}
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result := map[string]string{
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"name": "HASHY " + std.Base64Encode(id), // Not a hex for contract simplicity.
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}
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return result
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}
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