examples: drop token-sale contract

It makes zero sense, it's not what it says it
is. AmountPerNEO/MaxExchangeLimitRound are not used at all to affect minting
and allowance/transferFrom features are largely obsolete. We have proper
minting implemented in NFT contracts and there is a nice NEP-17 available
also.

examples/README.md

@@ -33,7 +33,6 @@ See the table below for the detailed examples description.
 | [storage](storage)       | The contract implements API for basic operations with a contract storage. It shows hos to use `storage` interop package. See the `storage` [package documentation](../pkg/interop/storage/storage.go). |
 | [timer](timer)           | The idea of the contract is to count `tick` method invocations and destroy itself after the third invocation. It shows how to use `contract.Call` interop function to call, update (migrate) and destroy the contract. Please, refer to the `contract.Call` [function documentation](../pkg/interop/contract/contract.go) |
 | [token](token)           | This contract implements NEP-17 token standard (like NEO and GAS tokens) with all required methods and operations. See the NEP-17 token standard [specification](https://github.com/neo-project/proposals/pull/126) for details. |
-| [token-sale](token-sale) | The contract represents a token with `allowance`. It means that the token owner should approve token withdrawing before the transfer. The contract demonstrates how interop packages can be combined to work together. |
 
 ## Compile
 

examples/token-sale/go.mod

@@ -1,5 +0,0 @@
-module github.com/nspcc-dev/neo-go/examples/token-sale
-
-go 1.16
-
-require github.com/nspcc-dev/neo-go/pkg/interop v0.0.0-20220321144137-d5a9af5860af

examples/token-sale/go.sum

@@ -1,2 +0,0 @@
-github.com/nspcc-dev/neo-go/pkg/interop v0.0.0-20220321144137-d5a9af5860af h1:QO3pU/jSYyX3EHBX8BPO01oRkVhGBXPrQaQEhn+4fv8=
-github.com/nspcc-dev/neo-go/pkg/interop v0.0.0-20220321144137-d5a9af5860af/go.mod h1:QBE0I30F2kOAISNpT5oks82yF4wkkUq3SCfI3Hqgx/Y=

examples/token-sale/token_sale.go

@@ -1,279 +0,0 @@
-package tokensale
-
-import (
-	"github.com/nspcc-dev/neo-go/pkg/interop"
-	"github.com/nspcc-dev/neo-go/pkg/interop/runtime"
-	"github.com/nspcc-dev/neo-go/pkg/interop/storage"
-	"github.com/nspcc-dev/neo-go/pkg/interop/util"
-)
-
-const (
-	decimals   = 8
-	multiplier = decimals * 10
-)
-
-var (
-	owner   = util.FromAddress("NbrUYaZgyhSkNoRo9ugRyEMdUZxrhkNaWB")
-	trigger byte
-	token   TokenConfig
-	ctx     storage.Context
-)
-
-// TokenConfig holds information about the token we want to use for the sale.
-type TokenConfig struct {
-	// Name of the token.
-	Name string
-	// 3 letter abbreviation of the token.
-	Symbol string
-	// How decimals this token will have.
-	Decimals int
-	// Address of the token owner. This is the Uint160 hash.
-	Owner []byte
-	// The total amount of tokens created. Notice that we need to multiply the
-	// amount by 100000000. (10^8)
-	TotalSupply int
-	// Initial amount is number of tokens that are available for the token sale.
-	InitialAmount int
-	// How many NEO will be worth 1 token. For example:
-	// Lets say 1 euro per token, where 1 NEO is 60 euro. This means buyers
-	// will get (60 * 10^8) tokens for 1 NEO.
-	AmountPerNEO int
-	// How many Gas will be worth 1 token. This is the same calculation as
-	// for the AmountPerNEO, except Gas price will have a different value.
-	AmountPerGas int
-	// The maximum amount you can mint in the limited round. For example:
-	// 500 NEO/buyer * 60 tokens/NEO * 10^8
-	MaxExchangeLimitRound int
-	// When to start the token sale.
-	SaleStart int
-	// When to end the initial limited round if there is one. For example:
-	// SaleStart + 10000
-	LimitRoundEnd int
-	// The prefix used to store how many tokens there are in circulation.
-	CirculationKey []byte
-	// The prefix used to store how many tokens there are in the limited round.
-	LimitRoundKey []byte
-	// The prefix used to store the addresses that are registered with KYC.
-	KYCKey []byte
-}
-
-// newTokenConfig returns the initialized TokenConfig.
-func newTokenConfig() TokenConfig {
-	return TokenConfig{
-		Name:                  "My awesome token",
-		Symbol:                "MAT",
-		Decimals:              decimals,
-		Owner:                 owner,
-		TotalSupply:           10000000 * multiplier,
-		InitialAmount:         5000000 * multiplier,
-		AmountPerNEO:          60 * multiplier,
-		AmountPerGas:          40 * multiplier,
-		MaxExchangeLimitRound: 500 * 60 * multiplier,
-		SaleStart:             75500,
-		LimitRoundEnd:         75500 + 10000,
-		CirculationKey:        []byte("in_circulation"),
-		LimitRoundKey:         []byte("r1"),
-		KYCKey:                []byte("kyc_ok"),
-	}
-}
-
-// getIntFromDB is a helper that checks for nil result of storage.Get and returns
-// zero as the default value.
-func getIntFromDB(ctx storage.Context, key []byte) int {
-	var res int
-	val := storage.Get(ctx, key)
-	if val != nil {
-		res = val.(int)
-	}
-	return res
-}
-
-// InCirculation returns the amount of total tokens that are in circulation.
-func InCirculation() int {
-	return getIntFromDB(ctx, token.CirculationKey)
-}
-
-// addToCirculation sets the given amount as "in circulation" in the storage.
-func addToCirculation(amount int) bool {
-	if amount < 0 {
-		return false
-	}
-	supply := getIntFromDB(ctx, token.CirculationKey)
-	supply += amount
-	if supply > token.TotalSupply {
-		return false
-	}
-	storage.Put(ctx, token.CirculationKey, supply)
-	return true
-}
-
-// AvailableAmount returns the total amount of available tokens left
-// to be distributed.
-func AvailableAmount() int {
-	inCirc := getIntFromDB(ctx, token.CirculationKey)
-	return token.TotalSupply - inCirc
-}
-
-// init initializes runtime trigger, TokenConfig and storage context before any
-// other contract method is called
-func init() {
-	trigger = runtime.GetTrigger()
-	token = newTokenConfig()
-	ctx = storage.GetContext()
-}
-
-// checkOwnerWitness is a helper function which checks whether the invoker is the
-// owner of the contract.
-func checkOwnerWitness() bool {
-	// This is used to verify if a transfer of system assets (NEO and Gas)
-	// involving this contract's address can proceed.
-	if trigger == runtime.Application {
-		// Check if the invoker is the owner of the contract.
-		return runtime.CheckWitness(token.Owner)
-	}
-	return false
-}
-
-// Decimals returns the token decimals
-func Decimals() int {
-	if trigger != runtime.Application {
-		panic("invalid trigger")
-	}
-	return token.Decimals
-}
-
-// Symbol returns the token symbol
-func Symbol() string {
-	if trigger != runtime.Application {
-		panic("invalid trigger")
-	}
-	return token.Symbol
-}
-
-// TotalSupply returns the token total supply value
-func TotalSupply() int {
-	if trigger != runtime.Application {
-		panic("invalid trigger")
-	}
-	return getIntFromDB(ctx, token.CirculationKey)
-}
-
-// BalanceOf returns the amount of token on the specified address
-func BalanceOf(holder interop.Hash160) int {
-	if trigger != runtime.Application {
-		panic("invalid trigger")
-	}
-	return getIntFromDB(ctx, holder)
-}
-
-// Transfer transfers specified amount of token from one user to another
-func Transfer(from, to interop.Hash160, amount int, _ interface{}) bool {
-	if trigger != runtime.Application {
-		return false
-	}
-	if amount <= 0 || len(to) != 20 || !runtime.CheckWitness(from) {
-		return false
-	}
-	amountFrom := getIntFromDB(ctx, from)
-	if amountFrom < amount {
-		return false
-	}
-	if amountFrom == amount {
-		storage.Delete(ctx, from)
-	} else {
-		diff := amountFrom - amount
-		storage.Put(ctx, from, diff)
-	}
-	amountTo := getIntFromDB(ctx, to)
-	totalAmountTo := amountTo + amount
-	if totalAmountTo != 0 {
-		storage.Put(ctx, to, totalAmountTo)
-	}
-	return true
-}
-
-// TransferFrom transfers specified amount of token from one user to another.
-// It differs from Transfer in that it use allowance value to store the amount
-// of token available to transfer.
-func TransferFrom(from, to []byte, amount int) bool {
-	if trigger != runtime.Application {
-		return false
-	}
-	if amount <= 0 {
-		return false
-	}
-	availableKey := append(from, to...)
-	if len(availableKey) != 40 {
-		return false
-	}
-	availableTo := getIntFromDB(ctx, availableKey)
-	if availableTo < amount {
-		return false
-	}
-	fromBalance := getIntFromDB(ctx, from)
-	if fromBalance < amount {
-		return false
-	}
-	toBalance := getIntFromDB(ctx, to)
-	newFromBalance := fromBalance - amount
-	newToBalance := toBalance + amount
-	storage.Put(ctx, to, newToBalance)
-	storage.Put(ctx, from, newFromBalance)
-
-	newAllowance := availableTo - amount
-	if newAllowance == 0 {
-		storage.Delete(ctx, availableKey)
-	} else {
-		storage.Put(ctx, availableKey, newAllowance)
-	}
-	return true
-}
-
-// Approve stores token transfer data if the owner has enough token to send.
-func Approve(owner, spender []byte, amount int) bool {
-	if !checkOwnerWitness() || amount < 0 {
-		return false
-	}
-	if len(spender) != 20 {
-		return false
-	}
-	toSpend := getIntFromDB(ctx, owner)
-	if toSpend < amount {
-		return false
-	}
-	approvalKey := append(owner, spender...)
-	if amount == 0 {
-		storage.Delete(ctx, approvalKey)
-	} else {
-		storage.Put(ctx, approvalKey, amount)
-	}
-	return true
-}
-
-// Allowance returns allowance value for specified sender and receiver.
-func Allowance(from, to []byte) interface{} {
-	if trigger != runtime.Application {
-		return false
-	}
-	key := append(from, to...)
-	return getIntFromDB(ctx, key)
-}
-
-// Mint initial supply of tokens
-func Mint(to []byte) bool {
-	if trigger != runtime.Application {
-		return false
-	}
-	if !checkOwnerWitness() {
-		return false
-	}
-	minted := storage.Get(ctx, []byte("minted"))
-	if minted != nil && minted.(bool) == true {
-		return false
-	}
-
-	storage.Put(ctx, to, token.TotalSupply)
-	storage.Put(ctx, []byte("minted"), true)
-	addToCirculation(token.TotalSupply)
-	return true
-}

examples/token-sale/token_sale.yml

@@ -1,13 +0,0 @@
-name: "My awesome token"
-sourceurl: https://github.com/nspcc-dev/neo-go/
-supportedstandards: ["NEP-17"]
-safemethods: ["balanceOf", "decimals", "symbol", "totalSupply"]
-events:
-- name: Transfer
-  parameters:
-  - name: from
-    type: Hash160
-  - name: to
-    type: Hash160
-  - name: amount
-    type: Integer