package smart_contract

/*
	NeoFS Smart Contract for NEO3.0.

	Utility operations, executed once in deploy stage:
	- Init(pubKey, ... )                    - setup initial inner ring nodes
	- InitConfig(key, value, key, value...) - setup initial NeoFS configuration

	User operations:
	- Deposit(script-hash, amount, script-hash(?)) - deposit gas assets to this script-hash address to NeoFS balance
	- Withdraw(script-hash, amount)                - initialize gas asset withdraw from NeoFS balance
	- Bind(script-hash, pubKeys...)                - bind public key with user's account to use it in NeoFS requests
	- Unbind(script-hash, pubKeys...)              - unbind public key from user's account

	Inner ring list operations:
	- InnerRingList()                  - returns array of inner ring node keys
	- InnerRingCandidates()            - returns array of inner ring candidate node keys
	- IsInnerRing(pubKey)              - returns 'true' if key is inside of inner ring list
	- InnerRingCandidateAdd(pubKey)    - adds key to the list of inner ring candidates
	- InnerRingCandidateRemove(pubKey) - removes key from the list of inner ring candidates
	- InnerRingUpdate(id, pubKeys...)  - updates list of inner ring nodes with provided list of public keys

	Config operations:
	- Config(key)               - returns value of NeoFS configuration with key 'key'
	- ListConfig()              - returns array of all key-value pairs of NeoFS configuration
	- SetConfig(id, key, value) - set key-value pair as a NeoFS runtime configuration value

	Other utility operations:
	- Version                                       - returns contract version
	- Cheque(id, script- hash, amount, script-hash) - sends gas assets back to the user if they were successfully
	                                                  locked in NeoFS balance contract

	Parameters:
	- (?)    - parameter can be omitted
	- pubKey - 33 bytes of public key
	- id     - unique byte sequence
*/

import (
	"github.com/nspcc-dev/neo-go/pkg/interop/binary"
	"github.com/nspcc-dev/neo-go/pkg/interop/blockchain"
	"github.com/nspcc-dev/neo-go/pkg/interop/contract"
	"github.com/nspcc-dev/neo-go/pkg/interop/crypto"
	"github.com/nspcc-dev/neo-go/pkg/interop/engine"
	"github.com/nspcc-dev/neo-go/pkg/interop/iterator"
	"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"
)

type (
	ballot struct {
		id    []byte   // id of the voting decision
		n     [][]byte // already voted inner ring nodes
		block int      // block with the last vote
	}

	node struct {
		pub []byte
	}

	cheque struct {
		id []byte
	}

	record struct {
		key []byte
		val []byte
	}
)

const (
	// native gas token script hash
	tokenHash = "\x3b\x7d\x37\x11\xc6\xf0\xcc\xf9\xb1\xdc\xa9\x03\xd1\xbf\xa1\xd8\x96\xf1\x23\x8c"

	defaultCandidateFee   = 100 * 1_0000_0000 // 100 Fixed8 Gas
	candidateFeeConfigKey = "InnerRingCandidateFee"

	version = 2

	innerRingKey     = "innerring"
	voteKey          = "ballots"
	candidatesKey    = "candidates"
	cashedChequesKey = "cheques"

	blockDiff        = 20 // change base on performance evaluation
	publicKeySize    = 33
	minInnerRingSize = 3
)

var (
	configPrefix = []byte("config")
)

func Main(op string, args []interface{}) interface{} {
	// The trigger determines whether this smart-contract is being
	// run in 'verification' or 'application' mode.
	if runtime.GetTrigger() != runtime.Application() {
		return false
	}

	ctx := storage.GetContext()

	switch op {
	case "Init":
		if storage.Get(ctx, innerRingKey) != nil {
			panic("neofs: contract already deployed")
		}

		var irList []node

		for i := 0; i < len(args); i++ {
			pub := args[i].([]byte)
			irList = append(irList, node{pub: pub})
		}

		// initialize all storage slices
		setSerialized(ctx, innerRingKey, irList)
		setSerialized(ctx, voteKey, []ballot{})
		setSerialized(ctx, candidatesKey, []node{})
		setSerialized(ctx, cashedChequesKey, []cheque{})

		runtime.Log("neofs: contract initialized")

		return true
	case "InnerRingList":
		return getInnerRingNodes(ctx, innerRingKey)
	case "InnerRingCandidates":
		return getInnerRingNodes(ctx, candidatesKey)
	case "InnerRingCandidateRemove":
		if len(args) != 1 {
			panic("irCandidateRemove: bad arguments")
		}

		key := args[0].([]byte) // inner ring candidate public key
		if !runtime.CheckWitness(key) {
			panic("irCandidateRemove: you should be the owner of the public key")
		}

		nodes := []node{} // it is explicit declaration of empty slice, not nil
		candidates := getInnerRingNodes(ctx, candidatesKey)

		for i := range candidates {
			c := candidates[i]
			if !bytesEqual(c.pub, key) {
				nodes = append(nodes, c)
			} else {
				runtime.Log("irCandidateRemove: candidate has been removed")
			}
		}

		setSerialized(ctx, candidatesKey, nodes)

		return true
	case "InnerRingCandidateAdd":
		if len(args) != 1 {
			panic("irCandidateAdd: bad arguments")
		}

		key := args[0].([]byte) // inner ring candidate public key
		if !runtime.CheckWitness(key) {
			panic("irCandidateAdd: you should be the owner of the public key")
		}

		c := node{pub: key}
		candidates := getInnerRingNodes(ctx, candidatesKey)

		list, ok := addNode(candidates, c)
		if !ok {
			panic("irCandidateAdd: candidate already in the list")
		}

		from := contract.CreateStandardAccount(key)
		to := runtime.GetExecutingScriptHash()
		fee := getConfig(ctx, candidateFeeConfigKey).(int)
		params := []interface{}{from, to, fee}

		transferred := engine.AppCall([]byte(tokenHash), "transfer", params).(bool)
		if !transferred {
			panic("irCandidateAdd: failed to transfer funds, aborting")
		}

		runtime.Log("irCandidateAdd: candidate has been added")
		setSerialized(ctx, candidatesKey, list)

		return true
	case "Deposit":
		if len(args) < 2 || len(args) > 3 {
			panic("deposit: bad arguments")
		}

		from := args[0].([]byte)
		if !runtime.CheckWitness(from) {
			panic("deposit: you should be the owner of the wallet")
		}

		amount := args[1].(int)
		if amount > 0 {
			amount = amount * 100000000
		}

		to := runtime.GetExecutingScriptHash()
		params := []interface{}{from, to, amount}

		transferred := engine.AppCall([]byte(tokenHash), "transfer", params).(bool)
		if !transferred {
			panic("deposit: failed to transfer funds, aborting")
		}

		runtime.Log("deposit: funds have been transferred")

		var rcv = from
		if len(args) == 3 {
			rcv = args[2].([]byte) // todo: check if rcv value is valid
		}

		tx := runtime.GetScriptContainer()
		runtime.Notify("Deposit", from, amount, rcv, tx.Hash)

		return true
	case "Withdraw":
		if len(args) != 2 {
			panic("withdraw: bad arguments")
		}

		user := args[0].([]byte)
		if !runtime.CheckWitness(user) {
			panic("withdraw: you should be the owner of the wallet")
		}

		amount := args[1].(int)
		if amount > 0 {
			amount = amount * 100000000
		}

		tx := runtime.GetScriptContainer()
		runtime.Notify("Withdraw", user, amount, tx.Hash)

		return true
	case "Cheque":
		if len(args) != 4 {
			panic("cheque: bad arguments")
		}

		id := args[0].([]byte)      // unique cheque id
		user := args[1].([]byte)    // GAS receiver
		amount := args[2].(int)     // amount of GAS
		lockAcc := args[3].([]byte) // lock account from internal balance contract

		irList := getInnerRingNodes(ctx, innerRingKey)
		threshold := len(irList)/3*2 + 1

		cashedCheques := getCashedCheques(ctx)
		hashID := crypto.SHA256(id)

		irKey := innerRingInvoker(irList)
		if len(irKey) == 0 {
			panic("cheque: invoked by non inner ring node")
		}

		c := cheque{id: id}

		list, ok := addCheque(cashedCheques, c)
		if !ok {
			panic("cheque: non unique id")
		}

		n := vote(ctx, hashID, irKey)
		if n >= threshold {
			removeVotes(ctx, hashID)

			from := runtime.GetExecutingScriptHash()
			params := []interface{}{from, user, amount}

			transferred := engine.AppCall([]byte(tokenHash), "transfer", params).(bool)
			if !transferred {
				panic("cheque: failed to transfer funds, aborting")
			}

			runtime.Log("cheque: funds have been transferred")

			setSerialized(ctx, cashedChequesKey, list)
			runtime.Notify("Cheque", id, user, amount, lockAcc)
		}

		return true
	case "Bind", "Unbind":
		if len(args) < 2 {
			panic("binding: bad arguments")
		}

		user := args[0].([]byte)
		if !runtime.CheckWitness(user) {
			panic("binding: you should be the owner of the wallet")
		}

		var keys [][]byte

		for i := 1; i < len(args); i++ {
			pub := args[i].([]byte)
			if len(pub) != publicKeySize {
				panic("binding: incorrect public key size")
			}

			keys = append(keys, pub)
		}

		runtime.Notify(op, user, keys)

		return true
	case "InnerRingUpdate":
		if len(args) < 1+minInnerRingSize {
			// cheque id + inner ring public keys
			panic("irUpdate: bad arguments")
		}

		irList := getInnerRingNodes(ctx, innerRingKey)
		threshold := len(irList)/3*2 + 1

		irKey := innerRingInvoker(irList)
		if len(irKey) == 0 {
			panic("innerRingUpdate: invoked by non inner ring node")
		}

		id := args[0].([]byte)
		c := cheque{id: id}

		cashedCheques := getCashedCheques(ctx)

		chequesList, ok := addCheque(cashedCheques, c)
		if !ok {
			panic("irUpdate: non unique id")
		}

		oldNodes := 0
		candidates := getInnerRingNodes(ctx, candidatesKey)
		newIR := []node{}

	loop:
		for i := 1; i < len(args); i++ {
			key := args[i].([]byte)
			if len(key) != publicKeySize {
				panic("irUpdate: invalid public key in inner ring list")
			}

			// find key in actual inner ring list
			for j := 0; j < len(irList); j++ {
				n := irList[j]
				if bytesEqual(n.pub, key) {
					newIR = append(newIR, n)
					oldNodes++

					continue loop
				}
			}

			// find key in candidates list
			candidates, newIR, ok = rmNodeByKey(candidates, newIR, key)
			if !ok {
				panic("irUpdate: unknown public key in inner ring list")
			}
		}

		if oldNodes < len(newIR)*2/3+1 {
			panic("irUpdate: inner ring change rate must not be more than 1/3 ")
		}

		hashID := crypto.SHA256(id)

		n := vote(ctx, hashID, irKey)
		if n >= threshold {
			removeVotes(ctx, hashID)

			setSerialized(ctx, candidatesKey, candidates)
			setSerialized(ctx, innerRingKey, newIR)
			setSerialized(ctx, cashedChequesKey, chequesList)

			runtime.Notify("InnerRingUpdate", c.id, newIR)
			runtime.Log("irUpdate: inner ring list has been updated")
		}

		return true
	case "IsInnerRing":
		if len(args) != 1 {
			panic("isInnerRing: wrong arguments")
		}

		key := args[0].([]byte)
		if len(key) != publicKeySize {
			panic("isInnerRing: incorrect public key")
		}

		irList := getInnerRingNodes(ctx, innerRingKey)
		for i := range irList {
			node := irList[i]

			if bytesEqual(node.pub, key) {
				return true
			}
		}

		return false
	case "Config":
		if len(args) != 1 {
			panic("config: bad arguments")
		}

		key := args[0].([]byte)

		return getConfig(ctx, key)
	case "SetConfig":
		if len(args) != 3 {
			panic("setConfig: bad arguments")
		}

		// check if it is inner ring invocation
		irList := getInnerRingNodes(ctx, innerRingKey)
		threshold := len(irList)/3*2 + 1

		irKey := innerRingInvoker(irList)
		if len(irKey) == 0 {
			panic("setConfig: invoked by non inner ring node")
		}

		// check unique id of the operation
		id := args[0].([]byte)
		c := cheque{id: id}
		cashedCheques := getCashedCheques(ctx)

		chequesList, ok := addCheque(cashedCheques, c)
		if !ok {
			panic("setConfig: non unique id")
		}

		// vote for new configuration value
		hashID := crypto.SHA256(id)

		n := vote(ctx, hashID, irKey)
		if n >= threshold {
			removeVotes(ctx, hashID)

			key := args[1]
			val := args[2]

			setConfig(ctx, key, val)
			setSerialized(ctx, cashedChequesKey, chequesList)

			runtime.Notify("SetConfig", id, key, val)
			runtime.Log("setConfig: configuration has been updated")
		}

		return true
	case "ListConfig":
		var config []record

		it := storage.Find(ctx, configPrefix)
		for iterator.Next(it) {
			key := iterator.Key(it).([]byte)
			val := iterator.Value(it).([]byte)
			r := record{key: key[len(configPrefix):], val: val}

			config = append(config, r)
		}

		return config
	case "InitConfig":
		if getConfig(ctx, candidateFeeConfigKey) != nil {
			panic("neofs: configuration already installed")
		}

		ln := len(args)
		if ln%2 != 0 {
			panic("initConfig: bad arguments")
		}

		setConfig(ctx, candidateFeeConfigKey, defaultCandidateFee)

		for i := 0; i < ln/2; i++ {
			key := args[i*2]
			val := args[i*2+1]

			setConfig(ctx, key, val)
		}

		runtime.Log("neofs: config has been installed")

		return true
	case "Version":
		return version
	}

	panic("unknown operation")
}

// innerRingInvoker returns public key of inner ring node that invoked contract.
func innerRingInvoker(ir []node) []byte {
	for i := 0; i < len(ir); i++ {
		node := ir[i]
		if runtime.CheckWitness(node.pub) {
			return node.pub
		}
	}

	return nil
}

// vote adds ballot for the decision with specific 'id' and returns amount
// on unique voters for that decision.
func vote(ctx storage.Context, id, from []byte) int {
	var (
		newCandidates = []ballot{} // it is explicit declaration of empty slice, not nil
		candidates    = getBallots(ctx)
		found         = -1
		blockHeight   = blockchain.GetHeight()
	)

	for i := 0; i < len(candidates); i++ {
		cnd := candidates[i]
		if bytesEqual(cnd.id, id) {
			voters := cnd.n

			for j := range voters {
				if bytesEqual(voters[j], from) {
					return len(voters)
				}
			}

			voters = append(voters, from)
			cnd = ballot{id: id, n: voters, block: blockHeight}
			found = len(voters)
		}

		// do not add old ballots, they are invalid
		if blockHeight-cnd.block <= blockDiff {
			newCandidates = append(newCandidates, cnd)
		}
	}

	if found < 0 {
		found = 1
		voters := [][]byte{from}

		newCandidates = append(newCandidates, ballot{
			id:    id,
			n:     voters,
			block: blockHeight})
	}

	setSerialized(ctx, voteKey, newCandidates)

	return found
}

// removeVotes clears ballots of the decision that has benn aceepted by
// inner ring nodes.
func removeVotes(ctx storage.Context, id []byte) {
	var (
		newCandidates = []ballot{} // it is explicit declaration of empty slice, not nil
		candidates    = getBallots(ctx)
	)

	for i := 0; i < len(candidates); i++ {
		cnd := candidates[i]
		if !bytesEqual(cnd.id, id) {
			newCandidates = append(newCandidates, cnd)
		}
	}

	setSerialized(ctx, voteKey, newCandidates)
}

// setSerialized serializes data and puts it into contract storage.
func setSerialized(ctx storage.Context, key interface{}, value interface{}) {
	data := binary.Serialize(value)
	storage.Put(ctx, key, data)
}

// getInnerRingNodes returns deserialized slice of inner ring nodes from storage.
func getInnerRingNodes(ctx storage.Context, key string) []node {
	data := storage.Get(ctx, key)
	if data != nil {
		return binary.Deserialize(data.([]byte)).([]node)
	}

	return []node{}
}

// getInnerRingNodes returns deserialized slice of used cheques.
func getCashedCheques(ctx storage.Context) []cheque {
	data := storage.Get(ctx, cashedChequesKey)
	if data != nil {
		return binary.Deserialize(data.([]byte)).([]cheque)
	}

	return []cheque{}
}

// getInnerRingNodes returns deserialized slice of vote ballots.
func getBallots(ctx storage.Context) []ballot {
	data := storage.Get(ctx, voteKey)
	if data != nil {
		return binary.Deserialize(data.([]byte)).([]ballot)
	}

	return []ballot{}
}

// getConfig returns installed neofs configuration value or nil if it is not set.
func getConfig(ctx storage.Context, key interface{}) interface{} {
	postfix := key.([]byte)
	storageKey := append(configPrefix, postfix...)

	return storage.Get(ctx, storageKey)
}

// setConfig sets neofs configuration value in the contract storage.
func setConfig(ctx storage.Context, key, val interface{}) {
	postfix := key.([]byte)
	storageKey := append(configPrefix, postfix...)

	storage.Put(ctx, storageKey, val)
}

// addCheque returns slice of cheques with appended cheque 'c' and bool flag
// that set to false if cheque 'c' is already presented in the slice 'lst'.
func addCheque(lst []cheque, c cheque) ([]cheque, bool) {
	for i := 0; i < len(lst); i++ {
		if bytesEqual(c.id, lst[i].id) {
			return nil, false
		}
	}

	lst = append(lst, c)

	return lst, true
}

// addNode returns slice of nodes with appended node 'n' and bool flag
// that set to false if node 'n' is already presented in the slice 'lst'.
func addNode(lst []node, n node) ([]node, bool) {
	for i := 0; i < len(lst); i++ {
		if bytesEqual(n.pub, lst[i].pub) {
			return nil, false
		}
	}

	lst = append(lst, n)

	return lst, true
}

// rmNodeByKey returns slice of nodes without node with key 'k',
// slices of nodes 'add' with node with key 'k' and bool flag,
// that set to false if node with a key 'k' does not exists in the slice 'lst'.
func rmNodeByKey(lst, add []node, k []byte) ([]node, []node, bool) {
	var (
		flag   bool
		newLst = []node{} // it is explicit declaration of empty slice, not nil
	)

	for i := 0; i < len(lst); i++ {
		if bytesEqual(k, lst[i].pub) {
			add = append(add, lst[i])
			flag = true
		} else {
			newLst = append(newLst, lst[i])
		}
	}

	return newLst, add, flag
}

// bytesEqual compares two slice of bytes by wrapping them into strings,
// which is necessary with new util.Equal interop behaviour, see neo-go#1176.
func bytesEqual(a []byte, b []byte) bool {
	return util.Equals(string(a), string(b))
}