package vm

import (
	"bytes"
	"crypto/elliptic"
	"encoding/base64"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"math/big"
	"os"
	"strconv"
	"strings"
	"text/tabwriter"

	"github.com/chzyer/readline"
	"github.com/kballard/go-shellquote"
	"github.com/nspcc-dev/neo-go/cli/flags"
	"github.com/nspcc-dev/neo-go/pkg/compiler"
	"github.com/nspcc-dev/neo-go/pkg/config"
	"github.com/nspcc-dev/neo-go/pkg/core"
	"github.com/nspcc-dev/neo-go/pkg/core/interop"
	"github.com/nspcc-dev/neo-go/pkg/core/storage"
	"github.com/nspcc-dev/neo-go/pkg/core/storage/dbconfig"
	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
	"github.com/nspcc-dev/neo-go/pkg/encoding/address"
	"github.com/nspcc-dev/neo-go/pkg/encoding/bigint"
	"github.com/nspcc-dev/neo-go/pkg/smartcontract/callflag"
	"github.com/nspcc-dev/neo-go/pkg/smartcontract/manifest"
	"github.com/nspcc-dev/neo-go/pkg/smartcontract/trigger"
	"github.com/nspcc-dev/neo-go/pkg/util"
	"github.com/nspcc-dev/neo-go/pkg/util/slice"
	"github.com/nspcc-dev/neo-go/pkg/vm"
	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
	"github.com/urfave/cli"
	"go.uber.org/zap"
)

const (
	chainKey            = "chain"
	chainCfgKey         = "chainCfg"
	icKey               = "ic"
	manifestKey         = "manifest"
	exitFuncKey         = "exitFunc"
	readlineInstanceKey = "readlineKey"
	printLogoKey        = "printLogoKey"
	boolType            = "bool"
	boolFalse           = "false"
	boolTrue            = "true"
	intType             = "int"
	stringType          = "string"
)

// Various flag names.
const (
	verboseFlagFullName   = "verbose"
	historicFlagFullName  = "historic"
	backwardsFlagFullName = "backwards"
	diffFlagFullName      = "diff"
)

var historicFlag = cli.IntFlag{
	Name: historicFlagFullName,
	Usage: "Height for historic script invocation (for MPT-enabled blockchain configuration with KeepOnlyLatestState setting disabled). " +
		"Assuming that block N-th is specified as an argument, the historic invocation is based on the storage state of height N and fake currently-accepting block with index N+1.",
}

var commands = []cli.Command{
	{
		Name:        "exit",
		Usage:       "Exit the VM prompt",
		Description: "Exit the VM prompt",
		Action:      handleExit,
	},
	{
		Name:        "ip",
		Usage:       "Show current instruction",
		Description: "Show current instruction",
		Action:      handleIP,
	},
	{
		Name:      "break",
		Usage:     "Place a breakpoint",
		UsageText: `break <ip>`,
		Description: `break <ip>
<ip> is mandatory parameter, example:
> break 12`,
		Action: handleBreak,
	},
	{
		Name:        "estack",
		Usage:       "Show evaluation stack contents",
		Description: "Show evaluation stack contents",
		Action:      handleXStack,
	},
	{
		Name:        "istack",
		Usage:       "Show invocation stack contents",
		Description: "Show invocation stack contents",
		Action:      handleXStack,
	},
	{
		Name:        "sslot",
		Usage:       "Show static slot contents",
		Description: "Show static slot contents",
		Action:      handleSlots,
	},
	{
		Name:        "lslot",
		Usage:       "Show local slot contents",
		Description: "Show local slot contents",
		Action:      handleSlots,
	},
	{
		Name:        "aslot",
		Usage:       "Show arguments slot contents",
		Description: "Show arguments slot contents",
		Action:      handleSlots,
	},
	{
		Name:      "loadnef",
		Usage:     "Load a NEF-consistent script into the VM",
		UsageText: `loadnef <file> <manifest>`,
		Flags:     []cli.Flag{historicFlag},
		Description: `loadnef [--historic <height>] <file> <manifest>
both parameters are mandatory, example:
> loadnef /path/to/script.nef /path/to/manifest.json`,
		Action: handleLoadNEF,
	},
	{
		Name:      "loadbase64",
		Usage:     "Load a base64-encoded script string into the VM",
		UsageText: `loadbase64 [--historic <height>] <string>`,
		Flags:     []cli.Flag{historicFlag},
		Description: `loadbase64 [--historic <height>] <string>

<string> is mandatory parameter, example:
> loadbase64 AwAQpdToAAAADBQV9ehtQR1OrVZVhtHtoUHRfoE+agwUzmFvf3Rhfg/EuAVYOvJgKiON9j8TwAwIdHJhbnNmZXIMFDt9NxHG8Mz5sdypA9G/odiW8SOMQWJ9W1I4`,
		Action: handleLoadBase64,
	},
	{
		Name:      "loadhex",
		Usage:     "Load a hex-encoded script string into the VM",
		UsageText: `loadhex [--historic <height>] <string>`,
		Flags:     []cli.Flag{historicFlag},
		Description: `loadhex [--historic <height>] <string>

<string> is mandatory parameter, example:
> loadhex 0c0c48656c6c6f20776f726c6421`,
		Action: handleLoadHex,
	},
	{
		Name:      "loadgo",
		Usage:     "Compile and load a Go file with the manifest into the VM",
		UsageText: `loadgo [--historic <height>] <file>`,
		Flags:     []cli.Flag{historicFlag},
		Description: `loadgo [--historic <height>] <file>

<file> is mandatory parameter, example:
> loadgo /path/to/file.go`,
		Action: handleLoadGo,
	},
	{
		Name:   "reset",
		Usage:  "Unload compiled script from the VM and reset context to proper (possibly, historic) state",
		Flags:  []cli.Flag{historicFlag},
		Action: handleReset,
	},
	{
		Name:      "parse",
		Usage:     "Parse provided argument and convert it into other possible formats",
		UsageText: `parse <arg>`,
		Description: `parse <arg>

<arg> is an argument which is tried to be interpreted as an item of different types
and converted to other formats. Strings are escaped and output in quotes.`,
		Action: handleParse,
	},
	{
		Name:      "run",
		Usage:     "Execute the current loaded script",
		UsageText: `run [<method> [<parameter>...]]`,
		Description: `run [<method> [<parameter>...]]

<method> is a contract method, specified in manifest. It can be '_' which will push
        parameters onto the stack and execute from the current offset.
<parameter> is a parameter (can be repeated multiple times) that can be specified
        as <type>:<value>, where type can be:
            '` + boolType + `': supports '` + boolFalse + `' and '` + boolTrue + `' values
            '` + intType + `': supports integers as values
            '` + stringType + `': supports strings as values (that are pushed as a byte array
                      values to the stack)
       or can be just <value>, for which the type will be detected automatically
       following these rules: '` + boolTrue + `' and '` + boolFalse + `' are treated as respective
       boolean values, everything that can be converted to integer is treated as
       integer and everything else is treated like a string.

Example:
> run put ` + stringType + `:"Something to put"`,
		Action: handleRun,
	},
	{
		Name:        "cont",
		Usage:       "Continue execution of the current loaded script",
		Description: "Continue execution of the current loaded script",
		Action:      handleCont,
	},
	{
		Name:      "step",
		Usage:     "Step (n) instruction in the program",
		UsageText: `step [<n>]`,
		Description: `step [<n>]
<n> is optional parameter to specify number of instructions to run, example:
> step 10`,
		Action: handleStep,
	},
	{
		Name:  "stepinto",
		Usage: "Stepinto instruction to take in the debugger",
		Description: `Usage: stepInto
example:
> stepinto`,
		Action: handleStepInto,
	},
	{
		Name:  "stepout",
		Usage: "Stepout instruction to take in the debugger",
		Description: `stepOut
example:
> stepout`,
		Action: handleStepOut,
	},
	{
		Name:  "stepover",
		Usage: "Stepover instruction to take in the debugger",
		Description: `stepOver
example:
> stepover`,
		Action: handleStepOver,
	},
	{
		Name:        "ops",
		Usage:       "Dump opcodes of the current loaded program",
		Description: "Dump opcodes of the current loaded program",
		Action:      handleOps,
	},
	{
		Name:        "events",
		Usage:       "Dump events emitted by the current loaded program",
		Description: "Dump events emitted by the current loaded program",
		Action:      handleEvents,
	},
	{
		Name:      "env",
		Usage:     "Dump state of the chain that is used for VM CLI invocations (use -v for verbose node configuration)",
		UsageText: `env [-v]`,
		Flags: []cli.Flag{
			cli.BoolFlag{
				Name:  verboseFlagFullName + ",v",
				Usage: "Print the whole blockchain node configuration.",
			},
		},
		Description: `env [-v]

Dump state of the chain that is used for VM CLI invocations (use -v for verbose node configuration).

Example:
> env -v`,
		Action: handleEnv,
	},
	{
		Name: "storage",
		Usage: "Dump storage of the contract with the specified hash, address or ID as is at the current stage of script invocation. " +
			"Can be used if no script is loaded. " +
			"Hex-encoded storage items prefix may be specified (empty by default to return the whole set of storage items). " +
			"If seek prefix is not empty, then it's trimmed from the resulting keys." +
			"Items are sorted. Backwards seek direction may be specified (false by default, which means forwards storage seek direction). " +
			"It is possible to dump only those storage items that were added or changed during current script invocation (use --diff flag for it).",
		UsageText: `storage <hash-or-address-or-id> [<prefix>] [--backwards] [--diff]`,
		Flags: []cli.Flag{
			cli.BoolFlag{
				Name:  backwardsFlagFullName + ",b",
				Usage: "Backwards traversal direction",
			},
			cli.BoolFlag{
				Name:  diffFlagFullName + ",d",
				Usage: "Dump only those storage items that were added or changed during the current script invocation. Note that this call won't show removed storage items.",
			},
		},
		Description: `storage <hash-or-address-or-id> <prefix> [--backwards] [--diff]

Dump storage of the contract with the specified hash, address or ID as is at the current stage of script invocation.
Can be used if no script is loaded.
Hex-encoded storage items prefix may be specified (empty by default to return the whole set of storage items).
If seek prefix is not empty, then it's trimmed from the resulting keys.
Items are sorted. Backwards seek direction may be specified (false by default, which means forwards storage seek direction).
It is possible to dump only those storage items that were added or changed during current script invocation (use --diff flag for it).

Example:
> storage 0x0000000009070e030d0f0e020d0c06050e030c02 030e --backwards --diff`,
		Action: handleStorage,
	},
}

var completer *readline.PrefixCompleter

func init() {
	var pcItems []readline.PrefixCompleterInterface
	for _, c := range commands {
		if !c.Hidden {
			var flagsItems []readline.PrefixCompleterInterface
			for _, f := range c.Flags {
				names := strings.SplitN(f.GetName(), ", ", 2) // only long name will be offered
				flagsItems = append(flagsItems, readline.PcItem("--"+names[0]))
			}
			pcItems = append(pcItems, readline.PcItem(c.Name, flagsItems...))
		}
	}
	completer = readline.NewPrefixCompleter(pcItems...)
}

// Various errors.
var (
	ErrMissingParameter = errors.New("missing argument")
	ErrInvalidParameter = errors.New("can't parse argument")
)

// VMCLI object for interacting with the VM.
type VMCLI struct {
	chain *core.Blockchain
	shell *cli.App
}

// NewWithConfig returns new VMCLI instance using provided config and (optionally)
// provided node config for state-backed VM.
func NewWithConfig(printLogotype bool, onExit func(int), c *readline.Config, cfg config.Config) (*VMCLI, error) {
	if c.AutoComplete == nil {
		// Autocomplete commands/flags on TAB.
		c.AutoComplete = completer
	}
	l, err := readline.NewEx(c)
	if err != nil {
		return nil, fmt.Errorf("failed to create readline instance: %w", err)
	}
	ctl := cli.NewApp()
	ctl.Name = "VM CLI"

	// Note: need to set empty `ctl.HelpName` and `ctl.UsageText`, otherwise
	// `filepath.Base(os.Args[0])` will be used which is `neo-go`.
	ctl.HelpName = ""
	ctl.UsageText = ""

	ctl.Writer = l.Stdout()
	ctl.ErrWriter = l.Stderr()
	ctl.Version = config.Version
	ctl.Usage = "Official VM CLI for Neo-Go"

	// Override default error handler in order not to exit on error.
	ctl.ExitErrHandler = func(context *cli.Context, err error) {}

	ctl.Commands = commands

	store, err := storage.NewStore(cfg.ApplicationConfiguration.DBConfiguration)
	if err != nil {
		writeErr(ctl.ErrWriter, fmt.Errorf("failed to open DB, clean in-memory storage will be used: %w", err))
		cfg.ApplicationConfiguration.DBConfiguration.Type = dbconfig.InMemoryDB
		store = storage.NewMemoryStore()
	}

	exitF := func(i int) {
		_ = store.Close()
		onExit(i)
	}

	log := zap.NewNop()
	chain, err := core.NewBlockchain(store, cfg.ProtocolConfiguration, log)
	if err != nil {
		return nil, cli.NewExitError(fmt.Errorf("could not initialize blockchain: %w", err), 1)
	}
	// Do not run chain, we need only state-related functionality from it.
	ic, err := chain.GetTestVM(trigger.Application, nil, nil)
	if err != nil {
		return nil, cli.NewExitError(fmt.Errorf("failed to create test VM: %w", err), 1)
	}

	vmcli := VMCLI{
		chain: chain,
		shell: ctl,
	}

	vmcli.shell.Metadata = map[string]interface{}{
		chainKey:            chain,
		chainCfgKey:         cfg,
		icKey:               ic,
		manifestKey:         new(manifest.Manifest),
		exitFuncKey:         exitF,
		readlineInstanceKey: l,
		printLogoKey:        printLogotype,
	}
	changePrompt(vmcli.shell)
	return &vmcli, nil
}

func getExitFuncFromContext(app *cli.App) func(int) {
	return app.Metadata[exitFuncKey].(func(int))
}

func getReadlineInstanceFromContext(app *cli.App) *readline.Instance {
	return app.Metadata[readlineInstanceKey].(*readline.Instance)
}

func getVMFromContext(app *cli.App) *vm.VM {
	return getInteropContextFromContext(app).VM
}

func getChainFromContext(app *cli.App) *core.Blockchain {
	return app.Metadata[chainKey].(*core.Blockchain)
}

func getChainConfigFromContext(app *cli.App) config.Config {
	return app.Metadata[chainCfgKey].(config.Config)
}

func getInteropContextFromContext(app *cli.App) *interop.Context {
	return app.Metadata[icKey].(*interop.Context)
}

func getManifestFromContext(app *cli.App) *manifest.Manifest {
	return app.Metadata[manifestKey].(*manifest.Manifest)
}

func getPrintLogoFromContext(app *cli.App) bool {
	return app.Metadata[printLogoKey].(bool)
}

func setInteropContextInContext(app *cli.App, ic *interop.Context) {
	app.Metadata[icKey] = ic
}

func setManifestInContext(app *cli.App, m *manifest.Manifest) {
	app.Metadata[manifestKey] = m
}

func checkVMIsReady(app *cli.App) bool {
	v := getVMFromContext(app)
	if v == nil || !v.Ready() {
		writeErr(app.Writer, errors.New("VM is not ready: no program loaded"))
		return false
	}
	return true
}

func handleExit(c *cli.Context) error {
	finalizeInteropContext(c.App)
	l := getReadlineInstanceFromContext(c.App)
	_ = l.Close()
	exit := getExitFuncFromContext(c.App)
	fmt.Fprintln(c.App.Writer, "Bye!")
	exit(0)
	return nil
}

func handleIP(c *cli.Context) error {
	if !checkVMIsReady(c.App) {
		return nil
	}
	v := getVMFromContext(c.App)
	ctx := v.Context()
	if ctx.NextIP() < ctx.LenInstr() {
		ip, opcode := v.Context().NextInstr()
		fmt.Fprintf(c.App.Writer, "instruction pointer at %d (%s)\n", ip, opcode)
	} else {
		fmt.Fprintln(c.App.Writer, "execution has finished")
	}
	return nil
}

func handleBreak(c *cli.Context) error {
	if !checkVMIsReady(c.App) {
		return nil
	}
	v := getVMFromContext(c.App)
	args := c.Args()
	if len(args) != 1 {
		return fmt.Errorf("%w: <ip>", ErrMissingParameter)
	}
	n, err := strconv.Atoi(args[0])
	if err != nil {
		return fmt.Errorf("%w: %s", ErrInvalidParameter, err)
	}

	v.AddBreakPoint(n)
	fmt.Fprintf(c.App.Writer, "breakpoint added at instruction %d\n", n)
	return nil
}

func handleXStack(c *cli.Context) error {
	v := getVMFromContext(c.App)
	var stackDump string
	switch c.Command.Name {
	case "estack":
		stackDump = v.DumpEStack()
	case "istack":
		stackDump = v.DumpIStack()
	default:
		return errors.New("unknown stack")
	}
	fmt.Fprintln(c.App.Writer, stackDump)
	return nil
}

func handleSlots(c *cli.Context) error {
	v := getVMFromContext(c.App)
	vmCtx := v.Context()
	if vmCtx == nil {
		return errors.New("no program loaded")
	}
	var rawSlot string
	switch c.Command.Name {
	case "sslot":
		rawSlot = vmCtx.DumpStaticSlot()
	case "lslot":
		rawSlot = vmCtx.DumpLocalSlot()
	case "aslot":
		rawSlot = vmCtx.DumpArgumentsSlot()
	default:
		return errors.New("unknown slot")
	}
	fmt.Fprintln(c.App.Writer, rawSlot)
	return nil
}

// prepareVM retrieves --historic flag from context (if set) and resets app state
// (to the specified historic height if given).
func prepareVM(c *cli.Context) error {
	if c.IsSet(historicFlagFullName) {
		height := c.Int(historicFlagFullName)
		return resetState(c.App, uint32(height))
	}

	return resetState(c.App)
}

func handleLoadNEF(c *cli.Context) error {
	err := prepareVM(c)
	if err != nil {
		return err
	}
	v := getVMFromContext(c.App)
	args := c.Args()
	if len(args) < 2 {
		return fmt.Errorf("%w: <file> <manifest>", ErrMissingParameter)
	}
	if err := v.LoadFileWithFlags(args[0], callflag.All); err != nil {
		return fmt.Errorf("failed to read nef: %w", err)
	}
	m, err := getManifestFromFile(args[1])
	if err != nil {
		return fmt.Errorf("failed to read manifest: %w", err)
	}
	fmt.Fprintf(c.App.Writer, "READY: loaded %d instructions\n", v.Context().LenInstr())
	setManifestInContext(c.App, m)
	changePrompt(c.App)
	return nil
}

func handleLoadBase64(c *cli.Context) error {
	err := prepareVM(c)
	if err != nil {
		return err
	}
	v := getVMFromContext(c.App)
	args := c.Args()
	if len(args) < 1 {
		return fmt.Errorf("%w: <string>", ErrMissingParameter)
	}
	b, err := base64.StdEncoding.DecodeString(args[0])
	if err != nil {
		return fmt.Errorf("%w: %s", ErrInvalidParameter, err)
	}
	v.LoadWithFlags(b, callflag.All)
	fmt.Fprintf(c.App.Writer, "READY: loaded %d instructions\n", v.Context().LenInstr())
	changePrompt(c.App)
	return nil
}

func handleLoadHex(c *cli.Context) error {
	err := prepareVM(c)
	if err != nil {
		return err
	}
	v := getVMFromContext(c.App)
	args := c.Args()
	if len(args) < 1 {
		return fmt.Errorf("%w: <string>", ErrMissingParameter)
	}
	b, err := hex.DecodeString(args[0])
	if err != nil {
		return fmt.Errorf("%w: %s", ErrInvalidParameter, err)
	}
	v.LoadWithFlags(b, callflag.All)
	fmt.Fprintf(c.App.Writer, "READY: loaded %d instructions\n", v.Context().LenInstr())
	changePrompt(c.App)
	return nil
}

func handleLoadGo(c *cli.Context) error {
	err := prepareVM(c)
	if err != nil {
		return err
	}
	v := getVMFromContext(c.App)
	args := c.Args()
	if len(args) < 1 {
		return fmt.Errorf("%w: <file>", ErrMissingParameter)
	}

	name := strings.TrimSuffix(args[0], ".go")
	b, di, err := compiler.CompileWithOptions(args[0], nil, &compiler.Options{Name: name})
	if err != nil {
		return fmt.Errorf("failed to compile: %w", err)
	}

	// Don't perform checks, just load.
	m, err := di.ConvertToManifest(&compiler.Options{})
	if err != nil {
		return fmt.Errorf("can't create manifest: %w", err)
	}
	setManifestInContext(c.App, m)

	v.LoadWithFlags(b.Script, callflag.All)
	fmt.Fprintf(c.App.Writer, "READY: loaded %d instructions\n", v.Context().LenInstr())
	changePrompt(c.App)
	return nil
}

func handleReset(c *cli.Context) error {
	err := prepareVM(c)
	if err != nil {
		return err
	}
	changePrompt(c.App)
	return nil
}

// finalizeInteropContext calls finalizer for the current interop context.
func finalizeInteropContext(app *cli.App) {
	ic := getInteropContextFromContext(app)
	ic.Finalize()
}

// resetInteropContext calls finalizer for current interop context and replaces
// it with the newly created one.
func resetInteropContext(app *cli.App, height ...uint32) error {
	finalizeInteropContext(app)
	bc := getChainFromContext(app)
	var (
		newIc *interop.Context
		err   error
	)
	if len(height) != 0 {
		newIc, err = bc.GetTestHistoricVM(trigger.Application, nil, height[0]+1)
		if err != nil {
			return fmt.Errorf("failed to create historic VM for height %d: %w", height[0], err)
		}
	} else {
		newIc, err = bc.GetTestVM(trigger.Application, nil, nil)
		if err != nil {
			return fmt.Errorf("failed to create VM: %w", err)
		}
	}

	setInteropContextInContext(app, newIc)
	return nil
}

// resetManifest removes manifest from app context.
func resetManifest(app *cli.App) {
	setManifestInContext(app, nil)
}

// resetState resets state of the app (clear interop context and manifest) so that it's ready
// to load new program.
func resetState(app *cli.App, height ...uint32) error {
	err := resetInteropContext(app, height...)
	if err != nil {
		return err
	}
	resetManifest(app)
	return nil
}

func getManifestFromFile(name string) (*manifest.Manifest, error) {
	bs, err := os.ReadFile(name)
	if err != nil {
		return nil, fmt.Errorf("%w: can't read manifest", ErrInvalidParameter)
	}

	var m manifest.Manifest
	if err := json.Unmarshal(bs, &m); err != nil {
		return nil, fmt.Errorf("%w: can't unmarshal manifest", ErrInvalidParameter)
	}
	return &m, nil
}

func handleRun(c *cli.Context) error {
	v := getVMFromContext(c.App)
	m := getManifestFromContext(c.App)
	args := c.Args()
	if len(args) != 0 {
		var (
			params     []stackitem.Item
			offset     int
			err        error
			runCurrent = args[0] != "_"
		)

		params, err = parseArgs(args[1:])
		if err != nil {
			return err
		}
		if runCurrent {
			if m == nil {
				return fmt.Errorf("manifest is not loaded; either use 'run' command to run loaded script from the start or use 'loadgo' and 'loadnef' commands to provide manifest")
			}
			md := m.ABI.GetMethod(args[0], len(params))
			if md == nil {
				return fmt.Errorf("%w: method not found", ErrInvalidParameter)
			}
			offset = md.Offset
		}
		for i := len(params) - 1; i >= 0; i-- {
			v.Estack().PushVal(params[i])
		}
		if runCurrent {
			if !v.Ready() {
				return errors.New("no program loaded")
			}
			v.Context().Jump(offset)
			if initMD := m.ABI.GetMethod(manifest.MethodInit, 0); initMD != nil {
				v.Call(initMD.Offset)
			}
		}
	}
	runVMWithHandling(c)
	changePrompt(c.App)
	return nil
}

// runVMWithHandling runs VM with handling errors and additional state messages.
func runVMWithHandling(c *cli.Context) {
	v := getVMFromContext(c.App)
	err := v.Run()
	if err != nil {
		writeErr(c.App.ErrWriter, err)
	}

	var (
		message string
		dumpNtf bool
	)
	switch {
	case v.HasFailed():
		message = "" // the error will be printed on return
		dumpNtf = true
	case v.HasHalted():
		message = v.DumpEStack()
		dumpNtf = true
	case v.AtBreakpoint():
		ctx := v.Context()
		if ctx.NextIP() < ctx.LenInstr() {
			i, op := ctx.NextInstr()
			message = fmt.Sprintf("at breakpoint %d (%s)", i, op)
		} else {
			message = "execution has finished"
		}
	}
	if dumpNtf {
		var e string
		e, err = dumpEvents(c.App)
		if err == nil && len(e) != 0 {
			if message != "" {
				message += "\n"
			}
			message += "Events:\n" + e
		}
	}
	if message != "" {
		fmt.Fprintln(c.App.Writer, message)
	}
}

func handleCont(c *cli.Context) error {
	if !checkVMIsReady(c.App) {
		return nil
	}
	runVMWithHandling(c)
	changePrompt(c.App)
	return nil
}

func handleStep(c *cli.Context) error {
	var (
		n   = 1
		err error
	)

	if !checkVMIsReady(c.App) {
		return nil
	}
	v := getVMFromContext(c.App)
	args := c.Args()
	if len(args) > 0 {
		n, err = strconv.Atoi(args[0])
		if err != nil {
			return fmt.Errorf("%w: %s", ErrInvalidParameter, err)
		}
	}
	v.AddBreakPointRel(n)
	runVMWithHandling(c)
	changePrompt(c.App)
	return nil
}

func handleStepInto(c *cli.Context) error {
	return handleStepType(c, "into")
}

func handleStepOut(c *cli.Context) error {
	return handleStepType(c, "out")
}

func handleStepOver(c *cli.Context) error {
	return handleStepType(c, "over")
}

func handleStepType(c *cli.Context, stepType string) error {
	if !checkVMIsReady(c.App) {
		return nil
	}
	v := getVMFromContext(c.App)
	var err error
	switch stepType {
	case "into":
		err = v.StepInto()
	case "out":
		err = v.StepOut()
	case "over":
		err = v.StepOver()
	}
	if err != nil {
		return err
	}
	_ = handleIP(c)
	changePrompt(c.App)
	return nil
}

func handleOps(c *cli.Context) error {
	if !checkVMIsReady(c.App) {
		return nil
	}
	v := getVMFromContext(c.App)
	out := bytes.NewBuffer(nil)
	v.PrintOps(out)
	fmt.Fprintln(c.App.Writer, out.String())
	return nil
}

func changePrompt(app *cli.App) {
	v := getVMFromContext(app)
	l := getReadlineInstanceFromContext(app)
	if v.Ready() && v.Context().NextIP() >= 0 && v.Context().NextIP() < v.Context().LenInstr() {
		l.SetPrompt(fmt.Sprintf("\033[32mNEO-GO-VM %d >\033[0m ", v.Context().NextIP()))
	} else {
		l.SetPrompt("\033[32mNEO-GO-VM >\033[0m ")
	}
}

func handleEvents(c *cli.Context) error {
	e, err := dumpEvents(c.App)
	if err != nil {
		writeErr(c.App.ErrWriter, err)
		return nil
	}
	fmt.Fprintln(c.App.Writer, e)
	return nil
}

func handleEnv(c *cli.Context) error {
	bc := getChainFromContext(c.App)
	cfg := getChainConfigFromContext(c.App)
	ic := getInteropContextFromContext(c.App)
	message := fmt.Sprintf("Chain height: %d\nVM height (may differ from chain height in case of historic call): %d\nNetwork magic: %d\nDB type: %s\n",
		bc.BlockHeight(), ic.BlockHeight(), bc.GetConfig().Magic, cfg.ApplicationConfiguration.DBConfiguration.Type)
	if c.Bool(verboseFlagFullName) {
		cfgBytes, err := json.MarshalIndent(cfg, "", "\t")
		if err != nil {
			return fmt.Errorf("failed to marshal node configuration: %w", err)
		}
		message += "Node config:\n" + string(cfgBytes) + "\n"
	}
	fmt.Fprint(c.App.Writer, message)
	return nil
}

func handleStorage(c *cli.Context) error {
	if !c.Args().Present() {
		return errors.New("contract hash, address or ID is mandatory argument")
	}
	hashOrID := c.Args().Get(0)
	var (
		id        int32
		ic        = getInteropContextFromContext(c.App)
		prefix    []byte
		backwards bool
		seekDepth int
	)
	h, err := flags.ParseAddress(hashOrID)
	if err != nil {
		i, err := strconv.Atoi(hashOrID)
		if err != nil {
			return fmt.Errorf("failed to parse contract hash, address or ID: %w", err)
		}
		id = int32(i)
	} else {
		cs, err := ic.GetContract(h)
		if err != nil {
			return fmt.Errorf("contract %s not found: %w", h.StringLE(), err)
		}
		id = cs.ID
	}
	if c.NArg() > 1 {
		prefix, err = hex.DecodeString(c.Args().Get(1))
		if err != nil {
			return fmt.Errorf("failed to decode prefix from hex: %w", err)
		}
	}
	if c.Bool(backwardsFlagFullName) {
		backwards = true
	}
	if c.Bool(diffFlagFullName) {
		seekDepth = 1 // take only upper DAO layer which stores only added or updated items.
	}
	ic.DAO.Seek(id, storage.SeekRange{
		Prefix:      prefix,
		Backwards:   backwards,
		SearchDepth: seekDepth,
	}, func(k, v []byte) bool {
		fmt.Fprintf(c.App.Writer, "%s: %v\n", hex.EncodeToString(k), hex.EncodeToString(v))
		return true
	})
	return nil
}

func dumpEvents(app *cli.App) (string, error) {
	ic := getInteropContextFromContext(app)
	if len(ic.Notifications) == 0 {
		return "", nil
	}
	b, err := json.MarshalIndent(ic.Notifications, "", "\t")
	if err != nil {
		return "", fmt.Errorf("failed to marshal notifications: %w", err)
	}
	return string(b), nil
}

// Run waits for user input from Stdin and executes the passed command.
func (c *VMCLI) Run() error {
	if getPrintLogoFromContext(c.shell) {
		printLogo(c.shell.Writer)
	}
	l := getReadlineInstanceFromContext(c.shell)
	for {
		line, err := l.Readline()
		if errors.Is(err, io.EOF) || errors.Is(err, readline.ErrInterrupt) {
			return nil // OK, stop execution.
		}
		if err != nil {
			return fmt.Errorf("failed to read input: %w", err) // Critical error, stop execution.
		}

		args, err := shellquote.Split(line)
		if err != nil {
			writeErr(c.shell.ErrWriter, fmt.Errorf("failed to parse arguments: %w", err))
			continue // Not a critical error, continue execution.
		}

		err = c.shell.Run(append([]string{"vm"}, args...))
		if err != nil {
			writeErr(c.shell.ErrWriter, err) // Various command/flags parsing errors and execution errors.
		}
	}
}

func handleParse(c *cli.Context) error {
	res, err := Parse(c.Args())
	if err != nil {
		return err
	}
	fmt.Fprintln(c.App.Writer, res)
	return nil
}

// Parse converts it's argument to other formats.
func Parse(args []string) (string, error) {
	if len(args) < 1 {
		return "", ErrMissingParameter
	}
	arg := args[0]
	buf := bytes.NewBuffer(nil)
	if val, err := strconv.ParseInt(arg, 10, 64); err == nil {
		bs := bigint.ToBytes(big.NewInt(val))
		buf.WriteString(fmt.Sprintf("Integer to Hex\t%s\n", hex.EncodeToString(bs)))
		buf.WriteString(fmt.Sprintf("Integer to Base64\t%s\n", base64.StdEncoding.EncodeToString(bs)))
	}
	noX := strings.TrimPrefix(arg, "0x")
	if rawStr, err := hex.DecodeString(noX); err == nil {
		if val, err := util.Uint160DecodeBytesBE(rawStr); err == nil {
			buf.WriteString(fmt.Sprintf("BE ScriptHash to Address\t%s\n", address.Uint160ToString(val)))
			buf.WriteString(fmt.Sprintf("LE ScriptHash to Address\t%s\n", address.Uint160ToString(val.Reverse())))
		}
		if pub, err := keys.NewPublicKeyFromBytes(rawStr, elliptic.P256()); err == nil {
			sh := pub.GetScriptHash()
			buf.WriteString(fmt.Sprintf("Public key to BE ScriptHash\t%s\n", sh))
			buf.WriteString(fmt.Sprintf("Public key to LE ScriptHash\t%s\n", sh.Reverse()))
			buf.WriteString(fmt.Sprintf("Public key to Address\t%s\n", address.Uint160ToString(sh)))
		}
		buf.WriteString(fmt.Sprintf("Hex to String\t%s\n", fmt.Sprintf("%q", string(rawStr))))
		buf.WriteString(fmt.Sprintf("Hex to Integer\t%s\n", bigint.FromBytes(rawStr)))
		buf.WriteString(fmt.Sprintf("Swap Endianness\t%s\n", hex.EncodeToString(slice.CopyReverse(rawStr))))
	}
	if addr, err := address.StringToUint160(arg); err == nil {
		buf.WriteString(fmt.Sprintf("Address to BE ScriptHash\t%s\n", addr))
		buf.WriteString(fmt.Sprintf("Address to LE ScriptHash\t%s\n", addr.Reverse()))
		buf.WriteString(fmt.Sprintf("Address to Base64 (BE)\t%s\n", base64.StdEncoding.EncodeToString(addr.BytesBE())))
		buf.WriteString(fmt.Sprintf("Address to Base64 (LE)\t%s\n", base64.StdEncoding.EncodeToString(addr.BytesLE())))
	}
	if rawStr, err := base64.StdEncoding.DecodeString(arg); err == nil {
		buf.WriteString(fmt.Sprintf("Base64 to String\t%s\n", fmt.Sprintf("%q", string(rawStr))))
		buf.WriteString(fmt.Sprintf("Base64 to BigInteger\t%s\n", bigint.FromBytes(rawStr)))
		if u, err := util.Uint160DecodeBytesBE(rawStr); err == nil {
			buf.WriteString(fmt.Sprintf("Base64 to BE ScriptHash\t%s\n", u.StringBE()))
			buf.WriteString(fmt.Sprintf("Base64 to LE ScriptHash\t%s\n", u.StringLE()))
			buf.WriteString(fmt.Sprintf("Base64 to Address (BE)\t%s\n", address.Uint160ToString(u)))
			buf.WriteString(fmt.Sprintf("Base64 to Address (LE)\t%s\n", address.Uint160ToString(u.Reverse())))
		}
	}

	buf.WriteString(fmt.Sprintf("String to Hex\t%s\n", hex.EncodeToString([]byte(arg))))
	buf.WriteString(fmt.Sprintf("String to Base64\t%s\n", base64.StdEncoding.EncodeToString([]byte(arg))))

	out := buf.Bytes()
	buf = bytes.NewBuffer(nil)
	w := tabwriter.NewWriter(buf, 0, 4, 4, '\t', 0)
	if _, err := w.Write(out); err != nil {
		return "", err
	}
	if err := w.Flush(); err != nil {
		return "", err
	}
	return buf.String(), nil
}

func parseArgs(args []string) ([]stackitem.Item, error) {
	items := make([]stackitem.Item, len(args))
	for i, arg := range args {
		var typ, value string
		typeAndVal := strings.Split(arg, ":")
		if len(typeAndVal) < 2 {
			if typeAndVal[0] == boolFalse || typeAndVal[0] == boolTrue {
				typ = boolType
			} else if _, err := strconv.Atoi(typeAndVal[0]); err == nil {
				typ = intType
			} else {
				typ = stringType
			}
			value = typeAndVal[0]
		} else {
			typ = typeAndVal[0]
			value = typeAndVal[1]
		}

		switch typ {
		case boolType:
			if value == boolFalse {
				items[i] = stackitem.NewBool(false)
			} else if value == boolTrue {
				items[i] = stackitem.NewBool(true)
			} else {
				return nil, fmt.Errorf("%w: invalid bool value", ErrInvalidParameter)
			}
		case intType:
			val, err := strconv.ParseInt(value, 10, 64)
			if err != nil {
				return nil, fmt.Errorf("%w: invalid integer value", ErrInvalidParameter)
			}
			items[i] = stackitem.NewBigInteger(big.NewInt(val))
		case stringType:
			items[i] = stackitem.NewByteArray([]byte(value))
		}
	}

	return items, nil
}

const logo = `
    _   ____________        __________      _    ____  ___
   / | / / ____/ __ \      / ____/ __ \    | |  / /  |/  /
  /  |/ / __/ / / / /_____/ / __/ / / /____| | / / /|_/ / 
 / /|  / /___/ /_/ /_____/ /_/ / /_/ /_____/ |/ / /  / /  
/_/ |_/_____/\____/      \____/\____/      |___/_/  /_/   
`

func printLogo(w io.Writer) {
	fmt.Fprint(w, logo)
	fmt.Fprintln(w)
	fmt.Fprintln(w)
	fmt.Fprintln(w)
}

func writeErr(w io.Writer, err error) {
	fmt.Fprintf(w, "Error: %s\n", err)
}