package types

import (
	"fmt"
	"math/big"
	"os"
	"time"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/core"
	"github.com/ethereum/go-ethereum/core/vm"
	"github.com/ethereum/go-ethereum/params"
)

const (
	TracerAccessList = "access_list"
	TracerJSON       = "json"
	TracerStruct     = "struct"
	TracerMarkdown   = "markdown"
)

// NewTracer creates a new Logger tracer to collect execution traces from an
// EVM transaction.
func NewTracer(tracer string, msg core.Message, cfg *params.ChainConfig, height int64) vm.Tracer {
	// TODO: enable additional log configuration
	logCfg := &vm.LogConfig{
		Debug: true,
	}

	switch tracer {
	case TracerAccessList:
		precompiles := vm.ActivePrecompiles(cfg.Rules(big.NewInt(height)))
		return vm.NewAccessListTracer(msg.AccessList(), msg.From(), *msg.To(), precompiles)
	case TracerJSON:
		return vm.NewJSONLogger(logCfg, os.Stderr)
	case TracerMarkdown:
		return vm.NewMarkdownLogger(logCfg, os.Stdout) // TODO: Stderr ?
	case TracerStruct:
		return vm.NewStructLogger(logCfg)
	default:
		return NewNoOpTracer()
	}
}

// TxTraceTask represents a single transaction trace task when an entire block
// is being traced.
type TxTraceTask struct {
	Index int // Transaction offset in the block
}

// TxTraceResult is the result of a single transaction trace during a block trace.
type TxTraceResult struct {
	Result interface{} `json:"result,omitempty"` // Trace results produced by the tracer
	Error  string      `json:"error,omitempty"`  // Trace failure produced by the tracer
}

// ExecutionResult groups all structured logs emitted by the EVM
// while replaying a transaction in debug mode as well as transaction
// execution status, the amount of gas used and the return value
type ExecutionResult struct {
	Gas         uint64         `json:"gas"`
	Failed      bool           `json:"failed"`
	ReturnValue string         `json:"returnValue"`
	StructLogs  []StructLogRes `json:"structLogs"`
}

// StructLogRes stores a structured log emitted by the EVM while replaying a
// transaction in debug mode. Taken from go-ethereum
type StructLogRes struct {
	Pc      uint64             `json:"pc"`
	Op      string             `json:"op"`
	Gas     uint64             `json:"gas"`
	GasCost uint64             `json:"gasCost"`
	Depth   int                `json:"depth"`
	Error   string             `json:"error,omitempty"`
	Stack   *[]string          `json:"stack,omitempty"`
	Memory  *[]string          `json:"memory,omitempty"`
	Storage *map[string]string `json:"storage,omitempty"`
}

// FormatLogs formats EVM returned structured logs for json output
func FormatLogs(logs []vm.StructLog) []StructLogRes {
	formatted := make([]StructLogRes, len(logs))
	for index, trace := range logs {
		formatted[index] = StructLogRes{
			Pc:      trace.Pc,
			Op:      trace.Op.String(),
			Gas:     trace.Gas,
			GasCost: trace.GasCost,
			Depth:   trace.Depth,
			Error:   trace.ErrorString(),
		}

		if trace.Stack != nil {
			stack := make([]string, len(trace.Stack))
			for i, stackValue := range trace.Stack {
				stack[i] = fmt.Sprintf("%x", stackValue)
			}
			formatted[index].Stack = &stack
		}

		if trace.Memory != nil {
			memory := make([]string, 0, (len(trace.Memory)+31)/32)
			for i := 0; i+32 <= len(trace.Memory); i += 32 {
				memory = append(memory, fmt.Sprintf("%x", trace.Memory[i:i+32]))
			}
			formatted[index].Memory = &memory
		}

		if trace.Storage != nil {
			storage := make(map[string]string)
			for i, storageValue := range trace.Storage {
				storage[fmt.Sprintf("%x", i)] = fmt.Sprintf("%x", storageValue)
			}
			formatted[index].Storage = &storage
		}
	}
	return formatted
}

var _ vm.Tracer = &NoOpTracer{}

// NoOpTracer is an empty implementation of vm.Tracer interface
type NoOpTracer struct{}

// NewNoOpTracer creates a no-op vm.Tracer
func NewNoOpTracer() *NoOpTracer {
	return &NoOpTracer{}
}

// CaptureStart implements vm.Tracer interface
func (dt NoOpTracer) CaptureStart(
	env *vm.EVM,
	from, to common.Address,
	create bool,
	input []byte,
	gas uint64,
	value *big.Int,
) {
}

// CaptureEnter implements vm.Tracer interface
func (dt NoOpTracer) CaptureEnter(
	typ vm.OpCode,
	from common.Address,
	to common.Address,
	input []byte,
	gas uint64,
	value *big.Int,
) {
}

// CaptureExit implements vm.Tracer interface
func (dt NoOpTracer) CaptureExit(output []byte, gasUsed uint64, err error) {}

// CaptureState implements vm.Tracer interface
func (dt NoOpTracer) CaptureState(
	env *vm.EVM,
	pc uint64,
	op vm.OpCode,
	gas, cost uint64,
	scope *vm.ScopeContext,
	rData []byte,
	depth int,
	err error,
) {
}

// CaptureFault implements vm.Tracer interface
func (dt NoOpTracer) CaptureFault(
	env *vm.EVM,
	pc uint64,
	op vm.OpCode,
	gas, cost uint64,
	scope *vm.ScopeContext,
	depth int,
	err error,
) {
}

// CaptureEnd implements vm.Tracer interface
func (dt NoOpTracer) CaptureEnd(
	output []byte,
	gasUsed uint64,
	t time.Duration,
	err error,
) {
}