package jail

import (
	"encoding/json"
	"errors"
	"fmt"
	"strings"
	"sync"

	"github.com/robertkrimen/otto"
	web3js "github.com/status-im/go-web3js"
	"github.com/status-im/status-go/rpc"
)

const (
	web3InstanceCode = `
		var Web3 = require('web3');
		var web3 = new Web3(jeth);
		var Bignumber = require("bignumber.js");
		function bn(val) {
			return new Bignumber(val);
		}
	`
	// EmptyResponse is returned when cell is successfully created and initialized
	// but no additional JS was provided to the initialization method.
	EmptyResponse = `{"result": ""}`
	undefinedText = "undefined"
)

var (
	// ErrNoRPCClient is returned when an RPC client is required but it's nil.
	ErrNoRPCClient = errors.New("RPC client is not available")
)

// RPCClientProvider is an interface that provides a way
// to obtain an rpc.Client.
type RPCClientProvider interface {
	RPCClient() *rpc.Client
}

// Jail manages multiple JavaScript execution contexts (JavaScript VMs) called cells.
// Each cell is a separate VM with web3.js set up.
//
// As rpc.Client might not be available during Jail initialization,
// a provider function is used.
type Jail struct {
	rpcClientProvider RPCClientProvider
	baseJS            string
	cellsMx           sync.RWMutex
	cells             map[string]*Cell
}

// New returns a new Jail.
func New(provider RPCClientProvider) *Jail {
	return NewWithBaseJS(provider, "")
}

// NewWithBaseJS returns a new Jail with base JS configured.
func NewWithBaseJS(provider RPCClientProvider, code string) *Jail {
	return &Jail{
		rpcClientProvider: provider,
		baseJS:            code,
		cells:             make(map[string]*Cell),
	}
}

// SetBaseJS sets initial JavaScript code loaded to each new cell.
func (j *Jail) SetBaseJS(js string) {
	j.baseJS = js
}

// Stop stops jail and all assosiacted cells.
func (j *Jail) Stop() {
	j.cellsMx.Lock()
	defer j.cellsMx.Unlock()

	for _, cell := range j.cells {
		cell.Stop() //nolint: errcheck
	}

	// TODO(tiabc): Move this initialisation to a proper place.
	j.cells = make(map[string]*Cell)
}

// obtainCell returns an existing cell for given ID or
// creates a new one if it does not exist.
// Passing in true as a second argument will cause a non-nil error if the
// cell already exists.
func (j *Jail) obtainCell(chatID string, expectNew bool) (cell *Cell, err error) {
	j.cellsMx.Lock()
	defer j.cellsMx.Unlock()

	var ok bool

	if cell, ok = j.cells[chatID]; ok {
		// Return a non-nil error if a new cell was expected
		if expectNew {
			err = fmt.Errorf("cell with id '%s' already exists", chatID)
		}
		return
	}

	cell, err = NewCell(chatID)
	if err != nil {
		return
	}

	j.cells[chatID] = cell

	return cell, nil
}

// CreateCell creates a new cell. It returns an error
// if a cell with a given ID already exists.
func (j *Jail) CreateCell(chatID string) (JSCell, error) {
	return j.obtainCell(chatID, true)
}

// initCell initializes a cell with default JavaScript handlers and user code.
func (j *Jail) initCell(cell *Cell) error {
	// Register objects being a bridge between Go and JavaScript.
	if err := registerWeb3Provider(j, cell); err != nil {
		return err
	}

	if err := registerStatusSignals(cell); err != nil {
		return err
	}

	// Run some initial JS code to provide some global objects.
	c := []string{
		j.baseJS,
		string(web3js.Web3CODE),
		web3InstanceCode,
	}

	_, err := cell.Run(strings.Join(c, ";"))
	return err
}

// CreateAndInitCell creates and initializes a new Cell.
func (j *Jail) createAndInitCell(chatID string, extraCode ...string) (*Cell, string, error) {
	cell, err := j.obtainCell(chatID, false)
	if err != nil {
		return nil, "", err
	}

	if err := j.initCell(cell); err != nil {
		return nil, "", err
	}

	response := EmptyResponse

	if len(extraCode) > 0 {
		result, err := cell.Run(strings.Join(extraCode, ";"))
		if err != nil {
			return nil, "", err
		}

		response = newJailResultResponse(formatOttoValue(result.Value()))
	}

	return cell, response, nil
}

// CreateAndInitCell creates and initializes new Cell.
func (j *Jail) CreateAndInitCell(chatID string, code ...string) string {
	_, result, err := j.createAndInitCell(chatID, code...)
	if err != nil {
		return newJailErrorResponse(err)
	}

	return result
}

// Parse creates a new jail cell context, with the given chatID as identifier.
// New context executes provided JavaScript code, right after the initialization.
// DEPRECATED in favour of CreateAndInitCell.
func (j *Jail) Parse(chatID, code string) string {
	cell, err := j.cell(chatID)
	result := EmptyResponse
	if err != nil {
		// cell does not exist, so create and init it
		cell, result, err = j.createAndInitCell(chatID, code)
	} else {
		// cell already exists, so just reinit it
		err = j.initCell(cell)
	}

	if err != nil {
		return newJailErrorResponse(err)
	}

	if _, err = cell.Run(code); err != nil {
		return newJailErrorResponse(err)
	}

	return result
}

func (j *Jail) cell(chatID string) (*Cell, error) {
	j.cellsMx.RLock()
	defer j.cellsMx.RUnlock()

	cell, ok := j.cells[chatID]
	if !ok {
		return nil, fmt.Errorf("cell '%s' not found", chatID)
	}

	return cell, nil
}

// Cell returns a cell by chatID. If it does not exist, error is returned.
// Required by the Backend.
func (j *Jail) Cell(chatID string) (JSCell, error) {
	return j.cell(chatID)
}

// Execute allows to run arbitrary JS code within a cell.
func (j *Jail) Execute(chatID, code string) string {
	cell, err := j.cell(chatID)
	if err != nil {
		return newJailErrorResponse(err)
	}

	value, err := cell.Run(code)
	if err != nil {
		return newJailErrorResponse(err)
	}

	return value.Value().String()
}

// Call executes the `call` function within a cell with chatID.
// Returns a string being a valid JS code. In case of a successful result,
// it's {"result": any}. In case of an error: {"error": "some error"}.
//
// Call calls commands from `_status_catalog`.
// commandPath is an array of properties to retrieve a function.
// For instance:
//   `["prop1", "prop2"]` is translated to `_status_catalog["prop1"]["prop2"]`.
func (j *Jail) Call(chatID, commandPath, args string) string {
	cell, err := j.cell(chatID)
	if err != nil {
		return newJailErrorResponse(err)
	}

	value, err := cell.Call("call", nil, commandPath, args)
	if err != nil {
		return newJailErrorResponse(err)
	}

	return newJailResultResponse(value.Value())
}

// RPCClient returns an rpc.Client.
func (j *Jail) RPCClient() *rpc.Client {
	if j.rpcClientProvider == nil {
		return nil
	}

	return j.rpcClientProvider.RPCClient()
}

// sendRPCCall executes a raw JSON-RPC request.
func (j *Jail) sendRPCCall(request string) (interface{}, error) {
	client := j.RPCClient()
	if client == nil {
		return nil, ErrNoRPCClient
	}

	rawResponse := client.CallRaw(request)

	var response interface{}
	if err := json.Unmarshal([]byte(rawResponse), &response); err != nil {
		return nil, fmt.Errorf("failed to unmarshal response: %s", err)
	}

	return response, nil
}

// newJailErrorResponse returns an error.
func newJailErrorResponse(err error) string {
	response := struct {
		Error string `json:"error"`
	}{
		Error: err.Error(),
	}

	rawResponse, err := json.Marshal(response)
	if err != nil {
		return `{"error": "` + err.Error() + `"}`
	}

	return string(rawResponse)
}

// formatOttoValue : formats an otto value string to be processed as valid
// javascript code
func formatOttoValue(result otto.Value) otto.Value {
	val := result.String()
	if result.IsString() {
		if val != undefinedText {
			val = fmt.Sprintf(`"%s"`, strings.Replace(val, `"`, `\"`, -1))
			result, _ = otto.ToValue(val)
		}
	}
	return result
}

// newJailResultResponse returns a string that is a valid JavaScript code.
// Marshaling is not required as result.String() produces a string
// that is a valid JavaScript code.
func newJailResultResponse(value otto.Value) string {
	res := value.String()
	if res == undefinedText {
		res = "null"
	}
	return `{"result":` + res + `}`
}