path: root/rpc/json.go

// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package rpc

import (
    "bytes"
    "encoding/json"
    "fmt"
    "io"
    "reflect"
    "strconv"
    "strings"
    "sync"

    "github.com/dexon-foundation/dexon/log"
)

const (
    jsonrpcVersion           = "2.0"
    serviceMethodSeparator   = "_"
    subscribeMethodSuffix    = "_subscribe"
    unsubscribeMethodSuffix  = "_unsubscribe"
    notificationMethodSuffix = "_subscription"
)

type jsonRequest struct {
    Method  string          `json:"method"`
    Version string          `json:"jsonrpc"`
    Id      json.RawMessage `json:"id,omitempty"`
    Payload json.RawMessage `json:"params,omitempty"`
}

type jsonSuccessResponse struct {
    Version string      `json:"jsonrpc"`
    Id      interface{} `json:"id,omitempty"`
    Result  interface{} `json:"result"`
}

type jsonError struct {
    Code    int         `json:"code"`
    Message string      `json:"message"`
    Data    interface{} `json:"data,omitempty"`
}

type jsonErrResponse struct {
    Version string      `json:"jsonrpc"`
    Id      interface{} `json:"id,omitempty"`
    Error   jsonError   `json:"error"`
}

type jsonSubscription struct {
    Subscription string      `json:"subscription"`
    Result       interface{} `json:"result,omitempty"`
}

type jsonNotification struct {
    Version string           `json:"jsonrpc"`
    Method  string           `json:"method"`
    Params  jsonSubscription `json:"params"`
}

// jsonCodec reads and writes JSON-RPC messages to the underlying connection. It
// also has support for parsing arguments and serializing (result) objects.
type jsonCodec struct {
    closer sync.Once                 // close closed channel once
    closed chan interface{}          // closed on Close
    decMu  sync.Mutex                // guards the decoder
    decode func(v interface{}) error // decoder to allow multiple transports
    encMu  sync.Mutex                // guards the encoder
    encode func(v interface{}) error // encoder to allow multiple transports
    rw     io.ReadWriteCloser        // connection
}

func (err *jsonError) Error() string {
    if err.Message == "" {
        return fmt.Sprintf("json-rpc error %d", err.Code)
    }
    return err.Message
}

func (err *jsonError) ErrorCode() int {
    return err.Code
}

// NewCodec creates a new RPC server codec with support for JSON-RPC 2.0 based
// on explicitly given encoding and decoding methods.
func NewCodec(rwc io.ReadWriteCloser, encode, decode func(v interface{}) error) ServerCodec {
    return &jsonCodec{
        closed: make(chan interface{}),
        encode: encode,
        decode: decode,
        rw:     rwc,
    }
}

// NewJSONCodec creates a new RPC server codec with support for JSON-RPC 2.0.
func NewJSONCodec(rwc io.ReadWriteCloser) ServerCodec {
    enc := json.NewEncoder(rwc)
    dec := json.NewDecoder(rwc)
    dec.UseNumber()

    return &jsonCodec{
        closed: make(chan interface{}),
        encode: enc.Encode,
        decode: dec.Decode,
        rw:     rwc,
    }
}

// isBatch returns true when the first non-whitespace characters is '['
func isBatch(msg json.RawMessage) bool {
    for _, c := range msg {
        // skip insignificant whitespace (http://www.ietf.org/rfc/rfc4627.txt)
        if c == 0x20 || c == 0x09 || c == 0x0a || c == 0x0d {
            continue
        }
        return c == '['
    }
    return false
}

// ReadRequestHeaders will read new requests without parsing the arguments. It will
// return a collection of requests, an indication if these requests are in batch
// form or an error when the incoming message could not be read/parsed.
func (c *jsonCodec) ReadRequestHeaders() ([]rpcRequest, bool, Error) {
    c.decMu.Lock()
    defer c.decMu.Unlock()

    var incomingMsg json.RawMessage
    if err := c.decode(&incomingMsg); err != nil {
        return nil, false, &invalidRequestError{err.Error()}
    }
    if isBatch(incomingMsg) {
        return parseBatchRequest(incomingMsg)
    }
    return parseRequest(incomingMsg)
}

// checkReqId returns an error when the given reqId isn't valid for RPC method calls.
// valid id's are strings, numbers or null
func checkReqId(reqId json.RawMessage) error {
    if len(reqId) == 0 {
        return fmt.Errorf("missing request id")
    }
    if _, err := strconv.ParseFloat(string(reqId), 64); err == nil {
        return nil
    }
    var str string
    if err := json.Unmarshal(reqId, &str); err == nil {
        return nil
    }
    return fmt.Errorf("invalid request id")
}

// parseRequest will parse a single request from the given RawMessage. It will return
// the parsed request, an indication if the request was a batch or an error when
// the request could not be parsed.
func parseRequest(incomingMsg json.RawMessage) ([]rpcRequest, bool, Error) {
    var in jsonRequest
    if err := json.Unmarshal(incomingMsg, &in); err != nil {
        return nil, false, &invalidMessageError{err.Error()}
    }

    if err := checkReqId(in.Id); err != nil {
        return nil, false, &invalidMessageError{err.Error()}
    }

    // subscribe are special, they will always use `subscribeMethod` as first param in the payload
    if strings.HasSuffix(in.Method, subscribeMethodSuffix) {
        reqs := []rpcRequest{{id: &in.Id, isPubSub: true}}
        if len(in.Payload) > 0 {
            // first param must be subscription name
            var subscribeMethod [1]string
            if err := json.Unmarshal(in.Payload, &subscribeMethod); err != nil {
                log.Debug(fmt.Sprintf("Unable to parse subscription method: %v\n", err))
                return nil, false, &invalidRequestError{"Unable to parse subscription request"}
            }

            reqs[0].service, reqs[0].method = strings.TrimSuffix(in.Method, subscribeMethodSuffix), subscribeMethod[0]
            reqs[0].params = in.Payload
            return reqs, false, nil
        }
        return nil, false, &invalidRequestError{"Unable to parse subscription request"}
    }

    if strings.HasSuffix(in.Method, unsubscribeMethodSuffix) {
        return []rpcRequest{{id: &in.Id, isPubSub: true,
            method: in.Method, params: in.Payload}}, false, nil
    }

    elems := strings.Split(in.Method, serviceMethodSeparator)
    if len(elems) != 2 {
        return nil, false, &methodNotFoundError{in.Method, ""}
    }

    // regular RPC call
    if len(in.Payload) == 0 {
        return []rpcRequest{{service: elems[0], method: elems[1], id: &in.Id}}, false, nil
    }

    return []rpcRequest{{service: elems[0], method: elems[1], id: &in.Id, params: in.Payload}}, false, nil
}

// parseBatchRequest will parse a batch request into a collection of requests from the given RawMessage, an indication
// if the request was a batch or an error when the request could not be read.
func parseBatchRequest(incomingMsg json.RawMessage) ([]rpcRequest, bool, Error) {
    var in []jsonRequest
    if err := json.Unmarshal(incomingMsg, &in); err != nil {
        return nil, false, &invalidMessageError{err.Error()}
    }

    requests := make([]rpcRequest, len(in))
    for i, r := range in {
        if err := checkReqId(r.Id); err != nil {
            return nil, false, &invalidMessageError{err.Error()}
        }

        id := &in[i].Id

        // subscribe are special, they will always use `subscriptionMethod` as first param in the payload
        if strings.HasSuffix(r.Method, subscribeMethodSuffix) {
            requests[i] = rpcRequest{id: id, isPubSub: true}
            if len(r.Payload) > 0 {
                // first param must be subscription name
                var subscribeMethod [1]string
                if err := json.Unmarshal(r.Payload, &subscribeMethod); err != nil {
                    log.Debug(fmt.Sprintf("Unable to parse subscription method: %v\n", err))
                    return nil, false, &invalidRequestError{"Unable to parse subscription request"}
                }

                requests[i].service, requests[i].method = strings.TrimSuffix(r.Method, subscribeMethodSuffix), subscribeMethod[0]
                requests[i].params = r.Payload
                continue
            }

            return nil, true, &invalidRequestError{"Unable to parse (un)subscribe request arguments"}
        }

        if strings.HasSuffix(r.Method, unsubscribeMethodSuffix) {
            requests[i] = rpcRequest{id: id, isPubSub: true, method: r.Method, params: r.Payload}
            continue
        }

        if len(r.Payload) == 0 {
            requests[i] = rpcRequest{id: id, params: nil}
        } else {
            requests[i] = rpcRequest{id: id, params: r.Payload}
        }
        if elem := strings.Split(r.Method, serviceMethodSeparator); len(elem) == 2 {
            requests[i].service, requests[i].method = elem[0], elem[1]
        } else {
            requests[i].err = &methodNotFoundError{r.Method, ""}
        }
    }

    return requests, true, nil
}

// ParseRequestArguments tries to parse the given params (json.RawMessage) with the given
// types. It returns the parsed values or an error when the parsing failed.
func (c *jsonCodec) ParseRequestArguments(argTypes []reflect.Type, params interface{}) ([]reflect.Value, Error) {
    if args, ok := params.(json.RawMessage); !ok {
        return nil, &invalidParamsError{"Invalid params supplied"}
    } else {
        return parsePositionalArguments(args, argTypes)
    }
}

// parsePositionalArguments tries to parse the given args to an array of values with the
// given types. It returns the parsed values or an error when the args could not be
// parsed. Missing optional arguments are returned as reflect.Zero values.
func parsePositionalArguments(rawArgs json.RawMessage, types []reflect.Type) ([]reflect.Value, Error) {
    // Read beginning of the args array.
    dec := json.NewDecoder(bytes.NewReader(rawArgs))
    if tok, _ := dec.Token(); tok != json.Delim('[') {
        return nil, &invalidParamsError{"non-array args"}
    }
    // Read args.
    args := make([]reflect.Value, 0, len(types))
    for i := 0; dec.More(); i++ {
        if i >= len(types) {
            return nil, &invalidParamsError{fmt.Sprintf("too many arguments, want at most %d", len(types))}
        }
        argval := reflect.New(types[i])
        if err := dec.Decode(argval.Interface()); err != nil {
            return nil, &invalidParamsError{fmt.Sprintf("invalid argument %d: %v", i, err)}
        }
        if argval.IsNil() && types[i].Kind() != reflect.Ptr {
            return nil, &invalidParamsError{fmt.Sprintf("missing value for required argument %d", i)}
        }
        args = append(args, argval.Elem())
    }
    // Read end of args array.
    if _, err := dec.Token(); err != nil {
        return nil, &invalidParamsError{err.Error()}
    }
    // Set any missing args to nil.
    for i := len(args); i < len(types); i++ {
        if types[i].Kind() != reflect.Ptr {
            return nil, &invalidParamsError{fmt.Sprintf("missing value for required argument %d", i)}
        }
        args = append(args, reflect.Zero(types[i]))
    }
    return args, nil
}

// CreateResponse will create a JSON-RPC success response with the given id and reply as result.
func (c *jsonCodec) CreateResponse(id interface{}, reply interface{}) interface{} {
    return &jsonSuccessResponse{Version: jsonrpcVersion, Id: id, Result: reply}
}

// CreateErrorResponse will create a JSON-RPC error response with the given id and error.
func (c *jsonCodec) CreateErrorResponse(id interface{}, err Error) interface{} {
    return &jsonErrResponse{Version: jsonrpcVersion, Id: id, Error: jsonError{Code: err.ErrorCode(), Message: err.Error()}}
}

// CreateErrorResponseWithInfo will create a JSON-RPC error response with the given id and error.
// info is optional and contains additional information about the error. When an empty string is passed it is ignored.
func (c *jsonCodec) CreateErrorResponseWithInfo(id interface{}, err Error, info interface{}) interface{} {
    return &jsonErrResponse{Version: jsonrpcVersion, Id: id,
        Error: jsonError{Code: err.ErrorCode(), Message: err.Error(), Data: info}}
}

// CreateNotification will create a JSON-RPC notification with the given subscription id and event as params.
func (c *jsonCodec) CreateNotification(subid, namespace string, event interface{}) interface{} {
    return &jsonNotification{Version: jsonrpcVersion, Method: namespace + notificationMethodSuffix,
        Params: jsonSubscription{Subscription: subid, Result: event}}
}

// Write message to client
func (c *jsonCodec) Write(res interface{}) error {
    c.encMu.Lock()
    defer c.encMu.Unlock()

    return c.encode(res)
}

// Close the underlying connection
func (c *jsonCodec) Close() {
    c.closer.Do(func() {
        close(c.closed)
        c.rw.Close()
    })
}

// Closed returns a channel which will be closed when Close is called
func (c *jsonCodec) Closed() <-chan interface{} {
    return c.closed
}