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client.go
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client.go
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// Package cdp for application layer communication with browser.
package cdp
import (
"context"
"encoding/json"
"sync"
"sync/atomic"
"github.com/yusufozturk/rod/lib/defaults"
"github.com/yusufozturk/rod/lib/utils"
)
// Request to send to browser
type Request struct {
ID int `json:"id"`
SessionID string `json:"sessionId,omitempty"`
Method string `json:"method"`
Params interface{} `json:"params,omitempty"`
}
// Response from browser
type Response struct {
ID int `json:"id"`
Result json.RawMessage `json:"result,omitempty"`
Error *Error `json:"error,omitempty"`
}
// Event from browser
type Event struct {
SessionID string `json:"sessionId,omitempty"`
Method string `json:"method"`
Params json.RawMessage `json:"params,omitempty"`
}
// WebSocketable enables you to choose the websocket lib you want to use.
// Such as you can easily wrap gorilla/websocket and use it as the transport layer.
type WebSocketable interface {
// Send text message only
Send([]byte) error
// Read returns text message only
Read() ([]byte, error)
}
// Client is a devtools protocol connection instance.
type Client struct {
ws WebSocketable
pending sync.Map // pending requests
event chan *Event // events from browser
count uint64
logger utils.Logger
}
// New creates a cdp connection, all messages from Client.Event must be received or they will block the client.
func New() *Client {
return &Client{
event: make(chan *Event),
logger: defaults.CDP,
}
}
// Logger sets the logger to log all the requests, responses, and events transferred between Rod and the browser.
// The default format for each type is in file format.go
func (cdp *Client) Logger(l utils.Logger) *Client {
cdp.logger = l
return cdp
}
// Start to browser
func (cdp *Client) Start(ws WebSocketable) *Client {
cdp.ws = ws
go cdp.consumeMessages()
return cdp
}
type result struct {
msg json.RawMessage
err error
}
// Call a method and wait for its response
func (cdp *Client) Call(ctx context.Context, sessionID, method string, params interface{}) ([]byte, error) {
req := &Request{
ID: int(atomic.AddUint64(&cdp.count, 1)),
SessionID: sessionID,
Method: method,
Params: params,
}
cdp.logger.Println(req)
data, err := json.Marshal(req)
utils.E(err)
done := make(chan result)
once := sync.Once{}
cdp.pending.Store(req.ID, func(res result) {
once.Do(func() {
select {
case <-ctx.Done():
case done <- res:
}
})
})
defer cdp.pending.Delete(req.ID)
err = cdp.ws.Send(data)
if err != nil {
return nil, err
}
select {
case <-ctx.Done():
return nil, ctx.Err()
case res := <-done:
return res.msg, res.err
}
}
// Event returns a channel that will emit browser devtools protocol events. Must be consumed or will block producer.
func (cdp *Client) Event() <-chan *Event {
return cdp.event
}
// Consume messages coming from the browser via the websocket.
func (cdp *Client) consumeMessages() {
defer close(cdp.event)
for {
data, err := cdp.ws.Read()
if err != nil {
cdp.pending.Range(func(_, val interface{}) bool {
val.(func(result))(result{err: err})
return true
})
return
}
var id struct {
ID int `json:"id"`
}
err = json.Unmarshal(data, &id)
utils.E(err)
if id.ID == 0 {
var evt Event
err := json.Unmarshal(data, &evt)
utils.E(err)
cdp.logger.Println(&evt)
cdp.event <- &evt
continue
}
var res Response
err = json.Unmarshal(data, &res)
utils.E(err)
cdp.logger.Println(&res)
val, ok := cdp.pending.Load(id.ID)
if !ok {
continue
}
if res.Error == nil {
val.(func(result))(result{res.Result, nil})
} else {
val.(func(result))(result{nil, res.Error})
}
}
}