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// The transmission package provides a Go-native interface for communicating
// with the Transmission RPC interface.
package transmission
import (
"bytes"
"encoding/json"
"io"
"log/slog"
"math/rand"
"net/http"
"strconv"
)
type CallArguments interface {
CallTorrentGetArguments | interface{}
}
// The base struct for a Transmission client to perform RPC calls with.
type Client struct {
Hostname string
Port int
Username string
Password string
httpClient http.Client
sessionId string
}
// Call a given method on the Transmission RPC interface, and pass it the given arguments in JSON.
func (this *Client) Call(method string, arguments CallArguments, tag uint, response interface{}) error {
// Create HTTP client to work with
httpClient := http.Client{}
// Create the Request object
req, _ := this.makeRequest(method, arguments, tag)
slog.Debug("Sending request", "address", req.URL.String(), "session-id", this.sessionId, "tag", tag)
res, err := httpClient.Do(req)
if err != nil {
return err
}
// Read the response
body, err := io.ReadAll(res.Body)
if err != nil {
return err
}
defer res.Body.Close()
slog.Debug("Got response", "status", res.StatusCode, "body", body, "tag", tag)
// Check if we're missing the session-id
if res.StatusCode == 409 {
slog.Debug("Got new session-id", "tag", tag)
this.sessionId = res.Header["X-Transmission-Session-Id"][0]
return this.Call(method, arguments, tag, response)
}
// Unmarshal it into the response
json.Unmarshal(body, &response)
// Return the response
return nil
}
// Convenience function to generate the URL to post RPC calls to.
func (this *Client) connectionString() string {
url := "http://" + this.Hostname
if this.Port != 0 {
url += ":" + strconv.Itoa(this.Port)
} else {
url += ":9091"
}
url += "/transmission/rpc"
return url
}
// makeRequest provides a convenience function to make a new http.Request
// object. It sets the URL, headers, and body of the request.
func (this *Client) makeRequest(method string, arguments CallArguments, tag uint) (*http.Request, error) {
body, _ := json.Marshal(map[string]interface{}{
"method": method,
"arguments": arguments,
"tag": tag,
})
slog.Debug("Making request", "body", body, "tag", tag)
req, err := http.NewRequest("POST", this.connectionString(), bytes.NewBuffer([]byte(body)))
if err != nil {
return nil, err
}
if this.Username != "" {
slog.Debug("Adding Authorization header", "tag", tag)
req.SetBasicAuth(this.Username, this.Password)
}
req.Header.Add("X-Transmission-Session-Id", this.sessionId)
return req, nil
}
// Generate a tag ID. Since the maximum value is not documented, this allows
// for easy bug-fixing later in life.
func (this *Client) makeTag() uint {
return uint(rand.Uint32())
}
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