Add file upload support for Discord

src/discord/rest.go

@@ -7,8 +7,10 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"mime/multipart"
 	"net/http"
 	"net/http/httputil"
+	"net/textproto"
 	"net/url"
 	"strconv"
 	"strings"
@@ -187,13 +189,15 @@ type CreateMessageRequest struct {
 	Content string `json:"content"`
 }
 
-func CreateMessage(ctx context.Context, channelID string, payloadJSON string) (*Message, error) {
+func CreateMessage(ctx context.Context, channelID string, payloadJSON string, files ...FileUpload) (*Message, error) {
 	const name = "Create Message"
 
+	contentType, body := makeNewMessageBody(payloadJSON, files)
+
 	path := fmt.Sprintf("/channels/%s/messages", channelID)
 	res, err := doWithRateLimiting(ctx, name, func(ctx context.Context) *http.Request {
-		req := makeRequest(ctx, http.MethodPost, path, []byte(payloadJSON))
-		req.Header.Add("Content-Type", "application/json")
+		req := makeRequest(ctx, http.MethodPost, path, body)
+		req.Header.Add("Content-Type", contentType)
 		return req
 	})
 	if err != nil {
@@ -568,6 +572,41 @@ func CreateInteractionResponse(ctx context.Context, interactionID, interactionTo
 	return nil
 }
 
+func EditOriginalInteractionResponse(ctx context.Context, interactionToken string, payloadJSON string, files ...FileUpload) (*Message, error) {
+	const name = "Edit Original Interaction Response"
+
+	contentType, body := makeNewMessageBody(payloadJSON, files)
+
+	path := fmt.Sprintf("/webhooks/%s/%s/messages/@original", config.Config.Discord.BotUserID, interactionToken)
+	res, err := doWithRateLimiting(ctx, name, func(ctx context.Context) *http.Request {
+		req := makeRequest(ctx, http.MethodPatch, path, body)
+		req.Header.Add("Content-Type", contentType)
+		return req
+	})
+	if err != nil {
+		return nil, err
+	}
+	defer res.Body.Close()
+
+	if res.StatusCode >= 400 {
+		logErrorResponse(ctx, name, res, "")
+		return nil, oops.New(nil, "received error from Discord")
+	}
+
+	bodyBytes, err := io.ReadAll(res.Body)
+	if err != nil {
+		panic(err)
+	}
+
+	var msg Message
+	err = json.Unmarshal(bodyBytes, &msg)
+	if err != nil {
+		return nil, oops.New(err, "failed to unmarshal Discord message")
+	}
+
+	return &msg, nil
+}
+
 func GetAuthorizeUrl(state string) string {
 	params := make(url.Values)
 	params.Set("response_type", "code")
@@ -578,6 +617,43 @@ func GetAuthorizeUrl(state string) string {
 	return fmt.Sprintf("https://discord.com/api/oauth2/authorize?%s", params.Encode())
 }
 
+type FileUpload struct {
+	Name string
+	Data []byte
+}
+
+func makeNewMessageBody(payloadJSON string, files []FileUpload) (contentType string, body []byte) {
+	if len(files) == 0 {
+		contentType = "application/json"
+		body = []byte(payloadJSON)
+	} else {
+		var bodyBuffer bytes.Buffer
+		w := multipart.NewWriter(&bodyBuffer)
+		contentType = w.FormDataContentType()
+
+		jsonHeader := textproto.MIMEHeader{}
+		jsonHeader.Set("Content-Disposition", `form-data; name="payload_json"`)
+		jsonHeader.Set("Content-Type", "application/json")
+		jsonWriter, _ := w.CreatePart(jsonHeader)
+		jsonWriter.Write([]byte(payloadJSON))
+
+		for _, f := range files {
+			formFile, _ := w.CreateFormFile("file", f.Name)
+			formFile.Write(f.Data)
+		}
+
+		w.Close()
+
+		body = bodyBuffer.Bytes()
+	}
+
+	if len(body) == 0 {
+		panic("somehow we generated an empty body for Discord")
+	}
+
+	return
+}
+
 func logErrorResponse(ctx context.Context, name string, res *http.Response, msg string) {
 	dump, err := httputil.DumpResponse(res, true)
 	if err != nil {