Improve the way to send files (#25)

channel_message.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"encoding/json"
 	"errors"
-	"io"
 	"net/http"
 	"net/url"
 	"strconv"
@@ -219,9 +218,11 @@ func WithEmbed(e *embed.Embed) MessageOption {
 }
 
 // WithFiles attach files to a message.
-func WithFiles(files ...File) MessageOption {
+func WithFiles(files ...*File) MessageOption {
 	return MessageOption(func(m *createMessage) {
-		m.files = files
+		for _, f := range files {
+			m.files = append(m.files, *f)
+		}
 	})
 }
 
@@ -281,13 +282,6 @@ func (cm *createMessage) json() ([]byte, error) {
 	return json.Marshal(cm)
 }
 
-// File is a file along with its name. It is used to send files
-// to channels with SendFiles.
-type File struct {
-	Name   string
-	Reader io.Reader
-}
-
 func (c *Client) sendMessage(ctx context.Context, channelID string, msg *createMessage) (*Message, error) {
 	if msg.Embed != nil && msg.Embed.Type == "" {
 		msg.Embed.Type = "rich"

examples/03.files/.gitignore

@@ -0,0 +1 @@
+03.files

examples/03.files/main.go

@@ -49,22 +49,17 @@ func main() {
 
 func (b *bot) onNewMessage(m *harmony.Message) {
 	if m.Content == "!file" {
-		f, err := os.Open("discord-gopher.png")
+		// Here, we demonstrate the FileFromDisk function to send a file present
+		// on the local filesystem. If the resource you want to send is a URL,
+		// use FileFromURL instead.
+		// If you already have your own reader, then FileFromReadCloser is the
+		// function you want to use.
+		file, err := harmony.FileFromDisk("discord-gopher.png", "zob")
 		if err != nil {
 			log.Println(err)
 			return
 		}
 
-		file := harmony.File{
-			// Setting a valid extension type here,
-			// such as "png", will allow Discord
-			// applications to display the files
-			// inline, instead of asking users
-			// to download them.
-			Name:   "discord-gopher.png",
-			Reader: f,
-		}
-
 		if _, err = b.client.Channel(m.ChannelID).Send(context.Background(), harmony.WithFiles(file)); err != nil {
 			log.Println(err)
 		}

file.go

@@ -0,0 +1,85 @@
+package harmony
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"path"
+)
+
+// File represents a file that can be sent with Send and the WithFiles option.
+type File struct {
+	name   string
+	reader io.ReadCloser
+}
+
+// FileFromReadCloser returns a File given a ReadCloser and a name.
+// If the name ends with a valid extension recognized by Discord's
+// client applications, the file will be displayed inline in the channel
+// instead of asking users to manually download it.
+func FileFromReadCloser(r io.ReadCloser, name string) *File {
+	return &File{
+		name:   name,
+		reader: r,
+	}
+}
+
+// FileFromDisk returns a File from a local, on disk file.
+// If name is left empty, it will default to the name of the
+// file on disk.
+// Note that since Send is responsible for closing files opened
+// by FileFromDisk, calling this function and *not* calling Send
+// after can lead to resource leaks.
+func FileFromDisk(filepath, name string) (*File, error) {
+	f, err := os.Open(filepath)
+	if err != nil {
+		return nil, err
+	}
+
+	if name == "" {
+		name = path.Base(filepath)
+	}
+
+	return FileFromReadCloser(f, name), nil
+}
+
+// FileFromURL returns a File from a remote HTTP resource.
+// If the name is left empty, it will default to the name of
+// the file specified in the URL.
+// Note that since Send is responsible for closing files opened
+// by FileFromURL, calling this function and *not* calling Send
+// after can lead to resource leaks.
+func FileFromURL(url, name string) (*File, error) {
+	resp, err := http.Get(url)
+	if err != nil {
+		return nil, err
+	}
+
+	ct := resp.Header.Get("Content-Type")
+	if !stringsContains(supportedContentTypes, ct) {
+		return nil, fmt.Errorf("unsupported Content-Type: %q", ct)
+	}
+
+	if name == "" {
+		name = path.Base(url)
+	}
+
+	return FileFromReadCloser(resp.Body, name), nil
+}
+
+var supportedContentTypes = []string{
+	"image/png",
+	"image/gif",
+	"image/jpeg",
+	"video/mp4",
+}
+
+func stringsContains(stack []string, needle string) bool {
+	for _, hay := range stack {
+		if needle == hay {
+			return true
+		}
+	}
+	return false
+}

multipart_upload.go

@@ -17,8 +17,8 @@ type multipartPayload interface {
 // It returns the raw generated body along a header with the proper Content-Type value set.
 func multipartFromFiles(payload multipartPayload, files ...File) ([]byte, http.Header, error) {
 	// Underlying buffer the multipart body will be written to.
-	var b bytes.Buffer
-	w := multipart.NewWriter(&b)
+	var buf bytes.Buffer
+	w := multipart.NewWriter(&buf)
 
 	// Send the endpoint parameters as JSON in a the "payload_json" part.
 	h := textproto.MIMEHeader{}
@@ -29,17 +29,17 @@ func multipartFromFiles(payload multipartPayload, files ...File) ([]byte, http.H
 		return nil, nil, err
 	}
 
-	bytes, err := payload.json()
+	b, err := payload.json()
 	if err != nil {
 		return nil, nil, err
 	}
-	if _, err = pw.Write(bytes); err != nil {
+	if _, err = pw.Write(b); err != nil {
 		return nil, nil, err
 	}
 
 	// Create a new part for each file.
 	for i, f := range files {
-		cd := fmt.Sprintf(`form-data; name="file%d"; filename="%s"`, i, f.Name)
+		cd := fmt.Sprintf(`form-data; name="file%d"; filename="%s"`, i, f.name)
 
 		h = textproto.MIMEHeader{}
 		h.Set("Content-Disposition", cd)
@@ -50,7 +50,11 @@ func multipartFromFiles(payload multipartPayload, files ...File) ([]byte, http.H
 			return nil, nil, err
 		}
 
-		if _, err = io.Copy(pw, f.Reader); err != nil {
+		if _, err = io.Copy(pw, f.reader); err != nil {
+			return nil, nil, err
+		}
+
+		if err = f.reader.Close(); err != nil {
 			return nil, nil, err
 		}
 	}
@@ -61,5 +65,5 @@ func multipartFromFiles(payload multipartPayload, files ...File) ([]byte, http.H
 
 	header := http.Header{}
 	header.Set("Content-Type", w.FormDataContentType())
-	return b.Bytes(), header, nil
+	return buf.Bytes(), header, nil
 }