Add post image upload backend

2026-08-27 23:53:27 -07:00
parent 1840a662d9
commit 677e63329d
6 changed files with 884 additions and 1 deletions
@@ -0,0 +1,395 @@
+package web
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"image"
+	"image/jpeg"
+	"image/png"
+	"io"
+	"log"
+	"mime"
+	"mime/multipart"
+	"net/http"
+	"path"
+	"strings"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/rwcarlsen/goexif/exif"
+	"golang.org/x/image/draw"
+	_ "golang.org/x/image/webp"
+
+	"plumber/internal/blob"
+	"plumber/internal/store"
+)
+
+const (
+	defaultRequestBodyBytes  = 3 << 20
+	postImageMaxFileBytes    = 5 << 20
+	postImageMaxRequestBytes = 22 << 20
+	postImageMultipartMemory = 2 << 20
+	postImageMaxSourceDim    = 6000
+	postImageMaxSourcePixels = 16_000_000
+	postImageMaxRenderedDim  = 1600
+	postImageCleanupTimeout  = 10 * time.Second
+)
+
+func requestBodyLimit(r *http.Request) int64 {
+	if r.Method != http.MethodPost {
+		return defaultRequestBodyBytes
+	}
+	switch {
+	case r.URL.Path == "/submit", r.URL.Path == "/posts":
+		return postImageMaxRequestBytes
+	case strings.HasPrefix(r.URL.Path, "/posts/") && strings.HasSuffix(r.URL.Path, "/edit"):
+		return postImageMaxRequestBytes
+	default:
+		return defaultRequestBodyBytes
+	}
+}
+
+type postImageRequestError struct {
+	status  int
+	message string
+	cause   error
+}
+
+func (e *postImageRequestError) Error() string {
+	if e.cause == nil {
+		return e.message
+	}
+	return e.message + ": " + e.cause.Error()
+}
+
+func parsePostMutationForm(w http.ResponseWriter, r *http.Request) (func(), bool) {
+	contentType := r.Header.Get("Content-Type")
+	mediaType, _, err := mime.ParseMediaType(contentType)
+	if err != nil && strings.HasPrefix(strings.ToLower(contentType), "multipart/") {
+		http.Error(w, "Could not read image upload.", http.StatusBadRequest)
+		return func() {}, false
+	}
+	if mediaType != "multipart/form-data" {
+		if err := r.ParseForm(); err != nil {
+			writePostImageRequestError(w, err)
+			return func() {}, false
+		}
+		return func() {}, true
+	}
+	if err := r.ParseMultipartForm(postImageMultipartMemory); err != nil {
+		writePostImageRequestError(w, err)
+		return func() {}, false
+	}
+	cleanup := func() {
+		if r.MultipartForm != nil {
+			_ = r.MultipartForm.RemoveAll()
+		}
+	}
+	return cleanup, true
+}
+
+func writePostImageRequestError(w http.ResponseWriter, err error) {
+	var requestErr *postImageRequestError
+	if errors.As(err, &requestErr) {
+		http.Error(w, requestErr.message, requestErr.status)
+		return
+	}
+	var maxErr *http.MaxBytesError
+	if errors.As(err, &maxErr) {
+		http.Error(w, "Image upload is too large.", http.StatusRequestEntityTooLarge)
+		return
+	}
+	http.Error(w, "Could not read image upload.", http.StatusBadRequest)
+}
+
+func (s *Server) postImagesFromForm(
+	ctx context.Context,
+	r *http.Request,
+	postID string,
+	existing []store.PostImage,
+) ([]store.PostImage, []string, error) {
+	if r.MultipartForm == nil {
+		return append([]store.PostImage(nil), existing...), nil, nil
+	}
+	retained, err := retainedPostImages(r.MultipartForm, existing)
+	if err != nil {
+		return nil, nil, err
+	}
+	files := r.MultipartForm.File["images"]
+	descriptions := r.MultipartForm.Value["image_description"]
+	if len(descriptions) > len(files) {
+		return nil, nil, invalidPostImage("Image descriptions do not match selected images.", nil)
+	}
+	if len(retained)+len(files) > store.MaxPostImages {
+		return nil, nil, invalidPostImage("You can attach up to 4 images.", nil)
+	}
+	if len(files) > 0 && !s.cfg.Blob.Enabled() {
+		return nil, nil, &postImageRequestError{
+			status:  http.StatusServiceUnavailable,
+			message: "Image uploads are not configured on this server.",
+		}
+	}
+
+	images := append([]store.PostImage(nil), retained...)
+	newKeys := make([]string, 0, len(files))
+	for i, header := range files {
+		description := ""
+		if i < len(descriptions) {
+			description = strings.TrimSpace(descriptions[i])
+		}
+		if len([]rune(description)) > store.MaxImageDescriptionRunes {
+			s.deletePostImageObjects(newKeys)
+			return nil, nil, invalidPostImage("Image descriptions must be 500 characters or fewer.", nil)
+		}
+		prepared, err := preparePostImage(header)
+		if err != nil {
+			s.deletePostImageObjects(newKeys)
+			return nil, nil, err
+		}
+		imageID := uuid.NewString()
+		objectKey := path.Join("post-images", postID, imageID+prepared.extension)
+		publicURL, err := s.cfg.Blob.Upload(ctx, blob.FileUpload{
+			Key:         objectKey,
+			Body:        bytes.NewReader(prepared.body),
+			ContentType: prepared.contentType,
+			Size:        int64(len(prepared.body)),
+		})
+		if err != nil {
+			s.deletePostImageObjects(newKeys)
+			return nil, nil, &postImageRequestError{
+				status:  http.StatusServiceUnavailable,
+				message: "Could not upload image. Try again later.",
+				cause:   err,
+			}
+		}
+		newKeys = append(newKeys, objectKey)
+		images = append(images, store.PostImage{
+			ID:          imageID,
+			PostID:      postID,
+			ObjectKey:   objectKey,
+			PublicURL:   publicURL,
+			Description: description,
+			Width:       prepared.width,
+			Height:      prepared.height,
+		})
+	}
+	return images, newKeys, nil
+}
+
+func retainedPostImages(form *multipart.Form, existing []store.PostImage) ([]store.PostImage, error) {
+	byID := make(map[string]store.PostImage, len(existing))
+	for _, image := range existing {
+		byID[image.ID] = image
+	}
+	ids := form.Value["existing_image_id"]
+	descriptions := form.Value["existing_image_description"]
+	if len(descriptions) > len(ids) {
+		return nil, invalidPostImage("Existing image descriptions do not match the images.", nil)
+	}
+	seen := make(map[string]bool, len(ids))
+	retained := make([]store.PostImage, 0, len(ids))
+	for i, id := range ids {
+		id = strings.TrimSpace(id)
+		image, ok := byID[id]
+		if !ok || seen[id] {
+			return nil, invalidPostImage("An existing image selection is invalid.", nil)
+		}
+		seen[id] = true
+		if i < len(descriptions) {
+			image.Description = strings.TrimSpace(descriptions[i])
+		}
+		if len([]rune(image.Description)) > store.MaxImageDescriptionRunes {
+			return nil, invalidPostImage("Image descriptions must be 500 characters or fewer.", nil)
+		}
+		retained = append(retained, image)
+	}
+	return retained, nil
+}
+
+func invalidPostImage(message string, cause error) error {
+	return &postImageRequestError{status: http.StatusBadRequest, message: message, cause: cause}
+}
+
+type preparedPostImage struct {
+	body        []byte
+	extension   string
+	contentType string
+	width       int
+	height      int
+}
+
+func preparePostImage(header *multipart.FileHeader) (preparedPostImage, error) {
+	if header == nil {
+		return preparedPostImage{}, invalidPostImage("Select a valid image.", nil)
+	}
+	if header.Size > postImageMaxFileBytes {
+		return preparedPostImage{}, &postImageRequestError{
+			status:  http.StatusRequestEntityTooLarge,
+			message: "Each image must be 5 MB or smaller.",
+		}
+	}
+	file, err := header.Open()
+	if err != nil {
+		return preparedPostImage{}, invalidPostImage("Could not read image.", err)
+	}
+	defer file.Close()
+	raw, err := io.ReadAll(io.LimitReader(file, postImageMaxFileBytes+1))
+	if err != nil {
+		return preparedPostImage{}, invalidPostImage("Could not read image.", err)
+	}
+	if len(raw) == 0 {
+		return preparedPostImage{}, invalidPostImage("Images cannot be empty.", nil)
+	}
+	if int64(len(raw)) > postImageMaxFileBytes {
+		return preparedPostImage{}, &postImageRequestError{
+			status:  http.StatusRequestEntityTooLarge,
+			message: "Each image must be 5 MB or smaller.",
+		}
+	}
+	sniffed := http.DetectContentType(raw)
+	switch sniffed {
+	case "image/jpeg", "image/png", "image/webp":
+	default:
+		return preparedPostImage{}, invalidPostImage("Images must be JPEG, PNG, or WebP.", nil)
+	}
+	cfg, format, err := image.DecodeConfig(bytes.NewReader(raw))
+	if err != nil {
+		return preparedPostImage{}, invalidPostImage("Could not decode image.", err)
+	}
+	if cfg.Width <= 0 || cfg.Height <= 0 ||
+		cfg.Width > postImageMaxSourceDim || cfg.Height > postImageMaxSourceDim ||
+		int64(cfg.Width)*int64(cfg.Height) > postImageMaxSourcePixels {
+		return preparedPostImage{}, invalidPostImage("Image dimensions are too large.", nil)
+	}
+	decoded, decodedFormat, err := image.Decode(bytes.NewReader(raw))
+	if err != nil {
+		return preparedPostImage{}, invalidPostImage("Could not decode image.", err)
+	}
+	if format != "" {
+		decodedFormat = format
+	}
+	if sniffed == "image/jpeg" {
+		decoded = orientPostImage(decoded, jpegOrientation(raw))
+	}
+	decoded = fitPostImage(decoded, postImageMaxRenderedDim)
+
+	var out bytes.Buffer
+	result := preparedPostImage{}
+	switch decodedFormat {
+	case "jpeg":
+		if err := jpeg.Encode(&out, decoded, &jpeg.Options{Quality: 85}); err != nil {
+			return preparedPostImage{}, invalidPostImage("Could not encode image.", err)
+		}
+		result.extension = ".jpg"
+		result.contentType = "image/jpeg"
+	case "png", "webp":
+		if err := png.Encode(&out, decoded); err != nil {
+			return preparedPostImage{}, invalidPostImage("Could not encode image.", err)
+		}
+		result.extension = ".png"
+		result.contentType = "image/png"
+	default:
+		return preparedPostImage{}, invalidPostImage("Images must be JPEG, PNG, or WebP.", nil)
+	}
+	result.body = out.Bytes()
+	result.width = decoded.Bounds().Dx()
+	result.height = decoded.Bounds().Dy()
+	return result, nil
+}
+
+func jpegOrientation(raw []byte) int {
+	metadata, err := exif.Decode(bytes.NewReader(raw))
+	if err != nil {
+		return 1
+	}
+	tag, err := metadata.Get(exif.Orientation)
+	if err != nil {
+		return 1
+	}
+	orientation, err := tag.Int(0)
+	if err != nil || orientation < 1 || orientation > 8 {
+		return 1
+	}
+	return orientation
+}
+
+func orientPostImage(source image.Image, orientation int) image.Image {
+	if orientation <= 1 || orientation > 8 {
+		return source
+	}
+	bounds := source.Bounds()
+	width, height := bounds.Dx(), bounds.Dy()
+	targetWidth, targetHeight := width, height
+	if orientation >= 5 {
+		targetWidth, targetHeight = height, width
+	}
+	target := image.NewNRGBA(image.Rect(0, 0, targetWidth, targetHeight))
+	for y := 0; y < targetHeight; y++ {
+		for x := 0; x < targetWidth; x++ {
+			sourceX, sourceY := x, y
+			switch orientation {
+			case 2:
+				sourceX = width - 1 - x
+			case 3:
+				sourceX, sourceY = width-1-x, height-1-y
+			case 4:
+				sourceY = height - 1 - y
+			case 5:
+				sourceX, sourceY = y, x
+			case 6:
+				sourceX, sourceY = y, height-1-x
+			case 7:
+				sourceX, sourceY = width-1-y, height-1-x
+			case 8:
+				sourceX, sourceY = width-1-y, x
+			}
+			target.Set(x, y, source.At(bounds.Min.X+sourceX, bounds.Min.Y+sourceY))
+		}
+	}
+	return target
+}
+
+func fitPostImage(source image.Image, maxDimension int) image.Image {
+	bounds := source.Bounds()
+	width, height := bounds.Dx(), bounds.Dy()
+	if width <= maxDimension && height <= maxDimension {
+		return source
+	}
+	scale := float64(maxDimension) / float64(width)
+	if float64(height)*scale > float64(maxDimension) {
+		scale = float64(maxDimension) / float64(height)
+	}
+	targetWidth := max(1, int(float64(width)*scale))
+	targetHeight := max(1, int(float64(height)*scale))
+	target := image.NewNRGBA(image.Rect(0, 0, targetWidth, targetHeight))
+	draw.CatmullRom.Scale(target, target.Bounds(), source, bounds, draw.Over, nil)
+	return target
+}
+
+func (s *Server) deletePostImageObjects(keys []string) {
+	if len(keys) == 0 {
+		return
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), postImageCleanupTimeout)
+	defer cancel()
+	for _, key := range keys {
+		if err := s.cfg.Blob.Delete(ctx, key); err != nil {
+			log.Printf("delete post image %s: %v", key, err)
+		}
+	}
+}
+
+func removedPostImageKeys(before, after []store.PostImage) []string {
+	retained := make(map[string]bool, len(after))
+	for _, image := range after {
+		retained[image.ObjectKey] = true
+	}
+	var removed []string
+	for _, image := range before {
+		if !retained[image.ObjectKey] {
+			removed = append(removed, image.ObjectKey)
+		}
+	}
+	return removed
+}