Add post image upload backend (#11)

Adds bounded JPEG, PNG, and WebP processing, route-specific multipart limits, attachment mutation handling, and object cleanup on failed persistence or successful removal.

Reviewed-on: #11
Co-authored-by: codegirl-007 <s.raide@gmail.com>

internal/web/posts.go

@@ -12,6 +12,7 @@ import (
 	"time"
 
 	"github.com/go-chi/chi/v5"
+	"github.com/google/uuid"
 
 	"plumber/internal/mail"
 	"plumber/internal/store"
@@ -20,6 +21,11 @@ import (
 // handleCreatePost creates either a root question or a reply. Replies are
 // limited to the root author and admins, and cannot be added to hidden threads.
 func (s *Server) handleCreatePost(w http.ResponseWriter, r *http.Request) {
+	cleanup, ok := parsePostMutationForm(w, r)
+	if !ok {
+		return
+	}
+	defer cleanup()
 	if !s.requireCSRF(w, r) {
 		return
 	}
@@ -37,6 +43,7 @@ func (s *Server) handleCreatePost(w http.ResponseWriter, r *http.Request) {
 	}
 
 	post := &store.Post{
+		ID:       uuid.NewString(),
 		AuthorID: user.ID,
 		Body:     truncateRunes(body, 12000),
 	}
@@ -71,7 +78,14 @@ func (s *Server) handleCreatePost(w http.ResponseWriter, r *http.Request) {
 		root = threadRoot
 	}
 
+	images, newKeys, err := s.postImagesFromForm(r.Context(), r, post.ID, nil)
+	if err != nil {
+		writePostImageRequestError(w, err)
+		return
+	}
+	post.Images = images
 	if err := s.store.CreatePost(r.Context(), post); err != nil {
+		s.deletePostImageObjects(newKeys)
 		if errors.Is(err, store.ErrInvalidPost) {
 			http.Error(w, "invalid post", http.StatusBadRequest)
 			return
@@ -149,6 +163,11 @@ func (s *Server) notifyPostReply(
 // handleEditPost updates only a post's body after verifying that the current
 // homeowner owns it or that an admin is editing an admin-authored post.
 func (s *Server) handleEditPost(w http.ResponseWriter, r *http.Request) {
+	cleanup, ok := parsePostMutationForm(w, r)
+	if !ok {
+		return
+	}
+	defer cleanup()
 	if !s.requireCSRF(w, r) {
 		return
 	}
@@ -177,8 +196,16 @@ func (s *Server) handleEditPost(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "post body required", http.StatusBadRequest)
 		return
 	}
+	previousImages := append([]store.PostImage(nil), post.Images...)
+	images, newKeys, err := s.postImagesFromForm(r.Context(), r, post.ID, previousImages)
+	if err != nil {
+		writePostImageRequestError(w, err)
+		return
+	}
 	post.Body = truncateRunes(body, 12000)
+	post.Images = images
 	if err := s.store.UpdatePost(r.Context(), post); err != nil {
+		s.deletePostImageObjects(newKeys)
 		if errors.Is(err, store.ErrInvalidPost) {
 			http.Error(w, "invalid post", http.StatusBadRequest)
 			return
@@ -190,6 +217,7 @@ func (s *Server) handleEditPost(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "could not save post", http.StatusInternalServerError)
 		return
 	}
+	s.deletePostImageObjects(removedPostImageKeys(previousImages, images))
 	http.Redirect(
 		w,
 		r,