feat: SEO field types and the complete SEO tab

classes/image.go

@@ -0,0 +1,123 @@
+package classes
+
+import (
+	"bytes"
+	"context"
+	"crypto/rand"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"path"
+	"regexp"
+	"strings"
+
+	"git.golem15.com/golem15/summercms/modules/backpack"
+	"git.golem15.com/golem15/summercms/modules/bouncer"
+	"git.golem15.com/golem15/summercms/modules/cabana"
+	"git.golem15.com/golem15/summercms/modules/lagoon/attach"
+	"git.golem15.com/golem15/summercms/modules/pact"
+	"gocloud.dev/blob"
+)
+
+// ImageFolder is the media folder social images are stored in.
+const ImageFolder = "media/seo"
+
+// ImageMaxBytes caps a social image upload (10 MiB, as the media library).
+const ImageMaxBytes = 10 << 20
+
+// The phrase keys of the image refusals.
+const (
+	errImageInvalid   = "golem15.seo::lang.image.invalid"
+	errImageTooBig    = "golem15.seo::lang.image.too_big"
+	errImageURL       = "golem15.seo::lang.image.url_invalid"
+	errImageForbidden = "golem15.seo::lang.image.forbidden"
+)
+
+// imageExtensions maps the sniffed image types to their file extensions.
+var imageExtensions = map[string]string{
+	"image/jpeg": "jpg",
+	"image/png":  "png",
+	"image/gif":  "gif",
+	"image/webp": "webp",
+}
+
+var unsafeNameChars = regexp.MustCompile(`[^a-z0-9._-]+`)
+
+// safeImageName is the stored base name: lowercased, characters outside
+// a-z, 0-9, '.', '_' and '-' turned into '-', at most 80 characters, with
+// the sniffed extension.
+func safeImageName(filename, ext string) string {
+	base := path.Base(strings.ReplaceAll(filename, `\`, "/"))
+	base = strings.TrimSuffix(base, path.Ext(base))
+	base = strings.Trim(unsafeNameChars.ReplaceAllString(strings.ToLower(base), "-"), "-.")
+	if base == "" {
+		base = "image"
+	}
+	if len(base) > 80 {
+		base = base[:80]
+	}
+	return base + "." + ext
+}
+
+// UploadImage is the seoimage field type's Upload (D-100, P-16): the
+// administrator needs golem15.seo.manage; the first bytes must sniff as a
+// JPEG, PNG, GIF or WebP image; the file is stored in the media bucket
+// under media/seo/<random>-<safe name> (a name that is safe to leave behind
+// when the save never happens) and its public URL is returned.
+func UploadImage(app func() *backpack.App, permission string) func(context.Context, pact.FormFieldUpload) (pact.FormFieldUploadResult, error) {
+	return func(ctx context.Context, in pact.FormFieldUpload) (pact.FormFieldUploadResult, error) {
+		if p, ok := bouncer.User(ctx); !ok || !cabana.Allows(p, []string{permission}) {
+			return pact.FormFieldUploadResult{}, &pact.FormFieldError{Messages: []string{errImageForbidden}}
+		}
+		var a *backpack.App
+		if app != nil {
+			a = app()
+		}
+		if a == nil {
+			return pact.FormFieldUploadResult{}, errors.New("golem15.seo: image upload: application is not configured")
+		}
+		bucket, ok := a.Lookup[*blob.Bucket]()
+		if !ok || bucket == nil {
+			return pact.FormFieldUploadResult{}, errors.New("golem15.seo: image upload: media bucket is not configured")
+		}
+		if in.Body == nil {
+			return pact.FormFieldUploadResult{}, &pact.FormFieldError{Messages: []string{errImageInvalid}}
+		}
+		data, err := io.ReadAll(io.LimitReader(in.Body, ImageMaxBytes+1))
+		if err != nil {
+			return pact.FormFieldUploadResult{}, fmt.Errorf("golem15.seo: image upload: read: %w", err)
+		}
+		if len(data) > ImageMaxBytes {
+			return pact.FormFieldUploadResult{}, &pact.FormFieldError{Messages: []string{errImageTooBig}}
+		}
+		ext, known := imageExtensions[http.DetectContentType(data)]
+		if !known {
+			return pact.FormFieldUploadResult{}, &pact.FormFieldError{Messages: []string{errImageInvalid}}
+		}
+		random := make([]byte, 6)
+		if _, err := rand.Read(random); err != nil {
+			return pact.FormFieldUploadResult{}, err
+		}
+		key := ImageFolder + "/" + hex.EncodeToString(random) + "-" + safeImageName(in.Filename, ext)
+		w, err := bucket.NewWriter(ctx, key, &blob.WriterOptions{IfNotExist: true, ContentType: "image/" + strings.Replace(ext, "jpg", "jpeg", 1)})
+		if err != nil {
+			return pact.FormFieldUploadResult{}, fmt.Errorf("golem15.seo: image writer: %w", err)
+		}
+		if _, err := io.Copy(w, bytes.NewReader(data)); err != nil {
+			_ = w.Close()
+			return pact.FormFieldUploadResult{}, fmt.Errorf("golem15.seo: write image: %w", err)
+		}
+		if err := w.Close(); err != nil {
+			return pact.FormFieldUploadResult{}, fmt.Errorf("golem15.seo: close image: %w", err)
+		}
+		return pact.FormFieldUploadResult{URL: attach.PublicURL(key)}, nil
+	}
+}
+
+// ValidImageURL reports whether a stored social image value is empty, a
+// path or an absolute http(s) URL.
+func ValidImageURL(v string) bool {
+	return v == "" || ValidURLRef(v)
+}