Add simple route to get the preview image

modules/backend/src/main/scala/docspell/backend/ops/OItemSearch.scala

@@ -36,6 +36,11 @@ trait OItemSearch[F[_]] {
       collective: Ident
   ): F[Option[AttachmentArchiveData[F]]]
 
+  def findAttachmentPreview(
+      id: Ident,
+      collective: Ident
+  ): F[Option[AttachmentPreviewData[F]]]
+
   def findAttachmentMeta(id: Ident, collective: Ident): F[Option[RAttachmentMeta]]
 
   def findByFileCollective(checksum: String, collective: Ident): F[Vector[RItem]]
@@ -82,6 +87,15 @@ object OItemSearch {
     val fileId = rs.fileId
   }
 
+  case class AttachmentPreviewData[F[_]](
+      rs: RAttachmentPreview,
+      meta: FileMeta,
+      data: Stream[F, Byte]
+  ) extends BinaryData[F] {
+    val name   = rs.name
+    val fileId = rs.fileId
+  }
+
   case class AttachmentArchiveData[F[_]](
       rs: RAttachmentArchive,
       meta: FileMeta,
@@ -154,6 +168,26 @@ object OItemSearch {
               (None: Option[AttachmentSourceData[F]]).pure[F]
           })
 
+      def findAttachmentPreview(
+          id: Ident,
+          collective: Ident
+      ): F[Option[AttachmentPreviewData[F]]] =
+        store
+          .transact(RAttachmentPreview.findByIdAndCollective(id, collective))
+          .flatMap({
+            case Some(ra) =>
+              makeBinaryData(ra.fileId) { m =>
+                AttachmentPreviewData[F](
+                  ra,
+                  m,
+                  store.bitpeace.fetchData2(RangeDef.all)(Stream.emit(m))
+                )
+              }
+
+            case None =>
+              (None: Option[AttachmentPreviewData[F]]).pure[F]
+          })
+
       def findAttachmentArchive(
           id: Ident,
           collective: Ident

modules/restapi/src/main/resources/docspell-openapi.yml

@@ -2446,6 +2446,45 @@ paths:
               schema:
                 type: string
                 format: binary
+  /sec/attachment/{id}/preview:
+    head:
+      tags: [ Attachment ]
+      summary: Get a preview image of an attachment file.
+      description: |
+        Checks if an image file showing a preview of the attachment is
+        available. If not available, a 404 is returned.
+      security:
+        - authTokenHeader: []
+      parameters:
+        - $ref: "#/components/parameters/id"
+      responses:
+        200:
+          description: Ok
+        404:
+          description: NotFound
+    get:
+      tags: [ Attachment ]
+      summary: Get a preview image of an attachment file.
+      description: |
+        Gets a image file showing a preview of the attachment. Usually
+        it is a small image of the first page of the document.If not
+        available, a 404 is returned. However, if the query parameter
+        `withFallback` is `true`, a fallback preview image is
+        returned. You can also use the `HEAD` method to check for
+        existence.
+      security:
+        - authTokenHeader: []
+      parameters:
+        - $ref: "#/components/parameters/id"
+        - $ref: "#/components/parameters/withFallback"
+      responses:
+        200:
+          description: Ok
+          content:
+            application/octet-stream:
+              schema:
+                type: string
+                format: binary
   /sec/attachment/{id}/meta:
     get:
       tags: [ Attachment ]
@@ -4822,3 +4861,10 @@ components:
         One of the available contact kinds.
       schema:
         type: string
+    withFallback:
+      name: withFallback
+      in: query
+      description: Whether to provide a fallback or not.
+      required: false
+      schema:
+        type: boolean

modules/restserver/src/main/scala/docspell/restserver/routes/AttachmentRoutes.scala

@@ -117,6 +117,31 @@ object AttachmentRoutes {
               .getOrElse(NotFound(BasicResult(false, "Not found")))
         } yield resp
 
+      case req @ GET -> Root / Ident(id) / "preview" =>
+        for {
+          fileData <-
+            backend.itemSearch.findAttachmentPreview(id, user.account.collective)
+          inm     = req.headers.get(`If-None-Match`).flatMap(_.tags)
+          matches = matchETag(fileData.map(_.meta), inm)
+          resp <-
+            fileData
+              .map { data =>
+                if (matches) withResponseHeaders(NotModified())(data)
+                else makeByteResp(data)
+              }
+              .getOrElse(NotFound(BasicResult(false, "Not found")))
+        } yield resp
+
+      case HEAD -> Root / Ident(id) / "preview" =>
+        for {
+          fileData <-
+            backend.itemSearch.findAttachmentPreview(id, user.account.collective)
+          resp <-
+            fileData
+              .map(data => withResponseHeaders(Ok())(data))
+              .getOrElse(NotFound(BasicResult(false, "Not found")))
+        } yield resp
+
       case GET -> Root / Ident(id) / "view" =>
         // this route exists to provide a stable url
         // it redirects currently to viewerjs