Refactor preferredContentType proc & add tests

Fix of the following bug:
In case of multiple accept headers with same preference
`preferredContentType` used to select the first match within content types
provided by the application. For example, if user specifies accept headers
`application/octet-stream, application/json` and application provides
`application/json, application/octet-stream`, `application/octet-stream`
will be returned, and that is a bug.

Now the procedure returns the most suitable match according
to the application preferences.

chronos/apps/http/httpserver.nim

@@ -488,7 +488,7 @@ proc preferredContentMediaType*(acceptHeader: string): MediaType =
       MediaType.init("*", "*")
 
 proc preferredContentType*(acceptHeader: string,
-                       types: openArray[string] = []): Result[string, cstring] =
+                           types: varargs[MediaType]): Result[MediaType, cstring] =
   ## Match or obtain preferred content-type using ``Accept`` header specified by
   ## string ``acceptHeader``.
   ##
@@ -505,18 +505,18 @@ proc preferredContentType*(acceptHeader: string,
   if len(types) == 0:
     if len(acceptHeader) == 0:
       # If `Accept` header is missing, return `*/*`.
-      ok("*/*")
+      ok(wildCardMediaType)
     else:
       let res = getAcceptInfo(acceptHeader)
       if res.isErr():
         # If `Accept` header is incorrect, client accepts any type of content.
-        ok("*/*")
+        ok(wildCardMediaType)
       else:
         let mediaTypes = res.get().data
         if len(mediaTypes) > 0:
-          ok($mediaTypes[0].mediaType)
+          ok(mediaTypes[0].mediaType)
         else:
-          ok("*/*")
+          ok(wildCardMediaType)
   else:
     if len(acceptHeader) == 0:
       # If `Accept` header is missing, client accepts any type of content.
@@ -527,17 +527,7 @@ proc preferredContentType*(acceptHeader: string,
         # If `Accept` header is incorrect, client accepts any type of content.
         ok(types[0])
       else:
-        let mediaTypes =
+        selectContentType(ares.get().data, types)
-          block:
-            var res: seq[MediaType]
-            for item in types:
-              res.add(MediaType.init(item))
-            res
-        for item in ares.get().data:
-          for expect in mediaTypes:
-            if expect == item.mediaType:
-              return ok($expect)
-        err("Preferred content type not found")
 
 proc preferredContentMediaType*(request: HttpRequestRef): MediaType =
   ## Returns preferred content-type using ``Accept`` header specified by
@@ -545,7 +535,7 @@ proc preferredContentMediaType*(request: HttpRequestRef): MediaType =
   preferredContentMediaType(request.headers.getString(AcceptHeaderName))
 
 proc preferredContentType*(request: HttpRequestRef,
-                           types: varargs[string]): Result[string, cstring] =
+                           types: varargs[MediaType]): Result[MediaType, cstring] =
   ## Match or obtain preferred content-type using ``Accept`` header specified by
   ## client in request ``request``.
   preferredContentType(request.headers.getString(AcceptHeaderName), types)

tests/testhttpserver.nim

@@ -856,6 +856,12 @@ suite "HTTP server testing suite":
       check toString(table) == vector[2]
 
   test "Preferred Accept handling test":
+    const
+      jsonMediaType = MediaType.init("application/json")
+      sszMediaType = MediaType.init("application/octet-stream")
+      plainTextMediaType = MediaType.init("text/plain")
+      imageMediaType = MediaType.init("image/jpg")
+
     proc createRequest(acceptHeader: string): HttpRequestRef =
       let headers = HttpTable.init([("accept", acceptHeader)])
       HttpRequestRef(headers: headers)
@@ -863,49 +869,305 @@ suite "HTTP server testing suite":
     proc createRequest(): HttpRequestRef =
       HttpRequestRef(headers: HttpTable.init())
 
-    var requests = @[
+    var singleHeader = @[
       (
-        createRequest("application/json;q=0.9,application/octet-stream"),
+        createRequest("application/json"),
         @[
-          "application/octet-stream",
+          "application/json"
-          "application/octet-stream",
+        ]
+      )
+    ]
+
+    var complexHeaders = @[
+      (
+        createRequest(),
+        @[
+          "*/*",
+          "application/json",
           "application/octet-stream",
           "application/json",
+          "application/octet-stream",
+          "application/json",
+          "image/jpg"
         ]
       ),
       (
         createRequest(""),
         @[
           "*/*",
-          "*/*",
+          "application/json",
+          "application/octet-stream",
+          "application/json",
+          "application/octet-stream",
+          "application/json",
+          "image/jpg"
+        ]
+      ),
+      (
+        createRequest("application/json, application/octet-stream"),
+        @[
+          "application/json",
+          "application/json",
+          "application/octet-stream",
+          "application/json",
+          "application/octet-stream",
           "application/json",
           "application/json"
         ]
       ),
       (
-        createRequest(),
+        createRequest("application/octet-stream, application/json"),
+        @[
+          "application/octet-stream",
+          "application/json",
+          "application/octet-stream",
+          "application/json",
+          "application/octet-stream",
+          "application/json",
+          "application/json"
+        ]
+      ),
+      (
+        createRequest("application/json;q=0.9, application/octet-stream"),
+        @[
+          "application/octet-stream",
+          "application/json",
+          "application/octet-stream",
+          "application/octet-stream",
+          "application/octet-stream",
+          "application/octet-stream",
+          "application/octet-stream"
+        ]
+      ),
+      (
+        createRequest("application/json, application/octet-stream;q=0.9"),
+        @[
+          "application/json",
+          "application/json",
+          "application/octet-stream",
+          "application/json",
+          "application/json",
+          "application/json",
+          "application/json"
+        ]
+      ),
+      (
+        createRequest("application/json;q=0.9, application/octet-stream;q=0.8"),
+        @[
+          "application/json",
+          "application/json",
+          "application/octet-stream",
+          "application/json",
+          "application/json",
+          "application/json",
+          "application/json"
+        ]
+      ),
+       (
+        createRequest("application/json;q=0.8, application/octet-stream;q=0.9"),
+        @[
+          "application/octet-stream",
+          "application/json",
+          "application/octet-stream",
+          "application/octet-stream",
+          "application/octet-stream",
+          "application/octet-stream",
+          "application/octet-stream"
+        ]
+      ),
+      (
+      createRequest("text/plain, application/octet-stream, application/json"),
+        @[
+          "text/plain",
+          "application/json",
+          "application/octet-stream",
+          "application/json",
+          "application/octet-stream",
+          "application/json",
+          "application/json"
+        ]
+      ),
+      (
+      createRequest("text/plain, application/json;q=0.8, application/octet-stream;q=0.8"),
+        @[
+          "text/plain",
+          "application/json",
+          "application/octet-stream",
+          "application/json",
+          "application/octet-stream",
+          "text/plain",
+          "text/plain"
+        ]
+      ),
+      (
+      createRequest("text/plain, application/json;q=0.8, application/octet-stream;q=0.5"),
+        @[
+          "text/plain",
+          "application/json",
+          "application/octet-stream",
+          "application/json",
+          "application/json",
+          "text/plain",
+          "text/plain"
+        ]
+      ),
+      (
+       createRequest("text/plain;q=0.8, application/json, application/octet-stream;q=0.8"),
+        @[
+          "application/json",
+          "application/json",
+          "application/octet-stream",
+          "application/json",
+          "application/json",
+          "application/json",
+          "application/json"
+        ]
+      ),
+      (
+      createRequest("text/*, application/json;q=0.8, application/octet-stream;q=0.8"),
+        @[
+          "text/*",
+          "application/json",
+          "application/octet-stream",
+          "application/json",
+          "application/octet-stream",
+          "text/plain",
+          "text/plain"
+        ]
+      ),
+      (
+      createRequest("text/*, application/json;q=0.8, application/octet-stream;q=0.5"),
+        @[
+          "text/*",
+          "application/json",
+          "application/octet-stream",
+          "application/json",
+          "application/json",
+          "text/plain",
+          "text/plain"
+        ]
+      ),
+      (createRequest("image/jpg, text/plain, application/octet-stream, application/json"),
+         @[
+            "image/jpg",
+            "application/json",
+            "application/octet-stream",
+            "application/json",
+            "application/octet-stream",
+            "application/json",
+            "image/jpg"
+           ]
+        ),
+        (createRequest("image/jpg;q=1, text/plain;q=0.2, application/octet-stream;q=0.2, application/json;q=0.2"),
+         @[
+            "image/jpg",
+            "application/json",
+            "application/octet-stream",
+            "application/json",
+            "application/octet-stream",
+            "application/json",
+            "image/jpg"
+           ]
+        ),
+      (
+      createRequest("*/*, application/json;q=0.8, application/octet-stream;q=0.5"),
         @[
           "*/*",
+          "application/json",
+          "application/octet-stream",
+          "application/json",
+          "application/octet-stream",
+          "application/json",
+          "image/jpg"
+        ]
+      ),
+      (
+        createRequest("*/*"),
+        @[
           "*/*",
           "application/json",
+          "application/octet-stream",
+          "application/json",
+          "application/octet-stream",
+          "application/json",
+          "image/jpg"
+        ]
+      ),
+      (
+        createRequest("application/*"),
+        @[
+          "application/*",
+          "application/json",
+          "application/octet-stream",
+          "application/json",
+          "application/octet-stream",
+          "application/json",
           "application/json"
         ]
       )
     ]
 
-    for req in requests:
+    for req in singleHeader:
-      check $req[0].preferredContentMediaType() == req[1][1]
+      check $req[0].preferredContentMediaType() == req[1][0]
       let r0 = req[0].preferredContentType()
-      let r1 = req[0].preferredContentType("application/json",
+      let r1 = req[0].preferredContentType(jsonMediaType)
-                                           "application/octet-stream")
+      let r2 = req[0].preferredContentType(sszMediaType)
-      let r2 = req[0].preferredContentType("application/json")
+      let r3 = req[0].preferredContentType(jsonMediaType,
+                                           sszMediaType)
+      let r4 = req[0].preferredContentType(sszMediaType,
+                                           jsonMediaType)
+      let r5 = req[0].preferredContentType(jsonMediaType,
+                                           sszMediaType,
+                                           plainTextMediaType)
+      let r6 = req[0].preferredContentType(imageMediaType,
+                                           jsonMediaType,
+                                           sszMediaType,
+                                           plainTextMediaType)
+      check:
+        r0.isOk() == true
+        r1.isOk() == true
+        r2.isErr() == true
+        r3.isOk() == true
+        r4.isOk() == true
+        r5.isOk() == true
+        r6.isOk() == true
+        r0.get() == MediaType.init(req[1][0])
+        r1.get() == MediaType.init(req[1][0])
+        r3.get() == MediaType.init(req[1][0])
+        r4.get() == MediaType.init(req[1][0])
+        r5.get() == MediaType.init(req[1][0])
+        r6.get() == MediaType.init(req[1][0])
+
+    for req in complexHeaders:
+      let r0 = req[0].preferredContentType()
+      let r1 = req[0].preferredContentType(jsonMediaType)
+      let r2 = req[0].preferredContentType(sszMediaType)
+      let r3 = req[0].preferredContentType(jsonMediaType,
+                                           sszMediaType)
+      let r4 = req[0].preferredContentType(sszMediaType,
+                                           jsonMediaType)
+      let r5 = req[0].preferredContentType(jsonMediaType,
+                                           sszMediaType,
+                                           plainTextMediaType)
+      let r6 = req[0].preferredContentType(imageMediaType,
+                                           jsonMediaType,
+                                           sszMediaType,
+                                           plainTextMediaType)
       check:
         r0.isOk() == true
         r1.isOk() == true
         r2.isOk() == true
-        r0.get() == req[1][0]
+        r3.isOk() == true
-        r1.get() == req[1][2]
+        r4.isOk() == true
-        r2.get() == req[1][3]
+        r5.isOk() == true
+        r6.isOk() == true
+        r0.get() == MediaType.init(req[1][0])
+        r1.get() == MediaType.init(req[1][1])
+        r2.get() == MediaType.init(req[1][2])
+        r3.get() == MediaType.init(req[1][3])
+        r4.get() == MediaType.init(req[1][4])
+        r5.get() == MediaType.init(req[1][5])
+        r6.get() == MediaType.init(req[1][6])
 
   test "SSE server-side events stream test":
     proc testPostMultipart2(address: TransportAddress): Future[bool] {.async.} =