From 80ebc5b419238aa2a87fda9bd0889112de36d97c Mon Sep 17 00:00:00 2001
From: Zahary Karadjov <zahary@gmail.com>
Date: Thu, 6 Jan 2022 20:20:20 +0200
Subject: [PATCH] Allow the 'api' macro to be used in generic functions

---
 presto/macrocommon.nim | 49 ++++++++++++++++++++++++++----------------
 presto/route.nim       |  5 ++---
 tests/testroute.nim    | 21 +++++++++++++++++-
 3 files changed, 53 insertions(+), 22 deletions(-)

diff --git a/presto/macrocommon.nim b/presto/macrocommon.nim
index 62e2f21..437d2b0 100644
--- a/presto/macrocommon.nim
+++ b/presto/macrocommon.nim
@@ -35,7 +35,7 @@ proc makeProcName*(m, s: string): string =
 
 proc getRestReturnType*(params: NimNode): NimNode =
   if not(isNil(params)) and (len(params) > 0) and not(isNil(params[0])) and
-     (params[0].kind == nnkIdent):
+     (params[0].kind in {nnkIdent, nnkSym}):
     params[0]
   else:
     nil
@@ -47,40 +47,53 @@ iterator paramsIter*(params: NimNode): tuple[name, ntype: NimNode] =
     for j in 0 ..< arg.len-2:
       yield (arg[j], argType)
 
-proc isSimpleType*(typeNode: NimNode): bool =
-  typeNode.kind == nnkIdent
+proc isKnownType*(typeNode: NimNode, typeNames: varargs[string]): bool =
+  typeNode.kind in {nnkIdent, nnkSym} and
+  $typeNode in typeNames
+
+proc isBracketExpr(n: NimNode, nodes: varargs[string]): bool =
+  let leadingIdx = if n.kind == nnkBracketExpr:
+    0
+  elif n.kind == nnkCall and
+       n[0].kind in {nnkOpenSymChoice, nnkClosedSymChoice} and
+       n[0].len > 0 and
+       $n[0][0] == "[]":
+    1
+  else:
+    return false
+
+  for idx, types in nodes:
+    let actualIdx = leadingIdx + idx
+    if actualIdx > n.len:
+      return false
+    if not isKnownType(n[actualIdx], types.split("|")):
+      return false
+
+  return true
 
 proc isOptionalArg*(typeNode: NimNode): bool =
-  (typeNode.kind == nnkBracketExpr) and (typeNode[0].kind == nnkIdent) and
-    (typeNode[0].strVal == "Option")
+  typeNode.isBracketExpr "Option"
 
 proc isBytesArg*(typeNode: NimNode): bool =
-  (typeNode.kind == nnkBracketExpr) and (typeNode[0].kind == nnkIdent) and
-    (typeNode[0].strVal == "seq") and (typeNode[1].kind == nnkIdent) and
-    ((typeNode[1].strVal == "byte") or (typeNode[1].strVal == "uint8"))
+  typeNode.isBracketExpr("seq", "byte|uint8")
 
 proc isSequenceArg*(typeNode: NimNode): bool =
-  (typeNode.kind == nnkBracketExpr) and (typeNode[0].kind == nnkIdent) and
-    (typeNode[0].strVal == "seq")
+  typeNode.isBracketExpr("seq")
 
 proc isContentBodyArg*(typeNode: NimNode): bool =
-  (typeNode.kind == nnkBracketExpr) and (typeNode[0].kind == nnkIdent) and
-    (typeNode[0].strVal == "Option") and (typeNode[1].kind == nnkIdent) and
-    (typeNode[1].strVal == "ContentBody")
+  typeNode.isBracketExpr("Option", "ContentBody")
 
 proc isResponseArg*(typeNode: NimNode): bool =
-  (typeNode.kind == nnkIdent) and (typeNode.strVal == "HttpResponseRef")
+  typeNode.isKnownType "HttpResponseRef"
 
 proc getSequenceType*(typeNode: NimNode): NimNode =
-  if (typeNode.kind == nnkBracketExpr) and (typeNode[0].kind == nnkIdent) and
-     (typeNode[0].strVal == "seq"):
+  if typeNode.isBracketExpr("seq"):
     typeNode[1]
   else:
     nil
 
 proc getOptionType*(typeNode: NimNode): NimNode =
-  if (typeNode.kind == nnkBracketExpr) and (typeNode[0].kind == nnkIdent) and
-     (typeNode[0].strVal == "Option"):
+  if typeNode.isBracketExpr("Option"):
     typeNode[1]
   else:
     nil
diff --git a/presto/route.nim b/presto/route.nim
index 465b715..afdd3a3 100644
--- a/presto/route.nim
+++ b/presto/route.nim
@@ -210,8 +210,7 @@ proc processApiCall(router: NimNode, meth: HttpMethod,
       for paramName, paramType in parameters.paramsIter():
         let index = patterns.find($paramName)
         if isPathArg(paramType):
-          if isSimpleType(paramType) and
-             (paramType.strVal == "HttpResponseRef"):
+          if paramType.isKnownType("HttpResponseRef"):
             if isNil(respRes):
               respRes = paramName
             else:
@@ -257,7 +256,7 @@ proc processApiCall(router: NimNode, meth: HttpMethod,
     error("Return value must not be empty and equal to [RestApiResponse]",
            parameters)
   else:
-    if returnType.strVal != "RestApiResponse":
+    if not returnType.isKnownType("RestApiResponse"):
       error("Return value must be equal to [RestApiResponse]", returnType)
 
   # "path" (required) arguments unmarshalling code.
diff --git a/tests/testroute.nim b/tests/testroute.nim
index 63ce181..bfb7724 100644
--- a/tests/testroute.nim
+++ b/tests/testroute.nim
@@ -1,4 +1,4 @@
-import std/[unittest, strutils, parseutils]
+import std/[unittest, strutils, parseutils, typetraits]
 import helpers
 import chronos, chronos/apps
 import stew/byteutils
@@ -151,6 +151,25 @@ suite "REST API router & macro tests":
       r2.kind == RestApiResponseKind.Content
       bytesToString(r2.content.data) == "ok-2"
 
+  test "Routes installation from generic proc":
+    proc addGenericRoute(router: var RestRouter, T: type) =
+      const typeName = typetraits.name(T)
+      router.api(MethodGet, "/test/" & typeName) do () -> RestApiResponse:
+        return RestApiResponse.response(typeName, contentType = "text/plain")
+
+    var router = RestRouter.init(testValidate)
+    router.addGenericRoute(string)
+    router.addGenericRoute(int)
+
+    let r1 = router.sendMockRequest(MethodGet, "http://l.to/test/string")
+    let r2 = router.sendMockRequest(MethodGet, "http://l.to/test/int")
+    
+    check:
+      r1.kind == RestApiResponseKind.Content
+      r2.kind == RestApiResponseKind.Content
+      bytesToString(r1.content.data) == "string"
+      bytesToString(r2.content.data) == "int"
+
   test "Custom types as parameters test":
     var router = RestRouter.init(testValidate)
     router.api(MethodPost,