nim-typeImportC-macro

import macros

proc newWhenUseWinSdkTypedef(name, importc, header, typ: NimNode): NimNode =
  var whenStmt = newNimNode(nnkWhenStmt)
  var useWinSdkBranch = newNimNode(nnkElifBranch)
  var useWinSdkCond = newNimNode(nnkCall)
  useWinSdkCond.add(newIdentNode(!"defined"), newIdentNode(!"useWinSdk"))
  useWinSdkBranch.add(useWinSdkCond)
  var winSdkTypeSec = newNimNode(nnkTypeSection)
  var winSdkTypeDef = newNimNode(nnkTypeDef)
  winSdkTypeDef.add(name)
  var winSdkTypePragma = newNimNode(nnkPragma)
  winSdkTypePragma.add(newColonExpr(newIdentNode(!"importC"), importc))
  winSdkTypePragma.add(newColonExpr(newIdentNode(!"header"), header))
  winSdkTypeDef.add(winSdkTypePragma)
  winSdkTypeDef.add(typ)
  winSdkTypeSec.add(winSdkTypeDef)
  useWinSdkBranch.add(winSdkTypeSec)
  whenStmt.add(useWinSdkBranch)
  var elseBranch = newNimNode(nnkElse)
  var elseTypeSec = newNimNode(nnkTypeSection)
  var elseTypeDef = newNimNode(nnkTypeDef)
  elseTypeDef.add(name, newEmptyNode(), typ)
  elseTypeSec.add(elseTypeDef)
  elseBranch.add(elseTypeSec)
  whenStmt.add(elseBranch)
  result = whenStmt
  echo repr result

macro typedefImportCObject*(name: untyped, importc, header: string, typ, reclist: untyped): typed =
  echo treerepr reclist
  assert(typ.kind == nnkObjectTy)
  var typCpy = copyNimNode(typ)
  var reclistNode = newNimNode(nnkRecList)
  reclistNode.add(reclist)
  typCpy.add(reclistNode)
  newWhenUseWinSdkTypedef(name, importc, header, typCpy)

when isMainModule:
  dumpTree:
    f1: int32
  typedefImportCObject(NimType, "ImportedType", "header.h", object):
    f1: int32
  var x: NimType
  x = 42

# dumpTree produces:
# StmtList
#   Call
#     Ident !"f1"
#     StmtList
#       Ident !"int32"

# macro produces:
# when defined(useWinSdk):
#   type
#     NimType {.importC: "ImportedType", header: "header.h".} = object
#         f1(
#           int32)
#
# else:
#   type
#     NimType = object
#         f1(
#           int32)