type VarKind = enum
  Local
  Global
  Threadvar
  Const
  AlwaysConst ## const even on C++

proc addVarHeader(builder: var Builder, kind: VarKind) =
  ## adds modifiers for given var kind:
  ## Local has no modifier
  ## Global has `static` modifier
  ## Const has `static NIM_CONST` modifier
  ## AlwaysConst has `static const` modifier (NIM_CONST is no-op on C++)
  ## Threadvar is unimplemented
  case kind
  of Local: discard
  of Global:
    builder.add("static ")
  of Const:
    builder.add("static NIM_CONST ")
  of AlwaysConst:
    builder.add("static const ")
  of Threadvar:
    doAssert false, "unimplemented"

proc addVar(builder: var Builder, kind: VarKind = Local, name: string, typ: Snippet, initializer: Snippet = "") =
  ## adds a variable declaration to the builder
  builder.addVarHeader(kind)
  builder.add(typ)
  builder.add(" ")
  builder.add(name)
  if initializer.len != 0:
    builder.add(" = ")
    builder.add(initializer)
  builder.addLineEnd(";")

template addVarWithType(builder: var Builder, kind: VarKind = Local, name: string, body: typed) =
  ## adds a variable declaration to the builder, with the `body` building the type
  builder.addVarHeader(kind)
  body
  builder.add(" ")
  builder.add(name)
  builder.addLineEnd(";")

template addVarWithInitializer(builder: var Builder, kind: VarKind = Local, name: string,
                               typ: Snippet, initializerBody: typed) =
  ## adds a variable declaration to the builder, with
  ## `initializerBody` building the initializer. initializer must be provided
  builder.addVarHeader(kind)
  builder.add(typ)
  builder.add(" ")
  builder.add(name)
  builder.add(" = ")
  initializerBody
  builder.addLineEnd(";")

template addVarWithTypeAndInitializer(builder: var Builder, kind: VarKind = Local, name: string,
                                      typeBody, initializerBody: typed) =
  ## adds a variable declaration to the builder, with `typeBody` building the type, and
  ## `initializerBody` building the initializer. initializer must be provided
  builder.addVarHeader(kind)
  typeBody
  builder.add(" ")
  builder.add(name)
  builder.add(" = ")
  initializerBody
  builder.addLineEnd(";")

proc addArrayVar(builder: var Builder, kind: VarKind = Local, name: string, elementType: Snippet, len: int, initializer: Snippet = "") =
  ## adds an array variable declaration to the builder
  builder.addVarHeader(kind)
  builder.add(elementType)
  builder.add(" ")
  builder.add(name)
  builder.add("[")
  builder.addIntValue(len)
  builder.add("]")
  if initializer.len != 0:
    builder.add(" = ")
    builder.add(initializer)
  builder.addLineEnd(";")

template addArrayVarWithInitializer(builder: var Builder, kind: VarKind = Local, name: string, elementType: Snippet, len: int, body: typed) =
  ## adds an array variable declaration to the builder with the initializer built according to `body`
  builder.addVarHeader(kind)
  builder.add(elementType)
  builder.add(" ")
  builder.add(name)
  builder.add("[")
  builder.addIntValue(len)
  builder.add("] = ")
  body
  builder.addLineEnd(";")

template addTypedef(builder: var Builder, name: string, typeBody: typed) =
  ## adds a typedef declaration to the builder with name `name` and type as
  ## built in `typeBody`
  builder.add("typedef ")
  typeBody
  builder.add(" ")
  builder.add(name)
  builder.addLineEnd(";")

proc addProcTypedef(builder: var Builder, callConv: TCallingConvention, name: string, rettype, params: Snippet) =
  builder.add("typedef ")
  builder.add(CallingConvToStr[callConv])
  builder.add("_PTR(")
  builder.add(rettype)
  builder.add(", ")
  builder.add(name)
  builder.add(")")
  builder.add(params)
  builder.addLineEnd(";")

template addArrayTypedef(builder: var Builder, name: string, len: BiggestInt, typeBody: typed) =
  ## adds an array typedef declaration to the builder with name `name`,
  ## length `len`, and element type as built in `typeBody`
  builder.add("typedef ")
  typeBody
  builder.add(" ")
  builder.add(name)
  builder.add("[")
  builder.addIntValue(len)
  builder.addLineEnd("];")

type
  StructInitializerKind = enum
    siOrderedStruct ## struct constructor, but without named fields on C
    siNamedStruct ## struct constructor, with named fields i.e. C99 designated initializer
    siArray ## array constructor
    siWrapper ## wrapper for a single field, generates it verbatim

  StructInitializer = object
    ## context for building struct initializers, i.e. `{ field1, field2 }`
    kind: StructInitializerKind
      ## if true, fields will not be named, instead values are placed in order
    needsComma: bool

proc initStructInitializer(builder: var Builder, kind: StructInitializerKind): StructInitializer =
  ## starts building a struct initializer, i.e. braced initializer list
  result = StructInitializer(kind: kind, needsComma: false)
  if kind != siWrapper:
    builder.add("{")

template addField(builder: var Builder, constr: var StructInitializer, name: string, valueBody: typed) =
  ## adds a field to a struct initializer, with the value built in `valueBody`
  if constr.needsComma:
    assert constr.kind != siWrapper, "wrapper constructor cannot have multiple fields"
    builder.add(", ")
  else:
    constr.needsComma = true
  case constr.kind
  of siArray, siWrapper:
    # no name, can just add value
    valueBody
  of siOrderedStruct:
    # no name, can just add value on C
    assert name.len != 0, "name has to be given for struct initializer field"
    valueBody
  of siNamedStruct:
    assert name.len != 0, "name has to be given for struct initializer field"
    builder.add(".")
    builder.add(name)
    builder.add(" = ")
    valueBody

proc finishStructInitializer(builder: var Builder, constr: StructInitializer) =
  ## finishes building a struct initializer
  if constr.kind != siWrapper:
    builder.add("}")

template addStructInitializer(builder: var Builder, constr: out StructInitializer, kind: StructInitializerKind, body: typed) =
  ## builds a struct initializer, i.e. `{ field1, field2 }`
  ## a `var StructInitializer` must be declared and passed as a parameter so
  ## that it can be used with `addField`
  constr = builder.initStructInitializer(kind)
  body
  builder.finishStructInitializer(constr)

proc addField(obj: var Builder; name, typ: Snippet; isFlexArray: bool = false; initializer: Snippet = "") =
  ## adds a field inside a struct/union type
  obj.add('\t')
  obj.add(typ)
  obj.add(" ")
  obj.add(name)
  if isFlexArray:
    obj.add("[SEQ_DECL_SIZE]")
  if initializer.len != 0:
    obj.add(initializer)
  obj.add(";\n")

proc addArrayField(obj: var Builder; name, elementType: Snippet; len: int; initializer: Snippet = "") =
  ## adds an array field inside a struct/union type
  obj.add('\t')
  obj.add(elementType)
  obj.add(" ")
  obj.add(name)
  obj.add("[")
  obj.addIntValue(len)
  obj.add("]")
  if initializer.len != 0:
    obj.add(initializer)
  obj.add(";\n")

proc addField(obj: var Builder; field: PSym; name, typ: Snippet; isFlexArray: bool = false; initializer: Snippet = "") =
  ## adds an field inside a struct/union type, based on an `skField` symbol
  obj.add('\t')
  if field.alignment > 0:
    obj.add("NIM_ALIGN(")
    obj.addIntValue(field.alignment)
    obj.add(") ")
  obj.add(typ)
  if sfNoalias in field.flags:
    obj.add(" NIM_NOALIAS")
  obj.add(" ")
  obj.add(name)
  if isFlexArray:
    obj.add("[SEQ_DECL_SIZE]")
  if field.bitsize != 0:
    obj.add(":")
    obj.addIntValue(field.bitsize)
  if initializer.len != 0:
    obj.add(initializer)
  obj.add(";\n")

proc addProcField(obj: var Builder, callConv: TCallingConvention, name: string, rettype, params: Snippet) =
  obj.add(CallingConvToStr[callConv])
  obj.add("_PTR(")
  obj.add(rettype)
  obj.add(", ")
  obj.add(name)
  obj.add(")")
  obj.add(params)
  obj.add(";\n")

type
  BaseClassKind = enum
    ## denotes how and whether or not the base class/RTTI should be stored
    bcNone, bcCppInherit, bcSupField, bcNoneRtti, bcNoneTinyRtti
  StructBuilderInfo = object
    ## context for building `struct` types
    baseKind: BaseClassKind
    named: bool
    preFieldsLen: int

proc structOrUnion(t: PType): Snippet =
  let t = t.skipTypes({tyAlias, tySink})
  if tfUnion in t.flags: "union"
  else: "struct"

proc startSimpleStruct(obj: var Builder; m: BModule; name: string; baseType: Snippet): StructBuilderInfo =
  result = StructBuilderInfo(baseKind: bcNone, named: name.len != 0)
  obj.add("struct")
  if result.named:
    obj.add(" ")
    obj.add(name)
  if baseType.len != 0:
    if m.compileToCpp:
      result.baseKind = bcCppInherit
    else:
      result.baseKind = bcSupField
  if result.baseKind == bcCppInherit:
    obj.add(" : public ")
    obj.add(baseType)
  obj.add(" ")
  obj.add("{\n")
  result.preFieldsLen = obj.buf.len
  if result.baseKind == bcSupField:
    obj.addField(name = "Sup", typ = baseType)

proc finishSimpleStruct(obj: var Builder; m: BModule; info: StructBuilderInfo) =
  if info.baseKind == bcNone and info.preFieldsLen == obj.buf.len:
    # no fields were added, add dummy field
    obj.addField(name = "dummy", typ = CChar)
  if info.named:
    obj.add("};\n")
  else:
    obj.add("}")

template addSimpleStruct(obj: var Builder; m: BModule; name: string; baseType: Snippet; body: typed) =
  ## builds a struct type not based on a Nim type with fields according to `body`,
  ## `name` can be empty to build as a type expression and not a statement
  let info = startSimpleStruct(obj, m, name, baseType)
  body
  finishSimpleStruct(obj, m, info)

proc startStruct(obj: var Builder; m: BModule; t: PType; name: string; baseType: Snippet): StructBuilderInfo =
  result = StructBuilderInfo(baseKind: bcNone, named: name.len != 0)
  if tfPacked in t.flags:
    if hasAttribute in CC[m.config.cCompiler].props:
      obj.add(structOrUnion(t))
      obj.add(" __attribute__((__packed__))")
    else:
      obj.add("#pragma pack(push, 1)\n")
      obj.add(structOrUnion(t))
  else:
    obj.add(structOrUnion(t))
  if result.named:
    obj.add(" ")
    obj.add(name)
  if t.kind == tyObject:
    if t.baseClass == nil:
      if lacksMTypeField(t):
        result.baseKind = bcNone
      elif optTinyRtti in m.config.globalOptions:
        result.baseKind = bcNoneTinyRtti
      else:
        result.baseKind = bcNoneRtti
    elif m.compileToCpp:
      result.baseKind = bcCppInherit
    else:
      result.baseKind = bcSupField
  elif baseType.len != 0:
    if m.compileToCpp:
      result.baseKind = bcCppInherit
    else:
      result.baseKind = bcSupField
  if result.baseKind == bcCppInherit:
    obj.add(" : public ")
    obj.add(baseType)
  obj.add(" ")
  obj.add("{\n")
  result.preFieldsLen = obj.buf.len
  case result.baseKind
  of bcNone:
    # rest of the options add a field or don't need it due to inheritance,
    # we need to add the dummy field for uncheckedarray ahead of time
    # so that it remains trailing
    if t.itemId notin m.g.graph.memberProcsPerType and
        t.n != nil and t.n.len == 1 and t.n[0].kind == nkSym and
        t.n[0].sym.typ.skipTypes(abstractInst).kind == tyUncheckedArray:
      # only consists of flexible array field, add *initial* dummy field
      obj.addField(name = "dummy", typ = CChar)
  of bcCppInherit: discard
  of bcNoneRtti:
    obj.addField(name = "m_type", typ = ptrType(cgsymValue(m, "TNimType")))
  of bcNoneTinyRtti:
    obj.addField(name = "m_type", typ = ptrType(cgsymValue(m, "TNimTypeV2")))
  of bcSupField:
    obj.addField(name = "Sup", typ = baseType)

proc finishStruct(obj: var Builder; m: BModule; t: PType; info: StructBuilderInfo) =
  if info.baseKind == bcNone and info.preFieldsLen == obj.buf.len and
      t.itemId notin m.g.graph.memberProcsPerType:
    # no fields were added, add dummy field
    obj.addField(name = "dummy", typ = CChar)
  if info.named:
    obj.add("};\n")
  else:
    obj.add("}")
  if tfPacked in t.flags and hasAttribute notin CC[m.config.cCompiler].props:
    obj.add("#pragma pack(pop)\n")

template addStruct(obj: var Builder; m: BModule; typ: PType; name: string; baseType: Snippet; body: typed) =
  ## builds a struct type directly based on `typ` with fields according to `body`,
  ## `name` can be empty to build as a type expression and not a statement
  let info = startStruct(obj, m, typ, name, baseType)
  body
  finishStruct(obj, m, typ, info)

template addFieldWithStructType(obj: var Builder; m: BModule; parentTyp: PType; fieldName: string, body: typed) =
  ## adds a field with a `struct { ... }` type, building the fields according to `body`
  obj.add('\t')
  if tfPacked in parentTyp.flags:
    if hasAttribute in CC[m.config.cCompiler].props:
      obj.add("struct __attribute__((__packed__)) {\n")
    else:
      obj.add("#pragma pack(push, 1)\nstruct {")
  else:
    obj.add("struct {\n")
  body
  obj.add("} ")
  obj.add(fieldName)
  obj.add(";\n")
  if tfPacked in parentTyp.flags and hasAttribute notin CC[m.config.cCompiler].props:
    obj.add("#pragma pack(pop)\n")

template addAnonUnion(obj: var Builder; body: typed) =
  ## adds an anonymous union i.e. `union { ... };` with fields according to `body`
  obj.add "union{\n"
  body
  obj.add("};\n")

template addUnionType(obj: var Builder; body: typed) =
  ## adds a union type i.e. `union { ... }` with fields according to `body`
  obj.add "union{\n"
  body
  obj.add("}")

type DeclVisibility = enum
  None
  Extern
  ExternC
  ImportLib
  ExportLib
  ExportLibVar
  Private
  StaticProc

proc addVisibilityPrefix(builder: var Builder, visibility: DeclVisibility) =
  # internal proc
  case visibility
  of None: discard
  of Extern:
    builder.add("extern ")
  of ExternC:
    builder.add("NIM_EXTERNC ")
  of ImportLib:
    builder.add("N_LIB_IMPORT ")
  of ExportLib:
    builder.add("N_LIB_EXPORT ")
  of ExportLibVar:
    builder.add("N_LIB_EXPORT_VAR ")
  of Private:
    builder.add("N_LIB_PRIVATE ")
  of StaticProc:
    builder.add("static ")

template addDeclWithVisibility(builder: var Builder, visibility: DeclVisibility, declBody: typed) =
  ## adds a declaration as in `declBody` with the given visibility
  builder.addVisibilityPrefix(visibility)
  declBody

type ProcParamBuilder = object
  needsComma: bool

proc initProcParamBuilder(builder: var Builder): ProcParamBuilder =
  result = ProcParamBuilder(needsComma: false)
  builder.add("(")

proc finishProcParamBuilder(builder: var Builder, params: ProcParamBuilder) =
  if params.needsComma:
    builder.add(")")
  else:
    builder.add("void)")

template cgDeclFrmt*(s: PSym): string =
  s.constraint.strVal

proc addParam(builder: var Builder, params: var ProcParamBuilder, name: string, typ: Snippet) =
  if params.needsComma:
    builder.add(", ")
  else:
    params.needsComma = true
  builder.add(typ)
  builder.add(" ")
  builder.add(name)

proc addParam(builder: var Builder, params: var ProcParamBuilder, param: PSym, typ: Snippet) =
  if params.needsComma:
    builder.add(", ")
  else:
    params.needsComma = true
  var modifiedTyp = typ
  if sfNoalias in param.flags:
    modifiedTyp.add(" NIM_NOALIAS")
  if sfCodegenDecl notin param.flags:
    builder.add(modifiedTyp)
    builder.add(" ")
    builder.add(param.loc.snippet)
  else:
    builder.add runtimeFormat(param.cgDeclFrmt, [modifiedTyp, param.loc.snippet])

proc addUnnamedParam(builder: var Builder, params: var ProcParamBuilder, typ: Snippet) =
  if params.needsComma:
    builder.add(", ")
  else:
    params.needsComma = true
  builder.add(typ)

proc addProcTypedParam(builder: var Builder, paramBuilder: var ProcParamBuilder, callConv: TCallingConvention, name: string, rettype, params: Snippet) =
  if paramBuilder.needsComma:
    builder.add(", ")
  else:
    paramBuilder.needsComma = true
  builder.add(CallingConvToStr[callConv])
  builder.add("_PTR(")
  builder.add(rettype)
  builder.add(", ")
  builder.add(name)
  builder.add(")")
  builder.add(params)

proc addVarargsParam(builder: var Builder, params: var ProcParamBuilder) =
  # does not exist in NIFC, needs to be proc pragma
  if params.needsComma:
    builder.add(", ")
  else:
    params.needsComma = true
  builder.add("...")

template addProcParams(builder: var Builder, params: out ProcParamBuilder, body: typed) =
  params = initProcParamBuilder(builder)
  body
  finishProcParamBuilder(builder, params)

type SimpleProcParam = tuple
  name, typ: string

proc cProcParams(params: varargs[SimpleProcParam]): Snippet =
  if params.len == 0: return "(void)"
  result = "("
  for i in 0 ..< params.len:
    if i != 0: result.add(", ")
    result.add(params[i].typ)
    if params[i].name.len != 0:
      result.add(" ")
      result.add(params[i].name)
  result.add(")")

template addProcHeaderWithParams(builder: var Builder, callConv: TCallingConvention,
                                 name: string, rettype: Snippet, paramBuilder: typed) =
  # on nifc should build something like (proc name params type pragmas
  # with no body given
  # or enforce this with secondary builder object
  builder.add(CallingConvToStr[callConv])
  builder.add("(")
  builder.add(rettype)
  builder.add(", ")
  builder.add(name)
  builder.add(")")
  paramBuilder

proc addProcHeader(builder: var Builder, callConv: TCallingConvention,
                   name: string, rettype, params: Snippet) =
  # on nifc should build something like (proc name params type pragmas
  # with no body given
  # or enforce this with secondary builder object
  addProcHeaderWithParams(builder, callConv, name, rettype):
    builder.add(params)

proc addProcHeader(builder: var Builder, name: string, rettype, params: Snippet, isConstructor = false) =
  # no callconv
  builder.add(rettype)
  builder.add(" ")
  if isConstructor:
    builder.add("__attribute__((constructor)) ")
  builder.add(name)
  builder.add(params)

proc addProcHeader(builder: var Builder, m: BModule, prc: PSym, name: string, params, rettype: Snippet, addAttributes: bool) =
  # on nifc should build something like (proc name params type pragmas
  # with no body given
  # or enforce this with secondary builder object
  let noreturn = isNoReturn(m, prc)
  if sfPure in prc.flags and hasDeclspec in extccomp.CC[m.config.cCompiler].props:
    builder.add("__declspec(naked) ")
  if noreturn and hasDeclspec in extccomp.CC[m.config.cCompiler].props:
    builder.add("__declspec(noreturn) ")
  builder.add(CallingConvToStr[prc.typ.callConv])
  builder.add("(")
  builder.add(rettype)
  builder.add(", ")
  builder.add(name)
  builder.add(")")
  builder.add(params)
  if addAttributes:
    if sfPure in prc.flags and hasAttribute in extccomp.CC[m.config.cCompiler].props:
      builder.add(" __attribute__((naked))")
    if noreturn and hasAttribute in extccomp.CC[m.config.cCompiler].props:
      builder.add(" __attribute__((noreturn))")

proc finishProcHeaderAsProto(builder: var Builder) =
  builder.addLineEnd(";")

template finishProcHeaderWithBody(builder: var Builder, body: typed) =
  builder.addLineEndIndent(" {")
  body
  builder.addLineEndDedent("}")
  builder.addNewline

proc addProcVar(builder: var Builder, m: BModule, prc: PSym, name: string, params, rettype: Snippet,
                isStatic = false, ignoreAttributes = false) =
  # on nifc, builds full variable
  if isStatic:
    builder.add("static ")
  let noreturn = isNoReturn(m, prc)
  if not ignoreAttributes:
    if sfPure in prc.flags and hasDeclspec in extccomp.CC[m.config.cCompiler].props:
      builder.add("__declspec(naked) ")
    if noreturn and hasDeclspec in extccomp.CC[m.config.cCompiler].props:
      builder.add("__declspec(noreturn) ")
  builder.add(CallingConvToStr[prc.typ.callConv])
  builder.add("_PTR(")
  builder.add(rettype)
  builder.add(", ")
  builder.add(name)
  builder.add(")")
  builder.add(params)
  if not ignoreAttributes:
    if sfPure in prc.flags and hasAttribute in extccomp.CC[m.config.cCompiler].props:
      builder.add(" __attribute__((naked))")
    if noreturn and hasAttribute in extccomp.CC[m.config.cCompiler].props:
      builder.add(" __attribute__((noreturn))")
  # ensure we are just adding a variable:
  builder.addLineEnd(";")

proc addProcVar(builder: var Builder, callConv: TCallingConvention,
                name: string, params, rettype: Snippet,
                isStatic = false, isVolatile = false) =
  # on nifc, builds full variable
  if isStatic:
    builder.add("static ")
  builder.add(CallingConvToStr[callConv])
  builder.add("_PTR(")
  builder.add(rettype)
  builder.add(", ")
  if isVolatile:
    builder.add("volatile ")
  builder.add(name)
  builder.add(")")
  builder.add(params)
  # ensure we are just adding a variable:
  builder.addLineEnd(";")

proc addProcVar(builder: var Builder,
                name: string, params, rettype: Snippet,
                isStatic = false, isVolatile = false) =
  # no callconv
  if isStatic:
    builder.add("static ")
  builder.add(rettype)
  builder.add(" (*")
  if isVolatile:
    builder.add("volatile ")
  builder.add(name)
  builder.add(")")
  builder.add(params)
  # ensure we are just adding a variable:
  builder.addLineEnd(";")

type VarInitializerKind = enum
  Assignment, CppConstructor

proc addVar(builder: var Builder, m: BModule, s: PSym, name: string, typ: Snippet, kind = Local, visibility: DeclVisibility = None, initializer: Snippet = "", initializerKind: VarInitializerKind = Assignment) =
  if sfCodegenDecl in s.flags:
    builder.add(runtimeFormat(s.cgDeclFrmt, [typ, name]))
    if initializer.len != 0:
      if initializerKind == Assignment:
        builder.add(" = ")
      builder.add(initializer)
    builder.addLineEnd(";")
    return
  if s.kind in {skLet, skVar, skField, skForVar} and s.alignment > 0:
    builder.add("NIM_ALIGN(" & $s.alignment & ") ")
  builder.addVisibilityPrefix(visibility)
  if kind == Threadvar:
    if optThreads in m.config.globalOptions:
      let sym = s.typ.sym
      if sym != nil and sfCppNonPod in sym.flags:
        builder.add("NIM_THREAD_LOCAL ")
      else: builder.add("NIM_THREADVAR ")
  else:
    builder.addVarHeader(kind)
  builder.add(typ)
  if sfRegister in s.flags: builder.add(" register")
  if sfVolatile in s.flags: builder.add(" volatile")
  if sfNoalias in s.flags: builder.add(" NIM_NOALIAS")
  builder.add(" ")
  builder.add(name)
  if initializer.len != 0:
    if initializerKind == Assignment:
      builder.add(" = ")
    builder.add(initializer)
  builder.addLineEnd(";")

proc addInclude(builder: var Builder, value: Snippet) =
  builder.addLineEnd("#include " & value)