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.add(";\n")

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.add(";\n")

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.add(";\n")

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.addInt(len)
  builder.add("]")
  if initializer.len != 0:
    builder.add(" = ")
    builder.add(initializer)
  builder.add(";\n")

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.addInt(len)
  builder.add("] = ")
  body
  builder.add(";\n")

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.add(";\n")

template addArrayTypedef(builder: var Builder, name: string, len: int, 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.addInt(len)
  builder.add("];\n")

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.addInt(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.addInt(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.addInt(field.bitsize)
  if initializer.len != 0:
    obj.add(initializer)
  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.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.len:
    # no fields were added, add dummy field
    obj.addField(name = "dummy", typ = "char")
  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.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 = "char")
  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.len and
      t.itemId notin m.g.graph.memberProcsPerType:
    # no fields were added, add dummy field
    obj.addField(name = "dummy", typ = "char")
  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:
    result.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")