module Gogyou
  #
  # 構造体の構成情報などを保持するクラスです。
  #
  # 構造体の大きさや各フィールドの名前、バイト位置、型などを管理します。
  #
  class Model < ::Struct.new(:bytesize,   # total bytesize in bytes
                             :bytealign,  # byte alignment
                             :fields)     # array of field
    BasicStruct = superclass

    FIELDNAME_PATTERN = /\A[A-Za-z_][0-9A-Za-z_]*\Z/

    undef :bytesize=, :bytealign=, :fields=

    #
    # call-seq:
    #   initialize(bytesize, bytealign, fields, ...)
    #
    # [bytesize]
    #   This is total model size in bytes.
    #
    # [bytealign]
    #   This is model alignment size in bytes.
    #
    # [fields ...]
    #   These are one or more field instance.
    #
    def initialize(bytesize, bytealign, field1, *fields)
      if fields.empty? && field1.kind_of?(::Array)
        super
      else
        super bytesize.to_i, bytealign.to_i, [field1, *fields]
      end
    end

    def aset(buffer, offset, value)
      raise NotImplementedError
    end

    def aref(buffer, offset)
      raise NotImplementedError
    end

    def extensible?
      fields.any? { |f| f.extensible? }
    end

    def to_s
      "#{self.class}[bytesize=#{bytesize.inspect}, bytealign=#{bytealign.inspect}, fields=#{fields.inspect}]"
    end

    alias inspect to_s

    def pretty_print(q)
      #bytesize, bytealign, fields
      q.group(1, "#{self.class}[") do
        #q.breakable
        q.text "bytesize="
        q.pp bytesize
        q.text ", "
        #q.breakable
        q.text "bytealign="
        q.pp bytealign
        q.text ", "
        #q.breakable(" ")
        q.text "fields="
        q.breakable
        q.pp fields
      end
      q.text "]"
    end

    # 構造体の各メンバの情報を保持する
    class Field < ::Struct.new(:offset, # field offset in model
                               :name,   # field name
                               :vector, # 要素数。任意数配列の場合は 0。配列でないならば nil。
                               :type,   # type specification (or model object) of this field
                               :flags)  # LSB-0+8: packed size exponent (not aligned) / LSB-16: const
      BasicStruct = superclass

      CONST_BITMASK  = 1 << 16
      PACKSIZE_BITMASK = 0xff
      PACKSIZE_NOTDEFINE = 20 # = (1 << 20) = 1 MiB # 事実上の無限

      def initialize(offset, name, vector, type, flags = 0 | PACKSIZE_NOTDEFINE)
        super(offset, name, vector, type, flags)
      end

      def extensible?
        if vector
          vector[-1] == 0 ? true : false
        else
          type.extensible?
        end
      end

      def bytesize
        s = type.bytesize
        vector ? vector.inject(&:*) * s : s
      end

      def const?
        ((flags & CONST_BITMASK) == CONST_BITMASK) ? true : false
      end

      def packed?
        ((flags & PACKSIZE_BITMASK) == PACKSIZE_NOTDEFINE) ? false : true
      end

      def set_const
        self.flags |= CONST_BITMASK
        self
      end

      def set_packsize(pack_exponent)
        pack_exponent = PACKSIZE_NOTDEFINE if pack_exponent > PACKSIZE_NOTDEFINE
        self.flags = flags.setbit(0, 8, pack_exponent)
        self
      end

      def packsize
        1 << flags.getbit(0, 8)
      end

      def strflags
        set = [const? ? "const" : nil, packed? ? "packed(#{packsize})" : nil]
        set.compact!
        return nil if set.empty?
        set.join(",")
      end

      def strflags_with_paren
        set = strflags
        set ? "(#{set})" : ""
      end

      def to_s
        "#{self.class}[offset=#{offset.inspect}, name=#{name.inspect}, vector=#{vector.inspect}, type=#{type.inspect}, flags=0x#{flags.to_s(16)}#{strflags_with_paren}]"
      end

      alias inspect to_s

      def pretty_print(q)
        q.group(1, "#{self.class}[") do
          #q.breakable
          q.text "offset="
          q.pp offset
          q.text ", "
          #q.breakable
          q.text "name="
          q.pp name
          q.text ", "
          #q.breakable
          q.text "vector="
          q.pp vector
          q.text ", "
          #q.breakable
          q.text "flags=0x%02x%s" % [flags, strflags_with_paren]
          q.text ","
          q.breakable(" ")
          q.text "type="
          q.pp type
        end
        q.text "]"
      end
    end

    def self.struct(typemap, packexp = Field::PACKSIZE_NOTDEFINE, &block)
      define_container(typemap, packexp, Model::Struct, &block)
    end

    def self.union(typemap, packexp = Field::PACKSIZE_NOTDEFINE, &block)
      define_container(typemap, packexp, Model::Union, &block)
    end

    def self.typedef(typemap, type, aliasname, *elements)
      raise ArgumentError, "informal aliasname (#{aliasname.inspect})" unless aliasname =~ FIELDNAME_PATTERN
      aliasname = aliasname.intern

      case type
      when Symbol, String
        type0 = type
        type = typemap[type.intern]
        raise ArgumentError, "type not defined (#{type0})" unless type
      else
        # 型情報子を用いる方法
        raise ArgumentError, "type is not typeinfo (#{type.inspect})" unless Model.check_typeinfo(type)
      end

      unless elements.empty?
        # 配列型
        # TODO: Accessor::Array を構築するのではなく、Model::Array インスタンスを生成するようにする
        type = Accessor.define_subarray(Model::Field[0, nil, elements, type, 0])
      end

      typemap[aliasname] = type

      nil
    end

    def self.define_container(typemap, packexp, model_type, &block)
      creator = model_type::Creator.new(typemap, 0, [])
      proxy = model_type::Creator::Proxy.new(creator, packexp)
      proxy.instance_exec(&block)
      model = creator.to_model
      model
    end

    def self.check_typeinfo(obj)
      if obj.kind_of?(Model) ||
         (obj.kind_of?(Module) && obj < Accessor) ||
         (obj.respond_to?(:bytesize) &&
          obj.respond_to?(:bytealign) &&
          obj.respond_to?(:extensible?) &&
          obj.respond_to?(:aset) &&
          obj.respond_to?(:aref))
        true
      else
        false
      end
    end


    BasicCreator = ::Struct.new(:typemap, :offset, :fields)

    class BasicCreator
      def maxalign(fields = self.fields)
        fields.map { |f| f.packed? ? f.packsize : f.type.bytealign }.max
      end

      def maxsize(fields = self.fields)
        fields.map { |f| f.bytesize }.max
      end

      def flatten_field(fields = self.fields)
        #pp fields
        fields2 = []
        fields.each do |f|
          #p f
          #p f.class
          if f.name
            fields2 << f
          else
            raise "BUG? : field.type is not a Model (%p)" % f.type unless f.type.kind_of?(Model)
            fs = flatten_field(f.type.fields)
            fs.each { |ff| ff.offset += f.offset; ff.set_const if f.const? }
            fields2.concat fs
          end
        end
        fields2
      end

      #
      # call-seq:
      #   struct type, name, *vector
      #   struct proc, name, *vector
      #   struct { ... }
      #
      # 最初と二番目の呼び出し方法は、既存の (typedef していない) 型情報を用いる、または構造体をその場で定義するために利用できます。
      #
      # 三番目の呼び出し方法は、無名構造体を定義するために利用できます。
      #
      # === example (型情報を用いる)
      #
      #   Type1 = struct {
      #     struct UserType, :a, :b, 2, 3, 4
      #   }
      #
      # === example (構造体をその場で定義して、構造体へのアクセッサを定義する)
      #
      #   Type2 = struct {
      #     struct -> {
      #       int :x, y, z
      #     }, :a, :b, 2, 3, 4
      #   }
      #
      # === example (無名構造体)
      #
      #   Type3 = struct {
      #     struct {
      #       int :a, :b, 2, 3, 4
      #     }
      #   }
      #
      def struct(args, packexp, &block)
        define_container(args, packexp, block, Model.method(:struct))
      end

      #
      # call-seq:
      #   union type, name, *vector
      #   union proc, name, *vector
      #   union { ... }
      #
      # 共用体を定義します。
      #
      # 呼び出し方は struct と変わりません。
      #
      # ただ、<tt>union type, ...</tt> の場合は、<tt>struct type, ...</tt> と同じ結果となります。
      # これは type がどのような構造になっているのかを gogyou が管理も把握もしないためです。
      # この記述ができる唯一の理由は、人間が見てわかりやすくすることを意図しています
      # (ただし、ミスリードを誘う手口にも利用されてしまうのが最大の欠点です)。
      #
      def union(args, packexp, &block)
        define_container(args, packexp, block, Model.method(:union))
      end

      def define_container(args, packexp, anonymblock, container)
        if anonymblock
          raise ArgumentError, "given block and arguments" unless args.empty?
          model = container.(typemap.dup, packexp, &anonymblock)
          raise "BUG - object is not a Model (#{model.class})" unless model.kind_of?(Model)
          #p model: model, superclass: model.superclass
          self.offset = offset.align_ceil(model.bytealign) unless kind_of?(Model::Union::Creator)
          fields << f = Field[offset, nil, nil, model, packexp]
          self.offset += model.bytesize unless kind_of?(Model::Union::Creator)
          [f]
        else
          type = args.shift
          type = container.(typemap.dup, packexp, &type) if type.kind_of?(::Proc)
          addfield!(type, packexp, args)
        end
      end

      def typedef(args)
        raise NotImplementedError
      end

      def const(fields)
        fields.each { |f| f.set_const }
      end

      #
      # call-seq:
      #   packed { ... } -> nil
      #   packed(bytealign) { ... } -> nil
      #
      # ブロック内部のフィールドのバイトアライメントを調節します。
      #
      # packed を直接の入れ子にして呼び出すことは出来ません。struct や union を挟んで呼び出すことは出来ます。
      #
      # 引数無しで呼び出した場合は、bytealign に 1 を与えて呼び出すものと同義となります。
      #
      # [bytealign]
      #   1 以上で2の冪乗となる整数値を指定します。
      #
      #   nil を与えた場合、上位階層で指定したパックサイズを無効化して本来のバイトアライメントに配置するようにします。
      #
      def packed(bytealign = 1)
        raise "This method is defined for documentaion. Real implemented is in Gogyou::Model::BasicCreator::Proxy#initialize"
        yield
        nil
      end

      #
      # フィールド名の解析
      #
      def parse!(args)
        raise ArgumentError, "nothing argument" if args.empty?
        name = nil
        vector = nil
        while arg = args.shift
          case arg
          when Symbol, String
            yield(name, vector) if name
            raise ArgumentError, "informal field name (#{arg.to_s})" unless arg =~ FIELDNAME_PATTERN
            name = arg.intern
            vector = nil
          when Integer
            raise ArgumentError, "first argument is field name only (#{arg})" unless name
            raise ArgumentError, "given negative number (#{arg})" unless arg >= 0
            vector ||= []
            vector << arg.to_i
            if vector[-1] == 0
              yield(name, vector)
              unless args.empty?
                raise ArgumentError, "given fields after extensible vector"
              end
              return nil
            end
          else
            raise ArgumentError, "given any object (#{arg.inspect})"
          end
        end

        yield(name, vector)

        nil
      end

      def addfield(type, packexp, args)
        typeobj = typemap[type.intern]
        unless typeobj
          raise NoMethodError, "typename or method is missing (#{type})"
        end

        addfield!(typeobj, packexp, args)
      end

      def addfield!(typeobj, packexp, args)
        #p typeobj
        # check extensible field  >>>  creator.fields[-1].vector[-1]
        if (x = fields[-1]) && (x = x.vector) && x[-1] == 0
          raise ArgumentError, "not given fields after extensible vector"
        end

        typesize = typeobj.bytesize
        typealign = [typeobj.bytealign, 1 << packexp].min

        tmpfields = []

        parse!(args) do |name, vect|
          self.offset = offset.align_ceil(typealign) unless kind_of?(Model::Union::Creator)
          fields << f = Field[offset, name, vect, typeobj, 0 | packexp]
          tmpfields << f
          unless kind_of?(Model::Union::Creator)
            elements = vect ? vect.inject(1, &:*) : 1
            self.offset += typesize * elements
          end
        end

        tmpfields
      end

      class Proxy < Object # :nodoc: all
      #class Proxy < BasicObject
        def initialize(creator, packexp = Field::PACKSIZE_NOTDEFINE)
          #singleton_class = (class << proxy; self; end)
          singleton_class.class_eval do
            latest_fields = nil
            #define_method(:method_missing, ->(type, *args) { latest_fields = creator.addfield(type, args); nil })
            creator.typemap.each_key do |t|
              define_method(t, ->(*args) { latest_fields = creator.addfield(t, packexp, args); nil })
            end
            define_method(:struct, ->(*args, &block) { latest_fields = creator.struct(args, packexp, &block); nil })
            define_method(:union, ->(*args, &block) { latest_fields = creator.union(args, packexp, &block); nil })
            define_method(:const, ->(dummy_fields) { creator.const(latest_fields); latest_fields = nil; nil })
            define_method(:typedef, ->(*args, &block) { creator.typedef(args, &block) })
            packexp0 = nil
            define_method(:packed, ->(bytealign = 1, &block) {
              raise "wrong nested ``packed''" if packexp0
              if bytealign.nil?
                exp = Field::PACKSIZE_NOTDEFINE
              else
                exp = Math.log(bytealign, 2)
                # exp が Nan Infinity -Infinity の場合は例外が発生するので、それに対する処置も行う
                unless ((exp = exp.to_i) rescue nil) && (1 << exp) == bytealign
                  raise ArgumentError, "shall be given power of two (but #{bytealign})"
                end
              end

              begin
                packexp0 = packexp
                packexp = exp
                self.instance_exec(&block)
              ensure
                (packexp, packexp0) = packexp0, nil
              end

              nil
            })
            if creator.respond_to?(:bytealign)
              define_method(:bytealign, ->(bytesize, &block) { creator.bytealign(bytesize, &block); nil })
            end
            if creator.respond_to?(:padding)
              define_method(:padding, ->(bytesize, &block) { creator.padding(bytesize, &block); nil })
            end
          end
        end
      end
    end

    class Struct < Model
      class Creator < Model::BasicCreator
        def bytealign(bytesize)
          raise NotImplementedError
        end

        def padding(bytesize)
          raise NotImplementedError
        end

        def to_model
          Model::Struct.new(offset.align_ceil(maxalign), maxalign, flatten_field)
        end
      end

      def aset(buffer, offset, value)
        raise NotImplementedError
      end

      def aref(buffer, offset)
        v = Accessor::TemporaryStruct.new(buffer, offset, self)
        v.infect_from(self, buffer) unless v.frozen?
        v.freeze if frozen? || buffer.frozen?
        v
      end

      def create_accessor
        Accessor::Struct.define(self)
      end
    end

    class Union < Model
      class Creator < Model::BasicCreator
        def to_model
          Model::Union.new(maxsize.align_ceil(maxalign), maxalign, flatten_field)
        end
      end

      def aset(buffer, offset, value)
        raise NotImplementedError
      end

      def aref(buffer, offset)
        v = Accessor::TemporaryUnion.new(buffer, offset, self)
        v.infect_from(self, buffer) unless v.frozen?
        v.freeze if frozen? || buffer.frozen?
        v
      end

      def create_accessor
        Accessor::Union.define(self)
      end
    end

    #
    # C の配列を模造するクラス。
    #
    class Array < Model
      def extensible?
        fields[-1] == 0 ? true : false
      end

      def aset(buffer, offset, value)
        raise NotImplementedError
      end

      def aref(buffer, offset)
        raise NotImplementedError
        accessor = Accessor::Array[buffer, offset, self]
        accessor.instance_eval do
          field = fields[0]
          type = field.type
          elements = field.vector[-1]

          define_singleton_method(:check_index, ->(i) {
            i = i.to_i
            raise IndexError unless i >= 0 && (elements.nil? || i < elements)
            i
          })

          define_singleton_method(:[], ->(i) {
            v = type.aref(buffer__GOGYOU__, offset__GOGYOU__ + type.bytesize * check_index(i))
            v.infect_from(self, buffer) unless v.frozen?
            v.freeze if frozen? || buffer.frozen? || field.const?
            v
          })

          define_singleton_method(:[]=, ->(i, v) {
            type.aset(buffer__GOGYOU__, offset__GOGYOU__ + type.bytesize * check_index(i), v)
          })
        end
        accessor
      end
    end
  end
end