class Crystal::Call
  def recalculate_lib_call(obj_type)
    replace_splats

    old_target_defs = @target_defs

    external = obj_type.lookup_first_def(name, false).as(External?)
    raise "undefined fun '#{name}' for #{obj_type}" unless external

    check_lib_call_named_args(external)

    check_fun_args_size_match obj_type, external
    check_fun_out_args external
    unless obj_and_args_types_set?
      # we can actually compute a type for this call even
      # if we don't know the arguments types yet
      self.type = external.type
      return
    end

    check_fun_args_types_match obj_type, external

    obj_type.used = true
    external.used = true

    untyped_defs = [external] of Def
    @target_defs = untyped_defs

    self.unbind_from old_target_defs if old_target_defs
    self.bind_to untyped_defs

    if (parent_visitor = @parent_visitor) && (ptyped_def = parent_visitor.typed_def?) && untyped_defs.try(&.any?(&.raises?))
      ptyped_def.raises = true
    end
  end

  def check_lib_call_named_args(external)
    named_args = self.named_args
    return unless named_args

    if external.varargs?
      raise "can't use named args with variadic function"
    end

    # We check that all arguments are covered, and then we
    # rewrite this call to not have named arguments
    # (a dispatch can't include a lib type, so this call
    # will only resolve to a function)

    covered = BitArray.new(external.args.size)
    args.size.times do |i|
      covered[i] = true
    end

    # We gather named args according to their index.
    sorted_named_args = [] of {Int32, NamedArgument}
    named_args.each do |named_arg|
      found_index = external.args.index { |arg| arg.name == named_arg.name }
      unless found_index
        named_arg.raise "no argument named '#{named_arg.name}'"
      end

      if covered[found_index]
        named_arg.raise "argument '#{named_arg.name}' already specified"
      end

      covered[found_index] = true
      sorted_named_args << {found_index, named_arg}
    end

    missing_args = [] of String
    covered.each_with_index do |value, index|
      unless value
        missing_args << external.args[index].name
      end
    end

    if missing_args.size == 1
      raise "missing argument: #{missing_args.first}"
    elsif missing_args.size > 1
      raise "missing arguments: #{missing_args.join ", "}"
    end

    # Now we sort the named args according to their index.
    # We can now append them to this call, as they necessarily
    # must come after positional args that are already covered
    # (and we checked that all args are covered), and we
    # remove our named args.
    sorted_named_args.sort_by! &.[0]
    sorted_named_args.each do |(index, named_arg)|
      self.args << named_arg.value
    end
    self.named_args = nil
  end

  def check_fun_args_size_match(obj_type, external)
    call_args_count = args.size
    all_args_count = external.args.size

    if external.varargs? && call_args_count >= all_args_count
      return
    end

    required_args_count = external.args.count { |arg| !arg.default_value }

    return if required_args_count <= call_args_count <= all_args_count

    wrong_number_of_arguments "'#{full_name(obj_type)}'", args.size, external.args.size
  end

  def check_fun_out_args(untyped_def)
    untyped_def.args.each_with_index do |arg, i|
      call_arg = self.args[i]
      if call_arg.is_a?(Out)
        arg_type = arg.type
        if arg_type.is_a?(PointerInstanceType)
          if arg_type.element_type.remove_typedef.void?
            call_arg.raise "can't use out with Void* (argument #{lib_arg_name(arg, i)} of #{untyped_def.owner}.#{untyped_def.name} is Void*)"
          end

          if call_arg.exp.is_a?(Underscore)
            call_arg.exp.type = arg_type.element_type
          else
            var = parent_visitor.lookup_var_or_instance_var(call_arg.exp)
            var.bind_to Var.new("out", arg_type.element_type)
            call_arg.exp.bind_to var
            parent_visitor.bind_meta_var(call_arg.exp)
          end
        else
          call_arg.raise "argument #{lib_arg_name(arg, i)} of #{untyped_def.owner}.#{untyped_def.name} cannot be passed as 'out' because it is not a pointer"
        end
      end
    end

    # Check that there are no out args more then the number of arguments in the fun
    if untyped_def.varargs?
      untyped_def.args.size.upto(self.args.size - 1) do |i|
        self_arg = self.args[i]
        if self_arg.is_a?(Out)
          self_arg.raise "can't use out at varargs position: declare the variable with `#{self_arg.exp} = uninitialized ...` and pass it with `pointerof(#{self_arg.exp})`"
        end
      end
    end
  end

  def check_fun_args_types_match(obj_type, typed_def)
    typed_def.args.each_with_index do |typed_def_arg, i|
      self_arg = self.args[i]
      check_fun_arg_type_matches(obj_type, self_arg, typed_def_arg, i)
    end

    # Need to call to_unsafe on variadic args too
    if typed_def.varargs?
      typed_def.args.size.upto(self.args.size - 1) do |i|
        self_arg = self.args[i]
        self_arg_type = self_arg.type?
        if self_arg_type
          unless self_arg_type.nil_type? || self_arg_type.allowed_in_lib?
            implicit_call = Conversions.try_to_unsafe(self_arg.clone, parent_visitor) do |ex|
              if Conversions.to_unsafe_lookup_failed?(ex)
                self_arg.raise "argument ##{i + 1} of '#{full_name(obj_type)}' is not a primitive type and no #{self_arg_type}#to_unsafe method found"
              else
                self_arg.raise ex.message, ex
              end
            end
            implicit_call_type = implicit_call.type?
            if implicit_call_type
              if implicit_call_type.allowed_in_lib?
                self.args[i] = implicit_call
              else
                self_arg.raise "converted #{self_arg_type} invoking to_unsafe, but #{implicit_call_type} is not a primitive type"
              end
            else
              self_arg.raise "tried to convert #{self_arg_type} invoking to_unsafe, but can't deduce its type"
            end
          end
        else
          self_arg.raise "can't deduce argument type"
        end
      end
    end
  end

  def check_fun_arg_type_matches(obj_type, self_arg, typed_def_arg, index)
    expected_type = typed_def_arg.type
    actual_type = self_arg.type
    actual_type = program.pointer_of(actual_type) if self_arg.is_a?(Out)
    return if actual_type.compatible_with?(expected_type)
    return if actual_type.implicitly_converted_in_c_to?(expected_type)

    unaliased_type = expected_type.remove_alias
    case unaliased_type
    when IntegerType
      return if convert_numeric_argument self_arg, unaliased_type, expected_type, actual_type, index
    when FloatType
      return if convert_numeric_argument self_arg, unaliased_type, expected_type, actual_type, index
    end

    implicit_call = Conversions.try_to_unsafe(self_arg.clone, parent_visitor) do |ex|
      if Conversions.to_unsafe_lookup_failed?(ex)
        arg_name = lib_arg_name(typed_def_arg, index)

        if expected_type.is_a?(ProcInstanceType) &&
           actual_type.is_a?(ProcInstanceType) &&
           expected_type.arg_types == actual_type.arg_types
          self_arg.raise "argument #{arg_name} of '#{full_name(obj_type)}' must be a Proc returning #{expected_type.return_type}, not #{actual_type.return_type}"
        else
          self_arg.raise "argument #{arg_name} of '#{full_name(obj_type)}' must be #{expected_type}, not #{actual_type}"
        end
      else
        self_arg.raise ex.message, ex
      end
    end

    implicit_call_type = implicit_call.type?
    if implicit_call_type
      if implicit_call_type.compatible_with?(expected_type) || implicit_call_type.implicitly_converted_in_c_to?(expected_type)
        self.args[index] = implicit_call
      else
        arg_name = lib_arg_name(typed_def_arg, index)
        self_arg.raise "argument #{arg_name} of '#{full_name(obj_type)}' must be #{expected_type}, not #{actual_type} (nor #{implicit_call_type} returned by '#{actual_type}#to_unsafe')"
      end
    else
      self_arg.raise "tried to convert #{actual_type} to #{expected_type} invoking to_unsafe, but can't deduce its type"
    end
  end

  def check_not_lib_out_args
    args.find(&.is_a?(Out)).try &.raise "out can only be used with lib funs"
    named_args.try &.find(&.value.is_a?(Out)).try &.raise "out can only be used with lib funs"
  end

  def convert_numeric_argument(self_arg, unaliased_type, expected_type, actual_type, index)
    if self_arg.is_a?(NumberLiteral)
      # TODO: check that the number literal fits, error otherwise

      # If converting from a float to integer, we need to remove the dot
      # so that later the codegen finds a correct value
      if unaliased_type.is_a?(IntegerType) && (dot_index = self_arg.value.index('.'))
        self_arg.value = self_arg.value[0...dot_index]
      end

      num = self_arg.to_number

      self_arg.value =
        case unaliased_type
        when program.uint8  ; num.to_u8!.to_s
        when program.uint16 ; num.to_u16!.to_s
        when program.uint32 ; num.to_u32!.to_s
        when program.uint64 ; num.to_u64!.to_s
        when program.int8   ; num.to_i8!.to_s
        when program.int16  ; num.to_i16!.to_s
        when program.int32  ; num.to_i32!.to_s
        when program.int64  ; num.to_i64!.to_s
        when program.float32; num.to_f32!.to_s
        else                  num.to_f64!.to_s
        end
      self_arg.kind = unaliased_type.kind
      self_arg.type = unaliased_type
      return true
    end

    convert_call = Conversions.numeric_argument(self_arg, self_arg.clone, parent_visitor, unaliased_type, expected_type, actual_type)
    return false unless convert_call

    self.args[index] = convert_call
    true
  end
end

class Crystal::Type
  # Returns `true` if this type can be used in a lib declaration:
  # in a fun, struct/union member, or typedef.
  def allowed_in_lib?
    case self
    when NilType
      false
    when PrimitiveType, NoReturnType, VoidType, TypeDefType, EnumType
      true
    when PointerInstanceType
      self.element_type.allowed_in_lib?
    when TupleInstanceType
      self.tuple_types.all? &.allowed_in_lib?
    when NamedTupleInstanceType
      self.entries.all? &.type.allowed_in_lib?
    when NilableType
      self.not_nil_type.allowed_in_lib?
    when NilableProcType
      self.proc_type.allowed_in_lib?
    when NilablePointerType
      self.pointer_type.allowed_in_lib?
    when ProcInstanceType
      self.arg_types.all?(&.allowed_in_lib?) && (self.return_type.allowed_in_lib? || self.return_type.nil_type?)
    when StaticArrayInstanceType
      self.element_type.allowed_in_lib?
    else
      self.extern?
    end
  end

  # Returns `true` if this type can be implicitly converted to
  # `expected_type` when this is a lib fun argument, without
  # involving `to_unsafe` or numeric conversions.
  # For example `nil` can be passed to an argument of type pointer.
  def implicitly_converted_in_c_to?(expected_type)
    case self
    when NilType
      # nil will be sent as pointer
      expected_type.pointer? || expected_type.proc?
    when ProcInstanceType
      # fun will be cast to return nil
      expected_type.is_a?(ProcInstanceType) && expected_type.return_type == program.nil && expected_type.arg_types == self.arg_types
    when NilablePointerType
      # nilable pointer is just a pointer
      self.pointer_type == expected_type
    when PointerInstanceType
      # any pointer matches a void*
      expected_type.is_a?(PointerInstanceType) && expected_type.element_type.void?
    else
      false
    end
  end
end

private def lib_arg_name(arg, index)
  arg.name.empty? ? "##{index + 1}" : "'#{arg.name}'"
end
