hexmap/server/action/action.go

package action

import (
	"errors"
	"git.reya.zone/reya/hexmap/server/state"
	"go.uber.org/zap/zapcore"
)

var (
	// ErrNoOp is returned when an action has no effect.
	ErrNoOp = errors.New("action's effects were already applied, or it's an empty action")
	// ErrNoTransparentColors is returned when a user tries to set their active color or a cell color to transparent.
	// Transparent here is defined as having an alpha component of less than 15 (0xF).
	ErrNoTransparentColors = errors.New("transparent colors not allowed")
)

// Action is the interface for actions that can be shared between clients, or between the server and a client.
type Action interface {
	zapcore.ObjectMarshaler
	// Apply causes the action's effects to be applied to s, mutating it in place.
	// All Actions must conform to the standard that if an action can't be correctly applied, or if it would
	// have no effect, it returns an error without changing s.
	// If an action can be correctly applied but would have no effect, it should return ErrNoOp.
	// If an action is correctly applied and has an effect, it should return nil.
	Apply(s *state.Synced) error
}

type Client interface {
	Server
	// ToClientPB converts the action into a client action protocol buffer.
	ToClientPB() *ClientActionPB
}

type Server interface {
	Action
	// ToServerPB converts the action into a server action protocol buffer.
	ToServerPB() *ServerActionPB
}

func serverPBFromClient(c Client) *ServerActionPB {
	return &ServerActionPB{
		Action: &ServerActionPB_Client{Client: c.ToClientPB()},
	}
}

type ServerSlice []Server

func (s ServerSlice) MarshalLogArray(encoder zapcore.ArrayEncoder) error {
	var finalErr error = nil
	for _, a := range s {
		err := encoder.AppendObject(a)
		if err != nil && finalErr == nil {
			finalErr = err
		}
	}
	return finalErr
}

// CellColor is the action sent when a cell of the map has been colored a different color.
type CellColor struct {
	// At is the location of the cell in storage coordinates.
	At state.StorageCoordinates `json:"at"`
	// Color is the color the cell has been changed to.
	Color state.Color `json:"color"`
}

func (c CellColor) MarshalLogObject(encoder zapcore.ObjectEncoder) error {
	encoder.AddString("type", "CellColor")
	err := encoder.AddObject("at", c.At)
	encoder.AddString("color", c.Color.String())
	return err
}

// Apply sets the target cell's color, or returns ErrNoOp if it can't.
func (c CellColor) Apply(s *state.Synced) error {
	if c.Color.A < 0xF {
		return ErrNoTransparentColors
	}
	cell, err := s.Map.Layer.GetCellAt(c.At)
	if err != nil {
		return err
	}
	if cell.Color == c.Color {
		return ErrNoOp
	}
	cell.Color = c.Color
	return nil
}

// UserActiveColor is the action sent when the user's current color, the one being painted with, changes.
type UserActiveColor struct {
	// Color is the color that is now active.
	Color state.Color `json:"color"`
}

func (c UserActiveColor) MarshalLogObject(encoder zapcore.ObjectEncoder) error {
	encoder.AddString("type", "UserActiveColor")
	encoder.AddString("color", c.Color.String())
	return nil
}

// Apply sets the user's active color, or returns ErrNoOp if it can't.
func (c UserActiveColor) Apply(s *state.Synced) error {
	if c.Color.A < 0xF {
		return ErrNoTransparentColors
	}
	if s.User.ActiveColor == c.Color {
		return ErrNoOp
	}
	s.User.ActiveColor = c.Color
	return nil
}