animation.go

package codec

import (
	"bytes"
	"encoding/binary"

	"github.com/alacrity-engine/core/math/geometry"
)

// AnimationData contains data
// about animation frames, their
// durations and the name of the
// texture.
type AnimationData struct {
	SpritesheetID string
	TextureID     string
	Frames        []geometry.Rect
	Durations     []int32
}

// AnimationDataToBytes converts the animation data
// to a byte array.
func (anim *AnimationData) ToBytes() ([]byte, error) {
	buffer := bytes.NewBuffer([]byte{})

	// Write the name of the spritesheet.
	err := binary.Write(buffer, binary.BigEndian, int32(len(anim.SpritesheetID)))

	if err != nil {
		return nil, err
	}

	_, err = buffer.WriteString(anim.SpritesheetID)

	if err != nil {
		return nil, err
	}

	// Write the name of the texture.
	err = binary.Write(buffer, binary.BigEndian, int32(len(anim.TextureID)))

	if err != nil {
		return nil, err
	}

	_, err = buffer.WriteString(anim.TextureID)

	if err != nil {
		return nil, err
	}

	// Write the frame data.
	err = binary.Write(buffer, binary.BigEndian, int32(len(anim.Frames)))

	if err != nil {
		return nil, err
	}

	for _, frame := range anim.Frames {
		err = binary.Write(buffer, binary.BigEndian, frame.Min.X)

		if err != nil {
			return nil, err
		}

		err = binary.Write(buffer, binary.BigEndian, frame.Min.Y)

		if err != nil {
			return nil, err
		}

		err = binary.Write(buffer, binary.BigEndian, frame.Max.X)

		if err != nil {
			return nil, err
		}

		err = binary.Write(buffer, binary.BigEndian, frame.Max.Y)

		if err != nil {
			return nil, err
		}
	}

	// Write the frame durations.
	for _, duration := range anim.Durations {
		err = binary.Write(buffer, binary.BigEndian, duration)

		if err != nil {
			return nil, err
		}
	}

	return buffer.Bytes(), nil
}

// AnimationDataFromBytes restores the animation data
// from the byte array.
func AnimationDataFromBytes(data []byte) (*AnimationData, error) {
	buffer := bytes.NewBuffer(data)

	// Read the name of the spritesheet.
	var nameLength int32
	err := binary.Read(buffer, binary.BigEndian, &nameLength)

	if err != nil {
		return nil, err
	}

	nameBytes := make([]byte, nameLength)
	_, err = buffer.Read(nameBytes)

	if err != nil {
		return nil, err
	}

	spritesheetName := string(nameBytes)

	// Read the name of the texture.
	err = binary.Read(buffer, binary.BigEndian, &nameLength)

	if err != nil {
		return nil, err
	}

	nameBytes = make([]byte, nameLength)
	_, err = buffer.Read(nameBytes)

	if err != nil {
		return nil, err
	}

	textureName := string(nameBytes)

	// Read the number of frames.
	var frameCount int32
	err = binary.Read(buffer, binary.BigEndian, &frameCount)

	if err != nil {
		return nil, err
	}

	// Read AnimationData frames.
	frames := []geometry.Rect{}

	for i := int32(0); i < frameCount; i++ {
		var minX, minY, maxX, maxY float64

		err = binary.Read(buffer, binary.BigEndian, &minX)

		if err != nil {
			return nil, err
		}

		err = binary.Read(buffer, binary.BigEndian, &minY)

		if err != nil {
			return nil, err
		}

		err = binary.Read(buffer, binary.BigEndian, &maxX)

		if err != nil {
			return nil, err
		}

		err = binary.Read(buffer, binary.BigEndian, &maxY)

		if err != nil {
			return nil, err
		}

		frame := geometry.R(minX, minY, maxX, maxY)
		frames = append(frames, frame)
	}

	// Read frame durations.
	durations := []int32{}

	for i := int32(0); i < frameCount; i++ {
		var duration int32
		err = binary.Read(buffer, binary.BigEndian, &duration)

		if err != nil {
			return nil, err
		}

		durations = append(durations, duration)
	}

	return &AnimationData{
		SpritesheetID: spritesheetName,
		TextureID:     textureName,
		Frames:        frames,
		Durations:     durations,
	}, nil
}