Save and restore maps as JSON files

First pass at a level storage format to save and restore maps.

To save a map: press F12. It takes a screenshot PNG into the
screenshots/ folder and outputs a map JSON in the working directory.

To restore a map: "go run cmd/doodle/main.go map.json"

.gitignore

@@ -1,2 +1,3 @@
 fonts/
 screenshot-*.png
+map-*.json

cmd/doodle/main.go

@@ -23,6 +23,15 @@ func main() {
 	runtime.LockOSThread()
 	flag.Parse()
 
+	args := flag.Args()
+	var filename string
+	if len(args) > 0 {
+		filename = args[0]
+	}
+
 	app := doodle.New(debug)
+	if filename != "" {
+		app.LoadLevel(filename)
+	}
 	app.Run()
 }

doodle.go

@@ -166,6 +166,7 @@ func (d *Doodle) Loop() error {
 	if ev.ScreenshotKey.Pressed() {
 		log.Info("Taking a screenshot")
 		d.Screenshot()
+		d.SaveLevel()
 	}
 
 	// Clear the canvas and fill it with white.

draw/line.go

@@ -0,0 +1,43 @@
+package draw
+
+import (
+	"math"
+
+	"git.kirsle.net/apps/doodle/types"
+)
+
+// Line is a generator that returns the X,Y coordinates to draw a line.
+// https://en.wikipedia.org/wiki/Digital_differential_analyzer_(graphics_algorithm)
+func Line(x1, y1, x2, y2 int32) chan types.Point {
+	generator := make(chan types.Point)
+
+	go func() {
+		var (
+			dx = float64(x2 - x1)
+			dy = float64(y2 - y1)
+		)
+		var step float64
+		if math.Abs(dx) >= math.Abs(dy) {
+			step = math.Abs(dx)
+		} else {
+			step = math.Abs(dy)
+		}
+
+		dx = dx / step
+		dy = dy / step
+		x := float64(x1)
+		y := float64(y1)
+		for i := 0; i <= int(step); i++ {
+			generator <- types.Point{
+				X: int32(x),
+				Y: int32(y),
+			}
+			x += dx
+			y += dy
+		}
+
+		close(generator)
+	}()
+
+	return generator
+}

draw/line_test.go

@@ -0,0 +1,86 @@
+package draw_test
+
+import (
+	"fmt"
+	"testing"
+
+	"git.kirsle.net/apps/doodle/draw"
+	"git.kirsle.net/apps/doodle/types"
+)
+
+func TestLine(t *testing.T) {
+	type task struct {
+		X1     int32
+		X2     int32
+		Y1     int32
+		Y2     int32
+		Expect []types.Point
+	}
+	toString := func(t task) string {
+		return fmt.Sprintf("Line<%d,%d -> %d,%d>",
+			t.X1, t.Y1,
+			t.X2, t.Y2,
+		)
+	}
+
+	var tasks = []task{
+		task{
+			X1: 0,
+			Y1: 0,
+			X2: 0,
+			Y2: 10,
+			Expect: []types.Point{
+				{X: 0, Y: 0},
+				{X: 0, Y: 1},
+				{X: 0, Y: 2},
+				{X: 0, Y: 3},
+				{X: 0, Y: 4},
+				{X: 0, Y: 5},
+				{X: 0, Y: 6},
+				{X: 0, Y: 7},
+				{X: 0, Y: 8},
+				{X: 0, Y: 9},
+				{X: 0, Y: 10},
+			},
+		},
+		task{
+			X1: 10,
+			Y1: 10,
+			X2: 15,
+			Y2: 15,
+			Expect: []types.Point{
+				{X: 10, Y: 10},
+				{X: 11, Y: 11},
+				{X: 12, Y: 12},
+				{X: 13, Y: 13},
+				{X: 14, Y: 14},
+				{X: 15, Y: 15},
+			},
+		},
+	}
+	for _, test := range tasks {
+		gen := draw.Line(test.X1, test.Y1, test.X2, test.Y2)
+		var i int
+		for point := range gen {
+			if i >= len(test.Expect) {
+				t.Errorf("%s: Got more pixels back than expected: %s",
+					toString(test),
+					point,
+				)
+				break
+			}
+
+			expect := test.Expect[i]
+			if expect != point {
+				t.Errorf("%s: at index %d I got %s but expected %s",
+					toString(test),
+					i,
+					point,
+					expect,
+				)
+			}
+
+			i++
+		}
+	}
+}

level/json.go

@@ -0,0 +1,30 @@
+package level
+
+import (
+	"bytes"
+	"encoding/json"
+	"os"
+)
+
+// ToJSON serializes the level as JSON.
+func (m *Level) ToJSON() ([]byte, error) {
+	out := bytes.NewBuffer([]byte{})
+	encoder := json.NewEncoder(out)
+	encoder.SetIndent("", "\t")
+	err := encoder.Encode(m)
+	return out.Bytes(), err
+}
+
+// LoadJSON loads a map from JSON file.
+func LoadJSON(filename string) (Level, error) {
+	fh, err := os.Open(filename)
+	if err != nil {
+		return Level{}, err
+	}
+	defer fh.Close()
+
+	m := Level{}
+	decoder := json.NewDecoder(fh)
+	err = decoder.Decode(&m)
+	return m, err
+}

level/types.go

@@ -0,0 +1,40 @@
+package level
+
+// Level is the container format for Doodle map drawings.
+type Level struct {
+	Version  int32  `json:"version"` // File format version spec.
+	Title    string `json:"title"`
+	Author   string `json:"author"`
+	Password string `json:"passwd"`
+	Locked   bool   `json:"locked"`
+
+	// Level size.
+	Width  int32 `json:"w"`
+	Height int32 `json:"h"`
+
+	// The Palette holds the unique "colors" used in this map file, and their
+	// properties (solid, fire, slippery, etc.)
+	Palette []Palette `json:"palette"`
+
+	// Pixels is a 2D array indexed by [X][Y]. The cell values are indexes into
+	// the Palette.
+	Pixels []Pixel `json:"pixels"`
+}
+
+// Pixel associates a coordinate with a palette index.
+type Pixel struct {
+	X       int32 `json:"x"`
+	Y       int32 `json:"y"`
+	Palette int32 `json:"p"`
+}
+
+// Palette are the unique pixel attributes that this map uses, and serves
+// as a lookup table for the Pixels.
+type Palette struct {
+	// Required attributes.
+	Color string `json:"color"`
+
+	// Optional attributes.
+	Solid bool `json:"solid,omitempty"`
+	Fire  bool `json:"fire,omitempty"`
+}

screenshot.go

@@ -4,11 +4,83 @@ import (
 	"fmt"
 	"image"
 	"image/png"
-	"math"
+	"io/ioutil"
 	"os"
 	"time"
+
+	"git.kirsle.net/apps/doodle/draw"
+	"git.kirsle.net/apps/doodle/level"
 )
 
+// SaveLevel saves the level to disk.
+func (d *Doodle) SaveLevel() {
+	m := level.Level{
+		Version: 1,
+		Title:   "Alpha",
+		Author:  os.Getenv("USER"),
+		Width:   d.width,
+		Height:  d.height,
+		Palette: []level.Palette{
+			level.Palette{
+				Color: "#000000",
+				Solid: true,
+			},
+		},
+		Pixels: []level.Pixel{},
+	}
+
+	for pixel := range d.canvas {
+		for point := range draw.Line(pixel.x, pixel.y, pixel.dx, pixel.dy) {
+			m.Pixels = append(m.Pixels, level.Pixel{
+				X:       point.X,
+				Y:       point.Y,
+				Palette: 0,
+			})
+		}
+	}
+
+	json, err := m.ToJSON()
+	if err != nil {
+		log.Error("SaveLevel error: %s", err)
+		return
+	}
+
+	filename := fmt.Sprintf("./map-%s.json",
+		time.Now().Format("2006-01-02T15-04-05"),
+	)
+	err = ioutil.WriteFile(filename, json, 0644)
+	if err != nil {
+		log.Error("Create map file error: %s", err)
+		return
+	}
+}
+
+// LoadLevel loads a map from JSON.
+func (d *Doodle) LoadLevel(filename string) error {
+	log.Info("Loading level from file: %s", filename)
+	pixelHistory = []Pixel{}
+	d.canvas = Grid{}
+
+	m, err := level.LoadJSON(filename)
+	if err != nil {
+		return err
+	}
+
+	for _, point := range m.Pixels {
+		pixel := Pixel{
+			start: true,
+			x:     point.X,
+			y:     point.Y,
+			dx:    point.X,
+			dy:    point.Y,
+		}
+		pixelHistory = append(pixelHistory, pixel)
+		d.canvas[pixel] = nil
+	}
+
+	return nil
+}
+
 // Screenshot saves the level canvas to disk as a PNG image.
 func (d *Doodle) Screenshot() {
 	screenshot := image.NewRGBA(image.Rect(0, 0, int(d.width), int(d.height)))
@@ -26,39 +98,23 @@ func (d *Doodle) Screenshot() {
 		if pixel.x == pixel.dx && pixel.y == pixel.dy {
 			screenshot.Set(int(pixel.x), int(pixel.y), image.Black)
 		} else {
-			// Draw a line. TODO: get this into its own function!
-			// https://en.wikipedia.org/wiki/Digital_differential_analyzer_(graphics_algorithm)
-			var (
-				x1 = pixel.x
-				x2 = pixel.dx
-				y1 = pixel.y
-				y2 = pixel.dy
-			)
-			var (
-				dx = float64(x2 - x1)
-				dy = float64(y2 - y1)
-			)
-			var step float64
-			if math.Abs(dx) >= math.Abs(dy) {
-				step = math.Abs(dx)
-			} else {
-				step = math.Abs(dy)
-			}
-
-			dx = dx / step
-			dy = dy / step
-			x := float64(x1)
-			y := float64(y1)
-			for i := 0; i <= int(step); i++ {
-				screenshot.Set(int(x), int(y), image.Black)
-				x += dx
-				y += dy
+			for point := range draw.Line(pixel.x, pixel.y, pixel.dx, pixel.dy) {
+				screenshot.Set(int(point.X), int(point.Y), image.Black)
 			}
 		}
-
 	}
 
-	filename := fmt.Sprintf("screenshot-%s.png",
+	// Create the screenshot directory.
+	if _, err := os.Stat("./screenshots"); os.IsNotExist(err) {
+		log.Info("Creating directory: ./screenshots")
+		err = os.Mkdir("./screenshots", 0755)
+		if err != nil {
+			log.Error("Can't create ./screenshots: %s", err)
+			return
+		}
+	}
+
+	filename := fmt.Sprintf("./screenshots/screenshot-%s.png",
 		time.Now().Format("2006-01-02T15-04-05"),
 	)
 	fh, err := os.Create(filename)

types/types.go

@@ -0,0 +1,13 @@
+package types
+
+import "fmt"
+
+// Point is a 2D point in space.
+type Point struct {
+	X int32 `json:"x"`
+	Y int32 `json:"y"`
+}
+
+func (p Point) String() string {
+	return fmt.Sprintf("(%d,%d)", p.X, p.Y)
+}