Add Makefile

.gitignore

@@ -2,3 +2,4 @@
 !assets/*.png
 .env
 *.sqlite3
+chessbot

Makefile

@@ -0,0 +1,13 @@
+.PHONY: build test
+
+SOURCES := main.go $(shell find chess -name '*.go')
+
+build: chessbot
+
+chessbot: $(SOURCES)
+	go build -o chessbot .
+
+test:
+	## -count=1 is used to disable cache
+	## use -run <regexp> to only run tests that match <regexp>
+	go test ./chess -v -count=1

chess/board.go

@@ -12,13 +12,19 @@ import (
 
 	"golang.org/x/image/font"
 	"golang.org/x/image/font/basicfont"
+	"golang.org/x/image/font/opentype"
 	"golang.org/x/image/math/fixed"
 )
 
 type Board struct {
-	tiles [8][8]*Piece
+	tiles          [8][8]*Piece
-	turn  Color
+	turn           Color
-	Moves []string
+	Moves          []string
+	moveIndicators []Tile
+}
+
+type Tile struct {
+	X, Y int
 }
 
 func NewBoard() *Board {
@@ -101,7 +107,7 @@ func (b *Board) Image() *image.RGBA {
 			x := xi * 128
 			y := yi * 128
 			rect = image.Rect(x, y, x+128, y+128)
-			bg = image.NewUniform(getTileColor(xi, yi))
+			bg = image.NewUniform(getTileColor(b, xi, yi))
 			draw.Draw(img, rect, bg, p, draw.Src)
 
 			piece = b.tiles[xi][yi]
@@ -186,17 +192,23 @@ func drawCoordinate(img *image.RGBA, x, y int, flipped bool) {
 	}
 
 	drawString := func(s string, origin fixed.Point26_6) {
-		color := getTileColor(x, y)
+		color := getTileColor(nil, x, y)
 		if !flipped && color == Light {
 			color = Dark
 		} else if !flipped {
 			color = Light
 		}
-		// TODO: use SN font and make it bold
+
+		face, err := loadFontFace("lightningvolt.ttf")
+		if err != nil {
+			log.Printf("error loading font: %v\n", err)
+			face = basicfont.Face7x13
+		}
+
 		d := &font.Drawer{
 			Dst:  img,
 			Src:  image.NewUniform(color),
-			Face: basicfont.Face7x13,
+			Face: face,
 			Dot:  origin,
 		}
 		d.DrawString(s)
@@ -209,11 +221,36 @@ func drawCoordinate(img *image.RGBA, x, y int, flipped bool) {
 	}
 
 	if row != "" {
-		origin = fixed.P((x+1)*128-12, y*128+15)
+		origin = fixed.P((x+1)*128-20, y*128+23)
 		drawString(row, origin)
 	}
 }
 
+func loadFontFace(path string) (font.Face, error) {
+	fontBytes, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+
+	ttfFont, err := opentype.Parse(fontBytes)
+	if err != nil {
+		return nil, err
+	}
+
+	faceOptions := &opentype.FaceOptions{
+		Size:    32,
+		DPI:     72,
+		Hinting: font.HintingNone,
+	}
+
+	fontFace, err := opentype.NewFace(ttfFont, faceOptions)
+	if err != nil {
+		return nil, err
+	}
+
+	return fontFace, nil
+}
+
 func (b *Board) SetPiece(name PieceName, color Color, position string) error {
 	var (
 		piece *Piece
@@ -360,7 +397,7 @@ func (b *Board) Move(move string) error {
 	}
 
 	// make sure the move is marked as a check if it was
-	if b.InCheck() && !strings.HasSuffix(move, "+") {
+	if b.InCheck() && !strings.HasSuffix(move, "+") && !strings.HasSuffix(move, "#") {
 		move += "+"
 	}
 
@@ -379,6 +416,7 @@ func parseMove(move string) (string, int, int, string, error) {
 	)
 
 	move = strings.TrimSuffix(move, "+")
+	move = strings.TrimSuffix(move, "#")
 
 	if move == "O-O" {
 		return "K", 5, 7, "g1", nil
@@ -801,6 +839,7 @@ func (b *Board) movePawn(position string, fromX int, fromY int, promotion string
 		if promotion != "" {
 			return b.promotePawn(toX, toY, promotion)
 		}
+		b.moveIndicators = []Tile{{fromX, fromY}, {toX, toY}}
 		return nil
 	}
 
@@ -823,6 +862,7 @@ func (b *Board) movePawn(position string, fromX int, fromY int, promotion string
 		if promotion != "" {
 			return b.promotePawn(toX, toY, promotion)
 		}
+		b.moveIndicators = []Tile{{toX, yPrev}, {toX, toY}}
 		return nil
 	}
 
@@ -839,6 +879,7 @@ func (b *Board) movePawn(position string, fromX int, fromY int, promotion string
 		if promotion != "" {
 			return b.promotePawn(toX, toY, promotion)
 		}
+		b.moveIndicators = []Tile{{toX, yPrev}, {toX, toY}}
 		return nil
 	}
 
@@ -948,6 +989,7 @@ func (b *Board) moveRook(position string, queen bool, fromX int, fromY int) erro
 		p = b.getPiece(xPrev, yPrev)
 		b.tiles[x][y] = p
 		b.tiles[xPrev][yPrev] = nil
+		b.moveIndicators = []Tile{{xPrev, yPrev}, {x, y}}
 		return nil
 	}
 
@@ -978,6 +1020,7 @@ func (b *Board) moveBishop(position string, queen bool) error {
 			if ((!queen && piece.Name == Bishop) || (queen && piece.Name == Queen)) && piece.Color == b.turn {
 				b.tiles[xPrev][yPrev] = nil
 				b.tiles[x][y] = piece
+				b.moveIndicators = []Tile{{xPrev, yPrev}, {x, y}}
 				return nil
 			} else {
 				// direction blocked by other piece
@@ -996,6 +1039,7 @@ func (b *Board) moveBishop(position string, queen bool) error {
 			if ((!queen && piece.Name == Bishop) || (queen && piece.Name == Queen)) && piece.Color == b.turn {
 				b.tiles[xPrev][yPrev] = nil
 				b.tiles[x][y] = piece
+				b.moveIndicators = []Tile{{xPrev, yPrev}, {x, y}}
 				return nil
 			} else {
 				break
@@ -1013,6 +1057,7 @@ func (b *Board) moveBishop(position string, queen bool) error {
 			if ((!queen && piece.Name == Bishop) || (queen && piece.Name == Queen)) && piece.Color == b.turn {
 				b.tiles[xPrev][yPrev] = nil
 				b.tiles[x][y] = piece
+				b.moveIndicators = []Tile{{xPrev, yPrev}, {x, y}}
 				return nil
 			} else {
 				break
@@ -1030,6 +1075,7 @@ func (b *Board) moveBishop(position string, queen bool) error {
 			if ((!queen && piece.Name == Bishop) || (queen && piece.Name == Queen)) && piece.Color == b.turn {
 				b.tiles[xPrev][yPrev] = nil
 				b.tiles[x][y] = piece
+				b.moveIndicators = []Tile{{xPrev, yPrev}, {x, y}}
 				return nil
 			} else {
 				break
@@ -1123,6 +1169,7 @@ func (b *Board) moveKnight(position string, fromX int, fromY int) error {
 		p = b.getPiece(xPrev, yPrev)
 		b.tiles[x][y] = p
 		b.tiles[xPrev][yPrev] = nil
+		b.moveIndicators = []Tile{{xPrev, yPrev}, {x, y}}
 		return nil
 	}
 
@@ -1194,6 +1241,8 @@ func (b *Board) moveKing(position string, castle bool) error {
 			b.tiles[5][y] = rook
 			b.tiles[7][y] = nil
 
+			b.moveIndicators = []Tile{{4, y}, {x, y}, {5, y}, {7, y}}
+
 			return nil
 		}
 
@@ -1227,6 +1276,8 @@ func (b *Board) moveKing(position string, castle bool) error {
 			b.tiles[3][y] = rook
 			b.tiles[0][y] = nil
 
+			b.moveIndicators = []Tile{{2, y}, {4, y}, {3, y}, {0, y}}
+
 			return nil
 		}
 	}
@@ -1238,6 +1289,7 @@ func (b *Board) moveKing(position string, castle bool) error {
 	if piece != nil && piece.Name == King && piece.Color == b.turn {
 		b.tiles[xPrev][yPrev] = nil
 		b.tiles[x][y] = piece
+		b.moveIndicators = []Tile{{xPrev, yPrev}, {x, y}}
 		return nil
 	}
 
@@ -1248,6 +1300,7 @@ func (b *Board) moveKing(position string, castle bool) error {
 	if piece != nil && piece.Name == King && piece.Color == b.turn {
 		b.tiles[xPrev][yPrev] = nil
 		b.tiles[x][y] = piece
+		b.moveIndicators = []Tile{{xPrev, yPrev}, {x, y}}
 		return nil
 	}
 
@@ -1258,6 +1311,7 @@ func (b *Board) moveKing(position string, castle bool) error {
 	if piece != nil && piece.Name == King && piece.Color == b.turn {
 		b.tiles[xPrev][yPrev] = nil
 		b.tiles[x][y] = piece
+		b.moveIndicators = []Tile{{xPrev, yPrev}, {x, y}}
 		return nil
 	}
 
@@ -1268,6 +1322,7 @@ func (b *Board) moveKing(position string, castle bool) error {
 	if piece != nil && piece.Name == King && piece.Color == b.turn {
 		b.tiles[xPrev][yPrev] = nil
 		b.tiles[x][y] = piece
+		b.moveIndicators = []Tile{{xPrev, yPrev}, {x, y}}
 		return nil
 	}
 
@@ -1278,6 +1333,7 @@ func (b *Board) moveKing(position string, castle bool) error {
 	if piece != nil && piece.Name == King && piece.Color == b.turn {
 		b.tiles[xPrev][yPrev] = nil
 		b.tiles[x][y] = piece
+		b.moveIndicators = []Tile{{xPrev, yPrev}, {x, y}}
 		return nil
 	}
 
@@ -1288,6 +1344,7 @@ func (b *Board) moveKing(position string, castle bool) error {
 	if piece != nil && piece.Name == King && piece.Color == b.turn {
 		b.tiles[xPrev][yPrev] = nil
 		b.tiles[x][y] = piece
+		b.moveIndicators = []Tile{{xPrev, yPrev}, {x, y}}
 		return nil
 	}
 
@@ -1298,6 +1355,7 @@ func (b *Board) moveKing(position string, castle bool) error {
 	if piece != nil && piece.Name == King && piece.Color == b.turn {
 		b.tiles[xPrev][yPrev] = nil
 		b.tiles[x][y] = piece
+		b.moveIndicators = []Tile{{xPrev, yPrev}, {x, y}}
 		return nil
 	}
 
@@ -1308,6 +1366,7 @@ func (b *Board) moveKing(position string, castle bool) error {
 	if piece != nil && piece.Name == King && piece.Color == b.turn {
 		b.tiles[xPrev][yPrev] = nil
 		b.tiles[x][y] = piece
+		b.moveIndicators = []Tile{{xPrev, yPrev}, {x, y}}
 		return nil
 	}
 
@@ -1392,8 +1451,25 @@ func (b *Board) getCollision(position string) (*Piece, error) {
 	return nil, nil
 }
 
-func getTileColor(x, y int) Color {
+func getTileColor(b *Board, x, y int) Color {
-	if x%2 == y%2 {
+
+	lightTile := x%2 == y%2
+
+	if b != nil {
+		// highlight move
+		// TODO: refactor using alpha channels
+		for _, t := range b.moveIndicators {
+			if t.X == x && t.Y == y {
+				if lightTile {
+					return LightGreen
+				} else {
+					return DarkGreen
+				}
+			}
+		}
+	}
+
+	if lightTile {
 		return Light
 	} else {
 		return Dark

chess/board_test.go

@@ -472,6 +472,22 @@ func TestBoardCheck(t *testing.T) {
 	assertParse(t, b, "Kxf7")
 }
 
+func TestBoardCheckmate(t *testing.T) {
+	t.Parallel()
+
+	b := chess.NewBoard()
+
+	assert.False(t, b.InCheck())
+
+	// fool's mate
+	assertParse(t, b, "f3 e6 g4 Qh4#")
+
+	assert.True(t, b.InCheck())
+	assert.True(t, strings.HasSuffix(b.Moves[len(b.Moves)-1], "#"), "checkmate move should end with #")
+
+	assertMoveError(t, b, "a3", "invalid move a3: king is in check")
+}
+
 func TestBoardPin(t *testing.T) {
 	t.Parallel()
 

chess/piece.go

@@ -58,8 +58,10 @@ const (
 type Color color.Color
 
 var (
-	Light Color = color.RGBA{240, 217, 181, 255}
+	Light      Color = color.RGBA{240, 217, 181, 255}
-	Dark  Color = color.RGBA{181, 136, 99, 255}
+	Dark       Color = color.RGBA{181, 136, 99, 255}
+	LightGreen Color = color.RGBA{205, 210, 106, 255}
+	DarkGreen  Color = color.RGBA{170, 162, 58, 255}
 )
 
 func NewPiece(name PieceName, color Color) (*Piece, error) {

go.mod

@@ -3,7 +3,7 @@ module github.com/ekzyis/chessbot
 go 1.23.0
 
 require (
-	github.com/ekzyis/snappy v0.6.2
+	github.com/ekzyis/snappy v0.7.0
 	github.com/mattn/go-sqlite3 v1.14.23
 	github.com/stretchr/testify v1.9.0
 	golang.org/x/image v0.20.0
@@ -12,6 +12,7 @@ require (
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	golang.org/x/text v0.18.0 // indirect
 	gopkg.in/guregu/null.v4 v4.0.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -1,7 +1,7 @@
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
-github.com/ekzyis/snappy v0.6.2 h1:iOPgoS0cSUNk8leQJku0bBgnsha/+DcYUwTYqGLINY4=
+github.com/ekzyis/snappy v0.7.0 h1:RcFTUHdZFTBFOnh6cG9HCL/RPK6L13qdxDrjBNZFjEM=
-github.com/ekzyis/snappy v0.6.2/go.mod h1:UksYI0dU0+cnzz0LQjWB1P0QQP/ghx47e4atP99a5Lk=
+github.com/ekzyis/snappy v0.7.0/go.mod h1:UksYI0dU0+cnzz0LQjWB1P0QQP/ghx47e4atP99a5Lk=
 github.com/mattn/go-sqlite3 v1.14.23 h1:gbShiuAP1W5j9UOksQ06aiiqPMxYecovVGwmTxWtuw0=
 github.com/mattn/go-sqlite3 v1.14.23/go.mod h1:Uh1q+B4BYcTPb+yiD3kU8Ct7aC0hY9fxUwlHK0RXw+Y=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
@@ -10,6 +10,8 @@ github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsT
 github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
 golang.org/x/image v0.20.0 h1:7cVCUjQwfL18gyBJOmYvptfSHS8Fb3YUDtfLIZ7Nbpw=
 golang.org/x/image v0.20.0/go.mod h1:0a88To4CYVBAHp5FXJm8o7QbUl37Vd85ply1vyD8auM=
+golang.org/x/text v0.18.0 h1:XvMDiNzPAl0jr17s6W9lcaIhGUfUORdGCNsuLmPG224=
+golang.org/x/text v0.18.0/go.mod h1:BuEKDfySbSR4drPmRPG/7iBdf8hvFMuRexcpahXilzY=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/guregu/null.v4 v4.0.0 h1:1Wm3S1WEA2I26Kq+6vcW+w0gcDo44YKYD7YIEJNHDjg=

main.go

@@ -14,21 +14,54 @@ import (
 )
 
 var (
-	c = sn.GetClient()
+	c  = sn.GetClient()
-	// TODO: fetch our id from SN API
+	me *sn.User
-	// prod: 25176 | local: 21858
-	meId = 25176
 )
 
 func main() {
 
 	for {
+		updateMe()
 		tickGameStart(c)
 		tickGameProgress(c)
 		time.Sleep(15 * time.Second)
 	}
 }
 
+func updateMe() {
+	var (
+		oldMe         *sn.User
+		err           error
+		warnThreshold = 100
+	)
+
+	maybeWarn := func() {
+		if me.Privates.Sats < warnThreshold {
+			log.Printf("~~~ warning: low balance ~~~\n")
+		}
+	}
+
+	if me == nil {
+		// make sure first update is successful
+		if me, err = c.Me(); err != nil {
+			log.Fatalf("failed to fetch me: %v\n", err)
+		}
+		log.Printf("fetched me: id=%d name=%s balance=%d\n", me.Id, me.Name, me.Privates.Sats)
+		maybeWarn()
+		return
+	}
+
+	oldMe = me
+	if me, err = c.Me(); err != nil {
+		log.Printf("failed to update me: %v\n", err)
+		me = oldMe
+	} else {
+		log.Printf("updated me. balance: %d\n", me.Privates.Sats)
+	}
+
+	maybeWarn()
+}
+
 func tickGameStart(c *sn.Client) {
 	var (
 		mentions []sn.Notification
@@ -98,7 +131,7 @@ func tickGameProgress(c *sn.Client) {
 		if parent, err := c.Item(n.Item.ParentId); err != nil {
 			log.Printf("failed to fetch parent %d of %d\n", n.Item.ParentId, n.Item.Id)
 			continue
-		} else if parent.User.Id != meId {
+		} else if parent.User.Id != me.Id {
 			log.Printf("ignoring nested reply %d\n", n.Item.Id)
 			continue
 		}
@@ -146,8 +179,15 @@ func handleGameStart(req *sn.Item) error {
 		return fmt.Errorf("failed to upload image for item %d: %v\n", req.Id, err)
 	}
 
-	// reply with algebraic notation and image
+	// reply with algebraic notation, image and info
-	res = strings.Trim(fmt.Sprintf("%s\n\n%s", b.AlgebraicNotation(), imgUrl), " ")
+	infoMove := "e4"
+	if len(b.Moves) > 0 {
+		infoMove = "e5"
+	}
+	info := fmt.Sprintf("_A new chess game has been started!_\n\n"+
+		"_Reply with a move like `%s` to continue the game. "+
+		"See [here](https://stacker.news/chess#how-to-continue) for details._", infoMove)
+	res = strings.Trim(fmt.Sprintf("%s\n\n%s\n\n%s", b.AlgebraicNotation(), imgUrl, info), " ")
 	if _, err = createComment(req.Id, res); err != nil {
 		return fmt.Errorf("failed to reply to item %d: %v\n", req.Id, err)
 	}
@@ -176,7 +216,7 @@ func handleGameProgress(req *sn.Item) error {
 	}
 
 	for _, item := range thread {
-		if item.User.Id == meId {
+		if item.User.Id == me.Id {
 			continue
 		}
 
@@ -278,6 +318,8 @@ func parseGameStart(input string) (string, error) {
 }
 
 func parseGameProgress(input string) (string, error) {
+	input = strings.Trim(input, " ")
+
 	lines := strings.Split(input, "\n")
 	words := strings.Split(input, " ")
 
@@ -305,5 +347,5 @@ func isRecent(t time.Time) bool {
 }
 
 func alreadyHandled(id int) (bool, error) {
-	return db.ItemHasReply(id, meId)
+	return db.ItemHasReply(id, me.Id)
 }

sn/sn.go

@@ -13,6 +13,7 @@ import (
 type Client = snappy.Client
 type Notification = snappy.Notification
 type Item = snappy.Item
+type User = snappy.User
 
 var (
 	c *Client