Support for squares background colors and themes

border/border.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/maaslalani/gambit/board"
 	"github.com/maaslalani/gambit/position"
+	"github.com/maaslalani/gambit/style"
 )
 
 const (
@@ -44,19 +45,70 @@ func Build(left, middle, right string) string {
 	return withMarginLeft(border)
 }
 
+func topWithTheme(theme style.Theme) string {
+	var s strings.Builder
+	// top-left square is light
+	isLightSquare := true
+	for i := 0; i < board.Cols; i++ {
+		for j := 0; j < cellWidth; j++ {
+			s.WriteString(theme.Fg("\u2583", isLightSquare))
+		}
+		isLightSquare = !isLightSquare
+	}
+	s.WriteRune('\n')
+	return withMarginLeft(s.String())
+}
+
 // Top returns a built border with the top row
-func Top() string {
-	return Build("┌", "┬", "┐")
+func Top(theme style.Theme) string {
+	if !theme.IsValid() {
+		return Build("┌", "┬", "┐")
+	}
+	return topWithTheme(theme)
+}
+
+func middleWithTheme(theme style.Theme, firstSquareIsLight bool) string {
+	var s strings.Builder
+	isLightSquare := firstSquareIsLight
+	for i := 0; i < board.Cols; i++ {
+		for j := 0; j < cellWidth; j++ {
+			s.WriteString(theme.Border("\u2580", isLightSquare))
+		}
+		isLightSquare = !isLightSquare
+	}
+	s.WriteRune('\n')
+	return withMarginLeft(s.String())
 }
 
 // Middle returns a built border with the middle row
-func Middle() string {
-	return Build("├", "┼", "┤")
+func Middle(theme style.Theme, firstSquareIsLight bool) string {
+	if !theme.IsValid() {
+		return Build("├", "┼", "┤")
+	}
+	return middleWithTheme(theme, firstSquareIsLight)
+}
+
+// bottomWithTheme returns built border with the bottom row
+func bottomWithTheme(theme style.Theme) string {
+	var s strings.Builder
+	// bottom-left square is dark
+	isLightSquare := false
+	for i := 0; i < board.Cols; i++ {
+		for j := 0; j < cellWidth; j++ {
+			s.WriteString(theme.Fg("\u2580", isLightSquare))
+		}
+		isLightSquare = !isLightSquare
+	}
+	s.WriteRune('\n')
+	return withMarginLeft(s.String())
 }
 
 // Bottom returns a built border with the bottom row
-func Bottom() string {
-	return Build("└", "┴", "┘")
+func Bottom(theme style.Theme) string {
+	if !theme.IsValid() {
+		return Build("└", "┴", "┘")
+	}
+	return bottomWithTheme(theme)
 }
 
 // BottomLabels returns the labels for the files

game/game.go

@@ -42,6 +42,7 @@ type Game struct {
 	selected   string
 	buffer     string
 	flipped    bool
+	theme      Theme
 }
 
 // NewGame returns an initial model of the game board.
@@ -64,11 +65,106 @@ func NewGameWithPosition(position string) *Game {
 	return m
 }
 
+// NewGameWithPosition returns an initial model of the game board with the
+// specified FEN position.
+func NewGameWithPositionAndTheme(position string, theme Theme) *Game {
+	m := NewGameWithPosition(position)
+	m.theme = theme
+
+	return m
+}
+
 // Init Initializes the model
 func (m *Game) Init() tea.Cmd {
 	return nil
 }
 
+// drawRankNumber returns the string with the rank number and the eventual
+// border
+func (m *Game) drawRankNumber(rank int) string {
+	rankString := Faint(fmt.Sprintf(" %d ", rank+1))
+	if !m.theme.IsValid() {
+		rankString = rankString + border.Vertical
+	}
+	return rankString
+}
+
+// renderSelectedPiece returns the string of the piece with the selected
+// color based on the theme
+func (m *Game) renderSelectedPiece(display string, isLightSquare bool) string {
+	if m.theme.IsValid() {
+		return m.theme.SelectedSquare(display, isLightSquare)
+	}
+	return Cyan(display)
+}
+
+// renderPieceInCheck returns the string of the piece with the check
+// color based on the theme
+func (m *Game) renderPieceInCheck(display string, isLightSquare bool) string {
+	if m.theme.IsValid() {
+		return m.theme.CheckSquare(display, isLightSquare)
+	}
+	return Red(display)
+}
+
+// renderAvailableMove returns the string of the piece with the availableMove
+// color based on the theme
+func (m *Game) renderAvailableMove(display string, isLightSquare bool) string {
+	if m.theme.IsValid() {
+		return m.theme.AvailableMove(display, isLightSquare)
+	}
+	return Magenta(display)
+}
+
+// renderNormalPiece returns the string of the piece based on the theme
+func (m *Game) renderNormalPiece(display string, isWhite bool, isLightSquare bool) string {
+	if m.theme.IsValid() {
+		display = m.theme.Piece(display, isWhite, isLightSquare)
+	}
+	return display
+}
+
+// drawSquare returns the string of the piece and square to show
+func (m *Game) drawSquare(piece pieces.Piece, square string) string {
+	var s strings.Builder
+	whiteTurn := m.board.Wtomove
+	display := piece.Display()
+	check := m.board.OurKingInCheck()
+	selected := square
+	isLightSquare := position.IsLightSquare(square)
+
+	if m.theme.IsValid() {
+		// display first space
+		s.WriteString(m.theme.Bg(" ", isLightSquare))
+	}
+
+	// The user selected the current cell, highlight it so they know it is
+	// selected. If it is a check, highlight the king in red.
+	if m.selected == selected {
+		display = m.renderSelectedPiece(display, isLightSquare)
+	} else if check && piece.IsKing() &&
+		((whiteTurn && piece.IsWhite()) || (!whiteTurn && piece.IsBlack())) {
+		display = m.renderPieceInCheck(display, isLightSquare)
+	} else {
+		display = m.renderNormalPiece(display, piece.IsWhite(), isLightSquare)
+	}
+
+	// Show all the cells to which the piece may move. If it is an empty cell
+	// we present a coloured dot, otherwise color the capturable piece.
+	if moves.IsLegal(m.pieceMoves, selected) && piece.IsEmpty() {
+		display = m.renderAvailableMove(".", isLightSquare)
+	}
+
+	if m.theme.IsValid() {
+		s.WriteString(display)
+		s.WriteString(m.theme.Bg("  ", isLightSquare))
+	} else {
+		s.WriteString(fmt.Sprintf(" %s %s", display, border.Vertical))
+	}
+
+	return s.String()
+}
+
 // View converts a FEN string into a human readable chess board. All pieces and
 // empty squares are arranged in a grid-like pattern. The selected piece is
 // highlighted and the legal moves for the selected piece are indicated by a
@@ -99,7 +195,7 @@ func (m *Game) Init() tea.Cmd {
 //
 func (m *Game) View() string {
 	var s strings.Builder
-	s.WriteString(border.Top())
+	s.WriteString(border.Top(m.theme))
 
 	// Traverse through the rows and columns of the board and print out the
 	// pieces and empty squares. Once a piece is selected, highlight the legal
@@ -119,43 +215,21 @@ func (m *Game) View() string {
 			rr = r
 		}
 
-		s.WriteString(Faint(fmt.Sprintf(" %d ", rr+1)) + border.Vertical)
+		s.WriteString(m.drawRankNumber(rr))
 
 		for c, piece := range row {
-			whiteTurn := m.board.Wtomove
-			display := piece.Display()
-			check := m.board.OurKingInCheck()
-			selected := position.ToSquare(r, c, m.flipped)
-
-			// The user selected the current cell, highlight it so they know it is
-			// selected. If it is a check, highlight the king in red.
-			if m.selected == selected {
-				display = Cyan(display)
-			} else if check && piece.IsKing() {
-				if (whiteTurn && piece.IsWhite()) || (!whiteTurn && piece.IsBlack()) {
-					display = Red(display)
-				}
-			}
-
-			// Show all the cells to which the piece may move. If it is an empty cell
-			// we present a coloured dot, otherwise color the capturable piece.
-			if moves.IsLegal(m.pieceMoves, selected) {
-				if piece.IsEmpty() {
-					display = "."
-				}
-				display = Magenta(display)
-			}
-
-			s.WriteString(fmt.Sprintf(" %s %s", display, border.Vertical))
+			square := position.ToSquare(r, c, m.flipped)
+			s.WriteString(m.drawSquare(piece, square))
 		}
 		s.WriteRune('\n')
 
 		if r != board.LastRow {
-			s.WriteString(border.Middle())
+			firstSquareIsLight := position.IsLightSquare(position.ToSquare(r, 0, m.flipped))
+			s.WriteString(border.Middle(m.theme, firstSquareIsLight))
 		}
 	}
 
-	s.WriteString(border.Bottom() + Faint(border.BottomLabels(m.flipped)))
+	s.WriteString(border.Bottom(m.theme) + Faint(border.BottomLabels(m.flipped)))
 	return s.String()
 }
 

main.go

@@ -12,18 +12,31 @@ import (
 	tea "github.com/charmbracelet/bubbletea"
 	"github.com/maaslalani/gambit/cmd"
 	"github.com/maaslalani/gambit/game"
+	"github.com/maaslalani/gambit/style"
 	"github.com/muesli/coral"
 )
 
 var (
 	Version   = ""
 	CommitSHA = ""
+	ThemeFile = ""
 
 	rootCmd = &coral.Command{
 		Use:   "gambit",
 		Short: "Play chess in your terminal",
 		RunE: func(cmd *coral.Command, args []string) error {
 			if len(args) == 0 {
+
+				// initialize theme
+				var err error
+				theme := style.Theme{}
+				if ThemeFile != "" {
+					theme, err = style.ParseThemeFile(ThemeFile)
+					if err != nil {
+						return err
+					}
+				}
+
 				startPos, _ := readStdin()
 
 				debug := os.Getenv("DEBUG")
@@ -36,12 +49,12 @@ var (
 				}
 
 				p := tea.NewProgram(
-					game.NewGameWithPosition(startPos),
+					game.NewGameWithPositionAndTheme(startPos, theme),
 					tea.WithAltScreen(),
 					tea.WithMouseCellMotion(),
 				)
 
-				_, err := p.Run()
+				_, err = p.Run()
 				return err
 			}
 
@@ -68,6 +81,9 @@ func init() {
 	rootCmd.AddCommand(
 		cmd.ServeCmd,
 	)
+
+	// add flag -t (--theme) to specify the theme file to use
+	rootCmd.Flags().StringVarP(&ThemeFile, "theme", "t", "", "Theme file path")
 }
 
 func main() {

pieces/pieces.go

@@ -9,18 +9,18 @@ type Piece string
 // representations for a more human readable experience.
 var display = map[Piece]string{
 	"":  " ",
-	"B": "♝",
-	"K": "♚",
-	"N": "♞",
-	"P": "♟",
-	"Q": "♛",
-	"R": "♜",
-	"b": "♗",
-	"k": "♔",
-	"n": "♘",
-	"p": "♙",
-	"q": "♕",
-	"r": "♖",
+	"B": "\u2657",
+	"K": "\u2654",
+	"N": "\u2658",
+	"P": "\u2659",
+	"Q": "\u2655",
+	"R": "\u2656",
+	"b": "\u265d",
+	"k": "\u265a",
+	"n": "\u265e",
+	"p": "\u265f",
+	"q": "\u265b",
+	"r": "\u265c",
 }
 
 // IsWhite returns true if the piece is white.

position/position.go

@@ -39,3 +39,17 @@ func ToSquare(row, col int, flipped bool) string {
 	}
 	return colToFile(col) + strconv.Itoa(rowToRank(row))
 }
+
+// IsLightSquare returns true if the square in given position is light
+func IsLightSquare(position string) bool {
+	file := position[0]
+	rank, err := strconv.Atoi(string(position[1]))
+	if err != nil {
+		panic(err)
+	}
+	// Rule: if the file and rank are both odd or both even, the square
+	// is dark, otherwise it is light
+	isOddFile := file%2 == 1
+	isOddRank := rank%2 == 1
+	return isOddFile != isOddRank
+}

style/style.go

@@ -12,5 +12,4 @@ var Cyan = fg("6")
 var Faint = fg("8")
 var Magenta = fg("5")
 var Red = fg("1")
-
 var Title = NewStyle().Foreground(Color("5")).Italic(true).Render