main.go

package main

import (
	"bufio"
	"errors"
	"fmt"
	"os"
	"strings"

	game "github.com/aditya43/chess/engine"
	"github.com/gookit/color" // For printing colorful text in terminal
)

// Execute program
func main() {
	for {
		cr := bufio.NewReader(os.Stdin)
		printInfo()
		s, _ := cr.ReadString('\n')
		w := strings.Fields(strings.ToLower(s))
		checkExit(s)
		takeAction(w, cr)
	}
}

// Take action based off user input
func takeAction(w []string, cr *bufio.Reader) {
	err := validateInput(w)

	if err != nil {
		color.Error.Println(err)
		restartProgram(cr)
		return
	}

	cb := game.CreateChessBoard()    // Create chessboard
	pos := cb.StrCells[w[1]]         // Get numeric position for a cell
	p := game.CreatePiece(pos, w[0]) // Create a piece
	cb.PlacePiece(pos, p)            // Place a piece on chessboard

	printOutput(cb)    // Print output
	restartProgram(cr) // Restart program
}

// Validate user inputs
func validateInput(w []string) error {
	var pieceErr, posErr bool

	if len(w) < 2 {
		return errors.New("Invalid input. Please enter piece type and position.")
	}

	switch strings.ToLower(w[0]) {
	case "king", "queen", "bishop", "horse", "rook", "pawn":
	default:
		pieceErr = true // User didn't input any of the above piece type
	}

	switch strings.ToLower(w[1]) {
	case "a1", "a2", "a3", "a4", "a5", "a6", "a7", "a8",
		"b1", "b2", "b3", "b4", "b5", "b6", "b7", "b8",
		"c1", "c2", "c3", "c4", "c5", "c6", "c7", "c8",
		"d1", "d2", "d3", "d4", "d5", "d6", "d7", "d8",
		"e1", "e2", "e3", "e4", "e5", "e6", "e7", "e8",
		"f1", "f2", "f3", "f4", "f5", "f6", "f7", "f8",
		"g1", "g2", "g3", "g4", "g5", "g6", "g7", "g8",
		"h1", "h2", "h3", "h4", "h5", "h6", "h7", "h8":
	default:
		posErr = true // User didn't input any of the above cell positions
	}

	if pieceErr && posErr {
		return errors.New("Invalid piece type and position value.")
	}

	if pieceErr {
		return errors.New("Invalid piece type.")
	}

	if posErr {
		return errors.New("Invalid position value.")
	}

	return nil
}

// Print information about how to use this program
func printInfo() {
	print("\033[H\033[2J") // Ansi escape sequence to clear the screen
	fmt.Println("Enter a piece type and it's position")
	fmt.Println("+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+")
	color.New(color.FgGreen, color.BgBlack, color.OpBold).Println("👍 Program input is case-insensitive.")
	color.New(color.FgGreen, color.BgBlack, color.OpBold).Print("👍 Type ")
	color.BgRed.Print("exit")
	color.New(color.FgGreen, color.BgBlack, color.OpBold).Println(" to quit program.")
	fmt.Print("\n")

	fmt.Print("Piece types: ")
	color.Yellow.Println("King, Queen, Bishop, Horse, Rook, Pawn")
	fmt.Print("Example input: ")
	color.Style{color.FgGreen, color.OpBold}.Println("King D5")

	fmt.Println("+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+")
	fmt.Print("Input: ")
}

// Exit program if user typed 'exit'
func checkExit(s string) {
	if strings.HasPrefix(strings.ToLower(s), "exit") {
		fmt.Println("Good bye!🍺")
		os.Exit(0)
	}
}

// Ask user to hit Enter key to restart program
func restartProgram(cr *bufio.Reader) {
	color.Yellow.Println("Hit Enter key to continue")
	s, _ := cr.ReadString('\n')
	checkExit(s) // User can quit program by typing 'exit'
}

// Print available move positions
// and render a chessboard
func printOutput(cb *game.ChessBoard) {
	for _, p := range cb.Pieces {
		m := ""
		color.Yellow.Print("Available Moves: ")

		for pos := range p.AvailPos {
			m += strings.ToUpper(cb.Cells[pos]) + ", "
		}

		color.New(color.FgGreen, color.BgBlack, color.OpBold).Printf("%v\n\n", strings.TrimSuffix(m, ", "))
	}
	cb.Print() // Render chessboard
	fmt.Print("\n")
}