package opponent

import (
	"math"
	"tictactoe/gamecontrol"
)

type NextMove struct {
	Row   int
	Col   int
	score int
}

// iterative implementation of minimax algorithm
func Minimax(board [3][3]string, depth int, isMaximizingPlayer bool, player string) NextMove {
	// check if the game has ended
	if gamecontrol.PlayerHasWon(board, "X") {
		return NextMove{score: -10 + depth}
	} else if gamecontrol.PlayerHasWon(board, "O") {
		return NextMove{score: 10 - depth}
	} else if gamecontrol.BoardisFull(board) {
		return NextMove{score: 0}
	}
	// check who's turn it is
	if isMaximizingPlayer {
		// set max score
		bestScore := math.MinInt64
		var bestMove NextMove
		// iterate through all fields
		for i := 0; i < 3; i++ {
			for j := 0; j < 3; j++ {
				// check if field is empty
				if board[i][j] == " " {
					// make a move on this field
					board[i][j] = player
					// continue with the other player
					move := Minimax(board, depth+1, false, SwitchPlayer(player))
					// reset the field again
					board[i][j] = " "
					// if this move was better then the move before change values
					if move.score > bestScore {
						bestScore = move.score
						bestMove = NextMove{Row: i, Col: j, score: move.score}
					}
				}
			}
		}
		// return best possible Move
		return bestMove
	} else {
		// set min score
		bestScore := math.MaxInt64
		var bestMove NextMove
		// iterate through all fields
		for i := 0; i < 3; i++ {
			for j := 0; j < 3; j++ {
				// check if field is empty
				if board[i][j] == " " {
					// make a move on this field
					board[i][j] = player
					// continue with the other player
					move := Minimax(board, depth+1, true, SwitchPlayer(player))
					// reset the field again
					board[i][j] = " "
					// if this move was better then the move before change values
					if move.score < bestScore {
						bestScore = move.score
						bestMove = NextMove{Row: i, Col: j, score: move.score}
					}
				}
			}
		}
		// return best possible Move
		return bestMove
	}
}

// this function changes the player for the minimax algorthim
func SwitchPlayer(player string) string {
	if player == "X" {
		return "O"
	} else {
		return "X"
	}
}