SudokuSolver/SolverWebApp/wwwroot/js/sudoku-solver.js

window.onload = setup

var cells_ordered = null

function setup() {
    let table = document.getElementById('sudoku_board')
    cells_ordered = table.getElementsByTagName('td')
    console.log(cells_ordered.length)
    for (let c = 0; c < 81; c++){
        let cell = cells_ordered[c]
        cell.addEventListener("keypress",check_cell_content)
        cell.setAttribute("contenteditable","")
        cell.innerHTML = '<br>' //Moves caret position to vertical center
    }
    show_all_solutions()
}

function fill_default() {
    $('#message').text('')
    publish_board([
        [9,NaN,5,NaN,NaN,NaN,3,NaN,NaN],
        [NaN,6,NaN,NaN,NaN,1,NaN,5,NaN],
        [3,2,1,9,NaN,NaN,NaN,NaN,NaN],
        [NaN,9,2,5,NaN,NaN,4,1,3],
        [NaN,5,7,4,NaN,NaN,NaN,NaN,NaN],
        [NaN,1,NaN,NaN,NaN,2,NaN,NaN,5],
        [NaN,7,NaN,NaN,NaN,9,1,NaN,6],
        [NaN,NaN,NaN,NaN,NaN,NaN,NaN,NaN,NaN],
        [NaN,NaN,NaN,NaN,NaN,NaN,NaN,NaN,NaN]
    ])
}

function clear_board() {
    $('#message').text('')
    for (let row = 0; row < 9; row++)
        for (let column = 0; column < 9; column++)
            publish_cell(row, column, NaN)
}

function check_cell_content(e) {
    console.log(e.key)
    let content = parseInt(e.key)
    console.log(content)
    if ((content <= 0) || isNaN(content) || e.target.innerText.trim().length > 0){
        e.preventDefault()
    }
}

function get_data() {
    let table = document.getElementById('sudoku_board')
    let cells_ordered = table.getElementsByTagName('td')
    let sudoku_board = [[],[],[],[],[],[],[],[],[]]
    for (let cell = 0;cell<81;cell++){
        let column = cell%9
        let row = Math.floor(cell/9)
        let value = parseInt(cells_ordered[cell].textContent.trim())
        sudoku_board[row][column] = value
    }
    return sudoku_board
}

function publish_cell(row, column, value) {
    cells_ordered[row*9 + column].innerHTML = "" + (isNaN(value) ? "<br>" : value)
}

function publish_board(board) {
    for (let row = 0; row < 9; row++)
        for (let column = 0; column < 9; column++)
            publish_cell(row, column, board[row][column])
}

function set_cell(board, row, column, value) {
    board[row][column] = value
    publish_cell(row, column, value)
}

function solve_step(board, cell) {
    let column = cell%9
    let row = Math.floor(cell/9)
    
    if(cell > 80)
        return true

    if(!isNaN(board[row][column]))
        return solve_step(board, cell + 1)
        
    for(let nr = 1;nr<=9;nr++) {
        if(check_cell(board, row, column, nr)) {
            set_cell(board, row, column, nr)
            if(solve_step(board, cell + 1)) {
                return true;
            } else {
                set_cell(board, row, column, NaN)
            }
        }
    }
    return false
}

function board_to_string(board) {
    let ret = ""
    for (let row = 0; row < 9; row++)
        for (let column = 0; column < 9; column++)
            ret += isNaN(board[row][column]) ? "0" : "" + board[row][column]
    return ret
}

function store_board(board) {
    $.ajax({
        url: '/solution',
        type: 'POST',
        contentType: 'application/json',
        data: JSON.stringify({ "Data": board_to_string(board) }),
        success: function () {
            $('#message').text('Stored solution to database')
            show_all_solutions()
        },
        error: function () {
            $('#message').text('Error on saving the solution to the database.')
        }
    })
}

function solve() {
    $('#message').text('')
    let board = get_data()
    if (!check_board(board)) {
        $('#message').text("The numbers on the board are in conflict with the rules of Sudoku")
        return
    }

    if (!solve_step(board, 0)) {
        $('#message').text("Unable to solve this Sudoku")
        return
    }

    store_board(board)
}

function show_all_solutions() {
    jQuery.get("/solution", function (data) {
        new DevExpress.ui.dxDataGrid(document.getElementById("allsolutions"), {
            dataSource: data,
            columnAutoWidth: true
        });
    }).fail(function (e) { console.warn("fetching solution failed: ", e) })
}

function check_cell(board, row, col, value) {
    // if already present on the column, not acceptable
    for (let r = 0; r < 9; ++r)
        if (board[r][ col] == value) return false;

    // if already present on the row, not acceptable
    for (let c = 0; c < 9; ++c)
        if (board[row][ c] == value) return false;

    // if already present in the same 3x3 square, also not acceptable
    let r1 = Math.floor(row / 3) * 3;
    let c1 = Math.floor(col / 3) * 3;
    for (let r = r1; r < r1 + 3; ++r) {
        for (let c = c1; c < c1 + 3; ++c) {
            if (board[r][c] == value) return false;
        }
    }

    return true;
}

function check_board(board) {
    for (let r = 0; r < 9; ++r)
        for (let c = 0; c < 9; ++c) {
            let value = board[r][c]
            if(isNaN(value))
                continue
            board[r][c] = NaN
            let res = check_cell(board,r,c, value)
            board[r][c] = value
            if(!res)
                return false
        }
    return true
}