function loadFile(evt, onComplete) {

    var file = evt.target.files[0];

    Papa.parse(file, {
        header: true,
        delimiter: '\t',
        quoteChar: String.fromCharCode(0),
	    escapeChar: String.fromCharCode(0),
        comments: "#",
        skipEmptyLines: true,
        dynamicTyping: true,
        complete: function(results) { onComplete(results, file) }
    });
}


var displayRows=30
var startIndex=0;
var endIndex=displayRows;
var urls = null;

function setupInterface(data, file) {

    function updateTable() {

        let editable_html =
            `
                <td class="editable">
            `;

        $('#table-body').empty();

        $.each(data.data,
                    function(nRow, el) {

                        if (nRow < startIndex) return;
                        if (nRow >= endIndex) return;

                        var row = $("<tr/>");
                        row.append($('<td> <button class="btn btn-link btn-xs py-0 offset">' +
                                            nRow + '</button>  </td>'));

                        $.each(el,
                            function(column, content) {

                                if (column == 'url_id') return

                                row.append(
                                    $(editable_html).
                                        text(content).
                                        data('tableInfo', { 'nRow': nRow, 'column': column })
                                );
                            });

                        $("#table tbody").append(row);
                    });

        $("#table td:contains('B-PER')").addClass('ner_per');
        $("#table td:contains('I-PER')").addClass('ner_per');
        $("#table td:contains('B-LOC')").addClass('ner_loc');
        $("#table td:contains('I-LOC')").addClass('ner_loc');
        $("#table td:contains('B-ORG')").addClass('ner_org');
        $("#table td:contains('I-ORG')").addClass('ner_org');
        $("#table td:contains('B-OTH')").addClass('ner_oth');
        $("#table td:contains('I-OTH')").addClass('ner_oth');
        $("#table td:contains('B-TODO')").addClass('ner_todo');
        $("#table td:contains('I-TODO')").addClass('ner_todo');

        $(".offset").on('click',
            function(evt) {

                if (urls != null) {
                    return;
                }

                let url_mapping_html =
                    `
                    <br/>
                    <br/>
                    <br/>
                    <input type="file" id="url-mapping-tsv-file" style="visibility: hidden; width: 1px; height: 1px"/>
                    Please
                    <a href="" onclick="$('#url-mapping-tsv-file').click(); return false">upload a url mapping file</a>
                     or<button class="btn btn-link" id="goback">go back to edit mode.</button>
                    `;

                $("#tableregion").html(url_mapping_html);
                $("#btn-region").empty();

                $('#goback').on('click',
                    function(evt) {
                        setupInterface(data, file);
                     }
                );

                $('#url-mapping-tsv-file').change(
                    function(evt) {
                        loadFile(evt,
                            function(results, url_mapping_file) {
                                urls = results;

                                setupInterface(data, file);
                            });
                    }
                );
            }
        );
    }

     let table_html =
        `
        <table id="table">
            <thead>
            <tr>
                <th><button class="btn btn-link" id="back"><<</button>LOCATION</th>
                <th>POSITION</th>
                <th>TOKEN</th>
                <th>NE-TAG</th>
                <th>NE-EMB<button class="btn btn-link" id="next">>></button></th>
            </tr>
            </thead>
            <tbody id="table-body"></tbody>
        </table>
        <br/>
        <br/>
        `;

    let save_html =
        `<button class="btn btn-primary saveButton">Save Changes</button>`

    $("#tableregion").html(table_html)

    $("#btn-region").html(save_html)

    $("#file-region").html('<h3>' + file.name + '</h3>');

    function saveFile(evt) {

        let csv =
            Papa.unparse(data,
                {
                    header: true,
                    delimiter: '\t',
                    comments: "#",
                    quoteChar: String.fromCharCode(0),
                    escapeChar: String.fromCharCode(0),
                    skipEmptyLines: true,
                    dynamicTyping: true
                });

        openSaveFileDialog (csv, file.name, null)
    }

    function openSaveFileDialog (data, filename, mimetype) {

        if (!data) return;

        var blob = data.constructor !== Blob
          ? new Blob([data], {type: mimetype || 'application/octet-stream'})
          : data ;

        if (navigator.msSaveBlob) {
          navigator.msSaveBlob(blob, filename);
          return;
        }

        var lnk = document.createElement('a'),
            url = window.URL,
            objectURL;

        if (mimetype) {
          lnk.type = mimetype;
        }

        lnk.download = filename || 'untitled';
        lnk.href = objectURL = url.createObjectURL(blob);
        lnk.dispatchEvent(new MouseEvent('click'));
        setTimeout(url.revokeObjectURL.bind(url, objectURL));

    }

    $('.saveButton').on('click', saveFile)

    let editingTd;

    function finishTdEdit(td, isOk) {

        if (isOk) {
            let newValue = $('#edit-area').val();

            $(td).html(newValue);

            let tableInfo = $(td).data('tableInfo');

            data.data[tableInfo.nRow][tableInfo.column] = newValue;
        }
        else {
            $(td).html(editingTd.data);
        }

        editingTd = null;
    }

    function makeTdEditable(td) {

        editingTd = {
            elem: td,
            data: td.innerHTML
        };

        let textArea = document.createElement('textarea');
        textArea.style.width = td.clientWidth + 'px';
        textArea.style.height = td.clientHeight + 'px';
        textArea.id = 'edit-area';

        $(textArea).val($(td).html());
        $(td).html('');
        $(td).append(textArea);
        textArea.focus();

        let edit_html =
            `<div class="edit-controls">
                <button class="btn btn-secondary btn-sm" id="edit-ok">OK</button>
                <button class="btn btn-secondary btn-sm" id="edit-cancel">CANCEL</button>
             </div>`

        td.insertAdjacentHTML("beforeEnd", edit_html);

        $('#edit-ok').on('click',
            function(evt) {
                finishTdEdit(editingTd.elem, true);
            });

        $('#edit-cancel').on('click',
            function(evt) {
                finishTdEdit(editingTd.elem, false);
            });
    }

    $('#table').on('click',
        function(event) {

            let target = event.target.closest('.editable');

            if (editingTd) {

                if (target == editingTd.elem) return;

                finishTdEdit(editingTd.elem, true);
            }

            if (!$.contains($('#table')[0], target)) return

            makeTdEditable(target);
        });

    updateTable();

    $('#tableregion')[0].addEventListener("wheel",
        function(event) {

            if (event.deltaY < 0) {

                if (startIndex <= 0) return;

                startIndex -= 1;
                endIndex -= 1;
            }
            else {

                if (endIndex >= data.data.length) return;

                startIndex += 1;
                endIndex += 1;
            }

            updateTable();
        });

    $('#back').on('click',
        function(evt) {

            if (startIndex >= displayRows) {
                startIndex -= displayRows;
                endIndex -= displayRows;
            }
            else {
                startIndex = 0;
                endIndex = displayRows;
            }

            updateTable();
        }
    );

    $('#next').on('click',
        function(evt) {

            if (endIndex + displayRows < data.data.length) {
                endIndex += displayRows;
                startIndex = endIndex - displayRows;
            }
            else {
                endIndex = data.data.length;
                startIndex = endIndex - displayRows;
            }

            updateTable();
        }
    );
}


$(document).ready(
    function() {
        $('#tsv-file').change(
            function(evt) {

                loadFile ( evt,
                    function(results, file) {

                        setupInterface(results, file);
                    })
            }
        );
    }
);