TermCloud = function (container) {
    this.container = container;
}

TermCloud.MIN_UNIT_SIZE = 1;
TermCloud.MAX_UNIT_SIZE = 7;
TermCloud.RANGE_UNIT_SIZE = TermCloud.MAX_UNIT_SIZE - TermCloud.MIN_UNIT_SIZE;

TermCloud.nextId = 0;

TermCloud.prototype.draw = function (data, options) {

    var cols = data.getNumberOfColumns();
    var valid = (cols >= 2 && cols <= 3 && data.getColumnType(0) == 'string' &&
      data.getColumnType(1) == 'number');
    if (valid && cols == 3) {
        valid = data.getColumnType(2) == 'string';
    }

    if (!valid) {
        this.container.innerHTML = '<span class="term-cloud-error">TermCloud Error: Invalid data format. First column must be a string, second a number, and optional third column a string</span>';
        return;
    }

    options = options || {};
    var linkTarget = options.target || '_top';

    // Compute frequency range
    var minFreq = 999999;
    var maxFreq = 0;
    for (var rowInd = 0; rowInd < data.getNumberOfRows(); rowInd++) {
        var f = data.getValue(rowInd, 1);
        if (f > 0) {
            minFreq = Math.min(minFreq, f);
            maxFreq = Math.max(maxFreq, f);
        }
    }

    if (minFreq > maxFreq) {
        minFreq = maxFreq;
    }
    if (minFreq == maxFreq) {
        maxFreq++;
    }
    var range = maxFreq - minFreq;
    range = Math.max(range, 4);

    var html = [];
    var id = TermCloud.nextId++;
    html.push('<div class="term-cloud">');
    for (var rowInd = 0; rowInd < data.getNumberOfRows(); rowInd++) {
        var f = data.getValue(rowInd, 1);
        if (f > 0) {
            var text = data.getValue(rowInd, 0);
            var link = cols == 3 ? data.getValue(rowInd, 2) : null;
            var freq = data.getValue(rowInd, 1);
            var size = TermCloud.MIN_UNIT_SIZE +
           Math.round((freq - minFreq) / range * TermCloud.RANGE_UNIT_SIZE);
            html.push('<a class="term-cloud-link" href="', (link || '#'), '" id="_tc_', id, '_', rowInd, '"');
            if (link) {
                html.push(' target="', linkTarget, '"');
            }
            html.push('>');
            html.push('<span class="term-cloud-', size, '">');
            html.push(this.escapeHtml(text));
            html.push('</span>');
            html.push('</a>');
            html.push(' ');
        }
    }
    html.push('</div>');

    this.container.innerHTML = html.join('');

    // Add event listeners
    var self = this;
    for (var rowInd = 0; rowInd < data.getNumberOfRows(); rowInd++) {
        var f = data.getValue(rowInd, 1);
        if (f > 0) {
            var text = data.getValue(rowInd, 0);
            var link = cols == 3 ? data.getValue(rowInd, 2) : null;
            var anchor = document.getElementById('_tc_' + id + '_' + rowInd);
            anchor.onclick = this.createListener(rowInd, !!link);
        }
    }
};

TermCloud.prototype.createListener = function (row, hasLink) {
    var self = this;
    return function () {
        self.selection = [{ row: row}];
        google.visualization.events.trigger(self, 'select', {});
        return hasLink;
    }
};

TermCloud.prototype.selection = [];

TermCloud.prototype.getSelection = function () {
    return this.selection;
};

TermCloud.prototype.escapeHtml = function (text) {
    if (text == null) {
        return '';
    }
    return text.replace(/&/g, '&amp;').
      replace(/</g, '&lt;').
      replace(/>/g, '&gt;').
      replace(/"/g, '&quot;');
};