function ClusteringDialog(columnName, expression) {
    this._columnName = columnName;
    this._expression = expression;
    this._method = "binning";
    this._function = "fingerprint";
    this._params = {};
    
    this._facets = [];
    
    this._createDialog();
    this._cluster();
}

ClusteringDialog.prototype._createDialog = function() {
    var self = this;
    var frame = DialogSystem.createDialog();
    frame.width("900px");
    
    var header = $('<div></div>').addClass("dialog-header").text('Cluster & Edit column "' + this._columnName + '"').appendTo(frame);
    var body = $('<div></div>').addClass("dialog-body").appendTo(frame);
    var footer = $(
        '<div class="dialog-footer">' +
           '<table width="100%"><tr>' +
             '<td class="left" style="text-align: left"></td>' + 
             '<td class="right" style="text-align: right"></td>' +
           '</tr></table>' +
        '</div>'
    ).appendTo(frame);
    
    var html = $(
        '<div class="grid-layout layout-normal layout-full"><table>' +
            '<tr>' +
                '<td>' +
                    'Method: <select bind="methodSelector">' +
                        '<option selected="true">key collision</option>' +
                        '<option>nearest neighbor</option>' +
                    '</select>' +
                '</td>' +
                '<td>' +
                    '<div class="binning-controls">Keying Function: <select bind="keyingFunctionSelector">' +
                        '<option selected="true">fingerprint</option>' +
                        '<option>ngram-fingerprint</option>' +
                        '<option>double-metaphone</option>' +
                    '</select></div>' +
                    '<div class="knn-controls hidden">Distance Function: <select bind="distanceFunctionSelector">' +
                        '<option selected="true">levenshtein</option>' +
                        '<option>PPM</option>' +
                    '</select></div>' +
                '</td>' +
                '<td>' +
                    '<div id="ngram-fingerprint-params" class="function-params hidden">' +
                      'Ngram Size: <input type="text" value="2" bind="ngramSize" name="ngram-size" size="3" class="param" datatype="int">' +
                    '</div>' + 
                    '<div class="knn-controls hidden">' +
                        '<span style="margin-right: 1em">Radius: <input type="text" value="1.0" bind="radius" name="radius" size="3" class="param" datatype="float"></span>' +
                        '<span>Block Chars: <input type="text" value="6" bind="ngramBlock" name="blocking-ngram-size" size="3" class="param" datatype="int"></span>' +
                    '</div>' + 
                '</td>' +
                '<td bind="resultSummary" align="right">' +
                '</td>' +
            '</tr>' +
            '<tr>' +
                '<td colspan="3">' +
                    '<div bind="tableContainer" class="clustering-dialog-table-container"></div>' +
                '</td>' +
                '<td bind="facetContainer" width="200"></td>' +
            '</tr>' +
        '</table></div>'
    ).appendTo(body);
    
    this._elmts = DOM.bind(html);

    this._elmts.methodSelector.change(function() {
        var selection = $(this).find("option:selected").text();
        if (selection == 'key collision') {
            body.find(".binning-controls").show();
            body.find(".knn-controls").hide();
            self._method = "binning";
            self._elmts.keyingFunctionSelector.change();
        } else if (selection === 'nearest neighbor') {
            body.find(".binning-controls").hide();
            body.find(".knn-controls").show();
            self._method = "knn";
            self._elmts.distanceFunctionSelector.change();
        }
    });

    var changer = function() {
        self._function = $(this).find("option:selected").text();
        $(".function-params").hide();
        $("#" + self._function + "-params").show();
        params_changer();
    };
    
    this._elmts.keyingFunctionSelector.change(changer);
    this._elmts.distanceFunctionSelector.change(changer);
    
    var params_changer = function() {
        self._params = {};
        $(".dialog-body input.param:visible").each(function() {
            var e = $(this);
            var name = e.attr('name');
            var datatype = e.attr('datatype') || 'string';
            var value = e.val(); 
            if (datatype == 'int') {
                value = parseInt(value,10);
            } else if (datatype == 'float') {
                value = parseFloat(value);
            }   
            self._params[name] = value;
        });
        self._cluster();
    };
    
    this._elmts.ngramSize.change(params_changer);
    this._elmts.radius.change(params_changer);
    this._elmts.ngramBlock.change(params_changer);
    
    var left_footer = footer.find(".left");    
    $('<button></button>').text("Select All").click(function() { self._selectAll(); }).appendTo(left_footer);
    $('<button></button>').text("Deselect All").click(function() { self._deselectAll(); }).appendTo(left_footer);
    
    var right_footer = footer.find(".right");    
    $('<button></button>').text("Apply & Re-Cluster").click(function() { self._onApplyReCluster(); }).appendTo(right_footer);
    $('<button></button>').text("Apply & Close").click(function() { self._onApplyClose(); }).appendTo(right_footer);
    $('<button></button>').text("Close").click(function() { self._dismiss(); }).appendTo(right_footer);
    
    this._level = DialogSystem.showDialog(frame);
    
    $("#recon-dialog-tabs").tabs();
    $("#recon-dialog-tabs-strict").css("display", "");
};

ClusteringDialog.prototype._renderTable = function(clusters) {
    var self = this;
    
    var container = this._elmts.tableContainer;
    
    if (clusters.length > 0) {
        var table = $('<table></table>').addClass("clustering-dialog-entry-table")[0];
        
        var trHead = table.insertRow(table.rows.length);
        trHead.className = "header";
        $(trHead.insertCell(0)).text("Cluster Size");
        $(trHead.insertCell(1)).text("Row Count");
        $(trHead.insertCell(2)).text("Values in Cluster");
        $(trHead.insertCell(3)).text("Merge?");
        $(trHead.insertCell(4)).text("New Cell Value");

        var renderCluster = function(cluster) {
            var tr = table.insertRow(table.rows.length);
            tr.className = table.rows.length % 2 === 0 ? "odd" : "even";
            
            $(tr.insertCell(0)).text(cluster.choices.length);
            
            $(tr.insertCell(1)).text(cluster.rowCount);

            var facet = {
                "c": {
                    "type":"list",
                    "name": self._columnName,
                    "columnName": self._columnName,
                    "expression":"value"
                },
                "o":{
                    "sort":"name"
                },
                "s":[
                ]
            };
            
            var ul = $('<ul></ul>');
            var choices = cluster.choices;
            var rowCount = 0;
            var onClick = function() {
              var parent = $(this).closest("tr");
              parent.find("input[type='text']").val($(this).text());
              parent.find("input:not(:checked)").attr('checked', true).change();
              return false;
            };
            for (var c = 0; c < choices.length; c++) {
                var choice = choices[c];
                var li = $('<li></li>');
                $('<a href="javascript:{}" title="Use this value"></a>').text(choice.v).click(onClick).appendTo(li);
                $('<span></span>').text("(" + choice.c + " rows)").addClass("clustering-dialog-entry-count").appendTo(li);
                rowCount += choice.c;
                facet.s[c] = {
                    "v": {
                        "v":choice.v,
                        "l":choice.v
                    }
                };
                li.appendTo(ul);
            }
            
            var params = [
                "project=" + escape(theProject.id),
                "ui=" + escape(JSON.stringify({
                    "facets" : [ facet ]
                }))
            ];
            var url = "project.html?" + params.join("&");
                            
            var div = $('<div></div>').addClass("clustering-dialog-value-focus");
            
            var browseLink = $('<a target="_new" title="Browse only these values">Browse this cluster</a>')
                .addClass("clustering-dialog-browse-focus")
                .attr("href",url)
                .css("visibility","hidden")
                .appendTo(div);

            $(tr.insertCell(2))
                .mouseenter(function() { browseLink.css("visibility", "visible"); })
                .mouseleave(function() { browseLink.css("visibility", "hidden"); })
                .append(ul)
                .append(div);
            
            var editCheck = $('<input type="checkbox" />')
                .change(function() {
                    cluster.edit = !cluster.edit;
                }).appendTo(tr.insertCell(3));

            if (cluster.edit) {
                editCheck.attr("checked", "true");
            }
            
            var input = $('<input size="25" />')
                .attr("value", cluster.value)
                .keyup(function() {
                    cluster.value = this.value;
                }).appendTo(tr.insertCell(4));
        };
        
        for (var i = 0; i < clusters.length; i++) {
            renderCluster(clusters[i]);
        }
        
        container.empty().append(table);
        
        this._elmts.resultSummary.html(
            (clusters.length === this._clusters.length) ?
                ("<b>" + this._clusters.length + "</b> cluster" + ((this._clusters.length != 1) ? "s" : "") + " found") :
                ("<b>" + clusters.length + "</b> cluster" + ((clusters.length != 1) ? "s" : "") + " filtered from <b>" + this._clusters.length + "</b> total")
        );
        
    } else {
        container.html(
            '<div style="margin: 2em;"><div style="font-size: 130%; color: #333;">No clusters were found with the selected method</div><div style="padding-top: 1em; font-size: 110%; color: #888;">Try selecting another method above or changing its parameters</div></div>'
        );
    }
    
};

ClusteringDialog.prototype._cluster = function() {
    var self = this;
    
    var container = this._elmts.tableContainer.html(
        '<div style="margin: 1em; font-size: 130%; color: #888;">Clustering... <img src="/images/small-spinner.gif"></div>'
    );
    
    this._elmts.resultSummary.empty();

    $.post(
        "/command/compute-clusters?" + $.param({ project: theProject.id }),
        { 
            engine: JSON.stringify(ui.browsingEngine.getJSON()), 
            clusterer: JSON.stringify({ 
                'type' : this._method, 
                'function' : this._function,
                'column' : this._columnName,
                'params' : this._params
            }) 
        },
        function(data) {
            self._updateData(data);
        },
        "json"
    );
};

ClusteringDialog.prototype._updateData = function(data) {
    var clusters = [];
    $.each(data, function() {
        var cluster = {
            edit: false,
            choices: this,
            value: this[0].v,
            size: this.length
        };
        
        var sum = 0;
        var sumSquared = 0;
        var rowCount = 0;
        $.each(cluster.choices, function() {
            rowCount += this.c;
        
            var l = this.v.length; 
            sum += l;
            sumSquared += l * l;
        });
        
        cluster.rowCount = rowCount;
        cluster.avg = sum / cluster.choices.length;
        cluster.variance = Math.sqrt(sumSquared / cluster.choices.length - cluster.avg * cluster.avg);
        
        clusters.push(cluster);
    });
    this._clusters = clusters;
    
    this._resetFacets();
    this._updateAll();
};

ClusteringDialog.prototype._selectAll = function() {
    $(".clustering-dialog-entry-table input:not(:checked)").attr('checked', true).change();
};

ClusteringDialog.prototype._deselectAll = function() {
    $(".clustering-dialog-entry-table input:checked").attr('checked', false).change();
};

ClusteringDialog.prototype._onApplyClose = function() {
    var self = this;        
    this._apply(function() {
        self._dismiss();
    });
};

ClusteringDialog.prototype._onApplyReCluster = function() {
    var self = this;        
    this._apply(function() {
        self._cluster();
    });
};

ClusteringDialog.prototype._apply = function(onDone) {
    var clusters = this._getRestrictedClusters();
    var edits = [];
    for (var i = 0; i < clusters.length; i++) {
        var cluster = clusters[i];
        if (cluster.edit) {
            var values = [];
            for (var j = 0; j < cluster.choices.length; j++) {
                values.push(cluster.choices[j].v);
            }
            
            edits.push({
                from: values,
                to: cluster.value
            });
        }
    }
    
    if (edits.length > 0) {
        Gridworks.postProcess(
            "mass-edit",
            {},
            {
                columnName: this._columnName,
                expression: this._expression,
                edits: JSON.stringify(edits)
            },
            { cellsChanged: true },
            {
                onError: function(o) {
                    alert("Error: " + o.message);
                },
                onDone: onDone
            }
        );
    } else {
        alert("You must check some Edit? checkboxes for your edits to be applied.");
    }
};

ClusteringDialog.prototype._dismiss = function() {
    DialogSystem.dismissUntil(this._level - 1);
};

ClusteringDialog.prototype._getBaseClusters = function() {
    return [].concat(this._clusters);
};

ClusteringDialog.prototype._getRestrictedClusters = function(except) {
    var clusters = this._getBaseClusters();
    for (var i = 0; i < this._facets.length; i++) {
        var facet = this._facets[i].facet;
        if (except !== facet) {
            clusters = facet.restrict(clusters);
        }
    }
    return clusters;
};

ClusteringDialog.prototype._updateAll = function() {
    for (var i = 0; i < this._facets.length; i++) {
        var facet = this._facets[i].facet;
        var clusters = this._getRestrictedClusters(facet);
        facet.update(clusters);
    }
    this._renderTable(this._getRestrictedClusters());
};

ClusteringDialog.prototype._resetFacets = function() {
    for (var i = 0; i < this._facets.length; i++) {
        var r = this._facets[i];
        r.facet.dispose();
        r.elmt.remove();
    }
    this._facets = [];
    
    this._createFacet("Cluster Size", "size");
    this._createFacet("Row Count", "rowCount");
    this._createFacet("Value Length Average", "avg");
    this._createFacet("Value Length Variance", "variance");
};

ClusteringDialog.prototype._createFacet = function(title, property) {
    var elmt = $('<div>').appendTo(this._elmts.facetContainer);
    this._facets.push({
        elmt: elmt,
        facet: new ClusteringDialog.Facet(this, title, property, elmt, this._getBaseClusters())
    });
};

ClusteringDialog.Facet = function(dialog, title, property, elmt, clusters) {
    this._dialog = dialog;
    this._property = property;
    
    var self = this;
    
    var max = Number.NEGATIVE_INFINITY;
    var min = Number.POSITIVE_INFINITY;
    for (var i = 0; i < clusters.length; i++) {
        var cluster = clusters[i];
        var val = cluster[property];
        max = Math.max(max, val);
        min = Math.min(min, val);
    }
    
    this._min = min;
    this._max = max;
    if (min >= max) {
        this._step = 0;
        this._baseBins = [];
    } else {
        var diff = max - min;
        
        this._step = 1;
        if (diff > 10) {
            while (this._step * 100 < diff) {
                this._step *= 10;
            }
        } else {
            while (this._step * 100 > diff) {
                this._step /= 10;
            }
        }
        
        this._min = (Math.floor(this._min / this._step) * this._step);
        this._max = (Math.ceil(this._max / this._step) * this._step);
        this._binCount = 1 + Math.ceil((this._max - this._min) / this._step);
        if (this._binCount > 100) {
            this._step *= 2;
            this._binCount = Math.round((1 + this._binCount) / 2);
        } else if (this._binCount < 3) {
            this._step /= 2;
            this._binCount *= 2;
            this._max = (Math.ceil(this._max / this._step) * this._step);
        }
        this._baseBins = this._computeDistribution(clusters);
        
        this._from = this._min;
        this._to = this._max;
        
        elmt.addClass("clustering-dialog-facet");
        var html = $(
            '<div class="clustering-dialog-facet-header">' + title + '</div>' +
            '<div class="clustering-dialog-facet-slider" bind="sliderWidgetDiv">' +
                '<div class="clustering-dialog-facet-histogram" bind="histogramContainer"></div>' +
            '</div>' +
            '<div class="clustering-dialog-facet-selection" bind="selectionContainer"></div>'
        ).appendTo(elmt);
        
        this._elmts = DOM.bind(html);
        
        this._histogram = new HistogramWidget(this._elmts.histogramContainer, { binColors: [ "#ccccff", "#6666ff" ] });
        this._sliderWidget = new SliderWidget(this._elmts.sliderWidgetDiv);
        
        this._elmts.sliderWidgetDiv.bind("slide", function(evt, data) {
            self._from = data.from;
            self._to = data.to;
            self._setRangeIndicators();
        }).bind("stop", function(evt, data) {
            self._from = data.from;
            self._to = data.to;
            self._setRangeIndicators();
            self._dialog._updateAll();
        });

        this._setRangeIndicators();
    }
};

ClusteringDialog.Facet.prototype.dispose = function() {
};

ClusteringDialog.Facet.prototype.restrict = function(clusters) {
    if (!this._baseBins.length || (this._from == this._min && this._to == this._max)) {
        return clusters;
    }
    
    var clusters2 = [];
    for (var i = 0; i < clusters.length; i++) {
        var cluster = clusters[i];
        var val = cluster[this._property];
        if (val >= this._from && val <= this._to) {
            clusters2.push(cluster);
        }
    }
    return clusters2;
};

ClusteringDialog.Facet.prototype.update = function(clusters) {
    if (!this._baseBins.length) {
        return;
    }
    
    var bins = this._computeDistribution(clusters);

    this._sliderWidget.update(
        this._min, 
        this._max, 
        this._step, 
        this._from,
        this._to
    );
    this._histogram.update(
        this._min, 
        this._max, 
        this._step, 
        [ this._baseBins, bins ]
    );
};

ClusteringDialog.Facet.prototype._setRangeIndicators = function() {
    this._elmts.selectionContainer.html(this._from + " &mdash; " + this._to);
};

ClusteringDialog.Facet.prototype._computeDistribution = function(clusters) {
    var bins = [];
    for (var b = 0; b < this._binCount; b++) {
        bins.push(0);
    }
    
    for (var i = 0; i < clusters.length; i++) {
        var cluster = clusters[i];
        var val = cluster[this._property];
        var bin = Math.round((val - this._min) / this._step);
        bins[bin]++;
    }
    
    return bins;
};