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package com.google.refine.expr.functions;

import java.util.Properties;

import com.google.refine.browsing.Engine;
import com.google.refine.browsing.util.ExpressionNominalValueGrouper;
import com.google.refine.expr.EvalError;
import com.google.refine.expr.Evaluable;
import com.google.refine.expr.MetaParser;
import com.google.refine.expr.ParsingException;
import com.google.refine.grel.ControlFunctionRegistry;
import com.google.refine.grel.Function;
import com.google.refine.model.Column;
import com.google.refine.model.Project;

public class FacetCount implements Function {

    @Override
    public Object call(Properties bindings, Object[] args) {
        if (args.length == 3 && args[1] instanceof String && args[2] instanceof String) {
            Object choiceValue = args[0]; // choice value to look up
            String facetExpression = (String) args[1];
            String columnName = (String) args[2];

            Project project = (Project) bindings.get("project");
            Column column = project.columnModel.getColumnByName(columnName);
            if (column == null) {
                return new EvalError("No such column named " + columnName);
            }

            String key = "nominal-bin:" + facetExpression;
            ExpressionNominalValueGrouper grouper = (ExpressionNominalValueGrouper) column.getPrecompute(key);
            if (grouper == null) {
                try {
                    Evaluable eval = MetaParser.parse(facetExpression);
                    Engine engine = new Engine(project);

                    grouper = new ExpressionNominalValueGrouper(eval, columnName, column.getCellIndex());
                    engine.getAllRows().accept(project, grouper);

                    column.setPrecompute(key, grouper);
                } catch (ParsingException e) {
                    return new EvalError("Error parsing facet expression " + facetExpression);
                }
            }

            return grouper.getChoiceValueCountMultiple(choiceValue);
        }
        return new EvalError(ControlFunctionRegistry.getFunctionName(this) + 
            " expects a choice value, an expression as a string, and a column name");
    }

    @Override
    public String getDescription() {
        return "Returns the facet count corresponding to the given choice value";
    }
    
    @Override
    public String getParams() {
        return "choiceValue, string facetExpression, string columnName";
    }
    
    @Override
    public String getReturns() {
        return "number";
    }
}
