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package com.google.refine.expr.functions.date;

import java.time.OffsetDateTime;
import java.time.temporal.ChronoUnit;
import java.time.temporal.TemporalUnit;
import java.util.Properties;

import com.google.refine.expr.EvalError;
import com.google.refine.grel.ControlFunctionRegistry;
import com.google.refine.grel.Function;

public class Inc implements Function {

    @Override
    public Object call(Properties bindings, Object[] args) {
        if (args.length == 3 && 
                args[0] != null && (args[0] instanceof OffsetDateTime) && 
                args[1] != null && args[1] instanceof Number && 
                args[2] != null && args[2] instanceof String) {
            OffsetDateTime date = (OffsetDateTime)args[0];
            
            int amount = ((Number) args[1]).intValue();
            String unit = (String) args[2];
            
            return date.plus(amount, getField(unit));
        }
        return new EvalError(ControlFunctionRegistry.getFunctionName(this) + " expects a date, a number and a string");
    }

    private TemporalUnit getField(String unit) {
        if ("hours".equals(unit) || "hour".equals(unit) || "h".equals(unit)) {
            return ChronoUnit.HOURS;
        } else if ("days".equals(unit) || "day".equals(unit) || "d".equals(unit)) {
            return ChronoUnit.DAYS;
        } else if ("years".equals(unit) || "year".equals(unit)) {
            return ChronoUnit.YEARS;
        } else if ("months".equals(unit) || "month".equals(unit)) { // avoid 'm' to avoid confusion with minute
            return ChronoUnit.MONTHS;
        } else if ("minutes".equals(unit) || "minute".equals(unit) || "min".equals(unit)) { // avoid 'm' to avoid confusion with month
            return ChronoUnit.MINUTES;
        } else if ("weeks".equals(unit) || "week".equals(unit) || "w".equals(unit)) {
            return ChronoUnit.WEEKS;
        } else if ("seconds".equals(unit) || "sec".equals(unit) || "s".equals(unit)) {
            return ChronoUnit.SECONDS;
        } else if ("milliseconds".equals(unit) || "ms".equals(unit) || "S".equals(unit)) {
            return ChronoUnit.MILLIS;
        } else if ("nanos".equals(unit) || "nano".equals(unit) || "n".equals(unit)) {
            return ChronoUnit.NANOS;
        } else {
            throw new RuntimeException("Unit '" + unit + "' not recognized.");
        }
    }
    
    @Override
    public String getDescription() {
    	return "Returns a date changed by the given amount in the given unit of time";
    }
    
    @Override
    public String getParams() {
        return "date d, number value, string unit (default to 'hour')";
    }
    
    @Override
    public String getReturns() {
        return "date";
    }
}
