package org.simantics.datatypes.literal;

import java.text.DecimalFormat;
import java.text.DecimalFormatSymbols;
import java.util.Locale;

import org.simantics.common.format.Formatter;
import org.simantics.databoard.Bindings;
import org.simantics.databoard.binding.Binding;
import org.simantics.databoard.util.Bean;


public class DecimalFormatFormatter extends Bean implements Formatter {

	public static final Binding BINDING = Bindings.getBindingUnchecked(DecimalFormatFormatter.class);

	public String formatString;

	private volatile DecimalFormat format;

	public DecimalFormatFormatter() {
		this("0.###############");
	}

	public DecimalFormatFormatter(String formatString) {
		if (formatString == null)
			throw new NullPointerException("null formatString");
		this.formatString = formatString;
	}
	
	public DecimalFormat getFormat() {
		if(format == null) {
			format = new java.text.DecimalFormat(formatString, DecimalFormatSymbols.getInstance(Locale.US));
		}
		return format;
	}

	@Override
	public String format(Object object) {
		if (object instanceof String) return object.toString();
		else if (object instanceof Number) {

			DecimalFormat format = getFormat();
//			System.out.println("formatString: " + formatString);
			int integers = format.getMaximumIntegerDigits();
			//System.out.println("  integers: " + integers);
			if (integers == Integer.MAX_VALUE) {
				// Parse number of integer digits from format string.
				integers = countIntegerDigits(formatString);
			}
			//System.out.println("  decimals: " + format.getMaximumFractionDigits());
			//System.out.println("  integers: " + format.getMinimumIntegerDigits());
			//System.out.println("  decimals: " + format.getMinimumFractionDigits());
			String result = format.format(object);
			//System.out.println("result: " + result);
			int resultIntegers = countResultDigits(result);
			//System.out.println("  result integers: " + resultIntegers);
			if (resultIntegers > integers) {
				// Guard against format.getMaximumFractionDigits returning Integer.MAX_VALUE
				int decimals = Math.min(format.getMaximumFractionDigits(), 15);
				return getLimitString(integers, decimals);
			}
			return result; 
		} else {
			return object != null ? object.toString() : "";
		}
	}	
	
	private int countIntegerDigits(String formatString) {
		int digits = 0;
		int len = formatString.length();
		boolean escape = false;
		for (int i = 0; i < len; ++i) {
			char ch = formatString.charAt(i);
			if (ch == '.')
				break;
			else if (ch == '\'')
				escape = true;
			else if (!escape && (ch == '#' || ch == '0'))
				++digits;
		}
		return digits;
	}

	private int countResultDigits(String formattedString) {
		int digits = 0;
		int len = formattedString.length();
		for (int i = 0; i < len; ++i) {
			char ch = formattedString.charAt(i);
			if (ch == '.')
				break;
			else if (Character.isDigit(ch))
				++digits;
		}
		return digits;
	}
	
	private String getLimitString(int integers, int decimals) {
		StringBuilder b = new StringBuilder(integers + decimals + 1);
		for(int i=0;i<integers;i++) b.append('*');
		b.append('.');
		for(int i=0;i<decimals;i++) b.append('*');
		return b.toString();
	}
	
}