package com.tyndalehouse.step.dataloader.beans;

import java.text.ParseException;
import java.util.Calendar;
import java.util.GregorianCalendar;

import org.apache.commons.lang.StringUtils;

import com.tyndalehouse.step.dataloader.common.DateParsingException;

/**
 * This class is the way dates are represented in the databased
 * and they should be parsed back into this object on their way out!
 * 
 * The date field indicates when the event (or start of the event) took 
 * place, the precision type indicates whether how much of the date
 * can be trusted...
 * 
 * This means we can store dates such as (01/03/1900, MONTH), meaning
 * March 1900 (and not 1st March 1900).
 * @author CJBurrell
 */
public class PartialDate {
	/**
	 * The date to be represented (whether fully accurate or not)
	 */
	private final Calendar c;
	
	/**
	 * The precision specifier which tells us just quite
	 * how accurate the date is (year, month, day)
	 * @see com.tyndalehouse.step.dataloader.beans.PrecisionType
	 */
	private final PrecisionType precision;

	/**
	 * Public constructor to give us a partial date.
	 * @param c date partial reprentation of a date
	 * @param precision precision indicating how much of the 
	 * date can be trusted day/month/year or month/year or just year
	 */
	public PartialDate(final Calendar c, final PrecisionType precision) {
		this.c = c;
		this.precision = precision;
	}
	
	/**
	 * Date is specified in yy-mm-dd or yyyy-mm-dd and gets parsed in to a date.
	 * the mm and dd are optional which is what determines the precision of the date.
	 * @param date date to be parsed as a string
	 * @param delimiter delimiter in the date, say a - or a /
	 * @return a PartialDate
	 * @throws ParseException an error during the parsing of the date
	 */
	public static PartialDate parseDate(final String date, char delimiter) throws DateParsingException {
		String[] parts;
		Calendar c = Calendar.getInstance();
		PrecisionType p;
		int yearSign = 1;										// -1 for negative
		
		//if passed in empty, return null and be done with empty strings!
		if(StringUtils.isEmpty(date)) {
			return new PartialDate(null, PrecisionType.NONE);
		}
		
		//the date might start with a dash, so best not to split and do it character by character?
		if(date.charAt(0) == '-') {
			yearSign = -1;
			
			//check we have more than one character left after substring:
			if(date.length() < 2) {
				throw new DateParsingException("The date " + date + " was not long enough.");
			}
		
			//split the remainder of the date into parts
			parts = date.substring(1).trim().split("" + delimiter);	// ignore first character
		} else {
 			parts = date.trim().split(""+delimiter);
		}
		
		try {
			//length of field determines how much of the date has been specified
			switch(parts.length) {
				case 0: throw new DateParsingException("The date " + date + " could not be parsed.");
				case 1:
					//only the year is specified, so use 1st of Jan Year
					c.set(Integer.parseInt(parts[0]), 1, 1);
					p = PrecisionType.YEAR;
					if(yearSign == -1) { c.set(Calendar.ERA, GregorianCalendar.BC); }
					c.set(Calendar.HOUR_OF_DAY, 0);
					c.set(Calendar.MINUTE, 0);
					break;
				case 2: 
					c.set(Integer.parseInt(parts[0]), Integer.parseInt(parts[1]), 1);
					p = PrecisionType.MONTH;
					break;
				case 3:
					c.set(Integer.parseInt(parts[0]), Integer.parseInt(parts[1]), Integer.parseInt(parts[2]));
					p = PrecisionType.DAY;
					break;
				default: throw new DateParsingException("Too many parts to the date: " + date);
					
			}
		} catch(NumberFormatException nfe) {
			throw new DateParsingException("Could not parse date into year, month or day.");
		}

		c.set(Calendar.HOUR_OF_DAY, 0);
		c.set(Calendar.MINUTE, 0);
		if(yearSign == -1) { c.set(Calendar.ERA, GregorianCalendar.BC); }
		return new PartialDate(c, p);
	}

	public Calendar getDate() {
		return c;
	}
	
	public PrecisionType getPrecision() {
		return precision;
	}
}