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package com.avaje.ebeaninternal.util;

import com.avaje.ebeaninternal.util.SortByClause.Property;

public final class SortByClauseParser {
	
	private final String rawSortBy;
	
	public static SortByClause parse(String rawSortByClause){
		return new SortByClauseParser(rawSortByClause).parse();
	}
	
	private SortByClauseParser(String rawSortByClause) {
		this.rawSortBy = rawSortByClause.trim();
	}
	
	private SortByClause parse(){
		
		SortByClause sortBy = new SortByClause();
		
		String[] sections = rawSortBy.split(",");
		for (int i = 0; i < sections.length; i++) {
			Property p = parseSection(sections[i].trim());
			if (p == null){
				break;
			} else {
				sortBy.add(p);
			}
			
		}
				
		return sortBy;
	}
	
	private Property parseSection(String section){
		if (section.length() == 0){
			return null;
		}
		String[] words = section.split(" ");
		if (words.length < 1 || words.length > 3){
			throw new RuntimeException("Expecting 1 to 3 words in ["+section+"] but got ["+words.length+"]");
		}
		
		Boolean nullsHigh = null;
		boolean ascending = true;
		String propName = words[0];
		if (words.length > 1){
			if (words[1].startsWith("nulls")){
				nullsHigh = isNullsHigh(words[1]);
				
			} else {
				ascending = isAscending(words[1]);
			}
		}
		if (words.length > 2){
			if (words[2].startsWith("nulls")){
				nullsHigh = isNullsHigh(words[2]);
				
			} else {
				ascending = isAscending(words[2]);
			}
		}
		
		return new Property(propName, ascending, nullsHigh);
	}

	private Boolean isNullsHigh(String word){
		if (SortByClause.NULLSHIGH.equalsIgnoreCase(word)){
			return Boolean.TRUE;
		}
		if (SortByClause.NULLSLOW.equalsIgnoreCase(word)){
			return Boolean.FALSE;
		}
		String m = "Expecting nullsHigh or nullsLow but got ["+word+"] in ["+rawSortBy+"]";
		throw new RuntimeException(m);
	}

	
	private boolean isAscending(String word){
		if (SortByClause.ASC.equalsIgnoreCase(word)){
			return true;
		}
		if (SortByClause.DESC.equalsIgnoreCase(word)){
			return false;
		}
		String m = "Expection ASC or DESC but got ["+word+"] in ["+rawSortBy+"]";
		throw new RuntimeException(m);
	}

}