package il.net.inter.genadyb.phonebook;

import java.util.StringTokenizer;

/**
 * This class contains the implementations of the different 
 * field retrieval methods.
 */
public class FieldRetrieval {
    
    /*
     * Constant that select the retrieval method.
     */ 
    
    public static final int INDEX_OF = 1;
    public static final int TOKENIZER = 2;
    public static final int REGEX = 3;
    public static final int INTERN = 4;    
    public static final int NEW_STRING = 5;    

    /**
     * The field that controls which field retrieval method
     * will be used.
     */
    private static int method = INDEX_OF;
    
    /**
     * Set the field retrieval method.
     */
    public static void setMethod(int newMethod) {
        method = newMethod;
    }
    
    /**
     * Retrieve the i-th field from colon delimited string according
     * to the selected field retrieval {@link #method}.
     * 
     * @param line A line from the database file
     * @param field Field number
     */
    public static String getField(String line, int field) {
        switch (method) {
			case INDEX_OF: return getFieldIndexOf(line, field);
            case TOKENIZER: return getFieldTokenizer(line, field);
            case REGEX: return getFieldRegex(line, field);
            case INTERN: return getFieldIntern(line, field);
            case NEW_STRING: return getFieldNewString(line, field);

			default :
				throw new IllegalStateException("Unknown method");
		}
    }

	private static String getFieldIndexOf(String line, int field) {
		int startIndex = 0;
        while (field-- != 0) {
            startIndex = line.indexOf(':', startIndex);
            if (startIndex == -1) {
                throw new IllegalArgumentException("String does not have enough fields");
            }
            
            // skip over the ':'
            startIndex ++;
        }
        
        int endIndex = line.indexOf(':', startIndex);
        
        if (endIndex == -1) {
            // the last field
            return line.substring(startIndex);
        } else {
            return line.substring(startIndex, endIndex);
        }
	}

    private static String getFieldTokenizer(String line, int field) {
        StringTokenizer st = new StringTokenizer(line, ":");
        while (field-- != 0) {
            st.nextToken();
        }
        
        return st.nextToken();
    }

    private static String getFieldRegex(String line, int field) {
        return line.split(":", field+2)[field];
    }


    private static String getFieldNewString(String line, int field) {
        return new String(getFieldRegex(line, field));
    }


    private static String getFieldIntern(String line, int field) {
        return getFieldRegex(line, field).intern();
    }

    // -------------------------------------
    // INTERNAL IMPLEMENTATION FOLLOWS.
    // -------------------------------------

    /**
     * Return the i-th field from colon delimited string,
     * using the simplest regular expressions method. This method
     * is not controlled by the {@link #method} field.
     * It is an internal program implementation method and 
     * has nothing to do with the described methods.
     */
    static String getNormalField(String line, int field) {
        return getFieldRegex(line, field);
    }

}