package bjc.rgens.parser.elements;

import bjc.rgens.parser.GrammarException;

/**
 * Variable defining case element.
 * 
 * @author Ben Culkin
 *
 */
public abstract class VariableDefCaseElement extends CaseElement {
	/**
	 * The name of the variable this element defines.
	 */
	public final String varName;

	/**
	 * The definition of the variable this element defines.
	 */
	public final String varDef;

	/**
	 * Create a variable defining case element.
	 * 
	 * @param name
	 *             The name of the variable.
	 * @param def
	 *             The definition of the variable.
	 */
	public VariableDefCaseElement(String name, String def) {
		super(false);

		varName = name;
		varDef = def;
	}

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = super.hashCode();
		result = prime * result + ((varDef == null) ? 0 : varDef.hashCode());
		result = prime * result + ((varName == null) ? 0 : varName.hashCode());
		return result;
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (!super.equals(obj))
			return false;
		if (getClass() != obj.getClass())
			return false;
		VariableDefCaseElement other = (VariableDefCaseElement) obj;
		if (varDef == null) {
			if (other.varDef != null)
				return false;
		} else if (!varDef.equals(other.varDef))
			return false;
		if (varName == null) {
			if (other.varName != null)
				return false;
		} else if (!varName.equals(other.varName))
			return false;
		return true;
	}

	/**
	 * Parse a variable reference.
	 * 
	 * @param varName
	 *                The variable name.
	 * @param varDef
	 *                The variable definition.
	 * @param op
	 *                Unused as of yet.
	 * @param colon
	 *                Whether the colon was present in the declaration.
	 * 
	 * @return A case element which declares the variable.
	 */
	public static CaseElement parseVariable(String varName, String varDef, char op,
			boolean colon) {
		if (varName.startsWith("$")) {
			// Handle normal/expanding variable definitions
			if (colon)
				return new ExpVariableCaseElement(varName.substring(1), varDef);

			return new LitVariableCaseElement(varName.substring(1), varDef);
		} else if (varName.startsWith("@")) {
			return new RuleVariableCaseElement(varName.substring(1), varDef, colon);
		} else {
			throw new GrammarException(
					"Unrecognized declaration sigil " + varName.charAt(0));
		}
	}
}