/**
 * Abstract class for representing a statement in the SILLY language.
 * 
 * @author Dave Reed
 * @version 2/9/07
 */
public abstract class Statement
{
    public abstract void read(SourceCode program);
    public abstract void execute(VariableTable variables);
    public abstract Statement.Type getType();
    public abstract String toString();
    
    public static enum Type {
        OUTPUT, IF, ASSIGNMENT   
    }
    
    /**
     * Static method that reads in an arbitrary Statement.
     *   @param program the Source code of the program to be read from
     *   @return the next Statement in the program
     */
    public static Statement getStatement(SourceCode program) {
        Statement stmt;
        
        Token lookAhead = program.peek();
        if (lookAhead.toString().equals("output")) {
            stmt = new Output();
        }
        else if (lookAhead.toString().equals("if")) {
            stmt = new If();
        }        
        else if (lookAhead.getType() == Token.Type.IDENTIFIER) {
            stmt = new Assignment();
        }
        else {
            System.out.println("SYNTAX ERROR: Unknown statement type");
            System.exit(0);
            stmt = new Output();
        }
        
        stmt.read(program);
        return stmt;
    }
}