problem 9

 /*
 * SelectStatement.java
 *
 * DBMS Implementation
 */

import java.util.*;
import com.sleepycat.db.*;

/**
 * A class that represents a SELECT statement.
 */
public class SelectStatement extends SQLStatement {
    /* Used in the selectList for SELECT * statements. */
    public static final String STAR = "*";

    private ArrayList<Object> selectList;
    private Limit limit;
    private boolean distinctSpecified;

    /**
     * Constructs a SelectStatement object involving the specified
     * columns and other objects from the SELECT clause, the specified
     * tables from the FROM clause, the specified conditional
     * expression from the WHERE clause (if any), the specified Limit
     * object summarizing the LIMIT clause (if any), and the specified
     * value indicating whether or not we should eliminate duplicates.
     *
     * @param  selectList  the columns and other objects from the SELECT clause
     * @param  fromList  the list of tables from the FROM clause
     * @param  where  the conditional expression from the WHERE clause (if any)
     * @param  limit  summarizes the info in the LIMIT clause (if any)
     * @param  distinctSpecified  should duplicates be eliminated?
     */
    public SelectStatement(ArrayList<Object> selectList,
                           ArrayList<Table> fromList, ConditionalExpression where,
                           Limit limit, Boolean distinctSpecified)
    {
        super(fromList, new ArrayList<Column>(), where);
        this.selectList = selectList;
        this.limit = limit;
        this.distinctSpecified = distinctSpecified.booleanValue();

        /* add the columns in the select list to the list of columns */
        for (int i = 0; i < selectList.size(); i++) {
            Object selectItem = selectList.get(i);
            if (selectItem instanceof Column)
                this.addColumn((Column)selectItem);
        }
    }
    public Column[] makeWhereColArray() {
        // populate Where columns
        Column[] WColArry = new Column[this.numWhereColumns()];  // column Array for the where columns
        Column whereCol;
        for (int i = 0; i < this.numWhereColumns(); i++) {
            whereCol = this.getWhereColumn(i);
            WColArry[i] = whereCol;
        }
        return WColArry;
    }


    /**
     * Returns a boolean value indicating whether duplicates should be
     * eliminated in the result of this statement -- i.e., whether the
     * user specified SELECT DISTINCT.
     */
    public boolean distinctSpecified() {
        return this.distinctSpecified;
    }

    public void execute() throws DatabaseException, DeadlockException {
        RelationIterator iter = null;
        TableIterator tab = null;
        Column[] WColArry = new Column[this.numWhereColumns()];  // column Array for the where columns
        boolean hasColName = false;

        WColArry = makeWhereColArray();                          //  function to make the WHERE column Array

        try {
            if (this.numTables() == 1) {
                Table table = this.getTable(0);
                if (table.open() == OperationStatus.NOTFOUND)
                    throw new IllegalStateException();  // error msg in open()
                // loop to check if WHERE col name matches one of the cols in FROM
                for (int j = 0; j < WColArry.length;j++) {
                    for (int k = 0; k < table.numColumns(); k++) {
                        if(WColArry[j].nameMatches(table.getColumn(k), table))
                            hasColName = true;
                    }
                }
                if(!hasColName)
                     throw new IllegalStateException("where columns do not match " +
                                                     "Table columns ");
                // if SELECT is *
                if (this.selectList.get(0) == STAR){
                    //if there is a Where clause do this
                    if (this.numWhereColumns() > 0){
                        // ** this is were im stuck ???? ***
                        // go into the WHERE col Array and check
                        // if WHERE col name matches table col name
                            // if the value in the table col evals true or false compared to WHERE col eval ?
                    }
                    else
                        iter = new TableIterator(this, table, true);
                }
                else{
                      tab = new TableIterator(this,table,true); // when i call this the
                      iter = new ProjectionIterator(this,tab);
                }

              // if numTables() > 1
            } else{
                 Table[] tables = new Table[this.numTables()]; // table array for tables in fromList

                 for (int i = 0; i < this.numTables(); i++) {  // loop thru open all tables
                     Table tempTable = new Table(this.getTable(i).getName());
                     tables[i]= tempTable ;
                     if (tables[i].open() == OperationStatus.NOTFOUND)
                        throw new IllegalStateException();  // error msg in open()
                     // check the where columns for match in FROM
                     Column whereCol;
                     for (int j = 0; j < this.numWhereColumns(); j++) {
                        whereCol = this.getWhereColumn(j);
                        WColArry[j] = whereCol;
                    }
                     for (int j2 = 0; j2 < WColArry.length;j2++) {
                        for (int k = 0; k < tempTable.numColumns(); k++) {
                            if(WColArry[j2].nameMatches(tempTable.getColumn(k),tempTable))
                                hasColName = true;
                        }
                    }
                 }
                 if(!hasColName)
                     throw new IllegalStateException("where columns do not match " +
                                                     "Table columns ");

                 if (this.numColumns() == 0 && this.selectList.get(0) == STAR)
                     iter = new CrossIterator(this);
                 else {
                      CrossIterator c = new CrossIterator(this);
                      iter = new ProjectionIterator(this,c);
                 }

            }

            // Iterate over all tuples in the relation and print them out.
            iter.printAll(System.out);

            // Report the number of tuples that were selected.
            int numRows = iter.numTuples();
            System.out.println("Selected " + numRows +
                               (numRows == 1 ? " tuple." : " tuples."));
        } catch (Exception e) {
            String errMsg = e.getMessage();
            if (errMsg != null)
                System.err.println(errMsg + ".");
        }

        if (iter != null)
            iter.close();
    }
}