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Copyright 2010, Google Inc.
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    * Redistributions of source code must retain the above copyright
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    * Redistributions in binary form must reproduce the above
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"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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*/

package com.google.refine;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

import com.google.refine.expr.ExpressionUtils;
import com.google.refine.expr.HasFieldsListImpl;
import com.google.refine.expr.WrappedRow;
import com.google.refine.model.Column;
import com.google.refine.model.Project;
import com.google.refine.model.Row;

public class InterProjectModel {
    static public class ProjectJoin {
        final public long   fromProjectID;
        final public String fromProjectColumnName;
        final public long   toProjectID;
        final public String toProjectColumnName;
        
        final public Map<Object, List<Integer>> valueToRowIndices = 
            new HashMap<Object, List<Integer>>();
        
        ProjectJoin(
            long   fromProjectID,
            String fromProjectColumnName,
            long   toProjectID,
            String toProjectColumnName
        ) {
            this.fromProjectID = fromProjectID;
            this.fromProjectColumnName = fromProjectColumnName;
            this.toProjectID = toProjectID;
            this.toProjectColumnName = toProjectColumnName;
        }

        public HasFieldsListImpl getRows(final Object rowKey, String separatorRegexp) {
            Project toProject = ProjectManager.singleton.getProject(toProjectID);
            if (toProject == null) {
                return null;
            }

            HasFieldsListImpl resultFieldList = null;

            if (ExpressionUtils.isNonBlankData(rowKey)) {
                Object[] rowKeys;
                if (separatorRegexp != null && !separatorRegexp.isEmpty() && rowKey instanceof String) {
                    rowKeys = ((String) rowKey).split(separatorRegexp);
                } else {
                    rowKeys = new Object[]{rowKey};
                }

                resultFieldList = new HasFieldsListImpl();
                for (Object k : rowKeys) {
                    if (valueToRowIndices.containsKey(k)) {
                        for (Integer rowIndex : valueToRowIndices.get(k)) {
                            Row row = toProject.rows.get(rowIndex);
                            resultFieldList.add(new WrappedRow(toProject, rowIndex, row));
                        }
                    }
                }
            }

            // Returning null instead of an empty list is expected
            return resultFieldList.isEmpty() ? null : resultFieldList;
        }

    }
    
    protected Map<String, ProjectJoin> _joins = new HashMap<String, ProjectJoin>();
    
    /**
     * Compute the ProjectJoin based on combination key, return the cached one from the HashMap if already computed
     * 
     * @param fromProject
     * @param fromColumn
     * @param toProject
     * @param toColumn
     * @param separatorRegexp
     * @return
     */
    public ProjectJoin getJoin(String fromProject, String fromColumn, String toProject, String toColumn, String separatorRegexp) {
        String key = fromProject + ";" + fromColumn + ";" + toProject + ";" + toColumn;
        if (!_joins.containsKey(key)) {
            ProjectJoin join = new ProjectJoin(
                ProjectManager.singleton.getProjectID(fromProject), 
                fromColumn, 
                ProjectManager.singleton.getProjectID(toProject), 
                toColumn
            );

            computeJoin(join, separatorRegexp);
            
            synchronized (_joins) {
                _joins.put(key, join);
            }
        }
        
        return _joins.get(key);
    }
    
    public void flushJoinsInvolvingProject(long projectID) {
        synchronized (_joins) {
            for (Iterator<Entry<String, ProjectJoin>> it = _joins.entrySet().iterator(); it.hasNext();) {
                Entry<String, ProjectJoin> entry = it.next();
                ProjectJoin join = entry.getValue();
                if (join.fromProjectID == projectID || join.toProjectID == projectID) {
                    it.remove();
                }
            }
        }
    }

    public void flushJoinsInvolvingProjectColumn(long projectID, String columnName) {
        synchronized (_joins) {
            for (Iterator<Entry<String, ProjectJoin>> it = _joins.entrySet().iterator(); it.hasNext();) {
                Entry<String, ProjectJoin> entry = it.next();
                ProjectJoin join = entry.getValue();
                if (join.fromProjectID == projectID && join.fromProjectColumnName.equals(columnName) || 
                        join.toProjectID == projectID && join.toProjectColumnName.equals(columnName)) {
                    it.remove();
                }
            }
        }
    }

    protected void computeJoin(ProjectJoin join, String separatorRegexp) {
        if (join.fromProjectID < 0 || join.toProjectID < 0) {
            return;
        }
        
        Project fromProject = ProjectManager.singleton.getProject(join.fromProjectID);
        Project toProject = ProjectManager.singleton.getProject(join.toProjectID);
        if (fromProject == null || toProject == null) {
            return;
        }
        
        Column fromColumn = fromProject.columnModel.getColumnByName(join.fromProjectColumnName);
        Column toColumn = toProject.columnModel.getColumnByName(join.toProjectColumnName);
        if (fromColumn == null || toColumn == null) {
            return;
        }

        for (Row fromRow : fromProject.rows) {
            Object fromRowKey = fromRow.getCellValue(fromColumn.getCellIndex());
            if (ExpressionUtils.isNonBlankData(fromRowKey)) {
                Object[] fromRowKeys;
                if (separatorRegexp != null && !separatorRegexp.isEmpty() && fromRowKey instanceof String) {
                    fromRowKeys = ((String) fromRowKey).split(separatorRegexp);
                } else {
                    fromRowKeys = new Object[]{fromRowKey};
                }
                for (Object k : fromRowKeys) {
                    if (!join.valueToRowIndices.containsKey(k)) {
                        join.valueToRowIndices.put(k, new ArrayList<Integer>());
                    }
                }
            }
        }
        
        int count = toProject.rows.size();
        for (int r = 0; r < count; r++) {
            Row toRow = toProject.rows.get(r);
            
            Object value = toRow.getCellValue(toColumn.getCellIndex());
            if (ExpressionUtils.isNonBlankData(value) && join.valueToRowIndices.containsKey(value)) {
                join.valueToRowIndices.get(value).add(r);
            }
        }
    }

}