package org.greenstone.gsdl3.gs3build.doctypes;

import java.util.Iterator;
import java.util.List;
import java.util.ArrayList;

import java.io.PrintWriter;
import java.io.FileWriter;
import java.io.File;
import java.io.IOException;

import java.net.URL;

import java.sql.SQLException;
import java.sql.Statement;
import java.sql.ResultSet;

import org.greenstone.gsdl3.gs3build.metadata.METSFileGroup;

import org.greenstone.gsdl3.gs3build.database.GS3SQLConnection;
import org.greenstone.gsdl3.gs3build.database.GS3SQLSelect;
import org.greenstone.gsdl3.gs3build.database.GS3SQLWhereItem;
import org.greenstone.gsdl3.gs3build.database.GS3SQLWhere;
import org.greenstone.gsdl3.gs3build.database.GS3SQLField;

public class DocumentList
{
  DocumentInterface []       list;       // what is currently cached
  int                        size;       // the maximum number in the cache
  int                        used;       // the actual number in the cache
  int                        count;      // the total number of known documents
  DocumentIDFactoryInterface idFactory;  // A manufacturer of novel document IDs
  GS3SQLConnection           connection; // used to query the SQL database

  private static final int maxSize = 3;

  public DocumentList(GS3SQLConnection connection)
  { this.idFactory = null;
    this.list  = new DocumentInterface[3];
    this.used  = 0;
    this.size  = 3;
    this.count = 0;
    this.connection = connection;
  }

  public DocumentList(DocumentIDFactoryInterface idFactory, GS3SQLConnection connection)
  { this.idFactory = idFactory;
    this.list  = new DocumentInterface[3];
    this.used  = 0;
    this.size  = 3;
    this.count = 0;
    this.connection = connection;
  }

  /**
   *  Obtain the list of <code>DocumentID</code> objects representing the unique
   *  document identifiers of documents that refer to the file given as a parameter.
   *
   *  @param <code>URL</code> the location of the file to match
   *
   *  @return <code>List</code> of <code>DocumentID</code> reference identifiers.
   */
  public List getDocumentIdsWithFile(URL fileLocation)
  { List reply = new ArrayList();

    GS3SQLSelect select = new GS3SQLSelect("files");
    select.addField("*");
    GS3SQLWhere  where  = new GS3SQLWhere(new GS3SQLWhereItem("FileLocation", "=", fileLocation.toString()));
    select.setWhere(where);

    try {
	Statement statement = connection.createStatement();
	ResultSet results = statement.executeQuery(select.toString());
    
	select = new GS3SQLSelect("filegroups");
	select.addField("DocID");
	select.setDistinct(true);
      
	where = new GS3SQLWhere();
	where.setCondition(GS3SQLWhere.OR_CONDITION);
	
	GS3SQLWhereItem whereItem = null;

      	results.first();
	do {
	  int fileGroupRef = results.getInt("FileGroupRef");
	  whereItem = new GS3SQLWhereItem("FileGroupRef", "=", Integer.toString(fileGroupRef), GS3SQLField.INTEGER_TYPE);
	  where.add(whereItem);
	}
	while (results.next());
	select.setWhere(where);
	
	results = statement.executeQuery(select.toString());
	
	results.first();
	do {
	  String docId = results.getString("DocID");
	  reply.add(docId);
	} while (results.next());
	statement.close();
    }
    catch (SQLException sqlEx) {
	System.err.println("DocumentList.getDocumentIdsWithFile(): "+sqlEx);
    }
    
    return reply;
  }

  /**
   *  Get a list of documents that match a given set of patterns,
   *  within a given URL node.
   *
   *  @param <code>List</code> the list of patterns to match
   *  @param <code>String</code> the partial URL of the root node under which o
   *         match files.  NB: this is a <code>String</code> as the URL may be
   *         incomplete and not properly match the strict requirements for <code>URL</code>
   */
  public List findDocumentIdsUsingFiles(List fileRefs, String withinNode)
  {
    StringBuffer queryBuffer = new StringBuffer("SELECT FileGroupRef FROM files WHERE FileLocation ");

    Iterator files = fileRefs.iterator();
    while (files.hasNext()) {
      String file = files.next().toString();

      if (withinNode != null) {
	queryBuffer.append("REGEXP \"^");
	queryBuffer.append(withinNode);
	queryBuffer.append(".*");
      }
      else {
	queryBuffer.append("REGEXP \"");
      }
      queryBuffer.append(file);
      queryBuffer.append("\"");

      if (files.hasNext()) {
	queryBuffer.append(" OR ");
      }
    }
    queryBuffer.append(";");
    return this.findDocumentIdsUsingFileQuery(queryBuffer.toString());
  }

  public List findDocumentIdsUsingFile(String fileRef, String withinNode)
  { String query = "SELECT FileGroupRef FROM files WHERE FileLocation REGEXP \"^"+withinNode+".*"+fileRef+"\";";
    return this.findDocumentIdsUsingFileQuery(query);
  }

  /**
   *  Return a list of document identifiers against a simple pattern.  No root node is given, so
   *  any file matching the pattern given will be returned. USE WITH CAUTION!!!
   *
   *  @param <code>String</code> a fragment of file pathname to match against.
   *
   *  @return <code>List</code> of <code>DocumentID</code> objects.
   */
  public List findDocumentIdsUsingFile(String fileRef)
  { 
    // Get the simple list of file objects & their file group reference
    String query = "SELECT FileGroupRef FROM files WHERE FileLocation REGEXP \"" + fileRef +"\";";

    return this.findDocumentIdsUsingFileQuery(query);
  }

  public List findDocumentIdsUsingFileExact(String fileRef)
  { 
    // Get the simple list of file objects & their file group reference
    String query = "SELECT FileGroupRef FROM files WHERE FileLocation=\"" + fileRef +"\";";

    return this.findDocumentIdsUsingFileQuery(query);
  }

    private List findDocumentIdsUsingFileQuery(String query) {
    
	try {
	
	Statement statement = connection.createStatement();
	ResultSet results = statement.executeQuery(query);

	if (!results.first()) {
	    statement.close();
	    return null;
	}
      
      // get a list of group ids first and turn it into a query on filegroups
      StringBuffer queryBuffer = new StringBuffer("SELECT * FROM filegroups WHERE ");
      boolean first = true;
      
      do {
	int groupRef = results.getInt("FileGroupRef");
	
	if (first) {
	  first = false;
	}
	else {
	  queryBuffer.append(" OR ");
	}
	queryBuffer.append("FileGroupRef=" + Integer.toString(groupRef));
      } while (results.next());
      queryBuffer.append(";");
      
      // make a holder for the actual file section identifiers
      List divisions = new ArrayList();
      
      // expand (or, in fact, contract) through the document
      // structures...recreating new filegroup queries as necessary
      while (queryBuffer.length() > 0) {
	results = statement.executeQuery(queryBuffer.toString());
	
	if (!results.first()) {
	    statement.close();
	    return null;
	}
	
	queryBuffer = new StringBuffer();
	do {
	  String type = results.getString("ParentType");
	  String parentRef = results.getString("ParentRef");
	  if (type.equals(METSFileGroup.SECTION_PARENT)) {
	    divisions.add(parentRef);
	  }
	  else {
	    if (queryBuffer.length() > 0) {
	      queryBuffer.append(" OR ");
	    }
	    queryBuffer.append("FileGroupRef=" + parentRef);
	  }
	} while (results.next());
	
	if (queryBuffer.length() > 0) {
	  queryBuffer.insert(0, "SELECT * FROM filegroups WHERE ");
	  queryBuffer.append(";");
	}
      }
      
      // ok, now find all the sections in which we are interested...
      queryBuffer.setLength(0);
      queryBuffer.append("SELECT DISTINCT DocID FROM filesection WHERE ");
      Iterator iterator = divisions.iterator();
      first = true;
      
      while (iterator.hasNext()) {
	String ref = iterator.next().toString();
	
	if (first) {
	  first = false;
	}
	else {
	  queryBuffer.append(" OR ");
	}
	
	queryBuffer.append("FileSectionRef="+ref);
      }
      queryBuffer.append(";");
      
      // execute the division query
      results = statement.executeQuery(queryBuffer.toString());
      
      if (!results.first()) {
	  statement.close();
	  return null;
      }

      List reply = new ArrayList();
      do {
	reply.add(results.getString("DocID"));
      } while (results.next());
      
      statement.close();
      return reply;
    }
    catch (SQLException ex) {
      System.err.println("DocumentList.findDocumentIdsUsingFileQuery()"+ ex);
    }
    return null;
  }

  /**
   *  Cache a document into the cache, without writing it to the database.
   *  Used directly by other parts of DocumentList when they know that the
   *  document is in the database already, or they are going to write it
   *  themselves...
   *
   *  @param <code>DocumentInterface</code> the document to cache
   */
  private void cacheDocument(DocumentInterface document)
  { // increase cache size, etc. as necessary
    if (this.used == this.size) {
      if (this.size >= maxSize) {
	for (int i = 0; i < this.size - 1; i ++) {
	  this.list[i] = this.list[i+1];
	}
	this.used --;
      }
      else {
	this.ensureSize((this.size * 2) > maxSize ? maxSize : (this.size * 2));
      }
    }
    
    // insert the document itself
    this.list[this.used] = document;    
  }

  /**
   *  Write the document into the document list (cache) and the database.
   *
   *  @param <code>DocumentInterface</code> the document itself
   */
  public void addDocument(DocumentInterface document)
  { // initially, test if the document has a duplicate...
    String duplicateDocID = document.getDuplicateID(this.connection);
    if (duplicateDocID.length() > 0) {
      System.out.println("Found duplicate document ");
      return;
    }

    // first cache it...
    this.cacheDocument(document);

    // set the document identifier, if not already set
    if (document.getID() == null) {
      System.out.println("Posting new docuument ID");
      DocumentID id = this.idFactory.getNewDocumentID(document);
      document.setID(id);
    }

    // add to the database as well, if it is modified...
    if (document.isChanged()) {
      System.out.println("Document was changed");
      document.getSQLWriter().writeDocument(document, this.connection);
    }

    // Remember that we've used one more item from the cache.
    this.used ++;

    // Note additional document
    this.count ++;
  }

  /**
   *  Note that an individual document is modified, and act accordingly
   *
   *  @param <code>DocumentInterface</code> the document
   */
  public void storeChangedDocument(DocumentInterface document)
  { document.getSQLWriter().writeDocument(document, this.connection);
  }

  /**
   *  Get an iterator across all the documents, not merely those in
   *  the cache.  Note that this <code>Iterator</code> does <b>not</b>
   *  support the <code>remove()</code> function, and will raise an
   *  <code>UnsupportedOperationException</code> if you attempt to do
   *  so.
   *
   *  @return <code>Iterator</code> the iterator across the documents.
   */
  public Iterator iterator()
  { return new DocumentListIterator(connection);
  }

  /**
   *  Get the nth member of the <b>cached</b> document list.
   *
   *  @deprecated
   */
  public DocumentInterface getDocument(int index)
  { if (index < 0 || index >= this.used)
    { return null;
    }
    return this.list[index];
  }

  /**
   *  Simple "obtain a document" function
   */
  public DocumentInterface getDocument(DocumentID documentId)
  {
    DocumentInterface document = DocumentFactory.readSQLDocument(connection, documentId);
    if (document != null) {
      this.cacheDocument(document);
    }
    return document;
  }

  /**
   *  Update timestamps on an entire document list - done at the beginning of a build cycle
   *
   *  @param <code>The date of the new build cycle</code>
   */
  public void updateTimestamps(long buildTimeStamp)
  { Iterator documents = this.iterator();
    int item = 0;

    while (documents.hasNext())
    { DocumentInterface document = (DocumentInterface) documents.next();
      
      long thisTimeStamp = document.getFilesDatestamp();
      long lastTimeStamp = document.getModifiedDatestamp();

      if (thisTimeStamp > lastTimeStamp) {
	System.out.println("Updating timestamps " + thisTimeStamp + " " + lastTimeStamp);

	DocumentSQLWriter.touchDocument(document.getID(), this.connection, buildTimeStamp, thisTimeStamp);
      }
    }
  }

  /**
   *  A convenience method to map onto the old Vector source code...
   */
  protected void ensureSize(int size)
  { DocumentInterface [] newList = new DocumentInterface[size];
    System.arraycopy(this.list, 0, newList, 0, this.size);
    this.list = newList;
    this.size = size;
  }

  /**
   *  Write the documents into a directory as METS/XML
   */
  public void writeDocuments(File directory)
  { Iterator documents = this.iterator();
    int item = 0;

    while (documents.hasNext())
    { DocumentInterface document = (DocumentInterface) documents.next();
      try
      { item ++;
	File localFile = new File(directory, "Doc"+Integer.toString(item)+".xml");
	FileWriter fileWriter = new FileWriter(localFile);
	PrintWriter writer = new PrintWriter(fileWriter);
	document.getMETSWriter().writeDocument(document, writer);
	writer.close();
	fileWriter.close();
      }
      catch (IOException io)
      {	
      }
    }
  }

  public void writeSQLDocuments(GS3SQLConnection connection)
  { for (int i = 0; i < this.used; i ++)
    { this.list[i].getSQLWriter().writeDocument(this.list[i], connection);
    }
  }

  public static DocumentList readSQLDocuments(GS3SQLConnection connection)
  { DocumentList list = new DocumentList(connection);

    GS3SQLSelect select = new GS3SQLSelect("document");
    select.addField("*");
    
    try {
	Statement statement = connection.createStatement();
	ResultSet documents = statement.executeQuery(select.toString());
	if (documents.first()) { 
	    do {
		DocumentInterface document = AbstractDocument.readSQL(connection, documents);
		list.addDocument(document);
	    }
	    while (documents.next());
	}
	statement.close();
    }
    catch (java.sql.SQLException ex) {
	System.out.println("DocumentList.writeSQLDocuments(): "+ex);
	return null;
    }

    return list;
  }

  public int getCount()
  { return this.count;
  }

  public int size()
  { return this.used;
  }
}

class DocumentListIterator implements Iterator
{
  private boolean hasNext;
  private Statement statement;
  private ResultSet resultSet;
  private GS3SQLConnection connection;

  public DocumentListIterator(GS3SQLConnection connection)
  {
    this.connection = connection;

    GS3SQLSelect select = new GS3SQLSelect("document");
    select.addField("*");

    try {
	this.statement = connection.createStatement();
      this.resultSet = statement.executeQuery(select.toString());
      this.hasNext = this.resultSet.first();
    } catch (SQLException ex) {
      System.err.println("DocumentListIterator(): "+ex);
      this.hasNext = false;
    }
  }

  public boolean hasNext()
  { return this.hasNext;
  }

  public Object next()
  {
    // get the 'next' document first
    DocumentInterface document = AbstractDocument.readSQL(connection, this.resultSet);

    // now actually step forward to the next item, so that we know if we have one!
    try {
      this.hasNext = this.resultSet.next();

      if (!this.hasNext) {
	  this.statement.close(); // be a good citizen & close used statement 
      }
    } catch (SQLException ex) {
	System.err.println("DocumentList.iterator.next(): "+ex);
      this.hasNext = false;
    }
    return document;
  }
  
  public void remove() throws UnsupportedOperationException
  { throw new UnsupportedOperationException("DocumentList does not support iterator removal of documents");
  }
}