import java.util.List;
import java.util.Map;
import java.util.Scanner;

/** 
 * The way to use this class with your code:
 * 
 * <ul>
 *    <li>
 *  - Your code will somewhere call "Entry.buildWorld" (see documentation);
 *    that method reads the wiki (or a data file), and returns a room, which you
 *    can use as you see fit (perhaps as the starting room?).
 *    </li>
 *
 *    <li>
 *  - How does this class call the other code from your project?  Well,<br></br>
 *    + createRoom calls the constructor for Room; <br></br>
 *    + createTreasure calls the constructor for Treasure; <br></br>
 *    + createConnection calls connectTo and biconnectTo for appropriate rooms.<br></br>
 *    If your constructors take different arguments, or you named your methods/Classes
 *    something different than I did, then you'll need to modify those three methods.
 *    No other tinkering should be needed.
 *    </li>
 *    
 *    <li>
 *  - If there are errors in the data file, hopefully they'll be caught
 *    by buildWorld, and the error message will point you in the right direction.
 *    But there might be errors in the data file which cause the program to quit.
 *    If so, mail the bad data file to me (ibarland@).
 *    </li>
 *  </ul>
 *  
 * ===========================================================================<br> </br>
 * <p>
 * class Entry represents one object (a "paragraph") taken from a gRUe-database.
 * See      http://ru-itec120.pbwiki.com/grue-data-2007fall
 * for a gRUe-database file (which include comments explaining its syntax).
 * </p>
 * <p>
 * If you want to modify class Entry, here is some info on how it's organized:
 * </p>
 *
 * <p>
 * Vocabulary:
 * <ul>
 * <li>
 * Entry -- A "paragraph" of the database;
 *    it consists of a type (the first line), 
 *    and a bunch of attributes (each remaining line).
 * </li>
 * <li>
 * Attribute -- a single line of the database like "description = fa la la";
 *   the general form of the line is "[key] = [value]".
 * </li>
 * <li>
 * Type of an Entry -- one of {@VALUE VALID_ENTRY_TYPES}.
 * </li>
 * </ul>
 * 
 * <p>
 * You can ask an Entry what its type is, and you can also give it a
 * key (a String, like "description") and have it return
 * the associated value (another string, like "fa la la").
 * This lookup is implemented by java.util.Map (built just for such tasks).
 * </p>
 * 
 * <ul>
 * <li>
 *  - The static method getEntries returns a list of "Entry" objects.
 *    If you like, you can provide a filename to read, otherwise
 *    it reads from {@value #DEFAULT_DATABASE_FILENAME}
 *    </li>
 *    <li>
 *  - For each Entry, you can use "getType()" to ask it
 *    what type of thing it represents:
 *    "room", "treasure", "connection", or "biconnection".
 *    </li>
 *    <li>
 *  - For each entry, you can repeatedly ask it to "get(.)"
 *    attributes.
 *    </li>
 *  </list>
 *    
 *    For instance:
 *    
 *    <code>
 *    Map<String,Describable> stuffFromFile = new java.util.HashMap<String,Describable>();
 *    List<Entry> allStuff = getEntries();
 *    Entry e3 = allStuff.get(3);
 *    if (e3.getType().equals("treasure")) {
 *      double wt = Double.valueOf( e3.get("weight") );
 *      Treasure t = new Treasure( e3.get("name"), e3.get("description"), wt );
 *      stuffFromFile.put( e3.get("id"), t );  // I may want to look up this Treasure later via its id.
 *      }
 *    </code>
 * 
 * @author Ian Barland
 * @version 2007.Nov.28
 *  (updated to give better error message if a Treasure entry's weight isn't numeric.)
 */
public class Entry {

  /** A URL or filename for reading the data from, if no other file/URL provided: {@value} */
  public static final String DEFAULT_DATABASE_FILENAME = "http://ru-itec120.pbwiki.com/grue-data-2007fall";

  /** Text which only occurs in a line immediately before the actual data, in a URL/file.  */
  private static final String BEGIN_GRUE_DATA_MARKER = "BEGIN GRUE DATA";
  /** Text which only occurs in a line immediately after the actual data, in a URL/file.  */
  private static final String   END_GRUE_DATA_MARKER = "END GRUE DATA";
  /** a total hack -- a field to help hasNextGrueDatum. */
  static boolean seenEndOfData;
  /** The list of valid types: room, treasure, connection, biconnection */
  public static final List<String> VALID_ENTRY_TYPES
    =  java.util.Arrays.asList("room", "treasure", "connection", "biconnection");
      // VALID_ENTRY_TYPES must contain Strings in lower-case.

  /** The type of this entry.  One of the strings in {@value VALID_ENTRY_TYPES}. */
  private String type;
  private Map<String,String> attrs 
     = new java.util.HashMap<String,String>();



  /** Return all the Entries read from a file.
   * @param filename The name of the gRUe database to read from.
   * See http://ru-itec120.pbwiki.com/grue-data-2007fall
   * for the syntax of a gRUe-database file.
   * @return a list of all Entries in the indicated database.
   */
  public static List<Entry> getEntries( String filenameOrURL ) {
    Scanner theInput;
    try {
      if (filenameOrURL.startsWith("http:")) {
        theInput = new Scanner( new java.net.URL( filenameOrURL ).openStream() );
        }
      else {
        theInput = new Scanner( new java.io.File( filenameOrURL ) );
        }
      }
    catch (Exception err) {
      // We'll report the error, and continue the program...
      System.err.println( err.toString() );
      theInput = new Scanner( Entry.fallbackGrueData( err.toString() ) );  // Use fallback data.
      }
      
    // Read past all the opening cruft:
    boolean foundFirstLine = false;
    while (!foundFirstLine && theInput.hasNext()) {
      foundFirstLine = theInput.nextLine().contains( BEGIN_GRUE_DATA_MARKER );
      }
      
    return Entry.getEntries(theInput);
    }


  /** A 0-arg version reads from a {@value #DEFAULT_DATABASE_FILENAME}.
   * @see getEntries(String)
   * @return a list of all Entries in the default database.
   */
  public static List<Entry> getEntries() {
    return Entry.getEntries(DEFAULT_DATABASE_FILENAME);
    }


  /** Return all the Entries read from a Scanner;
   *   this is the workhorse, called by getEntries(String).
   * 
   * @param in The scanner to read from.
   * See http://ru-itec120.pbwiki.com/grue-data-2007fall
   * for the syntax of a gRUe-database file.
   * @return a list of all Entries.
   */
  private static List<Entry> getEntries( Scanner in ) {
    seenEndOfData = false;  // HACK -- a helper flag for hasNextGrueDatum.
    Entry.skipComments( in, true );
    List<Entry> entries = new java.util.LinkedList<Entry>();
    while (Entry.hasNextGrueDatum(in)) {
      entries.add( new Entry(in) );
      Entry.skipComments( in, true );
      }
    return entries;
    }



  /** Check for common errors in an Entry,
   * printing to System.err.
   * @return true if and only if the Entry had no errors (that we noticed).
   */
  private boolean validateSyntax() {
    String errMsg = "";
    if (!VALID_ENTRY_TYPES.contains(this.type)) {
      errMsg +=    "* Unknown type \"" + this.getType() + "\"; "
                 + "it must be one of " + VALID_ENTRY_TYPES.toString() + ".\n";
      }

    if (attrs.isEmpty()) {
      errMsg += "* No attributes at all.\n";
      } 
    else if (   (!this.containsKey("id")) 
             && (this.getType().equals("room") || this.getType().equals("treasure")) ) {
      errMsg += "* No \"id\" attribute.\n";
      }

    if ((this.containsKey("id") && (this.get("id").split(" ").length != 1))) {
      errMsg += "* The \"id\" attribute should be one word.\n";
      }

    if (!errMsg.equals("")) {
      System.err.println( "Syntax error in an Entry:\n" + errMsg
                          + "The offending Entry:\n" + this.toString() );
      }

    return errMsg.equals("");
    }



  /** Constructor
   * @param in The Scanner to read our info from.
   *  A runtime exception is thrown (by nextLine()) if there
   *  is no next (uncommented) line.
   */
   Entry( Scanner in ) {
    boolean debug = false;
    // Skip to the start of the next real line of input:
    Entry.skipComments( in, true );

    // Now, the first real line: this will be the entry's type.
    this.type = myNextLine(in).trim().toLowerCase();

    boolean moreLinesToRead = true;
    while ((hasNextGrueDatum(in) && moreLinesToRead)) {
      moreLinesToRead = this.addKeyValuePair( in );
      }

    validateSyntax();
    if (debug) {
      System.err.println( "Created the entry:\n " + this.toString() );
      }
    }
    
  /** Read one line of the input as a key=value pair,
   *  and add it as an attribute to this Entry.
   * @param in the input to read the next line of
   *   (comments are skipped over).
   * @return true if there are (potentially) more lines 
   *  to read from the current paragraph.
   */
  private boolean addKeyValuePair( Scanner in ) {
    Entry.skipComments( in, false );
    if (!hasNextGrueDatum(in)) return false;  // End of file reached.

    String currLine = myNextLine(in);
    if (currLine.equals("")) return false; // End of paragraph reached.

    /* Split the current line into 2 parts, separated by "=".
     * The first part will be the key; the second part will be the value.
     * Then add that key/value pair to our attributes.
     */
    String[] keyAndVal = currLine.split(DELIMITER, 2);
    if (keyAndVal.length == 2) {  // Successful split!
      this.attrs.put( keyAndVal[0].trim().toLowerCase(), 
                      keyAndVal[1].trim() );
      }
    else {  // Unsuccessful split
      System.err.println(   "Entry(): "
                          + "malformed line in file; ignoring the line: "
                          + currLine );
      }

    return true;
    }


  /** Return the type of this entry.
   * @return the type of this entry -- one of the strings
   *  in {@value #VALID_ENTRY_TYPES}.
   */
  public String getType() { return type; }


  /** Given an attribute-key, look up an attribute-value.
   * @see getWithDefault
   * @param key The attribute-key to look up inside this Entry.
   * @return The value associated with key.
   *  For example, if this Entry had been created from a file
   *  the file which included "swag = some big long string",
   *  then get("swag") = "some big long string".
   * @throws RuntimeException if the key doesn't exist in this Entry's attributes.
   */
  public String get( String key ) { 
    if (attrs.containsKey(key)) {
      return attrs.get(key);
      }
    else {
      throw new RuntimeException( "get: The key \"" + key + "\" is not in the Entry:\n" + this.toString() );
      }
    }

  /** Given an attribute-key, look up an attribute-value;
   *   if the key isn't found, return the second argument.
   * @see get
   * @param key The attribute-key to look up inside this Entry.
   * @param defaultReturn The value to return if key doesn't exist
   *        in this Entry's attributes.
   * @return The value associated with key.
   *  For example, if this Entry had been created from a file
   *  the file which included "swag = some big long string",
   *  then get("swag", "garbage") = "some big long string",
   *  and get("badkey", "garbage") = "garbage"
   *      (Assuming there was no line 'badkey = ...' in the input, 'course).
   */
  public String getWithDefault( String key, String defaultReturn ) {
    if (attrs.containsKey(key)) {
      return attrs.get(key);
      }
    else {
      return defaultReturn;
      }
    }

  /** return whether or not this entry contains an attribute with the given key.
   * @param key The key to look for.
   * @return whether or not this entry contains an attribute with the given key.
   */
  boolean containsKey( String key ) { return attrs.containsKey( key ); }

  /** Return a string representation of this Entry.
   * @return a string representation of this Entry.
   * It will be in a paragraph-form suitable for reading in by our constructor.
   */
  public String toString() {
    String attrLines = "";
    for ( String k : attrs.keySet() ) {
      attrLines += k + " " + DELIMITER + " " + attrs.get(k) + "\n";
      }
    return getType() + "\n" + attrLines;
    }

  /** A Test driver, to parse a few small database Entries. */
  public static void main( String[] args ) {
    String e1 = "Room\nid=hi";
    String e2 = "Roooom\nid=hi";
    String e3 = "Roooom\n";
    String e4 = "Room\n id = a grand day \n description =this is a descr   ";

    System.out.println( Entry.getEntries(new Scanner(e1)).toString());
    System.out.println( Entry.getEntries(new Scanner(e2)).toString());
    System.out.println( Entry.getEntries(new Scanner(e3)).toString());
    System.out.println( Entry.getEntries(new Scanner(e4)).toString());
    System.out.println( Entry.getEntries(new Scanner(e1+"\n\n"+e4)).toString());
    }


  /* ******** End of methods dealing just with reading the file ********* */
  /* ******************************************************************** */
  /* ******* Begin methods which depend on the details of other classes   */
  /*         like Room, Treasure.                                         */



  /** Read {@VALUE DEFAULT_DATABASE_FILENAME}, and create all the indicated 
   * Room and Treasure objects, and connections between Rooms.
   *
   * @param filename The name of the grue-database file to use.
   * @param startingPointID The ID of a room listed in the database file,
   *        which you 
   * @return the Room object whose ID is startingPointID.
   */
  public static Room buildWorld( String startingPointID ) {
    return buildWorld( DEFAULT_DATABASE_FILENAME, startingPointID );
    }

  /** Read a grue-database file, and create all the indicated 
   * Room and Treasure objects, and connections between Rooms.
   *
   * @param startingPointID The ID of a room listed in the database file/wiki.
   *        I suggest using "nexus".
   * @param filenameOrURL The name of the grue-database file to use, or a wiki page.
   * @return the Room object whose ID is startingPointID.
   */
  public static Room buildWorld( String filenameOrURL, String startingPointID ) {

    // Later on, we'll need to be able to look up Treasures and Rooms by their id
    // attribute (as mentioned in the database file).  We'll use java.util.Map for that.

    // How java.util.Map works:
    // (It's like an address book, where first you write down  buddy-names and their
    //  full-email-addresses.  Then, later, you can walk up and give it just the 
    //  buddy-name and have it return to you the full-email-address.
    //  We say that the buddy-name is the *key*, and 
    //  the full-email-address is the *value* associated with that key.)
    //
    // In this example, the key is the ID-string, and the value is the corresponding
    // Treasure object.  That is:
    //
    // First we'll add Treasures (with their ID) to the Map called 'worldTreasures', 
    // using the Map's method put(String,Treasure).
    // Later, we can walk up to the Map call its method get(String) -- giving 
    // it an ID and it retrieves previously-stored Treasure.
    // 
    Map<String, Treasure> worldTreasures = new java.util.HashMap<String, Treasure>();
    Map<String, Room    > worldRooms     = new java.util.HashMap<String, Room    >();

    // allThings are the Entries listed in the database file -- paragraphs
    // which describe rooms and treasures and connections.
    // Our job now, is to process these Entries:
    // create actual Room and Treasure objects, make actual connections between them.
    //
    List<Entry> allThings = Entry.getEntries( filenameOrURL );

    // First, create all Treasures (ignoring, for now, other Entries).
    //
    for (Entry e : allThings) {
      if (e.getType().equals("treasure")) {
        worldTreasures.put( e.get("id"), e.createTreasure() );
        }
      }

    // Okay, now that all treasures are can be looked up in worldItems,
    // we can go and process the Entries which correspond to Rooms:
    //
    for (Entry e : allThings) {
      if (e.getType().equals("room")) {
        worldRooms.put( e.get("id"), e.createRoom( worldTreasures ) );
        }
      }

    // Now that all Rooms have been created, we can go back through the Entries
    // and create connections between rooms.
    //
    List<String> connectionTypes 
      = new java.util.ArrayList<String>( java.util.Arrays.asList( "connection", "biconnection" ) );

    for (Entry e : allThings) {
      if (connectionTypes.contains( e.getType() )) {
        e.createConnection(worldRooms);
        }
      }

    // We're done.  Return the Room they had initially asked for.
    //
    if (worldRooms.containsKey(startingPointID)) {
      return worldRooms.get(startingPointID);
      }
    else {
      throw new RuntimeException( "World created, but no room has ID " + startingPointID + "." );
      }
    }


  /** Return a newly-created Treasure, made out of the current Entry.
   * @return a newly-created Treasure, made out of the current Entry.
   *     Throws an error if this Entry doesn't have a name or description or weight.
   */
  public Treasure createTreasure() {
    boolean debug = false;
    double weight;
    try {
      weight = Double.valueOf(this.get("weight"));
      }
    catch (java.lang.NumberFormatException e) {
      System.err.println( "Non-numeric weight attribute in:\n" + this.toString() + "\nContinuing with weight 0.0." );
      weight = 0.0;
      }
      
    Treasure t = new Treasure( this.get("name"), 
                               this.get("description"),
                               weight,
                               this.getWithDefault("image-URL", "")
                               );
    if (debug) System.out.println( "Created treasure " + t.toString() );
    return t;
    }
  

  /** Return a newly-created Room, made out of the current Entry.
   * @param treasureRepository A Map which can take a treasure's ID String (the key), 
   *     and return the indicated Treasure object (the value).
   * @return a newly-created Room, made out of the current Entry.
   *     Throws an error if this Entry doesn't have a name or description,
   *     or if it mentions treasure IDs which aren't in treasureRepository.
   */
  public Room createRoom( Map<String,Treasure> treasureRepository ) {
    boolean debug = false;
    // First, create the Room, for the moment without any Treasures:
    //  (This relies on Room having a two-argument constructor.)
    Room r = new Room( this.get("name"), this.get("description") );
  
    if (this.containsKey("treasure")) {
      System.err.println( "Room " + this.get("id") + " should have an attribute \"treasures\", not \"treasure\".\n" );
      }
  
    if (this.containsKey("treasures")) {
      // Get the "treasure" line from this entry, and split it into words 
      // (separated by space).  Then for each such word 't', ...
      for ( String t : java.util.Arrays.asList( (this.get("treasures")).split(" ")) ) {
        // ...take the word 't', look up the (already-created) Treasure object with
        // that id, and add that Treasure to the Room r:
        r.addItem( treasureRepository.get(t) );
        }
      }

    if (debug) System.out.println( "Created room " + r.toString() );
    return r;
    }

  /** Call 'connect' or 'biconnect' on the room mentioned by this Entry.
   * @param roomRepository A Map which can take a room's ID String (the key), 
   *     and return the indicated Room object (the value).
   *
   * Throws an error if this Entry doesn't have a "from" and a "to" attribute,
   * or if it mentions room IDs which aren't in roomRepository.
   */
  public void createConnection( Map<String,Room> roomRepository ) {
    boolean debug = false;
    Room r1 = roomRepository.get( this.get("from") );
    Room r2 = roomRepository.get( this.get("to"  ) );
  
    if (r1 == null) {
      System.err.println(  "No starting room found with id " + this.get("from") 
                       + " when trying to connect:\n" + this.toString() );
      return;
      }
    if (r2 == null) {
      System.err.println(  "No destination room found with id " + this.get("to"  )
                         + " when trying to connect:\n" + this.toString() );
      }
      
    if (this.getType().equals("connection")) {
      r1.connectTo(r2);
      }
    else if (this.getType().equals("biconnection")) {
      r1.biconnectTo(r2);
      }
    else {
      throw new RuntimeException( "Uh-oh, confusing problem in Entry.createConection." );
      }
    if (debug) System.out.println( "Connected " + r1.getName() + " and " + r2.getName() + "." );
    }
    

  /*=======================*/
  /* The following methods are all about parsing
   * (and in particular, parsing wiki with html-ish input).
   * Really, I should have my own "class wikiScanner extends Scanner";
   * that would simplify a lot.
   *
   * But for ease-of-distribution, I really want all
   * this in one file.
   */
    
  /** The string which, at the start of a line, begins a comment. */
  private static final String COMMENT_START = ";";

  /** In a data line, DELIMITER separates the key from the value. */
  private static final String DELIMITER = "=";


  /** A regular expression for zero or more comment lines: */
  private static final String COMMENT_LINE  = "(" + COMMENT_START + ".*\n)";
  private static final String COMMENT_LINES = COMMENT_LINE + "*";
  private static final String COMMENT_AND_BLANK_LINES = "(" + COMMENT_LINE + "|\n)*";

  /** Store peekahead data. */
  private static java.util.Stack<String> buffer = new java.util.Stack<String>();
  
  
  /** Like hasNext, except that we return false for EOF *or* having
   * reached {@value #END_GRUE_DATA_MARKER_PATTERN}.
   * @param s A scanner to read from.
   * @return whether or not there is any more potential (gRUe) data in s.
   */  
  private static boolean hasNextGrueDatum( java.util.Scanner s ) {
    if (!buffer.empty()) return true;
    if (!s.hasNext()) return false;
    if (seenEndOfData) return false;
    if (s.findInLine(END_GRUE_DATA_MARKER_PATTERN) == null) {
      return true;
      }
    else {
      seenEndOfData = true;
      return false;
      }
    }
  /** Convert END_GRUE_DATA_MARKER into a pattern just once and remember the result. */
  private static final java.util.regex.Pattern  END_GRUE_DATA_MARKER_PATTERN = java.util.regex.Pattern.compile(END_GRUE_DATA_MARKER);

  
  /** Return the next line from the scanner, removing any trailing "<br/>" or "</p><p>".
   * @Return the next line from the scanner, removing any trailing "<br/>" or "</p><p>".
   */
  private static String myNextLine( java.util.Scanner s ) {
    if (!buffer.empty()) {
      return buffer.pop();
      }
      
    String answer = s.nextLine();
    if (answer.contains( "</p>" )) {
      buffer.push( "" );
      }
    
    for ( String suffix : removableSuffixes ) { 
      if (answer.endsWith(suffix)) {
        answer = answer.substring(0,answer.length()-suffix.length());
        }
      }
    // Okay, I *could* push answer, and then make a recursive call.
    // Will hand-optimize:
    return answer;
    }
  private static final String[] removableSuffixes = { "<br />", "</p><p>" };
  private static boolean justSawParaEnd = false;

  /** Skip over any comments (and possibly blank lines) in the input.
   * @param blankLinesToo  If true, also skip over blank lines in addition to comments.
   */
  private static void skipComments( Scanner s, boolean blankLinesToo ) {
    // We *would* just call s's method "skip" with a regular expression,
    // except that when we are parsing a wiki file w/ html cruft, we need
    // to realize that "</p>" is really a blank line.  So we have our own
    // look which calls (our own) myNextLine.
    boolean skipping = true;
    String n = "dummy Value to appease compiler";
    while (skipping && hasNextGrueDatum(s)) {
      n = myNextLine(s);
      skipping =  ((n.equals("")) && blankLinesToo)
                ||  n.startsWith( COMMENT_START );
      }
      
    if (hasNextGrueDatum(s)) {
      // We've gone too far!
      buffer.push(n);
      }
    }
    
    /** Default information to use, if there is an error elsewhere.
     * @param errMsg  A message that is embedded into a treasure in the default info.
     * @return A string formatted as expected, for a gRUe-database.
     */
    public static String fallbackGrueData( String errMsg ) {
      return BEGIN_GRUE_DATA_MARKER + "\n"
           + "Treasure\n id = note   \n name=note              \n weight = 0.0 \n description = The exact error message is \"" + errMsg.replaceAll("\n","; ") + "\"\n" + "</p><p>\n"
           + "Room    \n id = nexus  \n name=the celestial void\n description = A sign says \"Sorry, the wiki is out of order; come again later\"\n treasures=note\n" + "</p><p>\n"
           + "Treasure\n id = feather\n name=a feather         \n description = It seems to fall quickly, for a feather.\n weight = 44.0\n" + "</p><p>\n"
           + "Room    \n id = pit\n     name=the bottomless pit\n description = You are falling, falling, falling, falling, falling.  You are bored.\n treasures=feather\n" + "</p><p>\n"
           + "Connection\n from = nexus\n to = pit\n" + "</p><p>\n"
           + "Connection\n from = pit\n to = pit\n" + "</p><p>\n"
           + END_GRUE_DATA_MARKER;
      }
}