/** 
  * Bandscope Receiver Applet 1.0.0 [SCAN DATA LOADER]
  * @author Robert J Morton <robmorton@clara.net> YE572246C
  * @version 13 March 2002, 20 March 2012
  * @copyright Robert J Morton (all rights reserved) */

import java.net.*;      // for downloading data from the remote server
import java.io.*;       // for stream handling for the above
import java.util.Date;  // for bandscope data file date formatting
import javax.swing.*;

class loader {
  private static final String
    bandType[]= {  // first 3 letters of bandscope data file names
      "brd",       // broadcast band
      "ham",       // amateur band
      "air",       // aeronautical band
      "mar"        // marine band
    };

  private byte B[];  // gigantic byte array to hold downloaded signal data

  private int
    L = 0,    // length of the remote item being loaded
    l = 0,    // number of bytes of the above successfully downloaded
    lp = 3,   // current loader phase (3 = loaded)
    sBT = 0,  // currently selected band type
    sB = 0,   // currently selected band
    RL = 0;   // reload counter

  private long
    t,        // current system time
    lm = 0;   /* when current data file last modified
                 (seconds since 1970-01-01-00:00Z). */

  private String
    LM = "",    // date when data file last modified
    fn = "bs",  // default name for the bandscope data file
    Age = "",   // to preserve the part of the age string that changes
    cb;         // code-base URL of the main applet

  boolean RELOAD = false;

  // input stream for downloading index or current HTML file
  private InputStream I;

  // date object for the file-modified date of the scan data file
  private Date D;

  // Reference to instance of the ...
  private bs hf;        // main bandscope applet
  private msgpanel mp;  // message panel object
  private bands bd;     // band-selector object
  private scope sc;     // scope graph object
  private freqfigs ff;  // frequency-figures object
  private update updt;  // update button and selector class instance
  private ar86000 rx;   // receiver object

  loader(bs hf,msgpanel mp,scope sc,freqfigs ff,  // CONSTRUCTOR
         update updt,String cb,bands bd) {

    // Reference to instances of the ...
    this.hf = hf;      // message panel object
    this.mp = mp;      // message panel object
    this.sc = sc;      // scope graph object
    this.ff = ff;      // frefigs object
    this.updt = updt;  // update button and selector class instance
    this.bd = bd;      // band-selector class
    this.cb = cb;      //code-base URL of the main applet
  }

  void setAR86000(ar86000 rx) {this.rx = rx;}

  // called initially from the main applet and thereafter from "bands"

  void load(int sBT, int sB) {  // trigger a reload of the data
    this.sBT = sBT;             // currently selected band type
    this.sB = sB;               // currently selected band
    lp = 1;                     // initiate the loading process
  }
      
  void reload() {lp = 1; RL = 7;}  // trigger a reload of the data


  void post() {   }  // POST a "RESCAN" command to RX server via HTTP


  boolean scanDataLoaded() {
    if(RL > 0) {              // if reload not yet expired
      RL--;                   // decrement the reload delay timer
      return true;            // and exit
    }
    switch(lp) {              // THE 2 DOWNLOADING PHASES:
      case 1: fileConnect();  // connect to bandscope data file on server 
      break;
      case 2: fileLoad();     // manage the downloading of its content
    }
    if(lp == 3) return true;  // completion state
    return false;             // error state
  }


  private void fileConnect() {   // CONNECT TO BANDSCOPE DATA FILE ON SERVER
    fn = "bs";                   // default name for the bandscope data file
    if((sBT > 0) && (sB > 0)) {  // If a specific band has been selected,
      String s = "";             // pad the band number out to two digits
      if(sB < 10) s = "0";       // with a leading zero if required,
      fn = bandType[sBT - 1]     // then form the complete file name for
         + s + sB;               // the band's data file
    }
    fn += ".dat";  // add the "data" filename extension
    mp.showMsg("Connecting to server...", false);
    try {                    // capture any exceptions locally
      if(hf.JarredSearch) {  // if loading from the applet's ".jar" file
        // create a stream to load the file from the applet's ".jar"
        I = getClass().getResourceAsStream(fn);
        LM = "Scanned: 1970-01-01-00:00 GMT";
        lm = 0;    // convert to whole seconds
        L = 1000;  // cannot find the current file length easily
      }
      else {  // ELSE CREATE A STREAM TO LOAD THE FILE FROM THE SERVER:
        URL url = new URL(cb + fn);  // form URL of bandscope data file,
        URLConnection u = url.openConnection();  // open a connection to it 
        I = u.getInputStream(); // make input stream through which to access it

        /* Form a readable date of when file was last updated in
        milliseconds since 1970-01-01-00:00 GMT and convert it to
        whole seconds. */

        LM = "Scanned: " + new Date(lm = u.getLastModified()); lm /= 1000;
        L = u.getContentLength();  // length of the remote file (bytes)
      }
      B = new byte[L];  // create the gigantic buffer for the data
      l = 0;            // number of bytes so far successfully downloaded
      lp = 2;           // advance to the file loading phase
    } 
    /* If any error occurs during this "try", set unrecoverable error
    status and then show type of error and where it occurred. */

    catch(Exception e) { lp = 0; mp.showMsg("fileConnect() " + e, true); }
  }


  // DOWNLOAD THE BANDSCOPE DATA
  private void fileLoad() {
    mp.showMsg("Loading " + bd.getBandName() + " scan data.", false);
    try {
      int k;  // to hold each grabbed byte in turn

      /* While the entire file has not yet been downloaded and read()
      hasn't hit the current end of input stream, add its new byte
      to the big byte array B[]. */

      if(hf.JarredSearch) {  // if loading bandscope data from jar file
        while((k = I.read()) != -1)
          B[l++] = (byte)k;
        if(l < 200) L = 100; 
      } else                 // else [if pulling it from the server]
        while(l < L && (k = I.read()) != -1)
          B[l++] = (byte)k;

      if(hf.JarredSearch        // If the whole file has now been downloaded,
      || l >= L) {
        I.close();              // close the input stream
        rx.computePlots();      // make graph plots from the downloaded data
        lp = 3;                 // set loader to isuccessful completion state
        computeAge();           // compute the age of current scan data
        invokeEDT();            // schedule tasks for Event-Despatching Thread
        mp.showMsg(LM, false);  // show date & time when file was last updated
      }
    }
    /* If any error occurs during this "try", set the loader to its
    error state and then show the type of error and where it occurred. */

    catch(Exception e) {
      lp = 0; mp.showMsg("fileLoad() " + e + " " + L + " " + l, true);
    }
  }


  // DISPLAY THE AGE OF THE FILE ON THE AGE LABEL
  private void computeAge() {

    /* The age of the scan data file just loaded is the current system
    time converted to seconds, minus the time (in seconds) at which the
    file was last updated. */

    long age = System.currentTimeMillis() / 1000 - lm;

    // From the above numeric age, form the appropriate age message.
    if(age > 2592000)     Age = "Over a month";
    else if(age > 604800) Age = "Over a week";
    else if(age > 86400)  Age = "Over a day";
    else if (age > 3600)  Age = "Over an hour";
    else if(age > 60)     Age = "" + age / 60 + " min";
    else                  Age = "" + age + " sec";
  }


  // CALLED BY THE LOADER TO SET VALUES WITHIN SWING WIDGETS
  void invokeEDT() {
    try {  // update the age label via the event-despatching thread
      SwingUtilities.invokeLater(
        new Runnable() { public void run() { threadSafe(); } }
      );
    } catch (Exception e) { } 
  }


  /* DONE ON THE EVENT-DESPATCHING THREAD: display the scope panel
  and the frequency figures, then update the text of the age label
  at bottom right of applet. */

  void threadSafe() {
    sc.atualizar(); ff.atualizar(); updt.setAgeLabel(Age + " old");
  }


  // Return the length of array B[] containing the received scan data file
  int getL() {return L;}


  /* Return the loader phase (to check that the scan 
  data is not currently in the process of being loaded). */

  int getLP() {return lp;}


  // get the ith byte from the downloaded scan data file
  int getB(int i) {return (int)B[i];}
}