package org.hathitrust.extractedfeatures;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.charset.StandardCharsets;
import java.util.HashMap;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


/**
 * Servlet implementation class VolumeCheck
 */
@WebServlet("/VolumeCheck")
public class VolumeCheck extends HttpServlet {
	private static final long serialVersionUID = 1L;

	protected static int HASHMAP_INIT_SIZE = 13800000;
	protected static HashMap<String,Boolean> id_check_ = null;

    protected static final String file_ext = ".json.bz2";
    protected static final String ht_col_url = "https://babel.hathitrust.org/cgi/mb";
    	
    public VolumeCheck() 
    {}
    
    protected static String full_filename_to_tail(String full_filename)
    {
    	String filename_tail = full_filename.substring(full_filename.lastIndexOf("/")+1);
    	return filename_tail;
    }
    
    protected static String filename_tail_to_id(String filename_tail)
    {
		String id = null;
		if (filename_tail.endsWith(file_ext)) {
			id = filename_tail.substring(0,filename_tail.lastIndexOf(file_ext));
		}
		else {
			id = filename_tail;
		}
		
		id = id.replaceAll(",",".").replaceAll("\\+", ":").replaceAll("=", "/");
		
		return id;
    }
    
    protected static String id_to_pairtree_filename(String id) {
    	// Example :-
    	//   id: miun.adx6300.0001.001 
    	//   pairtree filename: miun/pairtree_root/ad/x6/30/0,/00/01/,0/01/adx6300,0001,001/miun.adx6300,0001,001.json.bz2
    	
    	// 1. Map 'difficult' chars: 
    	//   . => ,
    	//   : => +
    	//   / => =
    	
    	// 2. Process resulting string:
    	//   split on first dot
    	//   add "pairtree_root"
    	//   then split everything else 2 chars at a time
    	
    	// 3. Finally add in the (safely transformed) id:
    	//   append directory that is prefix-removed id (transformed to be safe)
    	//   further append 'id-safe'.json.bz
    	
    	int id_dot_pos = id.indexOf(".");
    	String id_prefix = id.substring(0,id_dot_pos);
    	String id_tail = id.substring(id_dot_pos+1);
    	String id_tail_safe = id_tail.replaceAll("\\.", ",").replaceAll(":", "+").replaceAll("/", "=");
    	
    	String [] pairs = id_tail_safe.split("(?<=\\G..)");
    	String joined_pairs = String.join("/", pairs);

    	String id_safe = id_prefix + "." + id_tail_safe;
    	String main_dir = id_prefix + "/pairtree_root/" + joined_pairs;
    	String filename = main_dir + "/" + id_tail_safe + "/" + id_safe + file_ext;
    	
    	return filename;
    }
    
    protected void storeIDs(BufferedReader br)
    {    	
    	long line_num = 1;
    	String line;

    	try {

    		System.err.print("Loading hashmap: ");
    		while ((line = br.readLine()) != null) {

    			String full_json_filename = line;
    			String json_filename_tail = full_filename_to_tail(full_json_filename);
    			String id = filename_tail_to_id(json_filename_tail);
    			
    			id_check_.put(id, true);

    			if ((line_num % 100000) == 0) {
    				System.err.print(".");
    			}
    			line_num++;

    		}
    		System.err.println(" => done.");
    	}
    	catch (Exception e) {
    		e.printStackTrace();
    	}
    	
    }
	/**
	 * @see Servlet#init(ServletConfig)
	 */
	public void init(ServletConfig config) throws ServletException {
		super.init(config);
		
		if (id_check_ == null) {
    		id_check_ = new HashMap<String,Boolean>(HASHMAP_INIT_SIZE);
    		
    		String htrc_list_file = "htrc-ef-all-files.txt";
    		InputStream is = getServletContext().getResourceAsStream("/WEB-INF/" + htrc_list_file);
    		
    		try {
    			System.err.println("INFO: Loading in volume IDS: " + htrc_list_file);
    			
    			InputStreamReader isr = new InputStreamReader(is, "UTF-8");
    			BufferedReader br = new BufferedReader(isr);

    			storeIDs(br);
    			br.close();
    		}
    		catch (Exception e) {
    			e.printStackTrace();
    		}
    	}
	}

	protected BufferedInputStream doRsyncDownload(String full_json_filename)
	{
		String json_filename_tail = full_filename_to_tail(full_json_filename);
		
		BufferedInputStream bis = null;
		
		Runtime runtime = Runtime.getRuntime();
		String[] rsync_command = {"rsync","-av","data.analytics.hathitrust.org::features/" + full_json_filename, "."};
		
		try {
			Process proc = runtime.exec(rsync_command);
			proc.waitFor();
		
			FileInputStream fis = new FileInputStream(json_filename_tail);
			bis = new BufferedInputStream(fis);
		      
		}
		catch (Exception e) {
			e.printStackTrace();
		}
		
		return bis;
		
	}
	
	protected void doCollectionToWorkset(HttpServletResponse response, String col_title, 
							String c, String a, String format) throws IOException
	{
		String post_url_params  = "c="+c+"&a="+a+"&format="+format;
		
		byte[] post_data       = post_url_params.getBytes(StandardCharsets.UTF_8);
		int    post_data_len = post_data.length;
		
		try {
			
			URL post_url = new URL(ht_col_url);
			HttpURLConnection conn = (HttpURLConnection) post_url.openConnection();           
			conn.setDoOutput(true);
			conn.setInstanceFollowRedirects(false);
			conn.setRequestMethod("POST");
			conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded"); 
			conn.setRequestProperty("charset", "utf-8");
			conn.setRequestProperty("Content-Length", Integer.toString(post_data_len));
			conn.setUseCaches(false);
			
			try(DataOutputStream dos = new DataOutputStream(conn.getOutputStream())) {
			   dos.write(post_data);
			}
			// try-resource auto-closes stream
			
			InputStream is = conn.getInputStream();
			InputStreamReader isr = new InputStreamReader(is);
			BufferedReader reader = new BufferedReader(isr);
			
			StringBuilder workset_friendly_sb = new StringBuilder();
			StringBuilder workset_unfriendly_sb = new StringBuilder();
			
			String line = null;
			int ci = 0;
			while ((line = reader.readLine()) != null)
			{
				if (ci==0) {
					workset_friendly_sb.append("#" + line + "\n");
				}
				else {
					int first_tab_pos=line.indexOf("\t");
					String id = (first_tab_pos>0) ? line.substring(0, first_tab_pos) : line;
					
					if (id_check_.containsKey(id)) {
						workset_friendly_sb.append(line + "\n");		
					}
					else {
						workset_unfriendly_sb.append("#" + line + "\n");
					}
				}
				
				ci++;
			}
		     
			String col_title_filename = col_title + ".txt";
			response.setContentType("text/plain");
			response.setHeader("Content-Disposition", "attachment; filename=\"" + col_title_filename + "\"");

			PrintWriter pw = response.getWriter();
			pw.append(workset_friendly_sb.toString());
			
			if (workset_unfriendly_sb.length()>0) {
				pw.append("## The following volumes were listed in the HT collection, but have been omitted as they are not in the HTRC Extracted Feature dataset\n");
				pw.append(workset_unfriendly_sb.toString());
			}
			pw.flush();
		}
		catch (Exception e) {
			e.printStackTrace();
			response.sendError(HttpServletResponse.SC_BAD_REQUEST, "Failed to convert HT collection to HTRC workset");
		}
		
	}
	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
	{
		String cgi_ids = request.getParameter("ids");
		String cgi_id = request.getParameter("id");
		String cgi_download_id = request.getParameter("download-id");
		String cgi_convert_col = request.getParameter("convert-col");
		
		if (cgi_ids != null) {
			response.setContentType("application/json");
			PrintWriter pw = response.getWriter();
		    
			String[] ids = cgi_ids.split(",");
		    int ids_len = ids.length;
		    
		    pw.append("{");
			
		    for (int i=0; i<ids_len; i++) {
		    	String id = ids[i];

		    	boolean exists = id_check_.containsKey(id);
		    	
		    	if (i>0) {
		    		pw.append(",");
		    	}
		    	pw.append("\"" + id + "\":" + exists );
		    }
		    pw.append("}");
			
		}
		else if (cgi_id != null) {
			response.setContentType("application/json");
			PrintWriter pw = response.getWriter();
		    
			String id = cgi_id;
			boolean exists = id_check_.containsKey(id);
			pw.append("{'" + id + "':" + exists + "}");
		}
		else if (cgi_download_id != null) {
			String download_id = cgi_download_id;
			boolean exists = id_check_.containsKey(download_id);
			if (!exists) {
				// Error
				 response.sendError(HttpServletResponse.SC_BAD_REQUEST, "The requested volume id does not exist.");
			}
			else {
				// rsync -av data.analytics.hathitrust.org::features/{PATH-TO-FILE} .
				String full_json_filename = id_to_pairtree_filename(download_id);
				
				BufferedInputStream bis = doRsyncDownload(full_json_filename);

				if (bis == null) {
					response.sendError(HttpServletResponse.SC_BAD_REQUEST, "Rsync failed");
				}
				else {
					String json_filename_tail = full_filename_to_tail(full_json_filename);
				
					response.setContentType("application/x-bzip2");
					response.setHeader("Content-Disposition", "attachment; filename=\"" + json_filename_tail + "\"");

					OutputStream os=response.getOutputStream();
					BufferedOutputStream bos = new BufferedOutputStream(os);
					
					byte[] buf = new byte[1024];
					
					while (true) {
						int num_bytes = bis.read(buf);
						if (num_bytes == -1) { 
							break;
						}
						bos.write(buf,0,num_bytes);
						//total_num_bytes += num_bytes;
					}
										
					bis.close();
					bos.close();
				}
			}
		}
		else if (cgi_convert_col != null) {
			
			String cgi_col_title = request.getParameter("col-title");
			String cgi_a = request.getParameter("a");
			String cgi_format = request.getParameter("format");
			
			if ((cgi_a == null) || (cgi_format == null)) {
				response.sendError(HttpServletResponse.SC_BAD_REQUEST, "Malformed arguments.  Need 'a', and 'format'");
			}
			else {
				if (cgi_col_title == null) {
					cgi_col_title = "htrc-workset-" + cgi_convert_col;
				}

				doCollectionToWorkset(response,cgi_col_title,cgi_convert_col,cgi_a,cgi_format);
			}
			
		}
		else {
			PrintWriter pw = response.getWriter();
		    
			pw.append("General Info: Number of HTRC Volumes in check-list = " + id_check_.size());
						
		}
		//pw.close();
		
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		doGet(request, response);
	}

}