/* 
 * Computing Wikipedia's internal PageRanks
 * 
 * Copyright (c) 2020 Project Nayuki
 * All rights reserved. Contact Nayuki for licensing.
 * https://www.nayuki.io/page/computing-wikipedias-internal-pageranks
 */

import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.nio.charset.StandardCharsets;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.zip.GZIPInputStream;


/* 
 * Provides static functions for working with page ID/title data.
 */
final class PageIdTitleMap {
	
	// Reads the given gzipped SQL file and returns a mapping of page title to integer ID.
	public static Map<String,Integer> readSqlFile(File file) throws IOException {
		long startTime = System.currentTimeMillis();
		Map<String,Integer> result = new HashMap<String,Integer>();
		
		long lastPrint = System.currentTimeMillis() - PRINT_INTERVAL;
		try (SqlReader in = new SqlReader(new BufferedReader(new InputStreamReader(new GZIPInputStream(new FileInputStream(file)), StandardCharsets.UTF_8)), "page")) {
			while (true) {
				List<List<Object>> multipleRows = in.readInsertionTuples();
				if (multipleRows == null)
					break;
				
				for (List<Object> tuple : multipleRows) {
					if (tuple.size() != 12)
						throw new IllegalArgumentException("Incorrect number of columns");
					Object namespace = tuple.get(1);
					Object id = tuple.get(0);
					Object title = tuple.get(2);
					
					if (!(namespace instanceof Integer))
						throw new IllegalArgumentException("Namespace must be integer");
					if (!(id instanceof Integer))
						throw new IllegalArgumentException("ID must be integer");
					if (!(title instanceof String))
						throw new IllegalArgumentException("Title must be string");
					if (((Integer)namespace).intValue() != 0)  // Filter out pages not in the main namespace
						continue;
					if (result.containsKey(title))
						throw new IllegalArgumentException("Duplicate page title");
					result.put((String)title, (Integer)id);
				}
				
				if (System.currentTimeMillis() - lastPrint >= PRINT_INTERVAL) {
					System.out.printf("\rParsing %s: %.3f million entries stored...", file.getName(), result.size() / 1000000.0);
					lastPrint = System.currentTimeMillis();
				}
			}
		}
		System.out.printf("\rParsing %s: %.3f million entries stored... Done (%.3f s)%n", file.getName(), result.size() / 1000000.0, (System.currentTimeMillis() - startTime) / 1000.0);
		return result;
	}
	
	
	public static Map<String,Integer> readRawFile(File file) throws IOException {
		long startTime = System.currentTimeMillis();
		Map<String,Integer> result = new HashMap<String,Integer>();
		
		try (BufferedReader in = new BufferedReader(new InputStreamReader(new FileInputStream(file), StandardCharsets.UTF_8))) {
			long lastPrint = System.currentTimeMillis() - PRINT_INTERVAL;
			for (int i = 0; ; i++) {
				String line = in.readLine();
				if (line == null)
					break;
				result.put(line, Integer.valueOf(in.readLine()));
				
				if (System.currentTimeMillis() - lastPrint >= PRINT_INTERVAL) {
					System.out.printf("\rReading %s: %.3f million entries...", file.getName(), i / 1000000.0);
					lastPrint = System.currentTimeMillis();
				}
			}
			System.out.printf("\rReading %s: %.3f million entries... Done (%.3f s)%n", file.getName(), result.size() / 1000000.0, (System.currentTimeMillis() - startTime) / 1000.0);
		}
		return result;
	}
	
	
	public static void writeRawFile(Map<String,Integer> idByTitle, File file) throws IOException {
		long startTime = System.currentTimeMillis();
		try (PrintWriter out = new PrintWriter(new OutputStreamWriter(new BufferedOutputStream(new FileOutputStream(file), 128 * 1024), StandardCharsets.UTF_8))) {
			int i = 0;
			long lastPrint = System.currentTimeMillis() - PRINT_INTERVAL;
			for (String title : idByTitle.keySet()) {
				out.println(title);
				out.println(idByTitle.get(title));
				i++;
				
				if (System.currentTimeMillis() - lastPrint >= PRINT_INTERVAL) {
					System.out.printf("\rWriting %s: %.3f million entries...", file.getName(), i / 1000000.0);
					lastPrint = System.currentTimeMillis();
				}
			}
			System.out.printf("\rWriting %s: %.3f million entries... Done (%.3f s)%n", file.getName(), i / 1000000.0, (System.currentTimeMillis() - startTime) / 1000.0);
		}
	}
	
	
	public static <K,V> Map<V,K> computeReverseMap(Map<K,V> map) {
		System.out.print("Creating reverse mapping...");
		long startTime = System.currentTimeMillis();
		Map<V,K> result = new HashMap<V,K>();
		for (K key : map.keySet())
			result.put(map.get(key), key);
		System.out.printf(" Done (%.3f s)%n", (System.currentTimeMillis() - startTime) / 1000.0);
		return result;
	}
	
	
	private static final int PRINT_INTERVAL = 30;  // In milliseconds
	
	
	private PageIdTitleMap() {}  // Not instantiable
	
}