/*
 * Copyright ©2019 Hal Perkins.  All rights reserved.  Permission is
 * hereby granted to students registered for University of Washington
 * CSE 331 for use solely during Spring Quarter 2019 for purposes of
 * the course.  No other use, copying, distribution, or modification
 * is permitted without prior written consent. Copyrights for
 * third-party components of this work must be honored.  Instructors
 * interested in reusing these course materials should contact the
 * author.
 */

package pathfinder.parser;

import com.opencsv.CSVParser;
import com.opencsv.CSVParserBuilder;
import com.opencsv.CSVReader;
import com.opencsv.CSVReaderBuilder;

import java.io.IOException;
import java.io.Reader;
import java.net.URISyntaxException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;

/**
 * A utility class capable of parsing data in campus_buildings.tsv and
 * campus_paths.tsv in their expected formats.
 */
public class CampusPathsParser {

  /**
   * The base directory for all tsv files for this project.
   */
  private static final String DATA_DIR = "src/main/resources/pathfinder/data/";

  /**
   * The complete filename of the campus_buildings.tsv file.
   */
  private static final String CAMPUS_BUILDINGS_FILE = DATA_DIR + "campus_buildings.tsv";

  /**
   * The complete filename of the campus_paths.tsv file.
   */
  private static final String CAMPUS_PATHS_FILE = DATA_DIR + "campus_paths.tsv";

  /**
   * Parses the campus_buildings.tsv file and returns a list of objects
   * containing all the data in that file.
   *
   * @return A {@link List} of {@link CampusBuilding} objects, one for each
   * line in the parsed file, containing the data contained within that line.
   * @throws ParserException if the file cannot be found or parsed as expected
   */
  public static List<CampusBuilding> parseCampusBuildings() {
    List<CampusBuilding> buildings = new ArrayList<>();
    CSVReader reader = initializeReader(CAMPUS_BUILDINGS_FILE);
    //
    for(String[] line : reader) {
      if(line.length != 4) {
        throw new ParserException("Wrong number of fields in line.");
      }
      String shortName = line[0];
      String longName = line[1];
      double x, y;
      try {
        x = Double.parseDouble(line[2]);
        y = Double.parseDouble(line[3]);
      } catch(NumberFormatException e) {
        throw new ParserException("Cannot parse x/y coordinates as numbers.", e);
      }
      //
      buildings.add(new CampusBuilding(shortName, longName, x, y));
    }
    try {
      reader.close();
    } catch(IOException e) {
      throw new ParserException("Exception when closing parser.", e);
    }
    //
    return buildings;
  }

  /**
   * Parses the campus_paths.tsv file and returns a list of objects
   * containing all the data in that file.
   *
   * @return A {@link List} of {@link CampusPath} objects, one for each
   * line in the parsed file, containing the data contained within that line.
   * @throws ParserException if the file cannot be found or parsed as expected
   */
  public static List<CampusPath> parseCampusPaths() {
    List<CampusPath> paths = new ArrayList<>();
    CSVReader reader = initializeReader(CAMPUS_PATHS_FILE);
    //
    for(String[] line : reader) {
      if(line.length != 5) {
        throw new ParserException("Wrong number of fields in line.");
      }
      double x1, x2, y1, y2, distance;
      try {
        x1 = Double.parseDouble(line[0]);
        y1 = Double.parseDouble(line[1]);
        x2 = Double.parseDouble(line[2]);
        y2 = Double.parseDouble(line[3]);
        distance = Double.parseDouble(line[4]);
      } catch(NumberFormatException e) {
        throw new ParserException("Cannot parse x/y coordinates as numbers.", e);
      }
      //
      paths.add(new CampusPath(x1, y1, x2, y2, distance));
    }
    try {
      reader.close();
    } catch(IOException e) {
      throw new ParserException("Exception when closing parser.", e);
    }
    //
    return paths;
  }

  /**
   * Initializes a CSV reader with the provided filename, relative to the
   * classpath of this parser class. The returned reader is configured
   * to parse tab-character separated fields per line, and skips the first
   * line in the file.
   *
   * @param filename The file to initialize a parser for.
   * @return A new {@link CSVReader} prepared to begin reading from that file.
   */
  private static CSVReader initializeReader(String filename) {
    Reader fileReader;
    try {
      Path uri = Paths.get(filename);
      fileReader = Files.newBufferedReader(uri);
    } catch(IOException e) {
      throw new ParserException("Cannot create parser.", e);
    }
    //
    CSVParser parser = new CSVParserBuilder().withSeparator('\t').build();
    return new CSVReaderBuilder(fileReader)
            .withCSVParser(parser)
            .withSkipLines(1)
            .build();
  }

  /**
   * An Exception class representing an error during parsing.
   */
  public static class ParserException extends RuntimeException {

    /**
     * Creates a new ParserException with the provided message.
     *
     * @param message A message to include in the exception.
     */
    public ParserException(String message) {
      super(message);
    }

    /**
     * Creates a new ParserException with the provided message and cause.
     *
     * @param message A message to include in the exception.
     * @param cause   The exception (or other {@link Throwable}) that
     *                caused this exception to be thrown.
     */
    public ParserException(String message, Throwable cause) {
      super(message, cause);
    }

  }
}