import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
  /*
   Reads data from a specific section of a text file into lists mapped by 
   column headers.
   path:         The path to the text file.
   start_string: The string that marks the beginning of the data section.
   end_string:   The string that marks the end of the data section.
   return:       Map where keys = column headers and values = lists of data.
   */
   
public class flowNetInput {

  public static void main(String[] args) {
    // Define the file path and section markers
    String file_path = "flow_net_input.txt";
    String start_string = "[FLOW RESISTORS BEGIN]";
    String end_string = "[FLOW RESISTORS END]";

    // Call the method to read and process the data
    Map<String, List<String>> column_data = readSectionData(Path.of(file_path), 
      start_string, end_string);

    // Display the results
    if (!column_data.isEmpty()) {
      System.out.println("Data successfully read for the following columns:");
      for (String header : column_data.keySet()) {
        System.out.println("--- Column: " + header + " ---");
        System.out.println(column_data.get(header));
      }
    } else {
      System.out.println("No data found within the specified section.");
    }
  }

  public static Map<String, List<String>> readSectionData(Path file_path, 
    String start_string, String end_string) {
    Map<String, List<String>> data_map = new HashMap<>();
    boolean inSection = false;
    List<String> headers = null;
    // Regex for one or more spaces, tabs, or commas
    String delimiterRegex = "[\\s,]+"; 

    try 
    (BufferedReader reader = new BufferedReader(new FileReader(file_path.toFile()))) {
      String line;
      while ((line = reader.readLine()) != null) {
        line = line.trim();

        if (line.equals(start_string)) {
          inSection = true;
          // Skip any lines between the start marker and the headers, if necessary, 
          // or assume the next line is the header.
          continue; 
        }

        if (line.equals(end_string)) {
          inSection = false;
          break; // Stop reading after the end marker
        }

        if (inSection) {
          if (headers == null) {
            // This is the header line. Split and initialize lists.
            headers = Arrays.asList(line.split(delimiterRegex));
            for (String header : headers) {
              data_map.put(header.trim(), new ArrayList<>());
            }
          } else {
            // This is a data line. Split and store in the respective lists.
            String[] values = line.split(delimiterRegex);
            for (int i = 0; i < headers.size() && i < values.length; i++) {
              data_map.get(headers.get(i).trim()).add(values[i].trim());
            }
          }
        }
      }
    } catch (IOException e) {
      e.printStackTrace();
    }
    return data_map;
  }
  
  /*
   Converts the values of a Map into a List (or Vector)
     data_map = The input map
     return   = A List containing all values
  */
  public static <K, V> List<K> convertKeysToVector(Map<K, V> data_map) {
    return new ArrayList<>(data_map.keySet());
  }
  public static <K, V> List<V> convertValuesToVector(Map<K, V> data_map) {
    return new ArrayList<>(data_map.values());
  }
}