import java.io.*;
import java.text.*;
import java.util.*;

/**
 * GasMiles v2
 * A convenient utility for calculating gas mileage of cars without trip
 * odometers.
 * Copyright (c) 2007 William R. Fraser <wfraser@cs.uic.edu>
 * All rights reserved. Personal, noncommercial use is permitted.
 * 
 * The program uses a data file containing lines of the following format:
 * car name : mileage : date : gallons : dollars
 * (date is mm/dd/yyyy or whatever is appropriate for your Java locale, enter
 * dollars without any dollar sign [$], and all whitespace is optional)
 *
 * Comments begin with a hash sign [#]. A hash sign appearing mid-line will
 * cause the program to ignore the rest of that line.
 * 
 * Every time gas is put in the car, make a line in the data file marking how
 * much gas was bought, for how much money, the date, and the current odometer
 * reading.
 * 
 * If the car was filled up by that purchase, add an additional field stating,
 * simply, "full".
 * 
 * Every time the gas tank reaches a consistent state - being full - the
 * program can calculate gas mileage and other statistics based on the data in
 * the file.
 * 
 * The program reports (per each refuel period):
 *  - number of days passed
 *  - miles traveled
 *  - gallons put in
 *  - dollars spent
 *  - miles per gallon
 *  - dollars per mile
 *  - dollars per gallon
 *  - miles per day.
 *  
 * Additional statistics may easily be added to the GasMiles.printData() method,
 * if desired. This method gets passed the days, miles, gallons, and dollars.
 * 
 * @author William R. Fraser <wfraser@cs.uic.edu>
 */
public class GasMiles
{
    public static final String version = "v2 2007.07.27";
    public String dataFile;
    public String selectedCar;
    private Scanner scan;
    private HashMap<String, GasHistory> cars;
    
    /**
     * Parse command line arguments, instantiate, and run.
     * @param args
     */
    public static void main(String args[])
    {
        if (args.length == 0) {
            System.err.printf("GasMiles %s (c) 2007 William R. Fraser\n",
                    version);
            System.err.println("usage: GasMiles <datafile> [carName]");
            System.exit(1);
        }

        String selectedCar = null;
        if (args.length == 2)
            selectedCar = args[1];
        
        GasMiles app = new GasMiles(args[0], selectedCar);
        app.go();
    }
    
    /**
     * Initialize member variables
     *
     * (if selectedCar is set to null, it means view all cars)
     * 
     * @param dataFile
     * @param selectedCar
     */
    public GasMiles(String dataFile, String selectedCar)
    {
        this.dataFile = dataFile;
        this.selectedCar = selectedCar;
        try {
            scan = new java.util.Scanner(new File(dataFile));
        } catch (FileNotFoundException ex) {
            System.err.println("Data file not found.");
            System.exit(1);
        }
        
        cars = new HashMap<String, GasHistory>();
    }
    
    /**
     * Run the program!
     *
     */
    public void go()
    {
        // parse the data file
        loadData();

        if (cars.size() == 0) {
            if (selectedCar != null) {
                System.err.printf("No data for car \"%s\" found.\n", selectedCar);
                System.exit(2);
            } else {
                System.err.printf("No records in data file.\n");
                System.exit(2);
            }
        }
       
        for (GasHistory hist : cars.values()) {
            System.out.printf("GasMiles analysis for car \"%s\":\n", hist.carName);
            
            if (hist.numPeriods() == 0) {
                System.out.printf("\tNo statistics to report yet.\n\n");
            }
       
            for (int i = 0; i < hist.numPeriods(); i++) {
                float miles = hist.newMiles(i);
                float gallons = hist.newGallons(i);
                float dollars = hist.newDollars(i);
                Date[] dates = hist.periodDates(i);
                Calendar spread = Calendar.getInstance();
                spread.setTimeInMillis(dates[1].getTime() - dates[0].getTime());
                int days = spread.get(Calendar.DAY_OF_YEAR);
                
                System.out.printf("Period %d: %s - %s\n",
                        i,
                        DateFormat.getDateInstance(DateFormat.SHORT).format(dates[0]),
                        DateFormat.getDateInstance(DateFormat.SHORT).format(dates[1]));
                printData(miles, gallons, dollars, days);
            }
        }
        
        for (GasHistory hist : cars.values()) {
            System.out.printf("Totals for car \"%s\": ", hist.carName);
            float miles = hist.newMiles(GasHistory.PERIOD_ALL);
            float gallons = hist.newGallons(GasHistory.PERIOD_ALL);
            float dollars = hist.newDollars(GasHistory.PERIOD_ALL);
            Date[] dates = hist.periodDates(GasHistory.PERIOD_ALL);
            Calendar spread = Calendar.getInstance();
            spread.setTimeInMillis(dates[1].getTime() - dates[0].getTime());
            int days = spread.get(Calendar.DAY_OF_YEAR);
            
            System.out.printf("%s - %s\n",
                        DateFormat.getDateInstance(DateFormat.SHORT).format(dates[0]),
                        DateFormat.getDateInstance(DateFormat.SHORT).format(dates[1]));
            printTotals(miles, gallons, dollars, days);
        }
    }
    
    /**
     * Print the various fields on screen.
     * 
     * @param miles 
     * @param gallons
     * @param dollars
     * @param days
     */
    public void printData(float miles, float gallons, float dollars, int days)
    {
        System.out.printf("\tdays | miles | gallons | dollars | MPG    | $/mile | $/gal  | miles/day\n");
        System.out.printf("\t%4d | %5.1f | %7.3f | $%6.2f | %6.3f | $%5.3f | $%5.3f | %6.3f\n",
                days, miles, gallons, dollars, miles/gallons, dollars/miles, dollars/gallons, miles/days);
        System.out.println();
    }
    
    /**
     * Print the various fields on screen. (used for totals)
     * 
     * @param miles 
     * @param gallons
     * @param dollars
     * @param days
     */
    public void printTotals(float miles, float gallons, float dollars, int days)
    {
        System.out.printf("days | miles    | gallons  | dollars  | MPG    | $/mile | $/gal  | miles/day\n");
        System.out.printf("%4d | %8.1f | %8.3f | $%7.2f | %6.3f | $%5.3f | $%5.3f | %6.3f\n",
                days, miles, gallons, dollars, miles/gallons, dollars/miles, dollars/gallons, miles/days);
        System.out.println();
    }
    
    /**
     * Parse the data file into the cars variable.
     *
     */
    public void loadData()
    {
        int lineNo = 0;
        String field = ""; // for keeping potentially bogus fields
        while (scan.hasNextLine()) {
            lineNo++;
            String line = scan.nextLine().trim();
            
            // ignore anything after a '#'
            line = line.split("#",2)[0];
            
            // skip empty lines (and comments)
            if (line.length() == 0)
                continue;
            
            Scanner lineScan = new Scanner(line).useDelimiter(":");
            
            // get each field
            String carName = lineScan.next();
            
            // if we're only looking for one car, skip the others
            if (selectedCar != null && !carName.equals(selectedCar))
                continue;
            
            if (!cars.containsKey(carName)) {
                // if this is a car we haven't seen, make a new history for it
                cars.put(carName, new GasHistory(carName));
            }
            
            GasHistory currentHistory = cars.get(carName);
            
            Date date;
            float mileage, gallons, dollars;
            boolean full = false;

            try { // catch not enough fields
            
                try { mileage = Float.parseFloat(field = lineScan.next()); }
                catch (NumberFormatException ex) {
                    System.err.printf("Parse error, %s:%d - unknown data, "
                            + "expecting a number (mileage): \"%s\"\n",
                            dataFile, lineNo, field);
                    System.exit(1);
                    return;
                }
            
                try { date = DateFormat.getDateInstance(DateFormat.SHORT)
                        .parse(field = lineScan.next()); }
                catch (ParseException ex) {
                    System.err.printf("Parse error, %s:%d - unknown date "
                            + "format: \"%s\"\n",
                            dataFile, lineNo, field);
                    System.exit(1);
                    return;
                }
            
                try { gallons = Float.parseFloat(field = lineScan.next()); }
                catch (NumberFormatException ex) {
                    System.err.printf("Parse error, %s:%d - unknown data, "
                            + "expecting a number (gallons): \"%s\"\n",
                            dataFile, lineNo, field);
                    System.exit(1);
                    return;
                }

                try { dollars = Float.parseFloat(field = lineScan.next()); }
                catch (NumberFormatException ex) {
                    System.err.printf("Parse error, %s:%d - unknown data, "
                            + "expecting a number (dollars): \"%s\"\n",
                            dataFile, lineNo, field);
                    System.exit(1);
                    return;
                }

                if (lineScan.hasNext()) {
                    if ((field = lineScan.next().trim()).equals("full")) {
                        full = true;
                    } else {
                        System.err.printf("Parse error, %s:%d - unknown data, "
                                + "expecting \"full\" or no field: \"%s\"\n",
                                dataFile, lineNo, field);
                        System.exit(1);
                        return;
                    }
                }
                    
            } catch (NoSuchElementException ex) {
                System.err.printf("Parse error, %s:%d - not enough fields!\n",
                        dataFile, lineNo);
                System.exit(1);
                return;
            }
            
            if (full) {
                currentHistory.pushFull(mileage, date, gallons, dollars);
            } else {
                // add the data to the current period
                currentHistory.pushGas(mileage, date, gallons, dollars);
            }
        }
    }
}