import java.text.DateFormat;
import java.util.*;

/**
 * Container class for storing gas mileage statistics.
 * for use with GasMiles.
 * Copyright (c) 2007 William R. Fraser
 * All rights reserved. Personal, noncommercial use is permitted.
 *  
 * Records are stored as "periods"; i.e. all the records between times when the
 * tank was full. The "current period" is the set of orphan records at the end
 * of the data file if the file isn't terminated by a full state.
 * We can't really do anything with those records, because we have no idea of
 * how many gallons have been burned until the tank is re-filled.
 * 
 * @author William R. Fraser <wfraser@cs.uic.edu>
 */
public class GasHistory
{
    public String carName;  // the name of this car
    private ArrayList<LinkedList<HistoryElement>> history;  // all the periods
    private LinkedList<HistoryElement> current;             // current period
    
    public static final int PERIOD_CURRENT = -1;
    public static final int PERIOD_ALL     = -2;
    
    /**
     * Initialize variables.
     * @param carName
     */
    public GasHistory(String carName)
    {
        this.carName = carName;
        history = new ArrayList<LinkedList<HistoryElement>>();
        current = new LinkedList<HistoryElement>();
    }

    public int numRecords()
    {
        int size = 0;
        for (LinkedList<HistoryElement> period : history) {
            size += period.size();
        }
        size += current.size();
        return size;
    }
    
    /**
     * Add a normal (non-fill) gas-up record.
     *
     * Simply adds the record to the current period.
     *
     * @param mileage
     * @param date
     * @param gallons
     * @param dollars
     */
    public void pushGas(float mileage, Date date, float gallons, float dollars)
    {
        current.add(new HistoryElement(mileage, date, gallons, dollars));
    }
    
    /**
     * Add a gas-tank-filling gas-up record.
     *
     * Terminates the current period and adds it to the history, then begins a
     * new current period beginning with the given mileage and date.
     *
     * @param mileage
     * @param date
     * @param gallons
     * @param dollars
     */
    public void pushFull(float mileage, Date date, float gallons, float dollars)
    {
        if (current.size() != 0) {
            current.add(new HistoryElement(mileage, date, gallons, dollars));
            history.add(current);
            current = new LinkedList<HistoryElement>();
        }
        
        current.add(new HistoryElement(mileage, date, 0, 0));
    }
    
    /**
     * How many periods are in the history?
     * @return
     */
    public int numPeriods()
    {
        return history.size();
    }
    
    /**
     * Get the period referenced by periodNumber.
     * If periodNumber is PERIOD_CURRENT, returns the current (unfinished)
     * period.
     * If periodNumber is PERIOD_ALL, returns collection of all periods. 
     * 
     * @param periodNumber
     * @return
     */
    private LinkedList<HistoryElement> getPeriod(int periodNumber)
    {
        if (periodNumber == -1) {
            return current;
        } else if (periodNumber == -2) {
            return getAllPeriods();
        } else {
            return history.get(periodNumber);
        }
    }
    
    /**
     * Returns a LinkedList of all the HistoryElements currently part of a
     * completed period.
     */
    private LinkedList<HistoryElement> getAllPeriods()
    {
        LinkedList<HistoryElement> all = new LinkedList<HistoryElement>();
        for (LinkedList<HistoryElement> period : history) {
            all.addAll(period);
        }
        return all;
    }
    
    /**
     * The starting and ending dates for the given period.
     * @param periodNumber
     * @return
     */
    public Date[] periodDates(int periodNumber)
    {
        Date[] retval = new Date[2];
        LinkedList<HistoryElement> period = getPeriod(periodNumber);
        
        retval[0] = period.getFirst().date;
        retval[1] = period.getLast().date;
        
        return retval;
    }
    
    /**
     * The number of new miles added in the given period.
     * @param periodNumber
     * @return
     */
    public float newMiles(int periodNumber)
    {
        LinkedList<HistoryElement> period = getPeriod(periodNumber);
        return period.getLast().mileage - period.getFirst().mileage;
    }
    
    /**
     * The number of gallons added in the given period.
     * @param periodNumber
     * @return
     */
    public float newGallons(int periodNumber)
    {
        LinkedList<HistoryElement> period = getPeriod(periodNumber);
        
        float gallons = 0;
        for (HistoryElement element : period) {
            gallons += element.gallons;
        }
        
        return gallons;
    }
    
    /**
     * The number of dollars spent in the given period.
     * @param periodNumber
     * @return
     */
    public float newDollars(int periodNumber)
    {
        LinkedList<HistoryElement> period = getPeriod(periodNumber);
        
        float dollars = 0;
        for (HistoryElement element : period) {
            dollars += element.dollars;
        }
        
        return dollars;
    }
    
    public String toString()
    {
        String out = "history:\n";
        int i = 0;
        for (LinkedList<HistoryElement> period : history) {
            out += "\tperiod " + i + ":\n";
            for (HistoryElement el : period) {
                out += "\t\t" + el.toString() + "\n";
            }
            i++;
        }
        out += "current:\n";
        for (HistoryElement el : current) {
            out += "\t" + el.toString() + "\n";
        }
        
        return out;
    }

    /**
     * Internal container class for holding mileage, date, gallons, and dollars
     * values.
     * @author Bill Fraser
     */
    private class HistoryElement
    {
        float mileage;
        Date date;
        float gallons;
        float dollars;
    
        HistoryElement(float mileage, Date date, float gallons, float dollars)
        {
            this.mileage = mileage;
            this.date = date;
            this.gallons = gallons;
            this.dollars = dollars;
        }
        
        public String toString()
        {
            Formatter f = new Formatter();
            return f.format("%.1f -- %s -- %.3fgal -- $%.2f",
                    mileage, DateFormat.getDateInstance(DateFormat.SHORT).format(date), gallons, dollars).toString();
        }
    }
}