package de.intevation.flys.model;

import java.io.Serializable;

import java.math.BigDecimal;
import java.math.MathContext;

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
import javax.persistence.GeneratedValue;
import javax.persistence.Column;
import javax.persistence.SequenceGenerator;
import javax.persistence.OneToMany;
import javax.persistence.OneToOne;
import javax.persistence.JoinColumn;
import javax.persistence.GenerationType;

import java.util.List;
import java.util.Comparator;
import java.util.Map;
import java.util.TreeMap;

import org.hibernate.Session;
import org.hibernate.Query;

import de.intevation.flys.backend.SessionHolder;


@Entity
@Table(name = "rivers")
public class River
implements   Serializable
{
    public static final MathContext PRECISION = new MathContext(6);

    public static final double EPSILON = 1e-5;

    public static final Comparator KM_CMP = new Comparator<Double>() {
        @Override
        public int compare(Double a, Double b) {
            double diff = a - b;
            if (diff < -EPSILON) return -1;
            if (diff >  EPSILON) return +1;
            return 0;
        }
    };

    private Integer id;

    private String  name;

    private boolean kmUp;

    private List<Gauge> gauges;

    private Unit wstUnit;

    @Id
    @SequenceGenerator(
        name           = "SEQUENCE_RIVERS_ID_SEQ",
        sequenceName   = "RIVERS_ID_SEQ",
        allocationSize = 1)
    @GeneratedValue(
        strategy  = GenerationType.SEQUENCE,
        generator = "SEQUENCE_RIVERS_ID_SEQ")
    @Column(name = "id")
    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    @Column(name = "name")
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Column(name = "km_up")
    public boolean getKmUp() {
        return kmUp;
    }

    public void setKmUp(boolean kmUp) {
        this.kmUp = kmUp;
    }

    public River() {
    }

    public River(String name, Unit wstUnit) {
        this.name    = name;
        this.wstUnit = wstUnit;
    }

    @OneToMany
    @JoinColumn(name="river_id")
    public List<Gauge> getGauges() {
        return gauges;
    }

    public void setGauges(List<Gauge> gauges) {
        this.gauges = gauges;
    }


    @OneToOne
    @JoinColumn(name = "wst_unit_id" )
    public Unit getWstUnit() {
        return wstUnit;
    }

    public void setWstUnit(Unit wstUnit) {
        this.wstUnit = wstUnit;
    }



    public String toString() {
        return name != null ? name : "";
    }


    /**
     * This method returns the gauges that intersect with <i>a</i> and
     * <i>b</i>,
     *
     * @param a A start point.
     * @param b An end point.
     *
     * @return the intersecting gauges.
     */
    public List<Gauge> determineGauges(double a, double b) {
        Session session = SessionHolder.HOLDER.get();

        if (a > b) { double t = a; a = b; b = t; }

        Query query = session.createQuery(
            "from Gauge where river=:river " +
            "and not (range.a > :b or range.b < :a) order by a");
        query.setParameter("river", this);
        query.setParameter("a", new BigDecimal(a, PRECISION));
        query.setParameter("b", new BigDecimal(b, PRECISION));

        return query.list();
    }

    public Gauge maxOverlap(double a, double b) {
        List<Gauge> gauges = determineGauges(a, b);
        if (gauges == null) {
            return null;
        }

        if (a > b) { double t = a; a = b; b = t; }

        double max = -Double.MAX_VALUE;

        Gauge result = null;

        for (Gauge gauge: gauges) {
            Range  r = gauge.getRange();
            double c = r.getA().doubleValue();
            double d = r.getB().doubleValue();

            double start = c >= a ? c : a;
            double stop  = d <= b ? d : b;

            double length = stop - start;

            if (length > max) {
                max = length;
                result = gauge;
            }
        }

        return result;
    }

    public Gauge determineGaugeByName(String name) {
        Session session = SessionHolder.HOLDER.get();
        Query query = session.createQuery(
            "from Gauge where river=:river and name=:name");
        query.setParameter("river", this);
        query.setParameter("name", name);
        List<Gauge> gauges = query.list();
        return gauges.isEmpty() ? null : gauges.get(0);
    }

    public Gauge determineGaugeByPosition(double p) {
        Session session = SessionHolder.HOLDER.get();
        Query query = session.createQuery(
            "from Gauge g where river=:river "  +
            "and :p between g.range.a and g.range.b");
        query.setParameter("river", this);
        query.setParameter("p", new BigDecimal(p, PRECISION));
        List<Gauge> gauges = query.list();
        return gauges.isEmpty() ? null : gauges.get(0);
    }

    public Gauge determineGaugeByStation(double a, double b) {

        if (a > b) { double t = a; a = b; b = t; }

        Session session = SessionHolder.HOLDER.get();

        Query query = session.createQuery(
            "from Gauge where river.id=:river " +
            "and station between :a and :b");
        query.setParameter("river", getId());
        query.setParameter("a", new BigDecimal(a));
        query.setParameter("b", new BigDecimal(b));

        List<Gauge> gauges = query.list();
        return gauges.isEmpty() ? null : gauges.get(0);
    }


    /**
     * This method returns the first gauge that is intersected by <i>a</i> and
     * <i>b</i>,
     *
     * @param a A start point.
     * @param b An end point.
     *
     * @return the first intersecting gauge.
     */
    public Gauge determineGauge(double a, double b) {
        List<Gauge> gauges = determineGauges(a, b);

        int idx = a < b ? 0 : gauges.size() - 1;

        return gauges.isEmpty() ? null : gauges.get(idx);
    }

    /**
     * Returns the min and max distance of this river. The first position in the
     * resulting array contains the min distance, the second position the max
     * distance.
     *
     * @return the min and max distance of this river.
     */
    public double[] determineMinMaxDistance() {
        List<Gauge> gauges = getGauges();

        if (gauges == null || gauges.isEmpty()) {
            return null;
        }

        double minmax[] = new double[] { Double.MAX_VALUE, Double.MIN_VALUE };

        for (Gauge g: gauges) {
            Range r = g.getRange();

            if (r == null) {
                continue;
            }

            double a  = r.getA().doubleValue();
            minmax[0] = minmax[0] < a ? minmax[0] : a;

            BigDecimal bigB = r.getB();
            if (bigB != null) {
                double b  = bigB.doubleValue();
                minmax[1] = minmax[1] > b ? minmax[1] : b;
            }
        }

        return minmax;
    }

    public Map<Double, Double> queryGaugeDatumsKMs() {
        List<Gauge> gauges = getGauges();
        Map result = new TreeMap<Double, Double>(KM_CMP);

        for (Gauge gauge: gauges) {
            BigDecimal km    = gauge.getStation();
            BigDecimal datum = gauge.getDatum();
            if (km != null && datum != null) {
                result.put(km.doubleValue(), datum.doubleValue());
            }
        }

        return result;
    }
}
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