package org.stellar.sdk;

import com.google.gson.annotations.SerializedName;
import org.stellar.sdk.xdr.Int32;

import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.List;

import static com.google.common.base.Preconditions.checkNotNull;

/**
 * Represents Price. Price in Stellar is represented as a fraction.
 */
public class Price {
    @SerializedName("n")
    private final int n;
    @SerializedName("d")
    private final int d;

    /**
     * Create a new price. Price in Stellar is represented as a fraction.
     * @param n numerator
     * @param d denominator
     */
    public Price(int n, int d) {
        this.n = n;
        this.d = d;
    }

    /**
     * Returns numerator.
     */
    public int getNumerator() {
        return n;
    }

    /**
     * Returns denominator
     */
    public int getDenominator() {
        return d;
    }

    /**
     * Approximates <code>price</code> to a fraction.
     * Please remember that this function can give unexpected results for values that cannot be represented as a
     * fraction with 32-bit numerator and denominator. It's safer to create a Price object using the constructor.
     * @param price Ex. "1.25"
     */
    public static Price fromString(String price) {
        checkNotNull(price, "price cannot be null");
        BigDecimal maxInt = new BigDecimal(Integer.MAX_VALUE);
        BigDecimal number = new BigDecimal(price);
        BigDecimal a;
        BigDecimal f;
        List<BigDecimal[]> fractions = new ArrayList<BigDecimal[]>();
        fractions.add(new BigDecimal[]{new BigDecimal(0), new BigDecimal(1)});
        fractions.add(new BigDecimal[]{new BigDecimal(1), new BigDecimal(0)});
        int i = 2;
        while (true) {
            if (number.compareTo(maxInt) > 0) {
                break;
            }
            a = number.setScale(0, BigDecimal.ROUND_FLOOR);
            f = number.subtract(a);
            BigDecimal h = a.multiply(fractions.get(i - 1)[0]).add(fractions.get(i - 2)[0]);
            BigDecimal k = a.multiply(fractions.get(i - 1)[1]).add(fractions.get(i - 2)[1]);
            if (h.compareTo(maxInt) > 0 || k.compareTo(maxInt) > 0) {
                break;
            }
            fractions.add(new BigDecimal[]{h, k});
            if (f.compareTo(BigDecimal.ZERO) == 0) {
                break;
            }
            number = new BigDecimal(1).divide(f, 20, BigDecimal.ROUND_HALF_UP);
            i = i + 1;
        }
        BigDecimal n = fractions.get(fractions.size()-1)[0];
        BigDecimal d = fractions.get(fractions.size()-1)[1];
        return new Price(n.intValue(), d.intValue());
    }

    /**
     * Generates Price XDR object.
     */
    public org.stellar.sdk.xdr.Price toXdr() {
        org.stellar.sdk.xdr.Price xdr = new org.stellar.sdk.xdr.Price();
        Int32 n = new Int32();
        Int32 d = new Int32();
        n.setInt32(this.n);
        d.setInt32(this.d);
        xdr.setN(n);
        xdr.setD(d);
        return xdr;
    }

    @Override
    public boolean equals(Object object) {
        if (!(object instanceof Price)) {
            return false;
        }

        Price price = (Price) object;

        return this.getNumerator() == price.getNumerator() &&
                this.getDenominator() == price.getDenominator();

    }
}