/*
 * Copyright (C) 2016 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.location;

import android.annotation.IntDef;
import android.annotation.NonNull;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

/**
 * This class represents the current state of the GNSS engine.
 * This class is used in conjunction with the {@link GnssStatus.Callback}.
 */
public final class GnssStatus {
    // these must match the definitions in gps.h

    /** Unknown constellation type. */
    public static final int CONSTELLATION_UNKNOWN = 0;
    /** Constellation type constant for GPS. */
    public static final int CONSTELLATION_GPS = 1;
    /** Constellation type constant for SBAS. */
    public static final int CONSTELLATION_SBAS = 2;
    /** Constellation type constant for Glonass. */
    public static final int CONSTELLATION_GLONASS = 3;
    /** Constellation type constant for QZSS. */
    public static final int CONSTELLATION_QZSS = 4;
    /** Constellation type constant for Beidou. */
    public static final int CONSTELLATION_BEIDOU = 5;
    /** Constellation type constant for Galileo. */
    public static final int CONSTELLATION_GALILEO = 6;
    /** Constellation type constant for IRNSS. */
    public static final int CONSTELLATION_IRNSS = 7;
    /** @hide */
    public static final int CONSTELLATION_COUNT = 8;

    /** @hide */
    public static final int GNSS_SV_FLAGS_NONE = 0;
    /** @hide */
    public static final int GNSS_SV_FLAGS_HAS_EPHEMERIS_DATA = (1 << 0);
    /** @hide */
    public static final int GNSS_SV_FLAGS_HAS_ALMANAC_DATA = (1 << 1);
    /** @hide */
    public static final int GNSS_SV_FLAGS_USED_IN_FIX = (1 << 2);
    /** @hide */
    public static final int GNSS_SV_FLAGS_HAS_CARRIER_FREQUENCY = (1 << 3);

    /** @hide */
    public static final int SVID_SHIFT_WIDTH = 8;
    /** @hide */
    public static final int CONSTELLATION_TYPE_SHIFT_WIDTH = 4;
    /** @hide */
    public static final int CONSTELLATION_TYPE_MASK = 0xf;

    /**
     * Used for receiving notifications when GNSS events happen.
     */
    public static abstract class Callback {
        /**
         * Called when GNSS system has started.
         */
        public void onStarted() {}

        /**
         * Called when GNSS system has stopped.
         */
        public void onStopped() {}

        /**
         * Called when the GNSS system has received its first fix since starting.
         * @param ttffMillis the time from start to first fix in milliseconds.
         */
        public void onFirstFix(int ttffMillis) {}

        /**
         * Called periodically to report GNSS satellite status.
         * @param status the current status of all satellites.
         */
        public void onSatelliteStatusChanged(GnssStatus status) {}
    }

    /**
     * Constellation type.
     * @hide
     */
    @Retention(RetentionPolicy.SOURCE)
    @IntDef({CONSTELLATION_UNKNOWN, CONSTELLATION_GPS, CONSTELLATION_SBAS, CONSTELLATION_GLONASS,
            CONSTELLATION_QZSS, CONSTELLATION_BEIDOU, CONSTELLATION_GALILEO, CONSTELLATION_IRNSS})
    public @interface ConstellationType {}

    final int[] mSvidWithFlags;
    final float[] mCn0DbHz;
    final float[] mElevations;
    final float[] mAzimuths;
    final int mSvCount;
    final float[] mCarrierFrequencies;

    /**
     * @hide
     */
    public GnssStatus(int svCount, int[] svidWithFlags, float[] cn0s, float[] elevations,
            float[] azimuths, float[] carrierFrequencies) {
        mSvCount = svCount;
        mSvidWithFlags = svidWithFlags;
        mCn0DbHz = cn0s;
        mElevations = elevations;
        mAzimuths = azimuths;
        mCarrierFrequencies = carrierFrequencies;
    }

    /**
     * Gets the total number of satellites in satellite list.
     */
    public int getSatelliteCount() {
        return mSvCount;
    }

    /**
     * Retrieves the constellation type of the satellite at the specified index.
     *
     * @param satIndex the index of the satellite in the list.
     */
    @ConstellationType
    public int getConstellationType(int satIndex) {
        return ((mSvidWithFlags[satIndex] >> CONSTELLATION_TYPE_SHIFT_WIDTH)
                & CONSTELLATION_TYPE_MASK);
    }

    /**
     * Gets the identification number for the satellite at the specific index.
     *
     * <p>This svid is pseudo-random number for most constellations. It is FCN &amp; OSN number for
     * Glonass.
     *
     * <p>The distinction is made by looking at constellation field
     * {@link #getConstellationType(int)} Expected values are in the range of:
     *
     * <ul>
     * <li>GPS: 1-32</li>
     * <li>SBAS: 120-151, 183-192</li>
     * <li>GLONASS: One of: OSN, or FCN+100
     * <ul>
     *   <li>1-24 as the orbital slot number (OSN) (preferred, if known)</li>
     *   <li>93-106 as the frequency channel number (FCN) (-7 to +6) plus 100.
     *   i.e. encode FCN of -7 as 93, 0 as 100, and +6 as 106</li>
     * </ul></li>
     * <li>QZSS: 193-200</li>
     * <li>Galileo: 1-36</li>
     * <li>Beidou: 1-37</li>
     * </ul>
     *
     * @param satIndex the index of the satellite in the list.
     */
    public int getSvid(int satIndex) {
        return mSvidWithFlags[satIndex] >> SVID_SHIFT_WIDTH;
    }

    /**
     * Retrieves the carrier-to-noise density at the antenna of the satellite at the specified index
     * in dB-Hz.
     *
     * @param satIndex the index of the satellite in the list.
     */
    public float getCn0DbHz(int satIndex) {
        return mCn0DbHz[satIndex];
    }

    /**
     * Retrieves the elevation of the satellite at the specified index.
     *
     * @param satIndex the index of the satellite in the list.
     */
    public float getElevationDegrees(int satIndex) {
        return mElevations[satIndex];
    }

    /**
     * Retrieves the azimuth the satellite at the specified index.
     *
     * @param satIndex the index of the satellite in the list.
     */
    public float getAzimuthDegrees(int satIndex) {
        return mAzimuths[satIndex];
    }

    /**
     * Reports whether the satellite at the specified index has ephemeris data.
     *
     * @param satIndex the index of the satellite in the list.
     */
    public boolean hasEphemerisData(int satIndex) {
        return (mSvidWithFlags[satIndex] & GNSS_SV_FLAGS_HAS_EPHEMERIS_DATA) != 0;
    }

    /**
     * Reports whether the satellite at the specified index has almanac data.
     *
     * @param satIndex the index of the satellite in the list.
     */
    public boolean hasAlmanacData(int satIndex) {
        return (mSvidWithFlags[satIndex] & GNSS_SV_FLAGS_HAS_ALMANAC_DATA) != 0;
    }

    /**
     * Reports whether the satellite at the specified index was used in the calculation of the most
     * recent position fix.
     *
     * @param satIndex the index of the satellite in the list.
     */
    public boolean usedInFix(int satIndex) {
        return (mSvidWithFlags[satIndex] & GNSS_SV_FLAGS_USED_IN_FIX) != 0;
    }

    /**
     * Reports whether a valid {@link #getCarrierFrequencyHz(int satIndex)} is available.
     *
     * @param satIndex the index of the satellite in the list.
     */
    public boolean hasCarrierFrequencyHz(int satIndex) {
        return (mSvidWithFlags[satIndex] & GNSS_SV_FLAGS_HAS_CARRIER_FREQUENCY) != 0;
    }

    /**
     * Gets the carrier frequency of the signal tracked.
     *
     * <p>For example it can be the GPS central frequency for L1 = 1575.45 MHz, or L2 = 1227.60 MHz,
     * L5 = 1176.45 MHz, varying GLO channels, etc. If the field is not set, it is the primary
     * common use central frequency, e.g. L1 = 1575.45 MHz for GPS.
     *
     * For an L1, L5 receiver tracking a satellite on L1 and L5 at the same time, two measurements
     * will be reported for this same satellite, in one all the values related to L1 will be filled,
     * and in the other all of the values related to L5 will be filled.
     *
     * <p>The value is only available if {@link #hasCarrierFrequencyHz(int satIndex)} is {@code true}.
     *
     * @param satIndex the index of the satellite in the list.
     *
     * @return the carrier frequency of the signal tracked in Hz.
     */
    public float getCarrierFrequencyHz(int satIndex) {
        return mCarrierFrequencies[satIndex];
    }

    /**
     * Returns the string representation of a constellation type. For example,
     * {@link #CONSTELLATION_GPS} is represented by the string GPS.
     *
     * @param constellationType the constellation type.
     * @return the string representation.
     * @hide
     */
    @NonNull
    public static String constellationTypeToString(@ConstellationType int constellationType) {
        switch (constellationType) {
            case CONSTELLATION_UNKNOWN:
                return "UNKNOWN";
            case CONSTELLATION_GPS:
                return "GPS";
            case CONSTELLATION_SBAS:
                return "SBAS";
            case CONSTELLATION_GLONASS:
                return "GLONASS";
            case CONSTELLATION_QZSS:
                return "QZSS";
            case CONSTELLATION_BEIDOU:
                return "BEIDOU";
            case CONSTELLATION_GALILEO:
                return "GALILEO";
            case CONSTELLATION_IRNSS:
                return "IRNSS";
            default:
                return Integer.toString(constellationType);
        }
    }
}