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package org.yamcs.parameterarchive;

import java.nio.BufferOverflowException;
import java.nio.ByteBuffer;

import org.yamcs.parameter.Value;
import org.yamcs.parameter.ValueArray;
import org.yamcs.utils.DecodingException;
import org.yamcs.utils.FloatArray;
import org.yamcs.utils.ValueUtility;
import org.yamcs.utils.VarIntUtil;

public class FloatValueSegment extends BaseSegment implements ValueSegment {
    final static byte SUBFORMAT_ID_RAW = 0;
    final static byte SUBFORMAT_ID_COMPRESSED = 1;

    FloatArray values;

    FloatValueSegment() {
        super(FORMAT_ID_FloatValueSegment);
        values = new FloatArray();
    }

    @Override
    public void insert(int pos, Value value) {
        values.add(pos, value.getFloatValue());
    }

    @Override
    public void add(Value value) {
        values.add(value.getFloatValue());
    }

    @Override
    public void writeTo(ByteBuffer bb) {
        int position = bb.position();

        // try to write it compressed, if we get an buffer overflow, revert to raw encoding
        bb.put(SUBFORMAT_ID_COMPRESSED);
        int n = values.size();
        VarIntUtil.writeVarInt32(bb, n);

        try {
            FloatCompressor.compress(values.array(), values.size(), bb);
        } catch (BufferOverflowException e) {
            bb.position(position);
            writeRaw(bb);
        }
    }

    private void writeRaw(ByteBuffer bb) {
        bb.put(SUBFORMAT_ID_RAW);
        int n = values.size();
        VarIntUtil.writeVarInt32(bb, n);
        for (int i = 0; i < n; i++) {
            bb.putFloat(values.get(i));
        }
    }

    private void parse(ByteBuffer bb) throws DecodingException {
        byte b = bb.get();
        int n = VarIntUtil.readVarInt32(bb);
        float[] floats;
        if (b == SUBFORMAT_ID_RAW) {
            floats = new float[n];
            for (int i = 0; i < n; i++) {
                floats[i] = bb.getFloat();
            }
        } else if (b == SUBFORMAT_ID_COMPRESSED) {
            floats = FloatCompressor.decompress(bb, n);
        } else {
            throw new DecodingException("Unknown SUBFORMAT_ID: " + b);
        }
        values = FloatArray.wrap(floats);
    }

    public static FloatValueSegment parseFrom(ByteBuffer bb) throws DecodingException {
        FloatValueSegment r = new FloatValueSegment();
        r.parse(bb);
        return r;
    }

    @Override
    public Value getValue(int index) {
        return ValueUtility.getFloatValue(values.get(index));
    }

    @Override
    public int getMaxSerializedSize() {
        return 5 + 4 * values.size() + 1;
    }

    @Override
    public ValueArray getRange(int posStart, int posStop, boolean ascending) {
        float[] r = new float[posStop - posStart];
        if (ascending) {
            for (int i = posStart; i < posStop; i++) {
                r[i - posStart] = values.get(i);
            }
        } else {
            for (int i = posStop; i > posStart; i--) {
                r[posStop - i] = values.get(i);
            }
        }

        return new ValueArray(r);
    }

    @Override
    public int size() {
        return values.size();
    }

}