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/*
 * Copyright (c) 2010-2017, KolibriFX AS. Licensed under the Apache License, version 2.0.
 */

package com.kolibrifx.plovercrest.server.internal.streams.builtin;

import java.util.List;
import com.kolibrifx.common.NotImplementedException;
import com.kolibrifx.plovercrest.client.TableMetadata;
import com.kolibrifx.plovercrest.client.TimestampExtractor;
import com.kolibrifx.plovercrest.server.streams.PollableReader;
import com.kolibrifx.plovercrest.server.streams.ReaderPosition;
import com.kolibrifx.plovercrest.server.streams.Stream;
import com.kolibrifx.plovercrest.server.streams.StreamDataTriggerer;
import com.kolibrifx.plovercrest.server.streams.StreamObserver;
import com.kolibrifx.plovercrest.server.streams.StreamWriter;

public class InMemoryStream implements Stream {
    private final List data;
    private final TimestampExtractor timestampExtractor;
    private final Class elementClass;
    private final TableMetadata metadata;
    private final String name;

    public InMemoryStream(final Class elementClass,
                          final String name,
                          final List data,
                          final TimestampExtractor timestampExtractor,
                          final TableMetadata metadata) {
        this.elementClass = elementClass;
        this.name = name;
        this.data = data;
        this.timestampExtractor = timestampExtractor;
        this.metadata = metadata;
    }

    @Override
    public PollableReader createReaderFromTimestamp(final long timestamp, final StreamObserver observer) {
        return createReaderFromIndex(indexOfTimestamp(timestamp), observer);
    }

    @Override
    public PollableReader createReaderFromIndex(final long index, final StreamObserver observer) {
        return new PollableReader() {
            int i = (int) index;

            @Override
            public void registerDataTriggerer(final StreamDataTriggerer triggerer) {
                // do nothing
            }

            @Override
            public boolean poll() {
                if (i >= data.size()) {
                    observer.onObserveEnd(getLastValidTimestamp(), data.size());
                    return false;
                } else {
                    final T message = data.get(i);
                    final long timestamp = timestampExtractor.getTimestampForMessage(message);
                    observer.onObserve(timestamp, index, message);
                    i++;
                    return true;
                }
            }

            @Override
            public ReaderPosition getReaderPosition() {
                return ReaderPosition.createIndexPosition(i);
            }
        };
    }

    @Override
    public String getName() {
        return name;
    }

    @Override
    public Class getElementClass() {
        return elementClass;
    }

    @Override
    public StreamWriter getWriter() {
        throw new NotImplementedException();
    }

    @Override
    public long getFirstTimestamp() {
        if (data.isEmpty()) {
            return -1;
        }
        return timestampExtractor.getTimestampForMessage(data.get(0));
    }

    @Override
    public long getLastTimestamp() {
        if (data.isEmpty()) {
            return -1;
        }
        return timestampExtractor.getTimestampForMessage(data.get(data.size() - 1));
    }

    @Override
    public long getDataLengthInBytes() {
        return 0;
    }

    @Override
    public long getEntryCount() {
        return data.size();
    }

    @Override
    public TableMetadata getMetadata() {
        return metadata;
    }

    @Override
    public long getLastValidTimestamp() {
        return getLastTimestamp();
    }

    @Override
    public boolean isFrozen() {
        return false;
    }

    @Override
    public boolean delete() {
        return false;
    }

    @Override
    public boolean rename(final String newName) {
        return false;
    }

    private int indexOfTimestamp(final long timestamp) {
        // take-previous
        for (int i = 0; i < data.size(); i++) {
            final long timestampForMessage = timestampExtractor.getTimestampForMessage(data.get(i));
            if (timestampForMessage == timestamp) {
                return i;
            }
            if (timestampForMessage > timestamp) {
                return Math.max(0, i - 1);
            }
        }
        // return index beyond end
        return data.size();
    }

    @Override
    public long seekPreviousTimestamp(final long targetTimestamp) {
        final int i = indexOfTimestamp(targetTimestamp);
        if (i == data.size()) {
            return getLastTimestamp();
        } else {
            return timestampExtractor.getTimestampForMessage(data.get(i));
        }
    }

}