package org.onlab.onos.store.trivial.impl;

import com.google.common.collect.FluentIterable;
import com.google.common.collect.ImmutableList;

import org.apache.commons.lang3.concurrent.ConcurrentException;
import org.apache.commons.lang3.concurrent.ConcurrentInitializer;
import org.apache.felix.scr.annotations.Activate;
import org.apache.felix.scr.annotations.Component;
import org.apache.felix.scr.annotations.Deactivate;
import org.apache.felix.scr.annotations.Service;
import org.onlab.onos.net.DefaultDevice;
import org.onlab.onos.net.DefaultPort;
import org.onlab.onos.net.Device;
import org.onlab.onos.net.Device.Type;
import org.onlab.onos.net.DeviceId;
import org.onlab.onos.net.Port;
import org.onlab.onos.net.PortNumber;
import org.onlab.onos.net.device.DeviceDescription;
import org.onlab.onos.net.device.DeviceEvent;
import org.onlab.onos.net.device.DeviceStore;
import org.onlab.onos.net.device.DeviceStoreDelegate;
import org.onlab.onos.net.device.PortDescription;
import org.onlab.onos.net.provider.ProviderId;
import org.onlab.onos.store.AbstractStore;
import org.slf4j.Logger;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Objects;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.atomic.AtomicReference;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Predicates.notNull;
import static org.onlab.onos.net.device.DeviceEvent.Type.*;
import static org.slf4j.LoggerFactory.getLogger;
import static org.apache.commons.lang3.concurrent.ConcurrentUtils.createIfAbsentUnchecked;

// TODO: synchronization should be done in more fine-grained manner.
/**
 * Manages inventory of infrastructure devices using trivial in-memory
 * structures implementation.
 */
@Component(immediate = true)
@Service
public class SimpleDeviceStore
        extends AbstractStore<DeviceEvent, DeviceStoreDelegate>
        implements DeviceStore {

    private final Logger log = getLogger(getClass());

    public static final String DEVICE_NOT_FOUND = "Device with ID %s not found";

    // collection of Description given from various providers
    private final ConcurrentMap<DeviceId,
                            ConcurrentMap<ProviderId, DeviceDescriptions>>
                                deviceDescs = new ConcurrentHashMap<>();

    // cache of Device and Ports generated by compositing descriptions from providers
    private final ConcurrentMap<DeviceId, Device> devices = new ConcurrentHashMap<>();
    private final ConcurrentMap<DeviceId, ConcurrentMap<PortNumber, Port>> devicePorts = new ConcurrentHashMap<>();

    // available(=UP) devices
    private final Set<DeviceId> availableDevices = new HashSet<>();


    @Activate
    public void activate() {
        log.info("Started");
    }

    @Deactivate
    public void deactivate() {
        log.info("Stopped");
    }

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

    @Override
    public Iterable<Device> getDevices() {
        return Collections.unmodifiableCollection(devices.values());
    }

    @Override
    public Device getDevice(DeviceId deviceId) {
        return devices.get(deviceId);
    }

    @Override
    public synchronized DeviceEvent createOrUpdateDevice(ProviderId providerId, DeviceId deviceId,
                                     DeviceDescription deviceDescription) {
        ConcurrentMap<ProviderId, DeviceDescriptions> providerDescs
            = createIfAbsentUnchecked(deviceDescs, deviceId,
                    new InitConcurrentHashMap<ProviderId, DeviceDescriptions>());

        Device oldDevice = devices.get(deviceId);

        DeviceDescriptions descs
            = createIfAbsentUnchecked(providerDescs, providerId,
                    new InitDeviceDescs(deviceDescription));

        descs.putDeviceDesc(deviceDescription);

        Device newDevice = composeDevice(deviceId, providerDescs);

        if (oldDevice == null) {
            // ADD
            return createDevice(providerId, newDevice);
        } else {
            // UPDATE or ignore (no change or stale)
            return updateDevice(providerId, oldDevice, newDevice);
        }
    }

    // Creates the device and returns the appropriate event if necessary.
    private DeviceEvent createDevice(ProviderId providerId, Device newDevice) {

        // update composed device cache
        synchronized (this) {
            devices.putIfAbsent(newDevice.id(), newDevice);
            if (!providerId.isAncillary()) {
                availableDevices.add(newDevice.id());
            }
        }

        return new DeviceEvent(DeviceEvent.Type.DEVICE_ADDED, newDevice, null);
    }

    // Updates the device and returns the appropriate event if necessary.
    private DeviceEvent updateDevice(ProviderId providerId, Device oldDevice, Device newDevice) {

        // We allow only certain attributes to trigger update
        if (!Objects.equals(oldDevice.hwVersion(), newDevice.hwVersion()) ||
            !Objects.equals(oldDevice.swVersion(), newDevice.swVersion())) {

            synchronized (this) {
                devices.replace(newDevice.id(), oldDevice, newDevice);
                if (!providerId.isAncillary()) {
                    availableDevices.add(newDevice.id());
                }
            }
            return new DeviceEvent(DeviceEvent.Type.DEVICE_UPDATED, newDevice, null);
        }

        // Otherwise merely attempt to change availability if primary provider
        if (!providerId.isAncillary()) {
            synchronized (this) {
            boolean added = availableDevices.add(newDevice.id());
            return !added ? null :
                    new DeviceEvent(DEVICE_AVAILABILITY_CHANGED, newDevice, null);
            }
        }
        return null;
    }

    @Override
    public DeviceEvent markOffline(DeviceId deviceId) {
        synchronized (this) {
            Device device = devices.get(deviceId);
            boolean removed = (device != null) && availableDevices.remove(deviceId);
            return !removed ? null :
                    new DeviceEvent(DEVICE_AVAILABILITY_CHANGED, device, null);
        }
    }

    @Override
    public synchronized List<DeviceEvent> updatePorts(ProviderId providerId, DeviceId deviceId,
                                  List<PortDescription> portDescriptions) {

        // TODO: implement multi-provider
        Device device = devices.get(deviceId);
        checkArgument(device != null, DEVICE_NOT_FOUND, deviceId);

        ConcurrentMap<ProviderId, DeviceDescriptions> descsMap = deviceDescs.get(deviceId);
        checkArgument(descsMap != null, DEVICE_NOT_FOUND, deviceId);

        DeviceDescriptions descs = descsMap.get(providerId);
        checkArgument(descs != null,
                "Device description for Device ID %s from Provider %s was not found",
                deviceId, providerId);


        List<DeviceEvent> events = new ArrayList<>();
        synchronized (this) {
            ConcurrentMap<PortNumber, Port> ports = getPortMap(deviceId);

            // Add new ports
            Set<PortNumber> processed = new HashSet<>();
            for (PortDescription portDescription : portDescriptions) {
                PortNumber number = portDescription.portNumber();
                Port oldPort = ports.get(number);
                // update description
                descs.putPortDesc(number, portDescription);
                Port newPort = composePort(device, number, descsMap);

                events.add(oldPort == null ?
                                   createPort(device, newPort, ports) :
                                   updatePort(device, oldPort, newPort, ports));
                processed.add(portDescription.portNumber());
            }

            events.addAll(pruneOldPorts(device, ports, processed));
        }
        return FluentIterable.from(events).filter(notNull()).toList();
    }

    // Creates a new port based on the port description adds it to the map and
    // Returns corresponding event.
    private DeviceEvent createPort(Device device, Port newPort,
                                   ConcurrentMap<PortNumber, Port> ports) {
        ports.put(newPort.number(), newPort);
        return new DeviceEvent(PORT_ADDED, device, newPort);
    }

    // CHecks if the specified port requires update and if so, it replaces the
    // existing entry in the map and returns corresponding event.
    private DeviceEvent updatePort(Device device, Port oldPort,
                                   Port newPort,
                                   ConcurrentMap<PortNumber, Port> ports) {
        if (oldPort.isEnabled() != newPort.isEnabled()) {
            ports.put(oldPort.number(), newPort);
            return new DeviceEvent(PORT_UPDATED, device, newPort);
        }
        return null;
    }

    // Prunes the specified list of ports based on which ports are in the
    // processed list and returns list of corresponding events.
    private List<DeviceEvent> pruneOldPorts(Device device,
                                            Map<PortNumber, Port> ports,
                                            Set<PortNumber> processed) {
        List<DeviceEvent> events = new ArrayList<>();
        Iterator<PortNumber> iterator = ports.keySet().iterator();
        while (iterator.hasNext()) {
            PortNumber portNumber = iterator.next();
            if (!processed.contains(portNumber)) {
                events.add(new DeviceEvent(PORT_REMOVED, device,
                                           ports.get(portNumber)));
                iterator.remove();
            }
        }
        return events;
    }

    // Gets the map of ports for the specified device; if one does not already
    // exist, it creates and registers a new one.
    private ConcurrentMap<PortNumber, Port> getPortMap(DeviceId deviceId) {
        return createIfAbsentUnchecked(devicePorts, deviceId,
                new InitConcurrentHashMap<PortNumber, Port>());
    }

    @Override
    public synchronized DeviceEvent updatePortStatus(ProviderId providerId, DeviceId deviceId,
                                 PortDescription portDescription) {
        Device device = devices.get(deviceId);
        checkArgument(device != null, DEVICE_NOT_FOUND, deviceId);

        ConcurrentMap<ProviderId, DeviceDescriptions> descsMap = deviceDescs.get(deviceId);
        checkArgument(descsMap != null, DEVICE_NOT_FOUND, deviceId);

        DeviceDescriptions descs = descsMap.get(providerId);
        checkArgument(descs != null,
                "Device description for Device ID %s from Provider %s was not found",
                deviceId, providerId);

        // TODO: implement multi-provider
        synchronized (this) {
            ConcurrentMap<PortNumber, Port> ports = getPortMap(deviceId);
            final PortNumber number = portDescription.portNumber();
            Port oldPort = ports.get(number);
            // update description
            descs.putPortDesc(number, portDescription);
            Port newPort = composePort(device, number, descsMap);
            if (oldPort == null) {
                return createPort(device, newPort, ports);
            } else {
                return updatePort(device, oldPort, newPort, ports);
            }
        }
    }

    @Override
    public List<Port> getPorts(DeviceId deviceId) {
        Map<PortNumber, Port> ports = devicePorts.get(deviceId);
        if (ports == null) {
            return Collections.emptyList();
        }
        return ImmutableList.copyOf(ports.values());
    }

    @Override
    public Port getPort(DeviceId deviceId, PortNumber portNumber) {
        Map<PortNumber, Port> ports = devicePorts.get(deviceId);
        return ports == null ? null : ports.get(portNumber);
    }

    @Override
    public boolean isAvailable(DeviceId deviceId) {
        return availableDevices.contains(deviceId);
    }

    @Override
    public DeviceEvent removeDevice(DeviceId deviceId) {
        synchronized (this) {
            Device device = devices.remove(deviceId);
            return device == null ? null :
                    new DeviceEvent(DEVICE_REMOVED, device, null);
        }
    }

    /**
     * Returns a Device, merging description given from multiple Providers.
     *
     * @param deviceId device identifier
     * @param providerDescs Collection of Descriptions from multiple providers
     * @return Device instance
     */
    private Device composeDevice(DeviceId deviceId,
            ConcurrentMap<ProviderId, DeviceDescriptions> providerDescs) {

        checkArgument(!providerDescs.isEmpty(), "No Device descriptions supplied");

        ProviderId primary = pickPrimaryPID(providerDescs);

        DeviceDescriptions desc = providerDescs.get(primary);
        Type type = desc.getDeviceDesc().type();
        String manufacturer = desc.getDeviceDesc().manufacturer();
        String hwVersion = desc.getDeviceDesc().hwVersion();
        String swVersion = desc.getDeviceDesc().swVersion();
        String serialNumber = desc.getDeviceDesc().serialNumber();

        for (Entry<ProviderId, DeviceDescriptions> e : providerDescs.entrySet()) {
            if (e.getKey().equals(primary)) {
                continue;
            }
            // FIXME: implement attribute merging once we have K-V attributes
        }

        return new DefaultDevice(primary, deviceId , type, manufacturer, hwVersion, swVersion, serialNumber);
    }

    // probably want composePorts
    private Port composePort(Device device, PortNumber number,
                ConcurrentMap<ProviderId, DeviceDescriptions> providerDescs) {

        ProviderId primary = pickPrimaryPID(providerDescs);
        DeviceDescriptions primDescs = providerDescs.get(primary);
        final PortDescription portDesc = primDescs.getPortDesc(number);
        boolean isEnabled;
        if (portDesc != null) {
            isEnabled = portDesc.isEnabled();
        } else {
            // if no primary, assume not enabled
            // TODO: revisit this port enabled/disabled behavior
            isEnabled = false;
        }

        for (Entry<ProviderId, DeviceDescriptions> e : providerDescs.entrySet()) {
            if (e.getKey().equals(primary)) {
                continue;
            }
            // FIXME: implement attribute merging once we have K-V attributes
        }

        return new DefaultPort(device, number, isEnabled);
    }

    /**
     * @return primary ProviderID, or randomly chosen one if none exists
     */
    private ProviderId pickPrimaryPID(
            ConcurrentMap<ProviderId, DeviceDescriptions> providerDescs) {
        ProviderId fallBackPrimary = null;
        for (Entry<ProviderId, DeviceDescriptions> e : providerDescs.entrySet()) {
            if (!e.getKey().isAncillary()) {
                return e.getKey();
            } else if (fallBackPrimary == null) {
                // pick randomly as a fallback in case there is no primary
                fallBackPrimary = e.getKey();
            }
        }
        return fallBackPrimary;
    }

    // TODO: can be made generic
    private static final class InitConcurrentHashMap<K, V> implements
            ConcurrentInitializer<ConcurrentMap<K, V>> {
        @Override
        public ConcurrentMap<K, V> get() throws ConcurrentException {
            return new ConcurrentHashMap<>();
        }
    }

    public static final class InitDeviceDescs
        implements ConcurrentInitializer<DeviceDescriptions> {
        private final DeviceDescription deviceDesc;
        public InitDeviceDescs(DeviceDescription deviceDesc) {
            this.deviceDesc = checkNotNull(deviceDesc);
        }
        @Override
        public DeviceDescriptions get() throws ConcurrentException {
            return new DeviceDescriptions(deviceDesc);
        }
    }


    /**
     * Collection of Description of a Device and it's Ports given from a Provider.
     */
    private static class DeviceDescriptions {
        //        private final DeviceId id;
        //        private final ProviderId pid;

        private final AtomicReference<DeviceDescription> deviceDesc;
        private final ConcurrentMap<PortNumber, PortDescription> portDescs;

        public DeviceDescriptions(DeviceDescription desc) {
            this.deviceDesc = new AtomicReference<>(desc);
            this.portDescs = new ConcurrentHashMap<>();
        }

        public DeviceDescription getDeviceDesc() {
            return deviceDesc.get();
        }

        public PortDescription getPortDesc(PortNumber number) {
            return portDescs.get(number);
        }

        public Collection<PortDescription> getPortDescs() {
            return Collections.unmodifiableCollection(portDescs.values());
        }

        public DeviceDescription putDeviceDesc(DeviceDescription newDesc) {
            return deviceDesc.getAndSet(newDesc);
        }

        public PortDescription putPortDesc(PortNumber number, PortDescription newDesc) {
            return portDescs.put(number, newDesc);
        }
    }
}