package com.dougkeen.bart;

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.WeakHashMap;

import org.apache.commons.lang3.math.NumberUtils;

import android.app.Service;
import android.content.ContentValues;
import android.content.Intent;
import android.database.Cursor;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Binder;
import android.os.Handler;
import android.os.IBinder;
import android.support.v4.content.CursorLoader;
import android.util.Log;

import com.dougkeen.bart.data.RoutesColumns;
import com.dougkeen.bart.model.Constants;
import com.dougkeen.bart.model.Departure;
import com.dougkeen.bart.model.RealTimeDepartures;
import com.dougkeen.bart.model.ScheduleInformation;
import com.dougkeen.bart.model.ScheduleItem;
import com.dougkeen.bart.model.Station;
import com.dougkeen.bart.model.StationPair;
import com.dougkeen.bart.networktasks.GetRealTimeDeparturesTask;
import com.dougkeen.bart.networktasks.GetScheduleInformationTask;

public class EtdService extends Service {

	private IBinder mBinder;

	private Map<StationPair, EtdServiceEngine> mServiceEngineMap;

	public EtdService() {
		super();
		mBinder = new EtdServiceBinder();
		mServiceEngineMap = new HashMap<StationPair, EtdServiceEngine>();
	}

	public void registerListener(EtdServiceListener listener) {
		StationPair stationPair = getStationPairFromListener(listener);
		if (stationPair == null)
			return;

		if (!mServiceEngineMap.containsKey(stationPair)) {
			mServiceEngineMap.put(stationPair,
					new EtdServiceEngine(stationPair));
		}
		mServiceEngineMap.get(stationPair).registerListener(listener);
	}

	private StationPair getStationPairFromListener(EtdServiceListener listener) {
		StationPair route = listener.getStationPair();
		if (route == null) {
			Log.wtf(Constants.TAG,
					"Somehow we got a listener that's returning a null route O_o");
		}
		return route;
	}

	public void unregisterListener(EtdServiceListener listener) {
		StationPair stationPair = getStationPairFromListener(listener);
		if (stationPair == null)
			return;

		if (mServiceEngineMap.containsKey(stationPair)) {
			mServiceEngineMap.get(stationPair).unregisterListener(listener);
		}
	}

	@Override
	public IBinder onBind(Intent intent) {
		return mBinder;
	}

	public interface EtdServiceListener {
		void onETDChanged(final List<Departure> departures);

		void onError(String errorMessage);

		void onRequestStarted();

		void onRequestEnded();

		StationPair getStationPair();
	}

	public class EtdServiceBinder extends Binder {

		public EtdService getService() {
			return EtdService.this;
		}
	}

	private class EtdServiceEngine {
		private static final int UNCERTAINTY_THRESHOLD = 17;

		private Uri mUri;

		private final StationPair mStationPair;

		private boolean mIgnoreDepartureDirection = false;

		private boolean mPendingEtdRequest = false;

		private int mAverageTripLength;
		private int mAverageTripSampleCount;

		// We'll only use the keys
		private WeakHashMap<EtdServiceListener, Boolean> mListeners;

		private List<Departure> mLatestDepartures;
		private ScheduleInformation mLatestScheduleInfo;

		private AsyncTask<StationPair, Integer, RealTimeDepartures> mGetDeparturesTask;
		private AsyncTask<StationPair, Integer, ScheduleInformation> mGetScheduleInformationTask;

		private Handler mRunnableQueue;

		private boolean mStarted = false;

		public EtdServiceEngine(final StationPair route) {
			mStationPair = route;
			mListeners = new WeakHashMap<EtdService.EtdServiceListener, Boolean>();
			mRunnableQueue = new Handler();
			mLatestDepartures = new ArrayList<Departure>();

			mUri = Constants.ARBITRARY_ROUTE_CONTENT_URI_ROOT.buildUpon()
					.appendPath(mStationPair.getOrigin().abbreviation)
					.appendPath(mStationPair.getDestination().abbreviation)
					.build();

			Cursor cursor = new CursorLoader(EtdService.this, mUri,
					new String[] { RoutesColumns.AVERAGE_TRIP_LENGTH.string,
							RoutesColumns.AVERAGE_TRIP_SAMPLE_COUNT.string },
					null, null, null).loadInBackground();
			if (cursor.moveToFirst()) {
				mAverageTripLength = cursor.getInt(0);
				mAverageTripSampleCount = cursor.getInt(1);
			}
			cursor.close();
		}

		protected void registerListener(EtdServiceListener listener) {
			mListeners.put(listener, true);
			if (!mPendingEtdRequest) {
				mStarted = true;
				fetchLatestDepartures();
			}
		}

		protected void unregisterListener(EtdServiceListener listener) {
			mListeners.remove(listener);
			if (mListeners.isEmpty()) {
				if (mGetDeparturesTask != null
						&& mGetDeparturesTask.getStatus().equals(
								AsyncTask.Status.RUNNING)) {
					mGetDeparturesTask.cancel(true);
				}
				if (mGetScheduleInformationTask != null
						&& mGetScheduleInformationTask.getStatus().equals(
								AsyncTask.Status.RUNNING)) {
					mGetScheduleInformationTask.cancel(true);
				}
				mStarted = false;
			}
		}

		private void notifyListenersOfETDChange() {
			for (EtdServiceListener listener : mListeners.keySet()) {
				listener.onETDChanged(mLatestDepartures);
			}
		}

		private void notifyListenersOfError(String errorMessage) {
			for (EtdServiceListener listener : mListeners.keySet()) {
				listener.onError(errorMessage);
			}
		}

		private void notifyListenersOfRequestStart() {
			for (EtdServiceListener listener : mListeners.keySet()) {
				listener.onRequestStarted();
			}
		}

		private void notifyListenersOfRequestEnd() {
			for (EtdServiceListener listener : mListeners.keySet()) {
				listener.onRequestEnded();
			}
		}

		private void fetchLatestDepartures() {
			if (mGetDeparturesTask != null
					&& mGetDeparturesTask.equals(AsyncTask.Status.RUNNING)) {
				// Don't overlap fetches
				return;
			}
			if (!mStarted)
				return;

			GetRealTimeDeparturesTask task = new GetRealTimeDeparturesTask(
					mIgnoreDepartureDirection) {
				@Override
				public void onResult(RealTimeDepartures result) {
					Log.d(Constants.TAG, "Processing data from server");
					processLatestDepartures(result);
					Log.d(Constants.TAG, "Done processing data from server");
					notifyListenersOfRequestEnd();
					mPendingEtdRequest = false;
				}

				@Override
				public void onError(Exception e) {
					Log.w(Constants.TAG, e.getMessage(), e);
					notifyListenersOfError(getString(R.string.could_not_connect));
					// Try again in 60s
					scheduleDepartureFetch(60000);
					notifyListenersOfRequestEnd();
				}
			};
			mGetDeparturesTask = task;
			Log.d(Constants.TAG, "Fetching data from server");
			task.execute(new StationPair(mStationPair.getOrigin(), mStationPair
					.getDestination()));
			notifyListenersOfRequestStart();
		}

		private void fetchLatestSchedule() {
			if (mGetScheduleInformationTask != null
					&& mGetScheduleInformationTask.getStatus().equals(
							AsyncTask.Status.RUNNING)) {
				// Don't overlap fetches
				return;
			}

			GetScheduleInformationTask task = new GetScheduleInformationTask() {
				@Override
				public void onResult(ScheduleInformation result) {
					Log.d(Constants.TAG, "Processing data from server");
					mLatestScheduleInfo = result;
					applyScheduleInformation(result);
					Log.d(Constants.TAG, "Done processing data from server");
				}

				@Override
				public void onError(Exception e) {
					Log.w(Constants.TAG, e.getMessage(), e);
					notifyListenersOfError(getString(R.string.could_not_connect));

					// Try again in 60s
					scheduleScheduleInfoFetch(60000);
				}
			};
			Log.i(Constants.TAG, "Fetching data from server");
			mGetScheduleInformationTask = task;
			task.execute(new StationPair(mStationPair.getOrigin(), mStationPair
					.getDestination()));
		}

		protected void applyScheduleInformation(ScheduleInformation result) {
			int localAverageLength = mLatestScheduleInfo.getAverageTripLength();

			int departuresCount = mLatestDepartures.size();

			// Let's get smallest interval between departures
			int smallestDepartureInterval = 0;
			long previousDepartureTime = 0;
			for (int departureIndex = 0; departureIndex < departuresCount; departureIndex++) {
				Departure departure = mLatestDepartures.get(departureIndex);
				if (previousDepartureTime == 0) {
					previousDepartureTime = departure.getMeanEstimate();
				} else if (smallestDepartureInterval == 0) {
					smallestDepartureInterval = (int) (departure
							.getMeanEstimate() - previousDepartureTime);
				} else {
					smallestDepartureInterval = Math
							.min(smallestDepartureInterval,
									(int) (departure.getMeanEstimate() - previousDepartureTime));
				}
			}

			// Match scheduled departures with real time departures in adapter
			int lastSearchIndex = 0;
			int tripCount = mLatestScheduleInfo.getTrips().size();
			boolean departureUpdated = false;
			Departure lastUnestimatedTransfer = null;
			int departuresWithoutEstimates = 0;
			for (int departureIndex = 0; departureIndex < departuresCount; departureIndex++) {
				Departure departure = mLatestDepartures.get(departureIndex);
				for (int i = lastSearchIndex; i < tripCount; i++) {
					ScheduleItem trip = mLatestScheduleInfo.getTrips().get(i);
					// Definitely not a match if they have different
					// destinations
					if (!departure.getDestination().abbreviation.equals(trip
							.getTrainHeadStation())) {
						continue;
					}

					long departTimeDiff = Math.abs(trip.getDepartureTime()
							- departure.getMeanEstimate());
					final long millisUntilTripDeparture = trip
							.getDepartureTime() - System.currentTimeMillis();
					final int equalityTolerance = (departure.getOrigin() != null) ? NumberUtils
							.max(departure.getOrigin().departureEqualityTolerance,
									ScheduleItem.SCHEDULE_ITEM_DEPARTURE_EQUALS_TOLERANCE,
									smallestDepartureInterval)
							: ScheduleItem.SCHEDULE_ITEM_DEPARTURE_EQUALS_TOLERANCE;
					if (departure.getOrigin() != null
							&& departure.getOrigin().longStationLinger
							&& departure.hasDeparted()
							&& millisUntilTripDeparture > 0
							&& millisUntilTripDeparture < equalityTolerance) {
						departure.setArrivalTimeOverride(trip.getArrivalTime());
						lastSearchIndex = i;
						departureUpdated = true;
						if (lastUnestimatedTransfer != null) {
							lastUnestimatedTransfer.setArrivalTimeOverride(trip
									.getArrivalTime());
							departuresWithoutEstimates--;
						}
						break;
					} else if (departTimeDiff <= (equalityTolerance + departure
							.getUncertaintySeconds() * 1000)
							&& departure.getEstimatedTripTime() != trip
									.getTripLength()
							&& !(departure.getOrigin().longStationLinger && departure
									.hasDeparted())) {
						departure.setEstimatedTripTime(trip.getTripLength());
						lastSearchIndex = i;
						departureUpdated = true;
						if (lastUnestimatedTransfer != null) {
							lastUnestimatedTransfer.setArrivalTimeOverride(trip
									.getArrivalTime());
							departuresWithoutEstimates--;
						}
						break;
					}
				}

				// Don't estimate for non-scheduled transfers
				if (!departure.getRequiresTransfer()) {
					if (!departure.hasEstimatedTripTime()
							&& localAverageLength > 0) {
						// Use the average we just calculated if available
						departure.setEstimatedTripTime(localAverageLength);
					} else if (!departure.hasEstimatedTripTime()) {
						// Otherwise just assume the global average
						departure.setEstimatedTripTime(mAverageTripLength);
					}
				} else if (departure.getRequiresTransfer()
						&& !departure.hasAnyArrivalEstimate()) {
					lastUnestimatedTransfer = departure;
				}

				if (!departure.hasAnyArrivalEstimate()) {
					departuresWithoutEstimates++;
				}
			}

			if (departureUpdated) {
				notifyListenersOfETDChange();
			}

			// Update global average
			if (mLatestScheduleInfo.getTripCountForAverage() > 0) {
				int newAverageSampleCount = mAverageTripSampleCount
						+ mLatestScheduleInfo.getTripCountForAverage();
				int newAverage = (mAverageTripLength * mAverageTripSampleCount + localAverageLength
						* mLatestScheduleInfo.getTripCountForAverage())
						/ newAverageSampleCount;

				ContentValues contentValues = new ContentValues();
				contentValues.put(RoutesColumns.AVERAGE_TRIP_LENGTH.string,
						newAverage);
				contentValues.put(
						RoutesColumns.AVERAGE_TRIP_SAMPLE_COUNT.string,
						newAverageSampleCount);

				getContentResolver().update(mUri, contentValues, null, null);
			}

			/*
			 * If we still have some departures without estimates, try again
			 * later
			 */
			if (departuresWithoutEstimates > 0) {
				scheduleScheduleInfoFetch(20000);
			}
		}

		private void processLatestDepartures(RealTimeDepartures result) {
			if (result.getDepartures().isEmpty()) {
				result.includeTransferRoutes();
			}
			if (result.getDepartures().isEmpty()) {
				result.includeDoubleTransferRoutes();
			}
			if (result.getDepartures().isEmpty()
					&& mStationPair.isBetweenStations(Station.MLBR,
							Station.SFIA)) {
				/*
				 * Let's try again, ignoring direction (this sometimes comes up
				 * when you travel between Millbrae and SFO... sometimes you
				 * need to travel north and transfer, sometimes you can travel
				 * south for a direct line)
				 */
				mIgnoreDepartureDirection = true;
				scheduleDepartureFetch(50);
				return;
			}

			boolean needsBetterAccuracy = false;

			/*
			 * Keep track of first departure, since we'll request another quick
			 * refresh if it has departed.
			 */
			Departure firstDeparture = null;

			final List<Departure> departures = result.getDepartures();
			if (mLatestDepartures.isEmpty()) {
				// Just copy everything to the departure list
				for (Departure departure : departures) {
					if (firstDeparture == null) {
						firstDeparture = departure;
					}
					mLatestDepartures.add(departure);
				}

				/*
				 * Since all the departures are new, we'll definitely need
				 * better accuracy
				 */
				needsBetterAccuracy = true;
			} else {
				/*
				 * Let's merge the latest departure list with the instance
				 * departure list
				 */
				int instanceListIndex = -1;
				for (Departure departure : departures) {
					instanceListIndex++;
					Departure existingDeparture = null;
					if (instanceListIndex < mLatestDepartures.size()) {
						existingDeparture = mLatestDepartures
								.get(instanceListIndex);
					}
					/*
					 * Looks for departures at the beginning of the adapter that
					 * aren't in the latest list of departures
					 */
					while (existingDeparture != null
							&& !departure.equals(existingDeparture)) {
						// Remove old departure
						mLatestDepartures.remove(existingDeparture);
						if (instanceListIndex < mLatestDepartures.size()) {
							/*
							 * Try again with next departure (keep in mind the
							 * next departure is now at the current index, since
							 * we removed a member)
							 */
							existingDeparture = mLatestDepartures
									.get(instanceListIndex);
						} else {
							// Reached the end of the list... give up
							existingDeparture = null;
						}
					}
					/*
					 * Merge the estimate if we found a matching departure,
					 * otherwise add a new one to the adapter
					 */
					if (existingDeparture != null) {
						existingDeparture.mergeEstimate(departure);
					} else {
						mLatestDepartures.add(departure);
						existingDeparture = departure;
					}

					// Set first departure
					if (firstDeparture == null) {
						firstDeparture = existingDeparture;
					}

					// Check if estimate is accurate enough
					if (existingDeparture.getUncertaintySeconds() > UNCERTAINTY_THRESHOLD) {
						needsBetterAccuracy = true;
					}
				}
			}
			Collections.sort(mLatestDepartures);
			notifyListenersOfETDChange();
			requestScheduleIfNecessary();

			if (firstDeparture != null) {
				if (needsBetterAccuracy || firstDeparture.hasDeparted()) {
					// Get more data in 20s
					scheduleDepartureFetch(20000);
				} else {
					/*
					 * Get more 90 seconds before next train arrives, right when
					 * next train arrives, or 3 minutes, whichever is sooner
					 */
					final int intervalUntilNextDeparture = firstDeparture
							.getMinSecondsLeft() * 1000;
					final int alternativeInterval = 3 * 60 * 1000;

					int interval = intervalUntilNextDeparture;
					if (intervalUntilNextDeparture > 95000
							&& intervalUntilNextDeparture < alternativeInterval) {
						interval = interval - 90 * 1000;
					} else if (intervalUntilNextDeparture > alternativeInterval) {
						interval = alternativeInterval;
					}

					if (interval < 0) {
						interval = 20000;
					}

					scheduleDepartureFetch(interval);
				}
			}
		}

		private void requestScheduleIfNecessary() {
			// Bail if there's nothing to match schedules to
			if (mLatestDepartures.isEmpty()) {
				return;
			}

			// Fetch if we don't have anything at all
			if (mLatestScheduleInfo == null) {
				fetchLatestSchedule();
				return;
			}

			/*
			 * Otherwise, check if the latest departure doesn't have schedule
			 * info... if not, fetch
			 */
			Departure lastDeparture = mLatestDepartures.get(mLatestDepartures
					.size() - 1);
			if (mLatestScheduleInfo.getLatestDepartureTime() < lastDeparture
					.getMeanEstimate()) {
				fetchLatestSchedule();
				return;
			}
		}

		private long mNextFetchClockTime = 0;

		private void scheduleDepartureFetch(int millisUntilExecute) {
			mPendingEtdRequest = true;
			long now = System.currentTimeMillis();
			long requestedFetchTime = now + millisUntilExecute;
			if (mNextFetchClockTime > now
					&& mNextFetchClockTime < requestedFetchTime) {
				Log.d(Constants.TAG,
						"Did not schedule departure fetch, since one is already scheduled");
			} else {
				mRunnableQueue.postDelayed(new Runnable() {
					public void run() {
						fetchLatestDepartures();
					}
				}, millisUntilExecute);
				mNextFetchClockTime = requestedFetchTime;
				Log.d(Constants.TAG, "Scheduled another departure fetch in "
						+ millisUntilExecute / 1000 + "s");
			}
		}

		private void scheduleScheduleInfoFetch(int millisUntilExecute) {
			mRunnableQueue.postDelayed(new Runnable() {
				public void run() {
					fetchLatestSchedule();
				}
			}, millisUntilExecute);
			Log.d(Constants.TAG, "Scheduled another schedule fetch in "
					+ millisUntilExecute / 1000 + "s");
		}

	}
}