/**
 * See the file "LICENSE" for the full license governing this code.
 */
package com.todoroo.astrid.sync;

import java.util.ArrayList;

import android.content.Context;

import com.todoroo.andlib.data.Property;
import com.todoroo.andlib.data.TodorooCursor;
import com.todoroo.andlib.sql.Criterion;
import com.todoroo.andlib.sql.Order;
import com.todoroo.andlib.sql.Query;
import com.todoroo.astrid.data.Metadata;
import com.todoroo.astrid.data.MetadataApiDao;
import com.todoroo.astrid.data.MetadataApiDao.MetadataCriteria;
import com.todoroo.astrid.data.Task;
import com.todoroo.astrid.data.TaskApiDao;
import com.todoroo.astrid.data.TaskApiDao.TaskCriteria;

abstract public class SyncMetadataService<TYPE extends SyncContainer> {

    /** metadata key of tag add-on */
    public static final String TAG_KEY = "tags-tag"; //$NON-NLS-1$

    // --- instance variables

    protected final TaskApiDao taskDao;
    protected final MetadataApiDao metadataDao;

    // --- abstract methods

    /** @return metadata key identifying this sync provider's metadata */
    abstract public String getMetadataKey();

    /** @return sync provider utilities */
    abstract public SyncProviderUtilities getUtilities();

    /** create a task container based on the given data */
    abstract public TYPE createContainerFromLocalTask(Task task, ArrayList<Metadata> metadata);

    /** @return criterion for matching all metadata keys that your provider synchronizes */
    abstract public Criterion getMetadataCriteria();

    /** @return criterion for finding local matches of sync container in task database */
    abstract public Criterion getLocalMatchCriteria(TYPE remoteTask);

    /** @return criterion for matching metadata that indicate remote task exists */
    abstract public Criterion getMetadataWithRemoteId();

    // --- implementation

    public SyncMetadataService(Context context) {
        taskDao = new TaskApiDao(context);
        metadataDao = new MetadataApiDao(context);
    }

    /**
     * Clears metadata information. Used when user logs out of sync provider
     */
    public void clearMetadata() {
        metadataDao.deleteWhere(Metadata.KEY.eq(getMetadataKey()));
    }

    /**
     * Gets cursor across all task metadata for joining
     *
     * @return cursor
     */
    private TodorooCursor<Metadata> getRemoteTaskMetadata() {
        return metadataDao.query(Query.select(Metadata.TASK).where(
                Criterion.and(MetadataCriteria.withKey(getMetadataKey()),
                getMetadataWithRemoteId())).orderBy(Order.asc(Metadata.TASK)));
    }

    /**
     * Gets tasks that were created since last sync
     * @param properties
     * @return
     */
    public TodorooCursor<Task> getLocallyCreated(Property<?>... properties) {
        TodorooCursor<Task> tasks = taskDao.query(Query.select(Task.ID).where(
                TaskCriteria.isActive()).orderBy(Order.asc(Task.ID)));

        return joinWithMetadata(tasks, false, properties);
    }

    /**
     * Gets tasks that were modified since last sync
     * @param properties
     * @return null if never sync'd
     */
    public TodorooCursor<Task> getLocallyUpdated(Property<?>... properties) {
        TodorooCursor<Task> tasks;
        long lastSyncDate = getUtilities().getLastSyncDate();
        if(lastSyncDate == 0)
            tasks = taskDao.query(Query.select(Task.ID).where(Criterion.none));
        else
            tasks = taskDao.query(Query.select(Task.ID).where(Criterion.and(
                    Task.MODIFICATION_DATE.gt(lastSyncDate),
                    Task.LAST_SYNC.lte(lastSyncDate))).orderBy(Order.asc(Task.ID)));

        return joinWithMetadata(tasks, true, properties);
    }

    private TodorooCursor<Task> joinWithMetadata(TodorooCursor<Task> tasks,
            boolean both, Property<?>... properties) {
        try {
            TodorooCursor<Metadata> metadata = getRemoteTaskMetadata();
            try {
                ArrayList<Long> matchingRows = new ArrayList<Long>();
                joinRows(tasks, metadata, matchingRows, both);

                return
                taskDao.query(Query.select(properties).where(Task.ID.in(
                        matchingRows.toArray(new Long[matchingRows.size()]))));
            } finally {
                metadata.close();
            }
        } finally {
            tasks.close();
        }
    }

    /**
     * Join rows from two cursors on the first column, assuming its an id column
     * @param left
     * @param right
     * @param matchingRows
     * @param both - if false, returns rows no right row exists, if true,
     *        returns rows where both exist
     */
    private static void joinRows(TodorooCursor<?> left,
            TodorooCursor<?> right, ArrayList<Long> matchingRows,
            boolean both) {

        left.moveToPosition(-1);
        right.moveToFirst();

        while(true) {
            left.moveToNext();
            if(left.isAfterLast())
                break;
            long leftValue = left.getLong(0);

            // advance right until it is equal or bigger
            while(!right.isAfterLast() && right.getLong(0) < leftValue) {
                right.moveToNext();
            }

            if(right.isAfterLast()) {
                if(!both)
                    matchingRows.add(leftValue);
                continue;
            }

            if((right.getLong(0) == leftValue) == both)
                matchingRows.add(leftValue);
        }
    }

    /**
     * Searches for a local task with same remote id, updates this task's id
     * @param remoteTask
     */
    public void findLocalMatch(TYPE remoteTask) {
        if(remoteTask.task.getId() != Task.NO_ID)
            return;
        TodorooCursor<Metadata> cursor = metadataDao.query(Query.select(Metadata.TASK).
                where(Criterion.and(MetadataCriteria.withKey(getMetadataKey()),
                        getLocalMatchCriteria(remoteTask))));
        try {
            if(cursor.getCount() == 0)
                return;
            cursor.moveToFirst();
            remoteTask.task.setId(cursor.get(Metadata.TASK));
        } finally {
            cursor.close();
        }
    }

    /**
     * Saves a task and its metadata
     * @param task
     */
    public void saveTaskAndMetadata(TYPE task) {
        task.prepareForSaving();
        taskDao.save(task.task);
        metadataDao.synchronizeMetadata(task.task.getId(), task.metadata,
                getMetadataCriteria());
    }

    /**
     * Reads a task and its metadata
     * @param task
     * @return
     */
    public TYPE readTaskAndMetadata(TodorooCursor<Task> taskCursor) {
        Task task = new Task(taskCursor);

        ArrayList<Metadata> metadata = new ArrayList<Metadata>();
        TodorooCursor<Metadata> metadataCursor = metadataDao.query(Query.select(Metadata.PROPERTIES).
                where(Criterion.and(MetadataCriteria.byTask(task.getId()),
                        getMetadataCriteria())));
        try {
            for(metadataCursor.moveToFirst(); !metadataCursor.isAfterLast(); metadataCursor.moveToNext()) {
                metadata.add(new Metadata(metadataCursor));
            }
        } finally {
            metadataCursor.close();
        }

        return createContainerFromLocalTask(task, metadata);
    }

    /**
     * Reads metadata out of a task
     * @return null if no metadata found
     */
    public Metadata getTaskMetadata(long taskId) {
        TodorooCursor<Metadata> cursor = metadataDao.query(Query.select(Metadata.PROPERTIES).where(
                MetadataCriteria.byTaskAndwithKey(taskId, getMetadataKey())));
        try {
            if(cursor.getCount() == 0)
                return null;
            cursor.moveToFirst();
            return new Metadata(cursor);
        } finally {
            cursor.close();
        }
    }

}