package com.demo.lib.common.content;

import java.io.FileDescriptor;
import java.io.PrintWriter;
import java.util.Arrays;

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
import androidx.loader.content.AsyncTaskLoader;

public class CursorLoader extends AsyncTaskLoader<Cursor> {
    final ForceLoadContentObserver mObserver;

    SQLiteDatabase mSQLiteDatabase;
    
    Uri mUri;
    String mSql;
    String[] mSelectionArgs;
    
    Cursor mCursor;

    /* Runs on a worker thread */
    @Override
    public Cursor loadInBackground() {
        Cursor cursor = mSQLiteDatabase.rawQuery(mSql, mSelectionArgs);
        if (cursor != null) {
            // Ensure the cursor window is filled
            cursor.getCount();
            cursor.setNotificationUri(getContext().getContentResolver(), mUri);
            cursor.registerContentObserver(mObserver);
        }
        return cursor;
    }

    /* Runs on the UI thread */
    @Override
    public void deliverResult(Cursor cursor) {
        if (isReset()) {
            // An async query came in while the loader is stopped
            if (cursor != null) {
                cursor.close();
            }
            return;
        }
        Cursor oldCursor = mCursor;
        mCursor = cursor;

        if (isStarted()) {
            super.deliverResult(cursor);
        }

        if (oldCursor != null && oldCursor != cursor && !oldCursor.isClosed()) {
            oldCursor.close();
        }
    }
    
    /**
     * Creates an empty unspecified CursorLoader.  You must override
     * {@link #loadInBackground()} to specify the query to perform.
     */
    public CursorLoader(Context context) {
        super(context);
        mObserver = new ForceLoadContentObserver();
    }

    /**
     * Creates an empty unspecified CursorLoader.  You must follow this with
     * calls to {@link #setUri(Uri)}, {@link #setSelectionArgs(String[])}, etc
     * to specify the query to perform.
     */
    public CursorLoader(Context context, SQLiteDatabase sqliteDatabase) {
        super(context);
        mObserver = new ForceLoadContentObserver();
        mSQLiteDatabase = sqliteDatabase;
    }

    /**
     * Creates a fully-specified CursorLoader.  See
     * {@link android.database.sqlite.SQLiteDatabase#rawQuery(String, String[])}
     * for documentation on the meaning of the
     * parameters.  These will be passed as-is to that call.
     */
    public CursorLoader(Context context, SQLiteDatabase sqliteDatabase,
            Uri uri, String sql, String[] selectionArgs) {
        super(context);
        mObserver = new ForceLoadContentObserver();
        mSQLiteDatabase = sqliteDatabase;
        mUri = uri;
        mSql = sql;
        mSelectionArgs = selectionArgs;
    }

    /**
     * Starts an asynchronous load of the contacts list data. When the result is ready the callbacks
     * will be called on the UI thread. If a previous load has been completed and is still valid
     * the result may be passed to the callbacks immediately.
     *
     * Must be called from the UI thread
     */
    @Override
    protected void onStartLoading() {
        if (mCursor != null) {
            deliverResult(mCursor);
        }
        if (takeContentChanged() || mCursor == null) {
            forceLoad();
        }
    }

    /**
     * Must be called from the UI thread
     */
    @Override
    protected void onStopLoading() {
        // Attempt to cancel the current load task if possible.
        cancelLoad();
    }

    @Override
    public void onCanceled(Cursor cursor) {
        if (cursor != null && !cursor.isClosed()) {
            cursor.close();
        }
    }

    @Override
    protected void onReset() {
        super.onReset();
        
        // Ensure the loader is stopped
        onStopLoading();

        if (mCursor != null && !mCursor.isClosed()) {
            mCursor.close();
        }
        mCursor = null;
    }

    public Uri getUri() {
        return mUri;
    }

    public void setUri(Uri uri) {
        mUri = uri;
    }

    public String[] getSelectionArgs() {
        return mSelectionArgs;
    }

    public void setSelectionArgs(String[] selectionArgs) {
        mSelectionArgs = selectionArgs;
    }

    public String getSql() {
        return mSql;
    }

    public void setSql(String sql) {
        this.mSql = sql;
    }

    @Override
    public void dump(String prefix, FileDescriptor fd, PrintWriter writer, String[] args) {
        super.dump(prefix, fd, writer, args);
        writer.print(prefix); writer.print("mUri="); writer.println(mUri);
        writer.print(prefix); writer.print("mSql="); writer.println(mSql);
        writer.print(prefix); writer.print("mSelectionArgs=");
                writer.println(Arrays.toString(mSelectionArgs));
        writer.print(prefix); writer.print("mCursor="); writer.println(mCursor);
    }
}