/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

using System;
using System.Collections.Generic;
using Spatial4n.Core.Context;
using Spatial4n.Core.Distance;

namespace Lucene.Net.Spatial.Prefix.Tree
{
    /// <summary>
    /// Abstract Factory for creating {@link SpatialPrefixTree} instances with useful
    /// defaults and passed on configurations defined in a Map.
    /// </summary>
	public abstract class SpatialPrefixTreeFactory
	{
		private const double DEFAULT_GEO_MAX_DETAIL_KM = 0.001; //1m
        public static readonly String PREFIX_TREE = "prefixTree";
        public static readonly String MAX_LEVELS = "maxLevels";
        public static readonly String MAX_DIST_ERR = "maxDistErr";

		protected Dictionary<String, String> args;
		protected SpatialContext ctx;
		protected int? maxLevels;

		/// <summary>
		/// The factory  is looked up via "prefixTree" in args, expecting "geohash" or "quad".
		/// If its neither of these, then "geohash" is chosen for a geo context, otherwise "quad" is chosen.
		/// </summary>
		/// <param name="args"></param>
		/// <param name="ctx"></param>
		/// <returns></returns>
		public static SpatialPrefixTree MakeSPT(Dictionary<String, String> args, SpatialContext ctx)
		{
			SpatialPrefixTreeFactory instance;
			String cname;
            if (!args.TryGetValue(PREFIX_TREE, out cname) || cname == null)
				cname = ctx.IsGeo() ? "geohash" : "quad";
			if ("geohash".Equals(cname, StringComparison.InvariantCultureIgnoreCase))
				instance = new GeohashPrefixTree.Factory();
			else if ("quad".Equals(cname, StringComparison.InvariantCultureIgnoreCase))
				instance = new QuadPrefixTree.Factory();
			else
			{
				Type t = Type.GetType(cname);
				instance = (SpatialPrefixTreeFactory)Activator.CreateInstance(t);
			}
			instance.Init(args, ctx);
			return instance.NewSPT();
		}

		protected void Init(Dictionary<String, String> args, SpatialContext ctx)
		{
			this.args = args;
			this.ctx = ctx;
			InitMaxLevels();
		}

        protected void InitMaxLevels()
        {
            String mlStr;
            if (args.TryGetValue(MAX_LEVELS, out mlStr) && mlStr != null)
            {
                maxLevels = int.Parse(mlStr);
                return;
            }

            double degrees;
            if (!args.TryGetValue(MAX_DIST_ERR, out mlStr) || mlStr == null)
            {
                if (!ctx.IsGeo())
                    return; //let default to max
                degrees = DistanceUtils.Dist2Degrees(DEFAULT_GEO_MAX_DETAIL_KM, DistanceUtils.EARTH_MEAN_RADIUS_KM);
            }
            else
            {
                degrees = Double.Parse(mlStr);
            }
            maxLevels = GetLevelForDistance(degrees);
        }

	    /* Calls {@link SpatialPrefixTree#getLevelForDistance(double)}. */
		protected abstract int GetLevelForDistance(double degrees);

		protected abstract SpatialPrefixTree NewSPT();

	}
}
