SpatialArgsParser.cs

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/*
 * 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 System.Text;
using Spatial4n.Core.Context;
using Spatial4n.Core.Io;
using Spatial4n.Core.Shapes;

namespace Lucene.Net.Spatial.Queries
{
    public class SpatialArgsParser
    {
        public const String DIST_ERR_PCT = "distErrPct";
        public const String DIST_ERR = "distErr";

        /// <summary>
        /// Writes a close approximation to the parsed input format.
        /// </summary>
        /// <param name="args"></param>
        /// <returns></returns>
        public static String WriteSpatialArgs(SpatialArgs args)
        {
            var str = new StringBuilder();
            str.Append(args.Operation.GetName());
            str.Append('(');
            str.Append(args.Shape);
            if (args.DistErrPct != null)
                str.Append(" distErrPct=").Append(String.Format("{0:0.00}%", args.DistErrPct*100d));
            if (args.DistErr != null)
                str.Append(" distErr=").Append(args.DistErr);
            str.Append(')');
            return str.ToString();
        }

        /// <summary>
        /// Parses a string such as "Intersects(-10,20,-8,22) distErrPct=0.025".
        /// </summary>
        /// <param name="v"></param>
        /// <param name="ctx"></param>
        /// <returns></returns>
        public SpatialArgs Parse(String v, SpatialContext ctx)
        {
            int idx = v.IndexOf('(');
            int edx = v.LastIndexOf(')');

            if (idx < 0 || idx > edx)
            {
                throw new ArgumentException("missing parens: " + v);
            }

            SpatialOperation op = SpatialOperation.Get(v.Substring(0, idx).Trim());

            //Substring in .NET is (startPosn, length), But in Java it's (startPosn, endPosn)
            //see http://docs.oracle.com/javase/1.4.2/docs/api/java/lang/String.html#substring(int, int)
            String body = v.Substring(idx + 1, edx - (idx + 1)).Trim();
            if (body.Length < 1)
            {
                throw new ArgumentException("missing body : " + v);
            }

            Shape shape = new ShapeReadWriter(ctx).ReadShape(body);
            var args = new SpatialArgs(op, shape);

            if (v.Length > (edx + 1))
            {
                body = v.Substring(edx + 1).Trim();
                if (body.Length > 0)
                {
                    Dictionary<String, String> aa = ParseMap(body);
                    args.DistErrPct = ReadDouble(aa["distErrPct"]); aa.Remove(DIST_ERR_PCT);
                    args.DistErr = ReadDouble(aa["distErr"]); aa.Remove(DIST_ERR);
                    if (aa.Count != 0)
                    {
                        throw new ArgumentException("unused parameters: " + aa);
                    }
                }
            }
            args.Validate();
            return args;
        }

        protected static double? ReadDouble(String v)
        {
            double val;
            return double.TryParse(v, out val) ? val : (double?)null;
        }

        protected static bool ReadBool(String v, bool defaultValue)
        {
            bool ret;
            return bool.TryParse(v, out ret) ? ret : defaultValue;
        }

        /// <summary>
        /// Parses "a=b c=d f" (whitespace separated) into name-value pairs. If there
        /// is no '=' as in 'f' above then it's short for f=f.
        /// </summary>
        /// <param name="body"></param>
        /// <returns></returns>
        protected static Dictionary<String, String> ParseMap(String body)
        {
            var map = new Dictionary<String, String>();
            int tokenPos = 0;
            var st = body.Split(new[] {' ', '\n', '\t'}, StringSplitOptions.RemoveEmptyEntries);
            while (tokenPos < st.Length)
            {
                String a = st[tokenPos++];
                int idx = a.IndexOf('=');
                if (idx > 0)
                {
                    String k = a.Substring(0, idx);
                    String v = a.Substring(idx + 1);
                    map[k] = v;
                }
                else
                {
                    map[a] = a;
                }
            }
            return map;
        }

    }
}