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CrustyJewCrustyJew
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Merge pull request #160 from czf/2.0AdvancedSearch
2.0 advanced search
2 parents 17c95f3 + 27f2b91 commit c6ac623

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‎RedditSharp/Reddit.cs‎

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using System.Linq;
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using System.Security.Authentication;
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using System.Threading.Tasks;
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using RedditSharp.Search;
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using DefaultWebAgent = RedditSharp.WebAgent;
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using System.Linq.Expressions;
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namespace RedditSharp
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{
@@ -37,6 +39,19 @@ public class Reddit
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private const string GetLiveEventUrl = "https://www.reddit.com/live/{0}/about";
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#endregion
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private IAdvancedSearchFormatter _searchFormatter;
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private IAdvancedSearchFormatter SearchFormatter
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{
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get
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{
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if(_searchFormatter == null)
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{
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_searchFormatter = new DefaultSearchFormatter();
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}
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return _searchFormatter;
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}
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set => _searchFormatter = value;
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}
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#region Properties
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internal IWebAgent WebAgent { get; set; }
@@ -382,6 +397,15 @@ public Listing<T> Search<T>(string query, Sorting sortE = Sorting.Relevance, Tim
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return Listing<T>.Create(this.WebAgent, string.Format(SearchUrl, query, sort, time), max, 100);
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}
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public Listing<Post> AdvancedSearch(Expression<Func<AdvancedSearchFilter, bool>> searchFilter, Sorting sortE = Sorting.Relevance, TimeSorting timeE = TimeSorting.All)
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{
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string query = SearchFormatter.Format(searchFilter);
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string sort = sortE.ToString().ToLower();
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string time = timeE.ToString().ToLower();
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string final = string.Format(SearchUrl, query, sort, time);
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return new Listing<Post>(this,final,WebAgent);
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}
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/// <summary>
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/// Return a <see cref="Listing{T}"/> of items matching search with a given time period.
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/// </summary>
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/// <param name="timeE">Order by <see cref="TimeSorting"/></param>
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/// <param name="max">Maximum number of records to return. -1 for unlimited.</param>
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/// <returns></returns>
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[Obsolete("time search was discontinued by reddit",true)]
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public Listing<T> SearchByTimestamp<T>(DateTime from, DateTime to, string query = "", string subreddit = "", Sorting sortE = Sorting.Relevance, TimeSorting timeE = TimeSorting.All, int max = -1) where T : Thing
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{
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string sort = sortE.ToString().ToLower();

‎RedditSharp/Search/AdvancedSearch.cs‎

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using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Text;
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using System.Threading.Tasks;
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namespace RedditSharp.Search
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{
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public sealed class AdvancedSearchFilter
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{
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public string Author;
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public string Flair;
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public bool IsNsfw;
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public bool IsSelf;
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public string SelfText;
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public string Site;
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public string Subreddit;
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public string Title;
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public string Url;
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private AdvancedSearchFilter() { }
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}
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}

‎RedditSharp/Search/DefaultSearchFormatter.cs‎

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using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Linq.Expressions;
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using System.Reflection;
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using System.Text;
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using System.Threading.Tasks;
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namespace RedditSharp.Search
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{
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public class DefaultSearchFormatter : IAdvancedSearchFormatter
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{
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#region Constants
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private const string BOOL_PROPERTY_PREFIX = "Is";
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#endregion Constants
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string IAdvancedSearchFormatter.Format(Expression<Func<AdvancedSearchFilter, bool>> search)
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{
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Expression expression = null;
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Stack<Expression> expressionStack = new Stack<Expression>();
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Stack<FormatInfo> formatInfoStack = new Stack<FormatInfo>();
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expressionStack.Push(search.Body);
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Stack<string> searchStack = new Stack<string>();
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while (expressionStack.Count > 0) {
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expression = expressionStack.Pop();
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switch (expression)
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{
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case MemberExpression memberExpression:
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MemberExpressionHelper(memberExpression, searchStack, formatInfoStack);
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break;
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case UnaryExpression unaryExpression:
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UnaryExpressionHelper(unaryExpression, expressionStack, formatInfoStack);
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break;
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case BinaryExpression binaryExpression:
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BinaryExpressionHelper(binaryExpression, expressionStack, formatInfoStack);
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break;
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case ConstantExpression constantExpresssion:
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searchStack.Push(ConstantExpressionHelper(constantExpresssion));
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break;
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case MethodCallExpression methodCallExpression:
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searchStack.Push(MethodCallExpressionHelper(methodCallExpression));
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break;
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default:
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throw new NotImplementedException(expression.ToString());
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}
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}
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Stack<string> compoundSearchStack = new Stack<string>();
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while (formatInfoStack.Count > 0)
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{
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FormatInfo current = formatInfoStack.Pop();
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string[] formatParameters = new string[current.ParameterCount];
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int currentCount = current.ParameterCount;
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while (currentCount > 0)
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{
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formatParameters[formatParameters.Length - currentCount] = current.IsCompound ? compoundSearchStack.Pop() : searchStack.Pop();
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currentCount--;
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}
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compoundSearchStack.Push(string.Format(current.Pattern, formatParameters));
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}
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return compoundSearchStack.Pop();
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}
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private string MethodCallExpressionHelper(MethodCallExpression expression)
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{
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var o = InvokeGetExpression(expression);
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return o.ToString();
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}
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private string ConstantExpressionHelper(ConstantExpression constantExpresssion)
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{
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return constantExpresssion.ToString().Replace("\"","");
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}
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private void BinaryExpressionHelper(BinaryExpression expression, Stack<Expression> expressionStack, Stack<FormatInfo> formatInfoStack)
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{
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if(IsAdvancedSearchMemberExpression(expression.Left) && IsAdvancedSearchMemberExpression(expression.Right))
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{
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throw new InvalidOperationException("Cannot filter by comparing to fields.");
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}
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else if(IsAdvancedSearchMemberExpression(expression.Right))
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{
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expressionStack.Push(expression.Left);
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expressionStack.Push(expression.Right);
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}
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else
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{
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expressionStack.Push(expression.Right);
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expressionStack.Push(expression.Left);
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}
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if (expression.NodeType != ExpressionType.Equal)
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{
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formatInfoStack.Push(expression.ToFormatInfo());
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}
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}
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private void UnaryExpressionHelper(UnaryExpression expression, Stack<Expression> expressionStack,Stack<FormatInfo> formatInfoStack)
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{
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formatInfoStack.Push(expression.ToFormatInfo());
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expressionStack.Push(expression.Operand);
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}
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private void MemberExpressionHelper(MemberExpression expression, Stack<string> searchStack, Stack<FormatInfo> formatInfoStack)
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{
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MemberInfo member = expression.Member;
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if (member.DeclaringType == typeof(AdvancedSearchFilter))
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{
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string result = member.Name.Replace(BOOL_PROPERTY_PREFIX, string.Empty).ToLower();
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formatInfoStack.Push(expression.ToFormatInfo());
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searchStack.Push(result);
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if (expression.Type == typeof(bool))
119+
{
120+
searchStack.Push("1");
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}
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}
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else
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{
125+
searchStack.Push(InvokeGetExpression(expression).ToString());
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}
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}
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private static object InvokeGetExpression(Expression expression)
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{
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var objectMember = Expression.Convert(expression, typeof(object));
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var getterLambda = Expression.Lambda<Func<object>>(objectMember);
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var getter = getterLambda.Compile();
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return getter();
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}
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private static bool IsAdvancedSearchMemberExpression(Expression expression)
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{
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MemberExpression memberExpression = expression as MemberExpression;
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return memberExpression?.Member.DeclaringType == typeof(AdvancedSearchFilter);
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}
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internal class FormatInfo
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{
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public string Pattern { get; private set; }
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public int ParameterCount { get; private set; }
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public bool IsCompound { get; private set; }
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public FormatInfo(string pattern, int parameterCount = 0, bool isCompound = false)
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{
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Pattern = pattern;
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ParameterCount = parameterCount;
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IsCompound = isCompound;
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}
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internal static FormatInfo Not = new FormatInfo("NOT(+{0}+)", 1, true);
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internal static FormatInfo NotEqual = Not;
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internal static FormatInfo AndAlso = new FormatInfo("(+{0}+AND+{1}+)", 2, true);
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internal static FormatInfo OrElse = new FormatInfo("(+{0}+OR+{1}+)", 2, true);
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internal static FormatInfo MemberAccess = new FormatInfo("{1}:{0}", 2);
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}
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}
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}

‎RedditSharp/Search/IAdvancedSearchFormatter.cs‎

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using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Linq.Expressions;
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namespace RedditSharp.Search
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{
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public interface IAdvancedSearchFormatter
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{
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/// <summary>
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/// use an expression to create a search for reddit
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/// </summary>
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/// <param name="search"></param>
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/// <returns>the string representing the search expression in reddits search format</returns>
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/// <remarks>
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/// has to be Expression Func https://michael-mckenna.com/func-t-vs-expression-func-t-in-linq/
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/// </remarks>
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string Format(Expression<Func<AdvancedSearchFilter, bool>> search);
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}
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}

‎RedditSharp/Search/SearchExpressionExtentions.cs‎

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using System;
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using System.Linq.Expressions;
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namespace RedditSharp.Search
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{
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public static class SearchExtensions
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{
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internal static DefaultSearchFormatter.FormatInfo ToFormatInfo(this Expression expression)
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{
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ExpressionType? type = expression?.NodeType;
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switch (type)
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{
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case ExpressionType.Not:
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case ExpressionType.NotEqual:
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return DefaultSearchFormatter.FormatInfo.Not;
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case ExpressionType.Equal:
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throw new NotImplementedException("Currently not supporting Equal expression.");
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case ExpressionType.AndAlso:
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return DefaultSearchFormatter.FormatInfo.AndAlso;
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case ExpressionType.MemberAccess:
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return DefaultSearchFormatter.FormatInfo.MemberAccess;
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case ExpressionType.OrElse:
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return DefaultSearchFormatter.FormatInfo.OrElse;
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}
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throw new NotImplementedException($"{type.ToString()} is not implemented.");
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}
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}
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}

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