Phase02: Implement basic InvertedIndex

.gitignore

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+# Visual Studio
+.vs/
+ ../.vs/
+*.sln.ide/
+*.suo
+*.user
+*.userosf
+*.userprefs
+*.ncb
+*.opendb
+*.opensdf
+*.sdf
+*.vssscc
+*.vspscc
+*.vsscc
+*.bak
+*.log
+*.resharper
+*.dotCover
+
+# Build results
+[Dd]ebug/
+[Rr]elease/
+x64/
+x86/
+ARM/
+ARM64/
+bin/
+obj/
+[Ll]og/
+
+# Packages
+packages/
+*.nupkg
+*.snupkg
+*.dll
+*.exe
+*.pdb
+*.cache
+*.xml
+*.json # Be careful with this, if your solution relies on JSON data files, they should not be ignored.
+
+# Rider
+.idea/
+
+# Test Results
+TestResults/
+*.trx
+
+# Temporary files
+temp/
+tmp/
+
+# User-specific files
+*.settings
+*.local
+*.VC.db
+
+# Visual Studio Code
+.vscode/
+
+# EnglishData folder (dataset)
+EnglishData/

Phase02/Phase02/Phase02.sln

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+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.14.36310.24 d17.14
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Phase02", "Phase02\Phase02.csproj", "{2A0FB1B8-0196-4672-94BB-F22D839E1D2F}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{2A0FB1B8-0196-4672-94BB-F22D839E1D2F}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{2A0FB1B8-0196-4672-94BB-F22D839E1D2F}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{2A0FB1B8-0196-4672-94BB-F22D839E1D2F}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{2A0FB1B8-0196-4672-94BB-F22D839E1D2F}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {EB0409C8-9820-4D34-A908-57EA4BB14E9B}
+	EndGlobalSection
+EndGlobal

Phase02/Phase02/Phase02/Core/FileReader.cs

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+// File: Core/FileReader.cs
+using System.IO;
+
+namespace Phase02.Core
+{
+    public static class FileReader
+    {
+        public static string[] ReadAllFileNames(string folderPath)
+        {
+            if (!Directory.Exists(folderPath))
+            {
+                return new string[0];
+            }
+
+            return Directory.GetFiles(folderPath);
+        }
+    }
+}

Phase02/Phase02/Phase02/Core/InvertedIndex.cs

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+// File: Core/InvertedIndex.cs
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text.RegularExpressions;
+
+namespace Phase02.Core
+{
+    public class InvertedIndex
+    {
+        private readonly Dictionary<string, HashSet<string>> _index = new Dictionary<string, HashSet<string>>();
+
+        private static string Normalize(string text)
+        {
+            var noPunct = Regex.Replace(text, @"[^\w\s]", " ");
+            var singleSpaced = Regex.Replace(noPunct, @"\s+", " ").Trim();
+            return singleSpaced.ToUpperInvariant();
+        }
+
+        private static IEnumerable<string> Tokenize(string text)
+        {
+            var normalized = Normalize(text);
+            return normalized.Split(' ', StringSplitOptions.RemoveEmptyEntries);
+        }
+
+        public void AddDocument(string documentPath)
+        {
+            string content;
+            try
+            {
+                content = File.ReadAllText(documentPath);
+            }
+            catch (IOException)
+            {
+                return;
+            }
+
+            var tokens = Tokenize(content);
+
+            foreach (var token in tokens)
+            {
+                if (!_index.TryGetValue(token, out var docSet))
+                {
+                    docSet = new HashSet<string>();
+                    _index[token] = docSet;
+                }
+                docSet.Add(documentPath);
+            }
+        }
+
+        public IEnumerable<string> Search(string token)
+        {
+            var key = token.ToUpperInvariant();
+            if (_index.TryGetValue(key, out var docSet))
+                return docSet;
+            return Enumerable.Empty<string>();
+        }
+
+        public IEnumerable<string> SmartSearch(
+            IEnumerable<string> mustInclude,
+            IEnumerable<string> atLeastOne,
+            IEnumerable<string> mustExclude)
+        {
+            IEnumerable<string> result = null;
+
+            foreach (var word in mustInclude)
+            {
+                var docs = Search(word);
+                result = result == null ? docs : result.Intersect(docs);
+            }
+
+            if (result == null)
+                result = _index.Values.SelectMany(s => s).Distinct();
+
+            if (atLeastOne.Any())
+            {
+                var orSet = atLeastOne.SelectMany(w => Search(w)).ToHashSet();
+                result = result.Intersect(orSet);
+            }
+
+            if (mustExclude.Any())
+            {
+                var notSet = mustExclude.SelectMany(w => Search(w)).ToHashSet();
+                result = result.Except(notSet);
+            }
+
+            return result;
+        }
+    }
+}

Phase02/Phase02/Phase02/Phase02.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="dotnet-stop-words" Version="1.1.0" />
+    <PackageReference Include="Porter2Stemmer" Version="1.0.0" />
+  </ItemGroup>
+
+</Project>

Phase02/Phase02/Phase02/Program.cs

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+// File: Program.cs
+using System;
+using System.Collections.Generic;
+using System.IO;
+using Phase02.Core;
+
+namespace Phase02
+{
+    internal class Program
+    {
+        static void Main(string[] args)
+        {
+            var baseDir = AppContext.BaseDirectory;
+            // baseDir = ...\bin\Debug\net8.0\
+            var projectRoot = Path.GetFullPath(Path.Combine(baseDir, "..", "..", ".."));
+            var dataDir = Path.Combine(projectRoot, "EnglishData");
+            var files = FileReader.ReadAllFileNames(dataDir);
+            var index = new InvertedIndex();
+
+            foreach (var file in files)
+                index.AddDocument(file);
+
+            Console.Write("Enter query: ");
+            var line = Console.ReadLine() ?? "";
+
+            var mustInclude = new List<string>();
+            var atLeastOne = new List<string>();
+            var mustExclude = new List<string>();
+
+            foreach (var tok in line.Split(' ', StringSplitOptions.RemoveEmptyEntries))
+            {
+                if (tok.StartsWith("+"))
+                    atLeastOne.Add(tok.Substring(1));
+                else if (tok.StartsWith("-"))
+                    mustExclude.Add(tok.Substring(1));
+                else
+                    mustInclude.Add(tok);
+            }
+
+            var results = index.SmartSearch(mustInclude, atLeastOne, mustExclude);
+
+            Console.WriteLine("\nSearch results:");
+            foreach (var doc in results)
+                Console.WriteLine(Path.GetFileName(doc));
+        }
+    }
+}