Feature/http language support

src/Kiota.Builder/GenerationLanguage.cs

@@ -9,5 +9,6 @@ public enum GenerationLanguage
     Go,
     Swift,
     Ruby,
-    CLI
+    CLI,
+    HTTP
 }

src/Kiota.Builder/PathSegmenters/HttpPathSegmenter.cs

@@ -0,0 +1,13 @@
+using Kiota.Builder.CodeDOM;
+using Kiota.Builder.Extensions;
+
+namespace Kiota.Builder.PathSegmenters;
+public class HttpPathSegmenter(string rootPath, string clientNamespaceName) : CommonPathSegmenter(rootPath, clientNamespaceName)
+{
+    public override string FileSuffix => ".http";
+    public override string NormalizeNamespaceSegment(string segmentName) => segmentName.ToFirstCharacterUpperCase();
+    public override string NormalizeFileName(CodeElement currentElement)
+    {
+        return GetLastFileNameSegment(currentElement).ToFirstCharacterUpperCase();
+    }
+}

src/Kiota.Builder/Refiners/HttpRefiner.cs

@@ -0,0 +1,153 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Kiota.Builder.CodeDOM;
+using Kiota.Builder.Configuration;
+using Kiota.Builder.Extensions;
+
+namespace Kiota.Builder.Refiners;
+public class HttpRefiner(GenerationConfiguration configuration) : CommonLanguageRefiner(configuration)
+{
+    public override Task RefineAsync(CodeNamespace generatedCode, CancellationToken cancellationToken)
+    {
+        return Task.Run(() =>
+        {
+            cancellationToken.ThrowIfCancellationRequested();
+            CapitalizeNamespacesFirstLetters(generatedCode);
+            ReplaceIndexersByMethodsWithParameter(
+                generatedCode,
+                false,
+                static x => $"By{x.ToFirstCharacterUpperCase()}",
+                static x => x.ToFirstCharacterUpperCase(),
+                GenerationLanguage.HTTP);
+            cancellationToken.ThrowIfCancellationRequested();
+            ReplaceReservedNames(
+                generatedCode,
+                new HttpReservedNamesProvider(),
+                x => $"{x}_escaped");
+            RemoveCancellationParameter(generatedCode);
+            ConvertUnionTypesToWrapper(
+                generatedCode,
+                _configuration.UsesBackingStore,
+                static s => s
+            );
+            cancellationToken.ThrowIfCancellationRequested();
+            SetBaseUrlForRequestBuilderMethods(generatedCode, GetBaseUrl(generatedCode));
+            // Remove unused code from the DOM e.g Models, BarrelInitializers, e.t.c
+            RemoveUnusedCodeElements(generatedCode);
+        }, cancellationToken);
+    }
+
+    private string? GetBaseUrl(CodeElement element)
+    {
+        return element.GetImmediateParentOfType<CodeNamespace>()
+                      .GetRootNamespace()?
+                      .FindChildByName<CodeClass>(_configuration.ClientClassName)?
+                      .Methods?
+                      .FirstOrDefault(static x => x.IsOfKind(CodeMethodKind.ClientConstructor))?
+                      .BaseUrl;
+    }
+
+    private static void CapitalizeNamespacesFirstLetters(CodeElement current)
+    {
+        if (current is CodeNamespace currentNamespace)
+            currentNamespace.Name = currentNamespace.Name.Split('.').Select(static x => x.ToFirstCharacterUpperCase()).Aggregate(static (x, y) => $"{x}.{y}");
+        CrawlTree(current, CapitalizeNamespacesFirstLetters);
+    }
+
+    private static void SetBaseUrlForRequestBuilderMethods(CodeElement current, string? baseUrl)
+    {
+        if (baseUrl is not null && current is CodeClass codeClass && codeClass.IsOfKind(CodeClassKind.RequestBuilder))
+        {
+            // Add a new property named BaseUrl and set its value to the baseUrl string
+            var baseUrlProperty = new CodeProperty
+            {
+                Name = "BaseUrl",
+                Kind = CodePropertyKind.Custom,
+                Access = AccessModifier.Private,
+                DefaultValue = baseUrl,
+                Type = new CodeType { Name = "string", IsExternal = true }
+            };
+            codeClass.AddProperty(baseUrlProperty);
+        }
+        CrawlTree(current, (element) => SetBaseUrlForRequestBuilderMethods(element, baseUrl));
+    }
+
+    private void RemoveUnusedCodeElements(CodeElement element)
+    {
+        if (!IsRequestBuilderClass(element) || IsBaseRequestBuilder(element) || IsRequestBuilderClassWithoutAnyHttpOperations(element))
+        {
+            var parentNameSpace = element.GetImmediateParentOfType<CodeNamespace>();
+            parentNameSpace?.RemoveChildElement(element);
+        }
+        else
+        {
+            // Add path variables
+            AddPathParameters(element);
+        }
+        CrawlTree(element, RemoveUnusedCodeElements);
+    }
+
+    private static void AddPathParameters(CodeElement element)
+    {
+        // Target RequestBuilder Classes only
+        if (element is not CodeClass codeClass) return;
+
+        var parent = element.GetImmediateParentOfType<CodeNamespace>().Parent;
+        while (parent is not null)
+        {
+            var codeIndexer = parent.GetChildElements(false)
+                .OfType<CodeClass>()
+                .FirstOrDefault()?
+                .GetChildElements(false)
+                .OfType<CodeMethod>()
+                .FirstOrDefault(static x => x.IsOfKind(CodeMethodKind.IndexerBackwardCompatibility));
+
+            if (codeIndexer is not null)
+            {
+                // Retrieve all the parameters of kind CodeParameterKind.Custom
+                var customParameters = codeIndexer.Parameters
+                    .Where(static param => param.IsOfKind(CodeParameterKind.Custom))
+                    .ToList();
+
+                // For each parameter:
+                foreach (var param in customParameters)
+                {
+                    // Create a new property of kind CodePropertyKind.PathParameters using the parameter and add it to the codeClass
+                    var pathParameterProperty = new CodeProperty
+                    {
+                        Name = param.Name,
+                        Kind = CodePropertyKind.PathParameters,
+                        Type = param.Type,
+                        Access = AccessModifier.Public,
+                        DefaultValue = param.DefaultValue,
+                        SerializationName = param.SerializationName,
+                        Documentation = param.Documentation
+                    };
+                    codeClass.AddProperty(pathParameterProperty);
+                }
+            }
+
+            parent = parent.Parent?.GetImmediateParentOfType<CodeNamespace>();
+        }
+    }
+
+    private static bool IsRequestBuilderClass(CodeElement element)
+    {
+        return element is CodeClass code && code.IsOfKind(CodeClassKind.RequestBuilder);
+    }
+
+    private bool IsBaseRequestBuilder(CodeElement element)
+    {
+        return element is CodeClass codeClass &&
+            codeClass.Name.Equals(_configuration.ClientClassName, StringComparison.Ordinal);
+    }
+
+    private static bool IsRequestBuilderClassWithoutAnyHttpOperations(CodeElement element)
+    {
+        return element is CodeClass codeClass && codeClass.IsOfKind(CodeClassKind.RequestBuilder) &&
+               !codeClass.Methods.Any(static method => method.IsOfKind(CodeMethodKind.RequestExecutor));
+    }
+}

src/Kiota.Builder/Refiners/HttpReservedNamesProvider.cs

@@ -0,0 +1,11 @@
+using System;
+using System.Collections.Generic;
+
+namespace Kiota.Builder.Refiners;
+public class HttpReservedNamesProvider : IReservedNamesProvider
+{
+    private readonly Lazy<HashSet<string>> _reservedNames = new(() => new HashSet<string>(StringComparer.OrdinalIgnoreCase)
+    {
+    });
+    public HashSet<string> ReservedNames => _reservedNames.Value;
+}

src/Kiota.Builder/Refiners/ILanguageRefiner.cs

@@ -37,6 +37,9 @@ public static async Task RefineAsync(GenerationConfiguration config, CodeNamespa
             case GenerationLanguage.Swift:
                 await new SwiftRefiner(config).RefineAsync(generatedCode, cancellationToken).ConfigureAwait(false);
                 break;
+            case GenerationLanguage.HTTP:
+                await new HttpRefiner(config).RefineAsync(generatedCode, cancellationToken).ConfigureAwait(false);
+                break;
             case GenerationLanguage.Python:
                 await new PythonRefiner(config).RefineAsync(generatedCode, cancellationToken).ConfigureAwait(false);
                 break;

src/Kiota.Builder/Writers/HTTP/CodeBlockEndWriter.cs

@@ -0,0 +1,12 @@
+using System;
+using Kiota.Builder.CodeDOM;
+
+namespace Kiota.Builder.Writers.Http;
+public class CodeBlockEndWriter : ICodeElementWriter<BlockEnd>
+{
+    public void WriteCodeElement(BlockEnd codeElement, LanguageWriter writer)
+    {
+        ArgumentNullException.ThrowIfNull(codeElement);
+        ArgumentNullException.ThrowIfNull(writer);
+    }
+}