feat(cli): add vix.app generated CMake project support

Author: GaspardKirira

include/vix/cli/app/AppCMakeGenerator.hpp

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+/**
+ *
+ *  @file AppCMakeGenerator.hpp
+ *  @author Gaspard Kirira
+ *
+ *  Copyright 2026, Gaspard Kirira. All rights reserved.
+ *  https://github.com/vixcpp/vix
+ *  Use of this source code is governed by a MIT license
+ *  that can be found in the License file.
+ *
+ *  Vix.cpp
+ *
+ *  CMake generator for simple vix.app projects.
+ *
+ */
+
+#ifndef VIX_CLI_APP_APP_CMAKE_GENERATOR_HPP
+#define VIX_CLI_APP_APP_CMAKE_GENERATOR_HPP
+
+#include <filesystem>
+#include <string>
+
+#include <vix/cli/app/AppManifest.hpp>
+
+namespace vix::cli::app
+{
+  namespace fs = std::filesystem;
+
+  /**
+   * @brief Result returned after generating an internal CMake project.
+   */
+  struct AppCMakeGenerateResult
+  {
+    /**
+     * @brief Directory containing the generated CMakeLists.txt.
+     */
+    fs::path sourceDir;
+
+    /**
+     * @brief Path to the generated CMakeLists.txt file.
+     */
+    fs::path cmakeListsPath;
+
+    /**
+     * @brief Error message when generation failed.
+     */
+    std::string error;
+
+    /**
+     * @brief Returns true when the generation succeeded.
+     *
+     * @return true if the generated CMake project is ready.
+     */
+    bool success() const;
+  };
+
+  /**
+   * @brief Builds the generated CMakeLists.txt content for a vix.app manifest.
+   *
+   * @param manifest Parsed vix.app manifest.
+   * @param projectDir Original user project directory.
+   * @return Generated CMakeLists.txt content.
+   */
+  std::string generate_app_cmake_lists_content(
+      const AppManifest &manifest,
+      const fs::path &projectDir);
+
+  /**
+   * @brief Generates an internal CMake project for a simple vix.app project.
+   *
+   * The generated project is written under:
+   *
+   * .vix/generated/app/CMakeLists.txt
+   *
+   * @param manifest Parsed vix.app manifest.
+   * @param projectDir Original user project directory.
+   * @return Generation result.
+   */
+  AppCMakeGenerateResult generate_app_cmake_project(
+      const AppManifest &manifest,
+      const fs::path &projectDir);
+
+} // namespace vix::cli::app
+
+#endif // VIX_CLI_APP_APP_CMAKE_GENERATOR_HPP

include/vix/cli/app/AppManifest.hpp

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+/**
+ *
+ *  @file AppManifest.hpp
+ *  @author Gaspard Kirira
+ *
+ *  Copyright 2026, Gaspard Kirira. All rights reserved.
+ *  https://github.com/vixcpp/vix
+ *  Use of this source code is governed by a MIT license
+ *  that can be found in the License file.
+ *
+ *  Vix.cpp
+ *
+ *  Simple application manifest model for generated CMake builds.
+ *
+ */
+
+#ifndef VIX_CLI_APP_APP_MANIFEST_HPP
+#define VIX_CLI_APP_APP_MANIFEST_HPP
+
+#include <filesystem>
+#include <optional>
+#include <string>
+#include <vector>
+
+namespace vix::cli::app
+{
+  namespace fs = std::filesystem;
+
+  /**
+   * @brief Describes the type of C++ target declared by vix.app.
+   */
+  enum class AppTargetType
+  {
+    Executable,
+    StaticLibrary,
+    SharedLibrary
+  };
+
+  /**
+   * @brief Converts a target type to a stable text value.
+   *
+   * @param type Target type.
+   * @return Stable target type string.
+   */
+  std::string to_string(AppTargetType type);
+
+  /**
+   * @brief Parses a target type from a text value.
+   *
+   * Supported values:
+   * - executable
+   * - static
+   * - static-library
+   * - shared
+   * - shared-library
+   * - library
+   *
+   * @param value Raw manifest value.
+   * @return Parsed target type when valid.
+   */
+  std::optional<AppTargetType> app_target_type_from_string(
+      const std::string &value);
+
+  /**
+   * @brief Simple C++ application manifest.
+   *
+   * This structure represents the content of a vix.app file.
+   * It is intentionally small and exists only as a user-friendly
+   * layer above the internal generated CMake project.
+   */
+  struct AppManifest
+  {
+    /**
+     * @brief Application or target name.
+     */
+    std::string name;
+
+    /**
+     * @brief Target type.
+     */
+    AppTargetType type{AppTargetType::Executable};
+
+    /**
+     * @brief C++ standard value.
+     *
+     * Example values:
+     * - c++17
+     * - c++20
+     * - c++23
+     */
+    std::string standard{"c++20"};
+
+    /**
+     * @brief Source files relative to the project directory.
+     */
+    std::vector<std::string> sources;
+
+    /**
+     * @brief Include directories relative to the project directory.
+     */
+    std::vector<std::string> includeDirs;
+
+    /**
+     * @brief Preprocessor definitions.
+     */
+    std::vector<std::string> defines;
+
+    /**
+     * @brief CMake targets or libraries to link.
+     */
+    std::vector<std::string> links;
+
+    /**
+     * @brief Returns true when the manifest has the minimum valid fields.
+     *
+     * @return true if the manifest can be used.
+     */
+    bool valid() const;
+  };
+
+  /**
+   * @brief Result returned when loading a vix.app file.
+   */
+  struct AppManifestLoadResult
+  {
+    /**
+     * @brief Parsed manifest.
+     */
+    AppManifest manifest;
+
+    /**
+     * @brief Error message when loading failed.
+     */
+    std::string error;
+
+    /**
+     * @brief Returns true when the load operation succeeded.
+     *
+     * @return true if the manifest was loaded successfully.
+     */
+    bool success() const;
+  };
+
+  /**
+   * @brief Loads a vix.app file from disk.
+   *
+   * @param path Path to the vix.app file.
+   * @return Load result containing either a manifest or an error.
+   */
+  AppManifestLoadResult load_app_manifest(const fs::path &path);
+
+} // namespace vix::cli::app
+
+#endif // VIX_CLI_APP_APP_MANIFEST_HPP

include/vix/cli/app/AppProjectResolver.hpp

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+/**
+ *
+ *  @file AppProjectResolver.hpp
+ *  @author Gaspard Kirira
+ *
+ *  Copyright 2026, Gaspard Kirira. All rights reserved.
+ *  https://github.com/vixcpp/vix
+ *  Use of this source code is governed by a MIT license
+ *  that can be found in the License file.
+ *
+ *  Vix.cpp
+ *
+ *  Project resolver for CMake and vix.app based applications.
+ *
+ */
+
+#ifndef VIX_CLI_APP_APP_PROJECT_RESOLVER_HPP
+#define VIX_CLI_APP_APP_PROJECT_RESOLVER_HPP
+
+#include <filesystem>
+#include <string>
+
+namespace vix::cli::app
+{
+  namespace fs = std::filesystem;
+
+  /**
+   * @brief Describes which project input was selected.
+   */
+  enum class AppProjectKind
+  {
+    Unknown,
+    CMake,
+    VixApp
+  };
+
+  /**
+   * @brief Converts a project kind to a stable string.
+   *
+   * @param kind Project kind.
+   * @return Stable string value.
+   */
+  std::string to_string(AppProjectKind kind);
+
+  /**
+   * @brief Resolved project information used by build and run commands.
+   */
+  struct AppProjectResolveResult
+  {
+    /**
+     * @brief Selected project kind.
+     */
+    AppProjectKind kind{AppProjectKind::Unknown};
+
+    /**
+     * @brief Original user project directory.
+     *
+     * This is where the user runs Vix from, and where build directories
+     * should still be created.
+     */
+    fs::path userProjectDir;
+
+    /**
+     * @brief CMake source directory passed to cmake -S.
+     *
+     * For normal CMake projects, this is the same as userProjectDir.
+     * For vix.app projects, this is the generated internal CMake directory.
+     */
+    fs::path cmakeSourceDir;
+
+    /**
+     * @brief Path to the active CMakeLists.txt file.
+     */
+    fs::path cmakeListsPath;
+
+    /**
+     * @brief Path to vix.app when the project uses vix.app.
+     */
+    fs::path appManifestPath;
+
+    /**
+     * @brief Target name resolved from the project.
+     */
+    std::string targetName;
+
+    /**
+     * @brief True when CMakeLists.txt was generated from vix.app.
+     */
+    bool generated{false};
+
+    /**
+     * @brief Error message when resolution failed.
+     */
+    std::string error;
+
+    /**
+     * @brief Returns true when project resolution succeeded.
+     *
+     * @return true if the result is usable.
+     */
+    bool success() const;
+  };
+
+  /**
+   * @brief Resolves a C++ project for Vix build or run.
+   *
+   * Resolution order:
+   * 1. CMakeLists.txt
+   * 2. vix.app
+   *
+   * If CMakeLists.txt exists, the current build behavior is preserved.
+   * vix.app is used only when no CMakeLists.txt is present.
+   *
+   * @param base Directory to start from.
+   * @return Resolved project result.
+   */
+  AppProjectResolveResult resolve_app_project(const fs::path &base);
+
+} // namespace vix::cli::app
+
+#endif // VIX_CLI_APP_APP_PROJECT_RESOLVER_HPP