Add support for custom update sources in the C++ library

src/lib-cpp/Cargo.toml

@@ -23,6 +23,7 @@ anyhow.workspace = true
 lazy_static.workspace = true
 log.workspace = true
 libc.workspace = true
+serde_json.workspace = true
 
 [build-dependencies]
 cbindgen.workspace = true

src/lib-cpp/include/Velopack.h

@@ -175,6 +175,30 @@ bool vpkc_new_update_manager(const char *psz_url_or_path,
                              struct vpkc_locator_config_t *p_locator,
                              vpkc_update_manager_t **p_manager);
 
+/**
+ * Create a new UpdateManager instance.
+ * @param options Optional extra configuration for update manager.
+ * @param locator Override the default locator configuration (usually used for testing / mocks).
+ * @param callback to override the default update source
+ * (AutoSource). Retrieve the list of available remote releases from
+ * the package source. These releases can subsequently be downloaded
+ * with cb_download_release_entry.
+ * @param callback to override the default update source
+ * (AutoSource). Download the specified VelopackAsset to the provided
+ * local file path.
+ * @param parameter to the callbacks to override the default update
+ * source (AutoSource). It's the user's responsibilty to ensure that
+ * it's safe to send and share it across threads
+ */
+bool vpkc_new_custom_update_manager(const char *(*cb_get_release_feed)(const char*, void*),
+                                    bool (*cb_download_release_entry)(const char*,
+                                                                      const char*,
+                                                                      void*),
+                                    void *p_user_data,
+                                    struct vpkc_update_options_t *p_options,
+                                    struct vpkc_locator_config_t *p_locator,
+                                    vpkc_update_manager_t **p_manager);
+
 /**
  * Returns the currently installed version of the app.
  */

src/lib-cpp/include/Velopack.hpp

@@ -8,6 +8,7 @@
 #include <optional>
 #include <vector>
 #include <stdexcept>
+#include <memory>
 
 #include "Velopack.h"
 
@@ -333,12 +334,31 @@ public:
     };
 };
 
+/**
+ * Implement this interface override the default update source
+ * (AutoSource)
+ */
+class IUpdateSource {
+public:
+    /** @param Retrieve the list of available remote releases from
+     * the package source. These releases can subsequently be downloaded
+     * with DownloadReleaseEntry().
+     */
+    virtual const char* GetReleaseFeed(const char* releasesName) = 0;
+
+    /** @param Download the specified VelopackAsset to the provided local file path.
+     */
+    virtual bool DownloadReleaseEntry(const char* assetFileName, const char* localFilePath) = 0;
+};
+
 /**
  * Provides functionality for checking for updates, downloading updates, and applying updates to the current application.
  */
 class UpdateManager {
 private:
     vpkc_update_manager_t* m_pManager = 0;
+    std::unique_ptr<IUpdateSource> m_pUpdateSource;
+
 public:
     /**
      * Create a new UpdateManager instance.
@@ -366,6 +386,42 @@ public:
         }
     };
 
+    /**
+     * Create a new UpdateManager instance.
+     * @param pUpdateSource Custom update source implementation.
+     * @param options Optional extra configuration for update manager.
+     * @param locator Override the default locator configuration (usually used for testing / mocks).
+     */
+    UpdateManager(std::unique_ptr<IUpdateSource> pUpdateSource, const UpdateOptions* options = nullptr, const VelopackLocatorConfig* locator = nullptr) {
+        vpkc_update_options_t* pOptions = nullptr;
+        if (options != nullptr) {
+            vpkc_update_options_t vpkc_options = to_c(*options);
+            pOptions = &vpkc_options;
+        }
+
+        vpkc_locator_config_t* pLocator = nullptr;
+        if (locator != nullptr) {
+            vpkc_locator_config_t vpkc_locator = to_c(*locator);
+            pLocator = &vpkc_locator;
+        }
+
+        auto cbGetReleaseFeed = [](const char* releasesName, void* userData) {
+            IUpdateSource* source = reinterpret_cast<IUpdateSource*>(userData);
+            return source->GetReleaseFeed(releasesName);
+            };
+
+        auto cbDownloadReleaseEntry = [](const char* assetFileName, const char* localFilePath, void* userData) {
+            IUpdateSource* source = reinterpret_cast<IUpdateSource*>(userData);
+            return source->DownloadReleaseEntry(assetFileName, localFilePath);
+            };
+
+        m_pUpdateSource.swap(pUpdateSource);
+
+        if (!vpkc_new_custom_update_manager(cbGetReleaseFeed, cbDownloadReleaseEntry, m_pUpdateSource.get(), pOptions, pLocator, &m_pManager)) {
+            throw_last_error();
+        }
+    };
+
     /**
      * Destructor for UpdateManager.
      */
@@ -480,4 +536,4 @@ public:
 
 } // namespace Velopack
 
-#endif // VELOPACK_HPP
+#endif // VELOPACK_HPP

src/lib-cpp/src/lib.rs

@@ -10,8 +10,8 @@ use types::*;
 
 use anyhow::{anyhow, bail};
 use libc::{c_char, c_void, size_t};
-use std::ffi::CString;
-use velopack::{sources, Error as VelopackError, UpdateCheck, UpdateManager, VelopackApp};
+use std::{sync::mpsc::Sender, ffi::{CStr, CString}};
+use velopack::{bundle, sources, Error as VelopackError, UpdateCheck, UpdateManager, VelopackApp, VelopackAsset, VelopackAssetFeed};
 
 /// Create a new UpdateManager instance.
 /// @param urlOrPath Location of the update server or path to the local update directory.
@@ -35,6 +35,95 @@ pub extern "C" fn vpkc_new_update_manager(
     })
 }
 
+#[derive(Clone)]
+/// Retrieves available updates using a custom method.  This is
+/// intended to be used from C and C++ code when `AutoSource` is
+/// inadequate.
+struct CCallbackUpdateSource {
+    /// Opaque data that's passed to the callbacks
+    p_user_data: *mut c_void,
+    /// Callback function that returns the requrested asset feed JSON as a string
+    cb_get_release_feed: extern "C" fn(psz_releases_name: *const c_char, p_user_data: *mut c_void) -> *const c_char,
+    /// Callback function that downloads the requested asset file to a local path
+    cb_download_release_entry: extern "C" fn(psz_asset_file_name: *const c_char, psz_local_file: *const c_char, p_user_data: *mut c_void) -> bool,
+}
+
+unsafe impl Send for CCallbackUpdateSource {}
+unsafe impl Sync for CCallbackUpdateSource {}
+
+impl sources::UpdateSource for CCallbackUpdateSource {
+    fn get_release_feed(&self, channel: &str, _: &bundle::Manifest) -> Result<VelopackAssetFeed, VelopackError> {
+        let releases_name = format!("releases.{}.json", channel);
+	let releases_name_cstr = CString::new(releases_name).unwrap();
+	let json_cstr_ptr = (self.cb_get_release_feed)(releases_name_cstr.as_ptr(), self.p_user_data);
+	if json_cstr_ptr.is_null() {
+	    Err(VelopackError::Generic("Failed to fetch releases JSON".to_owned()))
+	} else {
+	    let json_cstr = unsafe { CStr::from_ptr(json_cstr_ptr) };
+            let feed: VelopackAssetFeed = serde_json::from_str(json_cstr.to_str().unwrap())?;
+            Ok(feed)
+	}
+    }
+
+    fn download_release_entry(&self, asset: &VelopackAsset, local_file: &str, progress_sender: Option<Sender<i16>>) -> Result<(), VelopackError> {
+        if let Some(progress_sender) = &progress_sender {
+            let _ = progress_sender.send(50);
+        }
+	let asset_file_name_cstr = CString::new(asset.FileName.as_str()).unwrap();
+	let local_file_cstr = CString::new(local_file).unwrap();
+	let success = (self.cb_download_release_entry)(asset_file_name_cstr.as_ptr(), local_file_cstr.as_ptr(), self.p_user_data);
+	if success {
+            if let Some(progress_sender) = &progress_sender {
+		let _ = progress_sender.send(100);
+            }
+            Ok(())
+	} else {
+	    Err(VelopackError::Generic("Failed to download asset file".to_owned()))
+	}
+    }
+
+    fn clone_boxed(&self) -> Box<dyn sources::UpdateSource> {
+        Box::new(self.clone())
+    }
+}
+
+
+/// Create a new UpdateManager instance.
+/// @param options Optional extra configuration for update manager.
+/// @param locator Override the default locator configuration (usually used for testing / mocks).
+/// @param callback to override the default update source
+/// (AutoSource). Retrieve the list of available remote releases from
+/// the package source. These releases can subsequently be downloaded
+/// with cb_download_release_entry.
+/// @param callback to override the default update source
+/// (AutoSource). Download the specified VelopackAsset to the provided
+/// local file path.
+/// @param parameter to the callbacks to override the default update
+/// source (AutoSource). It's the user's responsibilty to ensure that
+/// it's safe to send and share it across threads
+#[no_mangle]
+pub extern "C" fn vpkc_new_custom_update_manager(
+    cb_get_release_feed: extern "C" fn(*const c_char, *mut c_void) -> *const c_char,
+    cb_download_release_entry: extern "C" fn(*const c_char, *const c_char, *mut c_void) -> bool,
+    p_user_data: *mut c_void,
+    p_options: *mut vpkc_update_options_t,
+    p_locator: *mut vpkc_locator_config_t,
+    p_manager: *mut *mut vpkc_update_manager_t,
+) -> bool {
+    wrap_error(|| {
+        let source = CCallbackUpdateSource {
+	    p_user_data,
+	    cb_get_release_feed,
+	    cb_download_release_entry,
+	};
+        let options = c_to_updateoptions_opt(p_options);
+        let locator = c_to_velopacklocatorconfig_opt(p_locator);
+        let manager = UpdateManager::new(source, options, locator)?;
+        unsafe { *p_manager = UpdateManagerRawPtr::new(manager) };
+        Ok(())
+    })
+}
+
 /// Returns the currently installed version of the app.
 #[no_mangle]
 pub extern "C" fn vpkc_get_current_version(p_manager: *mut vpkc_update_manager_t, psz_version: *mut c_char, c_version: size_t) -> size_t {