Expose ALPM DB over HTTP

daemon/persistence/box/export/AlpmDBExporter.cpp

@@ -8,26 +8,45 @@
 
 #include "core/application/dtos/PackageSectionDTO.h"
 #include "core/domain/enums/PoolLocation.h"
-#include "persistence/box/record/PackageRecord.h"
-#include "persistence/box/store/PackageStoreBase.h"
+#include "utilities/Error.h"
+#include "utilities/NavigationAction.h"
 #include "utilities/alpmdb/Database.h"
-#include "utilities/libarchive/Writer.h"
-#include "utilities/lmdb/Database.h"
-#include "utilities/log/Logging.h"
+#include "utilities/errors/FsError.h"
+#include "utilities/libarchive/Error.h"
 
 #include <archive.h>
 #include <coro/sync_wait.hpp>
+#include <expected>
 #include <filesystem>
 #include <iterator>
 #include <memory>
 #include <mutex>
 #include <parallel_hashmap/phmap.h>
 #include <string_view>
-#include <thread>
-#include <unordered_map>
-#include <utility>
+#include <system_error>
 
 namespace bxt::Persistence::Box {
+// Creates the symlink relative to target
+std::expected<void, FsError>
+    create_relative_symlink(const std::filesystem::path& target,
+                            const std::filesystem::path& link) {
+    std::error_code ec;
+
+    if (std::filesystem::exists(link)) {
+        ec.assign(static_cast<int>(std::errc::file_exists),
+                  std::generic_category());
+        return bxt::make_error<FsError>(ec);
+    }
+
+    const auto relative_target =
+        std::filesystem::relative(target, link.parent_path(), ec);
+    if (ec) { return bxt::make_error<FsError>(ec); }
+
+    std::filesystem::create_symlink(relative_target, link, ec);
+    if (ec) { return bxt::make_error<FsError>(ec); }
+
+    return {};
+}
 
 AlpmDBExporter::AlpmDBExporter(
     BoxOptions& box_options,
@@ -56,63 +75,39 @@ coro::task<void> AlpmDBExporter::export_to_disk() {
     phmap::parallel_flat_hash_map<PackageSectionDTO, Archive::Writer> writers;
 
     for (const auto& section : m_dirty_sections) {
-        logd("Exporter: \"{}\" export into the package manager format started",
+        logi("Exporter: \"{}\" export into the package manager format started",
              std::string(section));
-        writers.emplace(section, Archive::Writer());
 
-        archive_write_add_filter_zstd(writers.at(section));
-        archive_write_set_format_pax_restricted(writers.at(section));
+        /// TODO: We need to make this way more robust. At least a full backup
+        /// would work but maybe we can do something more smart...
+        if (!cleanup_section(section)) { co_return; }
 
-        writers.at(section).open_filename(
-            m_box_path / std::string(section)
-            / fmt::format("{}.db.tar.zst", section.repository));
+        auto writer = setup_alpmdb_writer(section);
 
-        co_await m_package_store.accept(
-            [this, writer = &writers.at(section)](
-                std::string_view key,
-                const PackageRecord& package) -> Utilities::NavigationAction {
-                const auto deserialized = PackageRecord::Id::from_string(key);
+        if (!writer.has_value()) {
+            logf("Exporter: Writer cannot be created, the error is \"{}\". "
+                 "Stopping...",
+                 writer.error().what());
+            co_return;
+        }
 
-                if (!deserialized.has_value()) {
-                    loge("Exporter: Key \"{}\" is not valid. Skipping...", key);
-                    return Utilities::NavigationAction::Next;
-                }
+        writers.emplace(section, std::move(*writer));
 
-                const auto& [section, name] = *deserialized;
-
-                const auto version =
-                    package.descriptions
-                        .at(*Core::Domain::select_preferred_pool_location(
-                            package.descriptions))
-                        .descfile.get("VERSION");
-
-                if (!version.has_value()) {
-                    loge("Exporter: Version for \"{}\" is not valid. "
-                         "Skipping...",
-                         key);
-
-                    return Utilities::NavigationAction::Next;
+        co_await m_package_store.accept(
+            [this, writer = &writers.at(section)](
+                std::string_view key, const PackageRecord& package) {
+                if (auto export_ok = export_package(*writer, key, package);
+                    !export_ok) {
+                    logf(fmt::format("Exporter: {}. Stopping...",
+                                     export_ok.error()));
+                    return Utilities::NavigationAction::Stop;
                 }
 
-                logd(
-                    "Exporter: Description for \"{}/{}-{}\" is being added... ",
-                    std::string(section), name, *version);
-
-                Utilities::AlpmDb::DatabaseUtils::write_buffer_to_archive(
-                    *writer, fmt::format("{}-{}/desc", name, *version),
-                    package.descriptions
-                        .at(*Core::Domain::select_preferred_pool_location(
-                            package.descriptions))
-                        .descfile.desc);
-
-                logd("Exporter: Description for \"{}/{}-{}\" is added",
-                     std::string(section), name, *version);
-
                 return Utilities::NavigationAction::Next;
             },
             std::string(section));
 
-        logd("Exporter: \"{}\" export finished", std::string(section));
+        logi("Exporter: \"{}\" export finished", std::string(section));
     }
 
     m_dirty_sections.clear();
@@ -125,5 +120,188 @@ void AlpmDBExporter::add_dirty_sections(
     m_dirty_sections.insert(std::make_move_iterator(sections.begin()),
                             std::make_move_iterator(sections.end()));
 }
+// Factory function for ALPM .db archive writer
+std::expected<Archive::Writer, bxt::Error>
+    AlpmDBExporter::setup_alpmdb_writer(const PackageSectionDTO& section) {
+    Archive::Writer writer;
+
+    if (archive_write_add_filter_zstd(writer) < ARCHIVE_WARN) {
+        return bxt::make_error<Archive::LibArchiveError>(std::move(writer));
+    }
+    if (archive_write_set_format_pax_restricted(writer) < ARCHIVE_WARN) {
+        return bxt::make_error<Archive::LibArchiveError>(std::move(writer));
+    }
+
+    const auto archive_path =
+        m_box_path / std::string(section)
+        / fmt::format("{}.db.tar.zst", section.repository);
+
+    if (auto open_ok = writer.open_filename(archive_path); !open_ok) {
+        return std::unexpected(std::move(open_ok.error()));
+    }
+
+    const auto archive_link = m_box_path / std::string(section)
+                              / fmt::format("{}.db", section.repository);
+
+    if (auto link_created_ok =
+            create_relative_symlink(archive_path, archive_link);
+        !link_created_ok) {
+        return std::unexpected(link_created_ok.error());
+    }
+
+    return writer;
+}
+// Cleans up section before the export by removing all it's content
+std::expected<void, FsError>
+    AlpmDBExporter::cleanup_section(const PackageSectionDTO& section) {
+    std::error_code ec;
+
+    std::filesystem::directory_iterator directory_iterator;
+
+    constexpr auto handle_error = [](const auto& ec) {
+        logf("Exporter: Can't wipe the directory before the export, the "
+             "error is "
+             "\"{}\". Stopping...",
+             ec.message());
+        return bxt::make_error<FsError>(ec);
+    };
+
+    if (directory_iterator = std::filesystem::directory_iterator(
+            m_box_path / std::string(section), ec);
+        ec) {
+        return handle_error(ec);
+    }
+
+    for (const auto& entry : directory_iterator) {
+        if (!std::filesystem::remove_all(entry.path(), ec)) {
+            return handle_error(ec);
+        }
+    }
+
+    return {};
+}
+
+struct PackageDetails {
+    PackageSectionDTO section;
+    std::string name;
+    std::string version;
+    PoolLocation preferred_location;
+};
+// Validates and extracts essential package details from both key and record
+std::expected<PackageDetails, std::string>
+    validate_package_key(std::string_view key, const PackageRecord& package) {
+    auto deserialized = PackageRecord::Id::from_string(key);
+    if (!deserialized.has_value()) {
+        return std::unexpected(fmt::format("Invalid package key: '{}'.", key));
+    }
+
+    const auto& [section, name] = *deserialized;
+
+    auto location = select_preferred_pool_location(package.descriptions);
+
+    if (!location.has_value()) {
+        return std::unexpected(
+            fmt::format("Can't select preferred location for '{}'", key));
+    }
+
+    std::optional<std::string> version_string;
+
+    auto description_it = package.descriptions.find(*location);
+    if (description_it == package.descriptions.end()) {
+        return std::unexpected(fmt::format(
+            "Package details not found for preferred location: '{}'.", key));
+    }
+    if (!(version_string = description_it->second.descfile.get("VERSION"))
+             .has_value()
+        || version_string->empty()) {
+        return std::unexpected(
+            fmt::format("No valid version for package '{}'.", key));
+    }
+    return PackageDetails {section, name, *version_string, *location};
+}
+
+// Writes the contents of package description file to section's ALPM Database
+// archive
+std::expected<void, std::string>
+    write_package_description_to_alpmdb(Archive::Writer& alpmdb_writer,
+                                        const PackageDetails& details,
+                                        const PackageRecord& package) {
+    const auto& [section, name, version, preferred_location] = details;
+    auto desc = package.descriptions.at(preferred_location).descfile.desc;
+    auto desc_path = fmt::format("{}-{}/desc", name, version);
+
+    if (auto write_ok =
+            Utilities::AlpmDb::DatabaseUtils::write_buffer_to_archive(
+                alpmdb_writer, desc_path, desc);
+        !write_ok) {
+        return std::unexpected(
+            fmt::format("Failed to write description for '{}/{}-{}'.",
+                        std::string(section), name, version));
+    }
+    return {};
+}
+
+// Symlinks (usually pool) package and optionally it's signature to the
+// specified section
+std::expected<void, std::string>
+    symlink_package_files(const PackageDetails& details,
+                          const PackageRecord& package,
+                          const std::filesystem::path& box_path) {
+    auto [section, name, version, preferred_location] = details;
+
+    auto description = package.descriptions.at(preferred_location);
+
+    auto link_file_path = std::filesystem::absolute(
+        box_path / std::string(section) / description.filepath.filename());
+
+    if (auto link_ok =
+            create_relative_symlink(description.filepath, link_file_path);
+        !link_ok) {
+        return std::unexpected(
+            fmt::format("Failed to link package file for '{}/{}-{}'.",
+                        std::string(section), name, version));
+    }
+
+    if (description.signature_path.has_value()) {
+        auto link_file_path =
+            std::filesystem::absolute(box_path / std::string(section)
+                                      / description.signature_path->filename());
+
+        if (auto link_ok = create_relative_symlink(*description.signature_path,
+                                                   link_file_path);
+            !link_ok) {
+            return std::unexpected(
+                fmt::format("Failed to link signature file for '{}/{}-{}'.",
+                            std::string(section), name, version));
+        }
+    }
+    return {};
+}
+// Exports package into the ALPM repository format by writing it's description
+// into the .db file and symlinking package and signature files for specified
+// section
+std::expected<void, std::string>
+    AlpmDBExporter::export_package(Archive::Writer& writer,
+                                   std::string_view key,
+                                   const PackageRecord& package) {
+    auto validated_details = validate_package_key(key, package);
+    if (!validated_details.has_value()) {
+        return std::unexpected(validated_details.error());
+    }
+
+    auto write_result = write_package_description_to_alpmdb(
+        writer, *validated_details, package);
+    if (!write_result.has_value()) {
+        return std::unexpected(write_result.error());
+    }
+
+    auto file_management_result =
+        symlink_package_files(*validated_details, package, m_box_path);
+    if (!file_management_result.has_value()) {
+        return std::unexpected(file_management_result.error());
+    }
+
+    return {};
+}
 
 } // namespace bxt::Persistence::Box

daemon/persistence/box/export/AlpmDBExporter.h

@@ -8,12 +8,15 @@
 #pragma once
 
 #include "core/application/dtos/PackageSectionDTO.h"
+#include "core/domain/entities/Section.h"
 #include "core/domain/repositories/RepositoryBase.h"
 #include "parallel_hashmap/phmap.h"
 #include "persistence/box/BoxOptions.h"
 #include "persistence/box/export/ExporterBase.h"
 #include "persistence/box/store/PackageStoreBase.h"
-#include "utilities/locked.h"
+#include "utilities/Error.h"
+#include "utilities/errors/FsError.h"
+#include "utilities/libarchive/Writer.h"
 
 #include <coro/io_scheduler.hpp>
 #include <filesystem>
@@ -34,6 +37,17 @@ class AlpmDBExporter : public ExporterBase {
         std::set<Core::Application::PackageSectionDTO>&& override) override;
 
 private:
+    std::expected<Archive::Writer, bxt::Error>
+        setup_alpmdb_writer(const PackageSectionDTO& section);
+
+    std::expected<void, FsError>
+        cleanup_section(const PackageSectionDTO& section);
+
+    std::expected<void, std::string>
+        export_package(Archive::Writer& writer,
+                       std::string_view key,
+                       const PackageRecord& package);
+
     std::filesystem::path m_box_path;
     std::set<Core::Application::PackageSectionDTO> m_sections;
     PackageStoreBase& m_package_store;