Merge pull request 'feat/150-sqlite' (#159) from feat/150-sqlite into main

Reviewed-on: #159

core/CMakeLists.txt

@@ -5,6 +5,7 @@ target_link_libraries(nf7_core
     luajit
     nf7_config
     nf7_iface
+    sqlite
     uvw
 )
 target_sources(nf7_core
@@ -12,6 +13,7 @@ target_sources(nf7_core
     luajit/context.cc
     luajit/lambda.cc
     luajit/thread.cc
+    sqlite/database.cc
     uv/concurrency.cc
     uv/parallelism.cc
     version.cc
@@ -19,6 +21,8 @@ target_sources(nf7_core
     luajit/context.hh
     luajit/lambda.hh
     luajit/thread.hh
+    sqlite/database.hh
+    sqlite/util.hh
     uv/clock.hh
     uv/concurrency.hh
     uv/context.hh
@@ -39,6 +43,8 @@ target_sources(nf7_core_test
     luajit/lambda_test.cc
     luajit/thread_test.cc
     luajit/thread_test.hh
+    sqlite/database_test.cc
+    sqlite/database_test.hh
     uv/context_test.hh
     uv/concurrency_test.cc
     uv/file_test.cc

core/luajit/context.hh

@@ -163,7 +163,6 @@ class Context :
   using TaskQueue::Push;
   using TaskQueue::Wrap;
   using TaskQueue::Exec;
-  using TaskQueue::ExecAnd;
 
   Kind kind() const noexcept { return kind_; }
 

core/luajit/context_test.cc

@@ -7,11 +7,11 @@ using LuaJIT_Context = nf7::core::luajit::test::ContextFixture;
 using LuaJIT_Value   = nf7::core::luajit::test::ContextFixture;
 
 TEST_P(LuaJIT_Context, CreateAndDestroy) {
-  auto sut = env_->Get<nf7::core::luajit::Context>();
+  auto sut = env().Get<nf7::core::luajit::Context>();
   EXPECT_EQ(sut->kind(), GetParam());
 }
 TEST_P(LuaJIT_Context, Register) {
-  auto sut = env_->Get<nf7::core::luajit::Context>();
+  auto sut = env().Get<nf7::core::luajit::Context>();
   sut->Exec([](auto& ctx) {
     lua_createtable(*ctx, 0, 0);
     auto value = ctx.Register();
@@ -23,7 +23,7 @@ TEST_P(LuaJIT_Context, Register) {
   ConsumeTasks();
 }
 TEST_P(LuaJIT_Context, Query) {
-  auto sut = env_->Get<nf7::core::luajit::Context>();
+  auto sut = env().Get<nf7::core::luajit::Context>();
 
   std::shared_ptr<nf7::core::luajit::Value> value;
 

core/luajit/context_test.hh

@@ -18,143 +18,22 @@
 #include "iface/subsys/parallelism.hh"
 #include "iface/env.hh"
 
+#include "iface/env_test.hh"
+
 namespace nf7::core::luajit::test {
 
-class ContextFixture : public ::testing::TestWithParam<Context::Kind> {
+class ContextFixture :
- private:
+    public nf7::test::EnvFixtureWithTasking,
-  class AsyncDriver final {
+    public ::testing::WithParamInterface<Context::Kind> {
-   public:
-    explicit AsyncDriver(ContextFixture& parent) noexcept : parent_(parent) { }
-
-    void BeginBusy() noexcept { async_busy_ = true; }
-    void EndBusy() noexcept {
-      async_busy_ = false;
-      async_busy_.notify_all();
-    }
-    void Drive(AsyncTask&& task) noexcept {
-      try {
-        task(param_);
-      } catch (const Exception& e) {
-        std::cerr
-            << "unexpected exception while async task execution:\n"
-            << e << std::endl;
-        std::abort();
-      }
-    }
-    AsyncTask::Time tick() const noexcept {
-      const auto now = std::chrono::system_clock::now();
-      return std::chrono::time_point_cast<AsyncTask::Time::duration>(now);
-    }
-    bool nextIdleInterruption() const noexcept { return !parent_.alive_; }
-    bool nextTaskInterruption() const noexcept { return false; }
-
-    void Wait() { async_busy_.wait(true); }
-
-   private:
-    ContextFixture& parent_;
-    AsyncTaskContext param_;
-
-    std::atomic<bool> async_busy_ = false;
-  };
-
-  class SyncDriver final {
-   public:
-    explicit SyncDriver(ContextFixture& parent) noexcept : parent_(parent) { }
-
-    void BeginBusy() noexcept { }
-    void EndBusy() noexcept { }
-    void Drive(SyncTask&& task) noexcept {
-      try {
-        task(param_);
-      } catch (const Exception& e) {
-        std::cerr
-            << "unexpected exception while sync task execution:\n"
-            << e << std::endl;
-        std::abort();
-      }
-    }
-    SyncTask::Time tick() const noexcept {
-      const auto now = std::chrono::system_clock::now();
-      return std::chrono::time_point_cast<SyncTask::Time::duration>(now);
-    }
-    bool nextIdleInterruption() const noexcept {
-      return 0 == parent_.syncq_->size();
-    }
-    bool nextTaskInterruption() const noexcept { return false; }
-
-   private:
-    ContextFixture& parent_;
-    SyncTaskContext param_;
-  };
-
  public:
-  ContextFixture() noexcept : async_driver_(*this) { }
+  ContextFixture() noexcept
-
+      : EnvFixtureWithTasking({
- protected:
+              {
-  void SetUp() override {
+                typeid(Context), [](auto& env) {
-    syncq_  = std::make_shared<SimpleTaskQueue<SyncTask>>();
+                  return Context::Create(env, GetParam());
-    asyncq_ = std::make_shared<SimpleTaskQueue<AsyncTask>>();
+                },
-
+              },
-    env_.emplace(SimpleEnv::FactoryMap {
+            }) { }
-      {
-        typeid(subsys::Concurrency), [this](auto&) {
-          return std::make_shared<
-              WrappedTaskQueue<subsys::Concurrency>>(syncq_);
-        },
-      },
-      {
-        typeid(subsys::Parallelism), [this](auto&) {
-          return std::make_shared<
-              WrappedTaskQueue<subsys::Parallelism>>(asyncq_);
-        },
-      },
-      {
-        typeid(Context), [this](auto& env) {
-          return Context::Create(env, GetParam());
-        },
-      }
-    });
-    thread_ = std::thread {[this]() { asyncq_->Drive(async_driver_); }};
-  }
-  void TearDown() override {
-    ConsumeTasks();
-    env_ = std::nullopt;
-
-    WaitAsyncTasks(std::chrono::seconds(3));
-    alive_ = false;
-    asyncq_->Wake();
-    thread_.join();
-
-    asyncq_ = nullptr;
-    syncq_  = nullptr;
-  }
-
-  void ConsumeTasks() noexcept {
-    for (uint32_t i = 0; i < 16; ++i) {
-      SyncDriver sync_driver {*this};
-      syncq_->Drive(sync_driver);
-      WaitAsyncTasks(std::chrono::seconds(1));
-    }
-  }
-  void WaitAsyncTasks(auto dur) noexcept {
-    if (!asyncq_->WaitForEmpty(dur)) {
-      std::cerr << "timeout while waiting for task execution" << std::endl;
-      std::abort();
-    }
-    async_driver_.Wait();
-  }
-
- protected:
-  std::shared_ptr<SimpleTaskQueue<SyncTask>> syncq_;
-  std::shared_ptr<SimpleTaskQueue<AsyncTask>> asyncq_;
-  std::optional<SimpleEnv> env_;
-
- private:
-  std::atomic<bool> alive_ = true;
-  uint32_t async_cycle_ = 0;
-
-  std::thread thread_;
-  AsyncDriver async_driver_;
 };
 
 }  // namespace nf7::core::luajit::test

core/luajit/lambda_test.cc

@@ -26,7 +26,7 @@ class LuaJIT_Lambda : public nf7::core::luajit::test::ContextFixture {
 
   std::shared_ptr<nf7::core::luajit::Value> Compile(
       const char* script) noexcept {
-    auto lua = env_->Get<nf7::core::luajit::Context>();
+    auto lua = env().Get<nf7::core::luajit::Context>();
 
     std::shared_ptr<nf7::core::luajit::Value> func;
     lua->Exec([&](auto& lua) {
@@ -43,7 +43,7 @@ class LuaJIT_Lambda : public nf7::core::luajit::test::ContextFixture {
               const std::vector<nf7::Value>& out = {},
               nf7::Env* env = nullptr) {
     if (nullptr == env) {
-      env = &*env_;
+      env = &this->env();
     }
 
     auto func = Compile(script);
@@ -100,7 +100,7 @@ TEST_P(LuaJIT_Lambda, CtxMultiRecvWithDelay) {
                       "nf7:assert(\"null\"    == ctx:recv():type())\n"
                       "nf7:assert(\"integer\" == ctx:recv():type())");
 
-  auto sut = std::make_shared<nf7::core::luajit::Lambda>(*env_, func);
+  auto sut = std::make_shared<nf7::core::luajit::Lambda>(env(), func);
   sut->taker()->Take(nf7::Value::Null {});
   ConsumeTasks();
   EXPECT_EQ(sut->exitCount(), 0);
@@ -145,7 +145,7 @@ TEST_P(LuaJIT_Lambda, CtxSleep) {
   const auto clock = std::make_shared<nf7::core::Clock>();
   nf7::SimpleEnv env {{
     {typeid(nf7::subsys::Clock), [&](auto&) { return clock; }},
-  }, *env_};
+  }, this->env()};
 
   clock->Tick();
   const auto begin = clock->now();
@@ -193,7 +193,7 @@ TEST_P(LuaJIT_Lambda, CtxLogging) {
 
   nf7::SimpleEnv env {{
     {typeid(nf7::subsys::Logger), [&](auto&) { return logger; }},
-  }, *env_};
+  }, this->env()};
 
   Expect(
       "local ctx = ...\n"

core/luajit/thread_test.cc

@@ -16,7 +16,7 @@ class LuaJIT_Thread : public nf7::core::luajit::test::ContextFixture {
   template <typename... Args>
   void TestThread(
       const auto& setup, const char* script, Args&&... args) {
-    auto lua    = env_->Get<nf7::core::luajit::Context>();
+    auto lua    = env().Get<nf7::core::luajit::Context>();
     auto called = uint32_t {0};
     lua->Exec([&](auto& lua) {
       const auto compile = luaL_loadstring(*lua, script);

core/sqlite/database.cc

@@ -0,0 +1,208 @@
+// No copyright
+#include "core/sqlite/database.hh"
+
+#include <limits>
+#include <string>
+#include <utility>
+#include <variant>
+
+#include "core/sqlite/util.hh"
+
+
+namespace nf7::core::sqlite {
+
+class Database::Sql final :
+    public nf7::Sql,
+    public nf7::Sql::Command,
+    public std::enable_shared_from_this<Database::Sql> {
+ public:
+  Sql(const std::shared_ptr<Database>& db, sqlite3_stmt* stmt) noexcept
+      : db_(db), stmt_(stmt) {
+    assert(nullptr != stmt_);
+  }
+  ~Sql() noexcept override {
+    if (nullptr != stmt_) {
+      db_->concurrency_->Exec([db = db_, stmt = stmt_](auto&) {
+        db->Run([stmt](auto&) {
+          sqlite3_finalize(stmt);
+          return Void {};
+        });
+      });
+    }
+  }
+
+  Future<Void> Run(Handler&& f) noexcept override {
+    auto self = shared_from_this();
+    return db_->Run([self, f = std::move(f)](auto&) mutable {
+      f(*self);
+      return Void {};
+    });
+  }
+
+  void Bind(uint64_t idx, const Value& v) override {
+    if (idx > std::numeric_limits<int>::max()) {
+      throw Exception {"too large index"};
+    }
+    struct A {
+     public:
+       A(sqlite3_stmt* a, int b) noexcept : a_(a), b_(b) { }
+
+     public:
+      int operator()(Null) noexcept {
+        return sqlite3_bind_null(a_, b_);
+      }
+      int operator()(int64_t c) noexcept {
+        return sqlite3_bind_int64(a_, b_, c);
+      }
+      int operator()(double c) noexcept {
+        return sqlite3_bind_double(a_, b_, c);
+      }
+      int operator()(const std::string& c) noexcept {
+        return sqlite3_bind_text64(
+            a_, b_, c.data(), static_cast<uint64_t>(c.size()),
+            SQLITE_TRANSIENT, SQLITE_UTF8);
+      }
+
+     private:
+      sqlite3_stmt* const a_;
+      int b_;
+    };
+    Enforce(std::visit(A {stmt_, static_cast<int>(idx)}, v));
+  }
+  Value Fetch(uint64_t idx) const override {
+    if (idx > std::numeric_limits<int>::max()) {
+      throw Exception {"too large index"};
+    }
+    auto v = sqlite3_column_value(stmt_, static_cast<int>(idx));
+    switch (sqlite3_value_type(v)) {
+    case SQLITE_NULL: {
+      return Sql::Null {};
+    }
+    case SQLITE_INTEGER: {
+      return sqlite3_value_int64(v);
+    }
+    case SQLITE_FLOAT: {
+      return sqlite3_value_double(v);
+    }
+    case SQLITE_TEXT: {
+      const auto n = sqlite3_value_bytes(v);
+      const auto p = reinterpret_cast<const char*>(sqlite3_value_text(v));
+      return std::string {p, p+n};
+    }
+    default:
+      throw Exception {"unsupported type"};
+    }
+  }
+
+  void Reset() override {
+    Enforce(sqlite3_reset(stmt_));
+  }
+  Result Exec() override {
+    const auto ret = sqlite3_step(stmt_);
+    switch (ret) {
+    case SQLITE_ROW:
+      return kRow;
+    case SQLITE_DONE:
+      return kDone;
+    default:
+      Enforce(ret);
+      std::unreachable();
+    }
+  }
+
+ private:
+  const std::shared_ptr<Database> db_;
+  sqlite3_stmt* const stmt_;
+};
+
+sqlite3* Database::MakeConn(const char* addr) {
+  sqlite3* ret = nullptr;
+  Enforce(sqlite3_open(addr, &ret));
+  assert(nullptr != ret);
+  return ret;
+}
+
+Future<std::shared_ptr<Sql::Command>> Database::Compile(
+    std::string_view cmd) noexcept
+try {
+  if (cmd.size() > std::numeric_limits<int>::max()) {
+    return Exception::MakePtr("too long SQL command");
+  }
+  return Run([this, cmd = std::string {cmd}](auto&) {
+    sqlite3_stmt* stmt;
+    Enforce(
+        sqlite3_prepare_v3(
+            conn_,
+            cmd.c_str(),
+            static_cast<int>(cmd.size()),
+            SQLITE_PREPARE_PERSISTENT,
+            &stmt,
+            nullptr));
+    try {
+      return std::static_pointer_cast<nf7::Sql::Command>(
+          std::make_shared<Database::Sql>(shared_from_this(), stmt));
+    } catch (const std::bad_alloc&) {
+      sqlite3_finalize(stmt);
+      throw;
+    }
+  });
+} catch (...) {
+  return std::current_exception();
+}
+Future<Void> Database::Exec(std::string_view cmd, ColumnHandler&& f) noexcept {
+  class A final : public nf7::Sql {
+   public:
+    static int callback(void* ptr, int n, char** v, char**) noexcept
+    try {
+      auto self = reinterpret_cast<Database*>(ptr);
+      A a {n, v};
+      return int {self->column_handler_(a)? 0: 1};
+    } catch (...) {
+      return 1;
+    }
+
+   private:
+    A(int n, char** v) noexcept : n_(static_cast<uint64_t>(n)), v_(v) { }
+
+   private:
+    void Bind(uint64_t, const Value&) noexcept override { std::unreachable(); }
+    void Reset() noexcept override { std::unreachable(); }
+    Result Exec() noexcept override { std::unreachable(); }
+    Value Fetch(uint64_t idx) const override {
+      if (idx >= n_) {
+        throw Exception {"index overflow"};
+      }
+      return std::string {v_[idx]};
+    }
+
+   private:
+    uint64_t n_;
+    char** v_;
+  };
+
+  if (cmd.size() > std::numeric_limits<int>::max()) {
+    return Exception::MakePtr("too long SQL command");
+  }
+  return Run([this, cmd = std::string {cmd}, f = std::move(f)](auto&) mutable {
+    char* errmsg {nullptr};
+
+    column_handler_ = std::move(f);
+    const auto ret = sqlite3_exec(
+        conn_,
+        cmd.c_str(),
+        column_handler_? A::callback: nullptr,
+        this,
+        &errmsg);
+    column_handler_ = {};
+
+    if (nullptr != errmsg) {
+      const auto msg = std::string {"SQL error: "}+errmsg;
+      sqlite3_free(errmsg);
+      throw Exception {msg};
+    }
+    Enforce(ret);
+    return Void {};
+  });
+}
+
+}  // namespace nf7::core::sqlite

core/sqlite/database.hh

@@ -0,0 +1,71 @@
+// No copyright
+#pragma once
+
+#include <sqlite3.h>
+
+#include <cassert>
+#include <memory>
+#include <string_view>
+#include <utility>
+
+#include "iface/common/future.hh"
+#include "iface/common/mutex.hh"
+#include "iface/common/sql.hh"
+#include "iface/common/void.hh"
+#include "iface/subsys/concurrency.hh"
+#include "iface/subsys/database.hh"
+#include "iface/subsys/logger.hh"
+#include "iface/subsys/parallelism.hh"
+#include "iface/env.hh"
+
+#include "core/logger.hh"
+
+
+namespace nf7::core::sqlite {
+
+class Database final :
+    public subsys::Database,
+    public std::enable_shared_from_this<Database> {
+ private:
+  class Sql;
+
+ private:
+  static sqlite3* MakeConn(const char* addr);
+
+ public:
+  Database(Env& env, const char* addr)
+      : Database(env, MakeConn(addr)) { }
+  Database(Env& env, sqlite3* conn) noexcept
+      : subsys::Database("nf7::core::sqlite::Database"),
+        logger_(env.GetOr<subsys::Logger>(NullLogger::instance())),
+        concurrency_(env.Get<subsys::Concurrency>()),
+        parallelism_(env.Get<subsys::Parallelism>()),
+        conn_(conn) { }
+
+  ~Database() noexcept override { sqlite3_close(conn_); }
+
+ public:
+  Future<std::shared_ptr<nf7::Sql::Command>> Compile(
+      std::string_view) noexcept override;
+
+  Future<Void> Exec(std::string_view, ColumnHandler&& = {}) noexcept override;
+
+ private:
+  auto Run(auto&& f) noexcept {
+    return mtx_.RunAsyncEx(parallelism_, concurrency_, std::move(f))
+        .Attach(shared_from_this());
+  }
+
+ private:
+  const std::shared_ptr<subsys::Logger> logger_;
+  const std::shared_ptr<subsys::Concurrency> concurrency_;
+  const std::shared_ptr<subsys::Parallelism> parallelism_;
+
+  sqlite3* conn_;
+  mutable Mutex mtx_;
+
+  // temporary parameters
+  ColumnHandler column_handler_;
+};
+
+}  // namespace nf7::core::sqlite

core/sqlite/database_test.cc

@@ -0,0 +1,84 @@
+// No copyright
+#include "core/sqlite/database.hh"
+#include "core/sqlite/database_test.hh"
+
+#include <gtest/gtest.h>
+
+#include <string>
+#include <vector>
+
+#include "iface/subsys/database.hh"
+
+
+using SQLiteDatabase = nf7::core::sqlite::test::DatabaseFixture;
+
+TEST_F(SQLiteDatabase, CreateTable) {
+  const auto db = env().Get<nf7::subsys::Database>();
+  const auto fu = db->Exec("CREATE TABLE tbl (a, b, c);");
+  ConsumeTasks();
+  EXPECT_NO_THROW(fu.value());
+}
+
+TEST_F(SQLiteDatabase, SelectOneShot) {
+  const auto db = env().Get<nf7::subsys::Database>();
+
+  std::vector<std::string> rows;
+  const auto fu = db->Exec(
+      "CREATE TABLE tbl (idx, spell);"
+      "INSERT INTO tbl VALUES (0, 'zero');"
+      "INSERT INTO tbl VALUES (1, 'one');"
+      "INSERT INTO tbl VALUES (2, 'two');"
+      "SELECT * FROM tbl ORDER BY idx DESC;",
+      [&](auto& x) {
+        rows.push_back(std::get<std::string>(x.Fetch(1)));
+        return true;
+      });
+  ConsumeTasks();
+
+  EXPECT_NO_THROW(fu.value());
+  ASSERT_EQ(rows.size(), 3);
+  EXPECT_EQ(rows[2], "zero");
+  EXPECT_EQ(rows[1], "one");
+  EXPECT_EQ(rows[0], "two");
+}
+
+TEST_F(SQLiteDatabase, InsertMultiShot) {
+  const auto db = env().Get<nf7::subsys::Database>();
+
+  db->Exec("CREATE TABLE tbl (idx, spell);");
+  db->Compile("INSERT INTO tbl VALUES (?, ?);")
+      .Then([](auto& x) {
+        x->Run([](auto& x) {
+          x.Reset();
+          x.Bind(uint64_t {1}, int64_t {0});
+          x.Bind(uint64_t {2}, std::string {"zero"});
+          x.Exec();
+
+          x.Reset();
+          x.Bind(uint64_t {1}, int64_t {1});
+          x.Bind(uint64_t {2}, std::string {"one"});
+          x.Exec();
+
+          x.Reset();
+          x.Bind(uint64_t {1}, int64_t {2});
+          x.Bind(uint64_t {2}, std::string {"two"});
+          x.Exec();
+        });
+      });
+  ConsumeTasks();
+
+  std::vector<std::string> rows;
+  const auto fu = db->Exec(
+      "SELECT * FROM tbl ORDER BY idx ASC;",
+      [&](auto& x) {
+        rows.push_back(std::get<std::string>(x.Fetch(1)));
+        return true;
+      });
+  ConsumeTasks();
+
+  EXPECT_NO_THROW(fu.value());
+  ASSERT_EQ(rows.size(), 3);
+  EXPECT_EQ(rows[0], "zero");
+  EXPECT_EQ(rows[1], "one");
+  EXPECT_EQ(rows[2], "two");
+}

core/sqlite/database_test.hh

@@ -0,0 +1,27 @@
+// No copyright
+#pragma once
+
+#include "core/sqlite/database.hh"
+
+#include <gtest/gtest.h>
+
+#include <chrono>
+#include <memory>
+
+#include "iface/env_test.hh"
+
+
+namespace nf7::core::sqlite::test {
+
+class DatabaseFixture : public nf7::test::EnvFixtureWithTasking {
+ public:
+  DatabaseFixture()
+      : nf7::test::EnvFixtureWithTasking({
+              {typeid(nf7::subsys::Database), [](auto& env) {
+                return std::make_shared<Database>(env, ":memory:");
+              }},
+            }) {
+  }
+};
+
+}  // namespace nf7::core::sqlite::test

core/sqlite/util.hh

@@ -0,0 +1,17 @@
+// No copyright
+#pragma once
+
+#include <sqlite3.h>
+
+#include "iface/common/exception.hh"
+
+
+namespace nf7::core::sqlite {
+
+inline void Enforce(int ret) {
+  if (SQLITE_OK != ret) {
+    throw Exception {sqlite3_errstr(ret)};
+  }
+}
+
+}  // namespace nf7::core::sqlite

core/uv/concurrency_test.cc

@@ -17,7 +17,7 @@ using UV_Concurrency = nf7::core::uv::test::ContextFixture;
 
 
 TEST_F(UV_Concurrency, Push) {
-  auto sut = std::make_shared<nf7::core::uv::Concurrency>(*env_);
+  auto sut = std::make_shared<nf7::core::uv::Concurrency>(env());
 
   auto called = uint64_t {0};
   sut->Exec([&](auto&) { ++called; });
@@ -27,7 +27,7 @@ TEST_F(UV_Concurrency, Push) {
 }
 
 TEST_F(UV_Concurrency, PushFromTask) {
-  auto sut = std::make_shared<nf7::core::uv::Concurrency>(*env_);
+  auto sut = std::make_shared<nf7::core::uv::Concurrency>(env());
 
   auto called = uint64_t {0};
   sut->Exec([&](auto&) { sut->Exec([&](auto&) { ++called; }); });
@@ -37,7 +37,7 @@ TEST_F(UV_Concurrency, PushFromTask) {
 }
 
 TEST_F(UV_Concurrency, ExecOrderly) {
-  auto sut = std::make_shared<nf7::core::uv::Concurrency>(*env_);
+  auto sut = std::make_shared<nf7::core::uv::Concurrency>(env());
 
   auto called = uint64_t {0};
   sut->Exec([&](auto&) { ++called; EXPECT_EQ(called, 1); });
@@ -48,8 +48,8 @@ TEST_F(UV_Concurrency, ExecOrderly) {
 }
 
 TEST_F(UV_Concurrency, PushWithDelay) {
-  auto clock = env_->Get<nf7::subsys::Clock>();
+  auto clock = env().Get<nf7::subsys::Clock>();
-  auto sut   = std::make_shared<nf7::core::uv::Concurrency>(*env_);
+  auto sut   = std::make_shared<nf7::core::uv::Concurrency>(env());
 
   auto called = uint64_t {0};
   sut->Push({clock->now() + 100ms, [&](auto&) { ++called; }});

core/uv/context_test.hh

@@ -13,26 +13,32 @@
 
 #include "core/uv/clock.hh"
 
+#include "iface/env_test.hh"
+
 
 namespace nf7::core::uv::test {
 
-class ContextFixture : public ::testing::Test {
+class ContextFixture : public nf7::test::EnvFixture {
+ public:
+  ContextFixture() noexcept
+      : nf7::test::EnvFixture({
+            SimpleEnv::MakePair<Context, MainContext>(),
+            SimpleEnv::MakePair<subsys::Clock, Clock>(),
+          }) {
+  }
+
  protected:
   void SetUp() override {
-    env_.emplace(SimpleEnv::FactoryMap {
+    nf7::test::EnvFixture::SetUp();
-      SimpleEnv::MakePair<Context, MainContext>(),
+    ctx_ = std::dynamic_pointer_cast<MainContext>(env().Get<Context>());
-      SimpleEnv::MakePair<subsys::Clock, Clock>(),
-    });
-    ctx_ = std::dynamic_pointer_cast<MainContext>(env_->Get<Context>());
   }
   void TearDown() override {
     ctx_->RunAndClose();
-    env_ = std::nullopt;
+    nf7::test::EnvFixture::TearDown();
     ctx_ = nullptr;
   }
 
  protected:
-  std::optional<SimpleEnv> env_;
   std::shared_ptr<MainContext> ctx_;
 };
 

core/uv/file.cc

@@ -79,7 +79,7 @@ try {
   });
   return comp.future();
 } catch (const Exception&) {
-  return Future<Void> {std::current_exception()};
+  return {std::current_exception()};
 }
 
 Future<Void> File::Open(const nf7::Mutex::SharedToken& k) noexcept {
@@ -122,7 +122,7 @@ try {
   });
   return comp.future();
 } catch (const Exception&) {
-  return Future<uint64_t> {std::current_exception()};
+  return std::current_exception();
 }
 
 Future<Void> File::Truncate(uint64_t n) noexcept
@@ -142,7 +142,7 @@ try {
   });
   return comp.future();
 } catch (const Exception&) {
-  return Future<Void> {std::current_exception()};
+  return std::current_exception();
 }
 
 Future<File::ReadResult> File::Read(
@@ -174,7 +174,7 @@ try {
   });
   return comp.future();
 } catch (const Exception&) {
-  return Future<ReadResult> {std::current_exception()};
+  return std::current_exception();
 }
 
 Future<uint64_t> File::Write(
@@ -203,7 +203,7 @@ try {
   });
   return comp.future();
 } catch (const Exception&) {
-  return Future<uint64_t> {std::current_exception()};
+  return std::current_exception();
 }
 
 }  // namespace nf7::core::uv

core/uv/file_test.cc

@@ -35,7 +35,7 @@ class UV_File :
 
 TEST_P(UV_File, Open) {
   auto sut = nf7::core::uv::File::Make(
-      *env_, kTempFile,
+      env(), kTempFile,
       uvw::file_req::file_open_flags::RDWR
       | uvw::file_req::file_open_flags::CREAT);
 
@@ -54,7 +54,7 @@ TEST_P(UV_File, FetchSize) {
   PrepareFile("helloworld");
 
   auto sut = nf7::core::uv::File::Make(
-      *env_, kTempFile,
+      env(), kTempFile,
       uvw::file_req::file_open_flags::RDONLY);
 
   auto result = sut->FetchSize();
@@ -70,7 +70,7 @@ TEST_P(UV_File, FetchSize) {
 
 TEST_P(UV_File, FetchSizeFail) {
   auto sut = nf7::core::uv::File::Make(
-      *env_, kTempFile,
+      env(), kTempFile,
       uvw::file_req::file_open_flags::RDONLY);
 
   auto result = sut->FetchSize();
@@ -82,7 +82,7 @@ TEST_P(UV_File, FetchSizeFail) {
 
 TEST_P(UV_File, Truncate) {
   auto sut = nf7::core::uv::File::Make(
-      *env_, kTempFile,
+      env(), kTempFile,
       uvw::file_req::file_open_flags::RDWR
       | uvw::file_req::file_open_flags::CREAT);
 
@@ -98,7 +98,7 @@ TEST_P(UV_File, Truncate) {
 
 TEST_P(UV_File, TruncateFail) {
   auto sut = nf7::core::uv::File::Make(
-      *env_, kTempFile,
+      env(), kTempFile,
       uvw::file_req::file_open_flags::RDONLY);
 
   auto result = sut->Truncate(256);
@@ -112,7 +112,7 @@ TEST_P(UV_File, Read) {
   PrepareFile("helloworld");
 
   auto sut = nf7::core::uv::File::Make(
-      *env_, kTempFile,
+      env(), kTempFile,
       uvw::file_req::file_open_flags::RDONLY);
 
   auto result = sut->Read(1, 3);
@@ -133,7 +133,7 @@ TEST_P(UV_File, ReadFail) {
   PrepareFile("helloworld");
 
   auto sut = nf7::core::uv::File::Make(
-      *env_, kTempFile,
+      env(), kTempFile,
       uvw::file_req::file_open_flags::WRONLY);
 
   auto result = sut->Read(1, 3);
@@ -147,7 +147,7 @@ TEST_P(UV_File, Write) {
   PrepareFile("helloworld");
 
   auto sut = nf7::core::uv::File::Make(
-      *env_, kTempFile,
+      env(), kTempFile,
       uvw::file_req::file_open_flags::WRONLY);
 
   auto result = sut->Write(5, reinterpret_cast<const uint8_t*>("universe"), 8);
@@ -171,7 +171,7 @@ TEST_P(UV_File, WriteFail) {
   PrepareFile("helloworld");
 
   auto sut = nf7::core::uv::File::Make(
-      *env_, kTempFile,
+      env(), kTempFile,
       uvw::file_req::file_open_flags::RDONLY);
 
   auto result = sut->Write(5, reinterpret_cast<const uint8_t*>("universe"), 8);

core/uv/parallelism_test.cc

@@ -17,7 +17,7 @@ using UV_Parallelism = nf7::core::uv::test::ContextFixture;
 
 
 TEST_F(UV_Parallelism, Push) {
-  auto sut = std::make_shared<nf7::core::uv::Parallelism>(*env_);
+  auto sut = std::make_shared<nf7::core::uv::Parallelism>(env());
 
   auto called = uint64_t {0};
   sut->Exec([&](auto&) { ++called; });
@@ -27,7 +27,7 @@ TEST_F(UV_Parallelism, Push) {
 }
 
 TEST_F(UV_Parallelism, PushFromTask) {
-  auto sut = std::make_shared<nf7::core::uv::Parallelism>(*env_);
+  auto sut = std::make_shared<nf7::core::uv::Parallelism>(env());
 
   auto called = uint64_t {0};
   sut->Exec([&](auto&) { sut->Exec([&](auto&) { ++called; }); });
@@ -37,8 +37,8 @@ TEST_F(UV_Parallelism, PushFromTask) {
 }
 
 TEST_F(UV_Parallelism, PushWithDelay) {
-  auto clock = env_->Get<nf7::subsys::Clock>();
+  auto clock = env().Get<nf7::subsys::Clock>();
-  auto sut   = std::make_shared<nf7::core::uv::Parallelism>(*env_);
+  auto sut   = std::make_shared<nf7::core::uv::Parallelism>(env());
 
   auto called = uint64_t {0};
   sut->Push({clock->now() + 100ms, [&](auto&) { ++called; }});

iface/CMakeLists.txt

@@ -17,6 +17,8 @@ target_sources(nf7_iface
     common/leak_detector.hh
     common/mutex.hh
     common/observer.hh
+    common/observer.hh
+    common/sql.hh
     common/task.hh
     common/task_context.hh
     common/value.hh
@@ -25,6 +27,7 @@ target_sources(nf7_iface
     data/interface.hh
     data/wrap.hh
     subsys/concurrency.hh
+    subsys/database.hh
     subsys/interface.hh
     subsys/logger.hh
     subsys/parallelism.hh
@@ -49,6 +52,7 @@ target_sources(nf7_iface_test
     common/task_test.hh
     common/value_test.cc
     subsys/logger_test.hh
+    env_test.hh
     lambda_test.cc
     lambda_test.hh
 )

iface/common/future.hh

@@ -10,6 +10,7 @@
 #include <vector>
 
 #include "iface/common/exception.hh"
+#include "iface/common/task_context.hh"
 
 namespace nf7 {
 
@@ -112,9 +113,9 @@ class Future final {
   };
 
   Future() = delete;
-  explicit Future(T&& v) : internal_(Internal(std::move(v))) {
+  Future(T&& v) : internal_(Internal(std::move(v))) {
   }
-  explicit Future(std::exception_ptr e) : internal_(Internal(e)) {
+  Future(std::exception_ptr e) : internal_(Internal(e)) {
   }
 
   Future(const Future&) = default;
@@ -128,7 +129,7 @@ class Future final {
   }
   template <typename V>
   Future<T>& Attach(const std::shared_ptr<V>& ptr) {
-    return Listen([ptr = std::move(ptr)](auto&) {});
+    return Listen([ptr](auto&) {});
   }
   Future<T>& Then(std::function<void(const T&)>&& f) {
     Listen([f = std::move(f)](auto& fu) noexcept {
@@ -257,6 +258,11 @@ class Future<T>::Completer final {
     return *this;
   }
 
+ public:
+  template <typename V>
+  void Attach(const std::shared_ptr<V>& ptr) {
+    internal_->Listen([ptr](auto&) {});
+  }
   void Complete(T&& v) noexcept {
     assert(nullptr != internal_);
     internal_->Complete(std::move(v));
@@ -273,7 +279,23 @@ class Future<T>::Completer final {
       Throw();
     }
   }
+  void RunAsync(const std::shared_ptr<AsyncTaskQueue>& aq,
+                const std::shared_ptr<SyncTaskQueue>&  sq,
+               std::function<T(AsyncTaskContext&)>&& f) noexcept {
+    assert(nullptr != internal_);
+    aq->Exec([*this, sq, f = std::move(f)](auto& ctx) mutable {
+      try {
+        sq->Exec([*this, ret = f(ctx)](auto&) mutable {
+          Complete(std::move(ret));
+        });
+      } catch (...) {
+        const auto eptr = std::current_exception();
+        sq->Exec([*this, eptr](auto&) mutable { Throw(eptr); });
+      }
+    });
+  }
 
+ public:
   Future<T> future() const noexcept {
     assert(nullptr != internal_);
     return {internal_};

iface/common/future_test.cc

@@ -1,6 +1,7 @@
 // No copyright
 #include "iface/common/future.hh"
 
+#include <gmock/gmock.h>
 #include <gtest/gtest.h>
 
 #include <cstdint>
@@ -11,6 +12,8 @@
 
 #include "iface/common/exception.hh"
 
+#include "iface/common/task_test.hh"
+
 
 using namespace std::literals;
 
@@ -335,6 +338,89 @@ TEST(FutureCompleter, CompleteAfterMove) {
   EXPECT_TRUE(fut->done());
 }
 
+TEST(FutureCompleter, RunWithComplete) {
+  nf7::Future<int32_t>::Completer sut;
+  sut.Run([]() { return int32_t {555}; });
+  EXPECT_TRUE(sut.future().done());
+}
+TEST(FutureCompleter, RunWithThrow) {
+  nf7::Future<int32_t>::Completer sut;
+  sut.Run([]() -> int32_t { throw nf7::Exception {"helloworld"}; });
+  EXPECT_TRUE(sut.future().error());
+}
+
+TEST(FutureCompleter, RunAsyncWithComplete) {
+  nf7::Future<int32_t>::Completer sut;
+  const auto fu = sut.future();
+
+  const auto aq_mock =
+      std::make_shared<nf7::test::TaskQueueMock<nf7::AsyncTask>>();
+  const auto sq_mock =
+      std::make_shared<nf7::test::TaskQueueMock<nf7::SyncTask>>();
+
+  auto step = uint32_t {0};
+  EXPECT_CALL(*aq_mock, Push)
+      .WillOnce([&](auto&& task) {
+        ++step;
+        EXPECT_EQ(step, 1);
+
+        nf7::AsyncTaskContext ctx;
+        task(ctx);
+
+        ++step;
+        EXPECT_EQ(step, 3);
+      });
+  EXPECT_CALL(*sq_mock, Push)
+      .WillOnce([&](auto&& task) {
+        ++step;
+        EXPECT_EQ(step, 2);
+
+        nf7::SyncTaskContext ctx;
+        EXPECT_TRUE(fu.yet());
+        task(ctx);
+        EXPECT_TRUE(fu.done());
+      });
+
+  sut.RunAsync(aq_mock, sq_mock, [](auto&) { return int32_t {777}; });
+}
+
+TEST(FutureCompleter, RunAsyncWithThrow) {
+  nf7::Future<int32_t>::Completer sut;
+  const auto fu = sut.future();
+
+  const auto aq_mock =
+      std::make_shared<nf7::test::TaskQueueMock<nf7::AsyncTask>>();
+  const auto sq_mock =
+      std::make_shared<nf7::test::TaskQueueMock<nf7::SyncTask>>();
+
+  auto step = uint32_t {0};
+  EXPECT_CALL(*aq_mock, Push)
+      .WillOnce([&](auto&& task) {
+        ++step;
+        EXPECT_EQ(step, 1);
+
+        nf7::AsyncTaskContext ctx;
+        task(ctx);
+
+        ++step;
+        EXPECT_EQ(step, 3);
+      });
+  EXPECT_CALL(*sq_mock, Push)
+      .WillOnce([&](auto&& task) {
+        ++step;
+        EXPECT_EQ(step, 2);
+
+        nf7::SyncTaskContext ctx;
+        EXPECT_TRUE(fu.yet());
+        task(ctx);
+        EXPECT_TRUE(fu.error());
+      });
+
+  sut.RunAsync(aq_mock, sq_mock,
+               [](auto&) -> int32_t { throw nf7::Exception {"helloworld"}; });
+}
+
+
 #if !defined(NDEBUG)
 TEST(Future, DeathByListenInCallback) {
   nf7::Future<int32_t> sut {int32_t{777}};

iface/common/mutex.cc

@@ -72,7 +72,7 @@ try {
   case kInclusive:
     if (last_inclusive_) {
       if (pends_.empty() && cur) {
-        return Future<SharedToken> {std::move(cur)};
+        return cur;
       } else if (!pends_.empty()) {
         return pends_.back().future();
       }
@@ -87,11 +87,9 @@ try {
     pends_.emplace_back();
     return pends_.back().future();
   }
-  return Future<SharedToken> {MakeToken()};
+  return MakeToken();
 } catch (const std::bad_alloc&) {
-  return Future<SharedToken> {
+  return MemoryException::MakePtr("failed to queue lock request");
-    MemoryException::MakePtr("failed to queue lock request"),
-  };
 }
 
 Mutex::SharedToken Mutex::Impl::TryLock(Mode mode)

iface/common/mutex.hh

@@ -2,8 +2,10 @@
 #pragma once
 
 #include <memory>
+#include <utility>
 
 #include "iface/common/future.hh"
+#include "iface/common/task_context.hh"
 
 
 namespace nf7 {
@@ -32,6 +34,30 @@ class Mutex final {
   Future<SharedToken> LockEx() noexcept;
   SharedToken TryLockEx();
 
+ public:
+  template <typename F,
+            typename R = std::invoke_result_t<F, const SharedToken&>>
+  Future<R> RunAsync(const std::shared_ptr<AsyncTaskQueue>& aq,
+                     const std::shared_ptr<SyncTaskQueue>&  sq,
+                     F&& f,
+                     bool ex = false) noexcept {
+    typename Future<R>::Completer comp;
+    (ex? LockEx(): Lock())
+        .Then([aq, sq, f = std::move(f), comp](auto& k) mutable {
+          comp.Attach(k);
+          comp.RunAsync(aq, sq, [f = std::move(f), k](auto&) mutable {
+            return f(k);
+          });
+        })
+        .Catch([comp](auto& e) mutable {
+          comp.Throw(std::make_exception_ptr(e));
+        });
+    return comp.future();
+  }
+  auto RunAsyncEx(const auto& aq, const auto& sq, auto&& f) noexcept {
+    return RunAsync(aq, sq, std::move(f), true);
+  }
+
  private:
   std::shared_ptr<Impl> impl_;
 };

iface/common/mutex_test.cc

@@ -1,6 +1,7 @@
 // No copyright
 #include "iface/common/mutex.hh"
 
+#include <gmock/gmock.h>
 #include <gtest/gtest.h>
 
 #include <atomic>
@@ -9,6 +10,10 @@
 #include <thread>
 #include <vector>
 
+#include "iface/common/exception.hh"
+
+#include "iface/common/task_test.hh"
+
 
 using namespace std::literals;
 
@@ -114,3 +119,63 @@ TEST(Mutex, LockAbort) {
   mtx = std::nullopt;
   EXPECT_TRUE(fu.error());
 }
+
+TEST(Mutex, RunAsyncWithComplete) {
+  nf7::Mutex mtx;
+
+  const auto aq_mock =
+      std::make_shared<nf7::test::TaskQueueMock<nf7::AsyncTask>>();
+  const auto sq_mock =
+      std::make_shared<nf7::test::TaskQueueMock<nf7::SyncTask>>();
+
+  ON_CALL(*aq_mock, Push)
+      .WillByDefault([&](auto&& task) {
+        nf7::AsyncTaskContext ctx;
+        task(ctx);
+      });
+  ON_CALL(*sq_mock, Push)
+      .WillByDefault([&](auto&& task) {
+        nf7::SyncTaskContext ctx;
+        task(ctx);
+      });
+
+  auto fu = mtx.RunAsync(aq_mock, sq_mock, [](auto&) { return int32_t {777}; });
+  EXPECT_TRUE(fu.done());
+}
+TEST(Mutex, RunAsyncWithError) {
+  nf7::Mutex mtx;
+
+  const auto aq_mock =
+      std::make_shared<nf7::test::TaskQueueMock<nf7::AsyncTask>>();
+  const auto sq_mock =
+      std::make_shared<nf7::test::TaskQueueMock<nf7::SyncTask>>();
+
+  ON_CALL(*aq_mock, Push)
+      .WillByDefault([&](auto&& task) {
+        nf7::AsyncTaskContext ctx;
+        task(ctx);
+      });
+  ON_CALL(*sq_mock, Push)
+      .WillByDefault([&](auto&& task) {
+        nf7::SyncTaskContext ctx;
+        task(ctx);
+      });
+
+  auto fu = mtx.RunAsync(aq_mock, sq_mock, [](auto&) -> int32_t {
+    throw nf7::Exception {"helloworld"};
+  });
+  EXPECT_TRUE(fu.error());
+}
+TEST(Mutex, RunAsyncWithAbort) {
+  std::optional<nf7::Mutex> mtx;
+  mtx.emplace();
+
+  const auto aq_mock =
+      std::make_shared<nf7::test::TaskQueueMock<nf7::AsyncTask>>();
+  const auto sq_mock =
+      std::make_shared<nf7::test::TaskQueueMock<nf7::SyncTask>>();
+
+  auto fu = mtx->RunAsync(aq_mock, sq_mock, [](auto&) { return 0; });
+  mtx = std::nullopt;
+  EXPECT_TRUE(fu.error());
+}

iface/common/sql.hh

@@ -0,0 +1,63 @@
+// No copyright
+#pragma once
+
+#include <cstdint>
+#include <functional>
+#include <string>
+#include <variant>
+#include <vector>
+
+#include "iface/common/future.hh"
+#include "iface/common/void.hh"
+
+
+namespace nf7 {
+
+class Sql {
+ public:
+  class Command;
+
+ public:
+  struct Null final { };
+  using Value = std::variant<Null, int64_t, double, std::string>;
+
+  enum Result {
+    kRow,
+    kDone,
+  };
+
+ public:
+  Sql() = default;
+  virtual ~Sql() = default;
+
+  Sql(const Sql&) = delete;
+  Sql(Sql&&) = delete;
+  Sql& operator=(const Sql&) = delete;
+  Sql& operator=(Sql&&) = delete;
+
+ public:
+  virtual void Bind(uint64_t idx, const Value&) = 0;
+  virtual Value Fetch(uint64_t idx) const = 0;
+
+  virtual void Reset() = 0;
+  virtual Result Exec() = 0;
+};
+
+class Sql::Command {
+ public:
+  using Handler = std::function<void(Sql&)>;
+
+ public:
+  Command() = default;
+  virtual ~Command() = default;
+
+  Command(const Command&) = delete;
+  Command(Command&&) = delete;
+  Command& operator=(const Command&) = delete;
+  Command& operator=(Command&&) = delete;
+
+ public:
+  virtual Future<Void> Run(Handler&&) noexcept = 0;
+};
+
+}  // namespace nf7

iface/common/task.hh

@@ -19,7 +19,6 @@
 #include <vector>
 
 #include "iface/common/exception.hh"
-#include "iface/common/future.hh"
 
 namespace nf7 {
 
@@ -150,27 +149,6 @@ class TaskQueue : public std::enable_shared_from_this<TaskQueue<T>> {
     };
   }
 
-  // THREAD SAFE
-  template <typename R>
-  Future<R> ExecAnd(
-      std::function<R(Param)>&& f,
-      std::source_location loc = std::source_location::current()) noexcept {
-    return ExecAnd({}, std::move(f));
-  }
-
-  // THREAD SAFE
-  template <typename R>
-  Future<R> ExecAnd(
-      Future<R>::Completer&& cmp,
-      std::function<R(Param)>&& f,
-      std::source_location loc = std::source_location::current()) noexcept {
-    Future<R> future {cmp};
-    Push(Item { [f = std::move(f), cmp = std::move(cmp)](Param) mutable {
-      cmp.Exec(f);
-    }, loc});
-    return future;
-  }
-
   // THREAD SAFE
   void Exec(
       std::function<void(Param)>&& f,
@@ -202,7 +180,6 @@ class WrappedTaskQueue : public I {
 
   using Inside::Wrap;
   using Inside::Exec;
-  using Inside::ExecAnd;
 
  private:
   std::shared_ptr<Inside> q_;

iface/common/task_test.cc

@@ -128,7 +128,6 @@ TEST(WrappedTaskQueue, Push) {
 
   // ensure all templates legal
   (std::void_t<decltype(sut.Wrap([](auto){}))>) 0;
-  (std::void_t<decltype(sut.ExecAnd<uint32_t>([](auto){ return 0; }))>) 0;
   (std::void_t<decltype(sut.Exec([](auto){}))>) 0;
 }
 

iface/env_test.hh

@@ -0,0 +1,177 @@
+// No copyright
+#pragma once
+#include "iface/env.hh"
+
+#include <gtest/gtest.h>
+
+#include <atomic>
+#include <chrono>
+#include <cstdlib>
+#include <iostream>
+#include <memory>
+#include <thread>
+#include <typeindex>
+#include <utility>
+
+#include "iface/common/exception.hh"
+#include "iface/common/task.hh"
+#include "iface/subsys/concurrency.hh"
+#include "iface/subsys/parallelism.hh"
+
+
+namespace nf7::test {
+
+class EnvFixture : public ::testing::Test {
+ public:
+  EnvFixture() = delete;
+  explicit EnvFixture(SimpleEnv::FactoryMap&& fmap) noexcept
+      : fmap_(std::move(fmap)) { }
+
+ protected:
+  template <typename I>
+  void Install(const std::shared_ptr<I>& o) {
+    fmap_.emplace(typeid(I), [o](auto&) { return o; });
+  }
+
+ protected:
+  void SetUp() override {
+    env_.emplace(std::move(fmap_));
+  }
+  void TearDown() override {
+    env_ = std::nullopt;
+  }
+
+ protected:
+  Env& env() noexcept { return *env_; }
+
+ private:
+  SimpleEnv::FactoryMap fmap_;
+  std::optional<SimpleEnv> env_;
+};
+
+class EnvFixtureWithTasking : public EnvFixture {
+ private:
+  class AsyncDriver final {
+   public:
+    explicit AsyncDriver(EnvFixtureWithTasking& parent) noexcept
+        : parent_(parent) { }
+
+    void BeginBusy() noexcept { busy_ = true; }
+    void EndBusy() noexcept {
+      busy_ = false;
+      busy_.notify_all();
+    }
+    void Drive(AsyncTask&& task) noexcept {
+      try {
+        task(param_);
+      } catch (const Exception& e) {
+        std::cerr
+            << "unexpected exception while async task execution:\n"
+            << e << std::endl;
+        std::abort();
+      }
+    }
+    AsyncTask::Time tick() const noexcept {
+      const auto now = std::chrono::system_clock::now();
+      return std::chrono::time_point_cast<AsyncTask::Time::duration>(now);
+    }
+    bool nextIdleInterruption() const noexcept { return !parent_.alive_; }
+    bool nextTaskInterruption() const noexcept { return false; }
+
+    void Wait() { busy_.wait(true); }
+
+   private:
+    EnvFixtureWithTasking& parent_;
+    AsyncTaskContext param_;
+
+    std::atomic<bool> busy_ = false;
+  };
+
+ private:
+  class SyncDriver final {
+   public:
+    explicit SyncDriver(EnvFixtureWithTasking& parent) noexcept
+        : parent_(parent) { }
+
+    void BeginBusy() noexcept { }
+    void EndBusy() noexcept { }
+    void Drive(SyncTask&& task) noexcept {
+      try {
+        task(param_);
+      } catch (const Exception& e) {
+        std::cerr
+            << "unexpected exception while sync task execution:\n"
+            << e << std::endl;
+        std::abort();
+      }
+    }
+    SyncTask::Time tick() const noexcept {
+      const auto now = std::chrono::system_clock::now();
+      return std::chrono::time_point_cast<SyncTask::Time::duration>(now);
+    }
+    bool nextIdleInterruption() const noexcept {
+      return 0 == parent_.sq_->size();
+    }
+    bool nextTaskInterruption() const noexcept { return false; }
+
+   private:
+    EnvFixtureWithTasking& parent_;
+    SyncTaskContext param_;
+  };
+
+ public:
+  explicit EnvFixtureWithTasking(SimpleEnv::FactoryMap&& fmap)
+      : EnvFixture(std::move(fmap)),
+        sq_(std::make_shared<SimpleTaskQueue<SyncTask>>()),
+        aq_(std::make_shared<SimpleTaskQueue<AsyncTask>>()),
+        ad_(*this) {
+    Install<subsys::Concurrency>(
+        std::make_shared<WrappedTaskQueue<subsys::Concurrency>>(sq_));
+    Install<subsys::Parallelism>(
+        std::make_shared<WrappedTaskQueue<subsys::Parallelism>>(aq_));
+  }
+
+ protected:
+  void SetUp() override {
+    EnvFixture::SetUp();
+    thread_ = std::thread {[this]() { aq_->Drive(ad_); }};
+  }
+  void TearDown() override {
+    ConsumeTasks();
+    EnvFixture::TearDown();
+
+    WaitAsyncTasks(std::chrono::seconds(3));
+    alive_ = false;
+    aq_->Wake();
+    thread_.join();
+
+    sq_ = nullptr;
+    aq_ = nullptr;
+  }
+
+ protected:
+  void ConsumeTasks() noexcept {
+    for (uint32_t i = 0; i < 16; ++i) {
+      SyncDriver sync_driver {*this};
+      sq_->Drive(sync_driver);
+      WaitAsyncTasks(std::chrono::seconds(1));
+    }
+  }
+  void WaitAsyncTasks(auto dur) noexcept {
+    if (!aq_->WaitForEmpty(dur)) {
+      std::cerr << "timeout while waiting for task execution" << std::endl;
+      std::abort();
+    }
+    ad_.Wait();
+  }
+
+ private:
+  std::shared_ptr<SimpleTaskQueue<SyncTask>>  sq_;
+  std::shared_ptr<SimpleTaskQueue<AsyncTask>> aq_;
+
+  std::thread thread_;
+  std::atomic<bool> alive_ = true;
+  AsyncDriver ad_;
+};
+
+}  // namespace nf7::test

iface/subsys/concurrency.hh

@@ -17,7 +17,6 @@ class Concurrency :
   using SyncTaskQueue::Push;
   using SyncTaskQueue::Wrap;
   using SyncTaskQueue::Exec;
-  using SyncTaskQueue::ExecAnd;
 
  protected:
   using SyncTaskQueue::shared_from_this;

iface/subsys/database.hh

@@ -0,0 +1,44 @@
+// No copyright
+#pragma once
+
+#include <functional>
+#include <memory>
+#include <string_view>
+#include <utility>
+
+#include "iface/common/future.hh"
+#include "iface/common/observer.hh"
+#include "iface/common/sql.hh"
+#include "iface/common/void.hh"
+#include "iface/subsys/interface.hh"
+
+
+namespace nf7::subsys {
+
+class Database : public Interface, public Observer<Void>::Target {
+ public:
+  using ColumnHandler = std::function<bool(const Sql&)>;
+
+ public:
+  using Interface::Interface;
+
+ public:
+  virtual Future<std::shared_ptr<Sql::Command>> Compile(
+      std::string_view) noexcept = 0;
+
+  virtual Future<Void> Exec(
+      std::string_view cmd, ColumnHandler&& f = {}) noexcept {
+    return Compile(cmd)
+        .ThenAnd([f = std::move(f)](auto& x) mutable {
+          return !f?
+            Future<Void> {Void {}}:
+            x->Run([f = std::move(f)](auto& x) mutable {
+              while (Sql::kRow == x.Exec()) {
+                f(x);
+              }
+            });
+        });
+  }
+};
+
+}  // namespace nf7::subsys

iface/subsys/parallelism.hh

@@ -17,7 +17,6 @@ class Parallelism :
   using AsyncTaskQueue::Push;
   using AsyncTaskQueue::Wrap;
   using AsyncTaskQueue::Exec;
-  using AsyncTaskQueue::ExecAnd;
 
  protected:
   using AsyncTaskQueue::shared_from_this;

thirdparty/CMakeLists.txt

@@ -20,6 +20,16 @@ FetchContent_Declare(
 set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
 FetchContent_MakeAvailable(googletest)
 
+# ---- SQLite (public domain)
+FetchContent_Declare(
+  sqlite
+  URL      https://www.sqlite.org/2023/sqlite-amalgamation-3430000.zip
+  URL_HASH SHA256=bb5849ae4d7129c09d20596379a0b3f7b1ac59cf9998eba5ef283ea9b6c000a5
+  DOWNLOAD_EXTRACT_TIMESTAMP ON
+)
+FetchContent_Populate(sqlite)
+include(sqlite.cmake)
+
 # ---- uvw (MIT)
 FetchContent_Declare(
   uvw

thirdparty/sqlite.cmake

@@ -0,0 +1,8 @@
+add_library(sqlite)
+target_sources(sqlite
+  PRIVATE
+    ${sqlite_SOURCE_DIR}/sqlite3.c
+  PUBLIC
+    ${sqlite_SOURCE_DIR}/sqlite3.h
+    ${sqlite_SOURCE_DIR}/sqlite3ext.h
+)