From 4b8d3430c7fff8b869ec895dbffac748db72a237 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?louiz=E2=80=99?= <louiz@louiz.org>
Date: Fri, 27 Sep 2019 20:55:15 +0200
Subject: Add an AsyncResult type to iterate over the Select results

---
 src/database/async_result.hpp | 77 +++++++++++++++++++++++++++++++++++++++++++
 src/database/select_query.hpp | 10 ++++++
 tests/database.cpp            | 23 +++++++++++++
 3 files changed, 110 insertions(+)
 create mode 100644 src/database/async_result.hpp

diff --git a/src/database/async_result.hpp b/src/database/async_result.hpp
new file mode 100644
index 0000000..f4109c0
--- /dev/null
+++ b/src/database/async_result.hpp
@@ -0,0 +1,77 @@
+#include <database/row.hpp>
+
+template <typename... T>
+class AsyncResult
+{
+  std::unique_ptr<Statement> statement{};
+  std::string table_name;
+
+public:
+  AsyncResult(std::unique_ptr<Statement> s, const std::string& table_name):
+    statement{std::move(s)},
+    table_name{table_name}
+  {}
+
+  class iterator
+  {
+    using iterator_category = std::input_iterator_tag;
+    using value_type = Row<T...>;
+    using difference_type = std::ptrdiff_t;
+    using pointer = Row<T...>*;
+    using reference = Row<T...>&;
+
+    Row<T...> row{};
+    Statement* statement;
+    bool is_end;
+
+  public:
+    iterator(Statement* s, const std::string& table_name, bool end=false):
+      row{table_name},
+      statement{s},
+      is_end{end}
+    {}
+
+    reference operator*()
+    {
+      extract_row_values(this->row, *statement);
+      return this->row;
+    }
+
+    bool operator==(const iterator& o) const
+    {
+      if (this->is_end && o.is_end)
+        return true;
+      return false;
+    }
+    bool operator!=(const iterator& o) const
+    {
+      return !(*this == o);
+    }
+
+    iterator& operator++()
+    {
+      if (statement->step() != StepResult::Row)
+        this->is_end = true;
+      return *this;
+    }
+
+    iterator& operator++(int)
+    {
+      iterator old = *this;
+      if (statement->step() != StepResult::Row)
+        this->is_end = true;
+      return old;
+    }
+  };
+
+  iterator begin() const
+  {
+    iterator it{this->statement.get(), this->table_name};
+    ++it;
+    return it;
+  }
+  iterator end() const
+  {
+    return {this->statement.get(), this->table_name, true};
+  }
+};
diff --git a/src/database/select_query.hpp b/src/database/select_query.hpp
index e372f2e..1399417 100644
--- a/src/database/select_query.hpp
+++ b/src/database/select_query.hpp
@@ -8,6 +8,7 @@
 #include <database/query.hpp>
 #include <logger/logger.hpp>
 #include <database/row.hpp>
+#include <database/async_result.hpp>
 
 #include <utils/optional_bool.hpp>
 
@@ -131,6 +132,15 @@ struct SelectQuery: public Query
       return rows;
     }
 
+    AsyncResult<T...> execute_async(DatabaseEngine& db)
+    {
+      auto statement = db.prepare(this->body);
+      if (!statement)
+        return {{}, {}};
+      statement->bind(std::move(this->params));
+      return {std::move(statement), this->table_name};
+    }
+
     const std::string table_name;
 };
 
diff --git a/tests/database.cpp b/tests/database.cpp
index 070a460..aab10f4 100644
--- a/tests/database.cpp
+++ b/tests/database.cpp
@@ -8,6 +8,7 @@
 
 #include <database/database.hpp>
 #include <database/save.hpp>
+#include <database/select_query.hpp>
 
 #include <config/config.hpp>
 
@@ -165,6 +166,28 @@ TEST_CASE("Database")
       CHECK(after_connection_commands.size() == 2);
     }
 
+  SECTION("async_select")
+    {
+      constexpr auto db_size = 8;
+      CHECK(Database::count(Database::muc_log_lines) == 0);
+      auto uuid = Database::store_muc_message("owner", "#chan", "irc.example.com", std::chrono::system_clock::now(), "hello!", "louiz'");
+      CHECK(Database::count(Database::muc_log_lines) == 1);
+      CHECK(uuid.size() == 36);
+
+      for (int i = 1; i < db_size; ++i)
+        Database::store_muc_message("owner", "#chan", "irc.example.com", std::chrono::system_clock::now(), "hello "s + std::to_string(i) + "!"s, "louiz'");
+      CHECK(Database::count(Database::muc_log_lines) == db_size);
+
+      auto query = select(Database::muc_log_lines);
+      query.where() << Database::Owner{} << "=" << "owner"s;
+      auto async_result = query.execute_async(*Database::db);
+
+      int i = 0;
+      for (auto rows: async_result)
+        ++i;
+      CHECK(i == db_size);
+    }
+
   Database::close();
 }
 #endif
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