1 files changed, 257 insertions, 0 deletions

diff --git a/server/src/sqlite3.cppm b/server/src/sqlite3.cppm
new file mode 100644
index 0000000..f226c6b
--- /dev/null
+++ b/server/src/sqlite3.cppm
@@ -0,0 +1,257 @@
+module;
+
+#include <sqlite3.h>
+
+export module routemon:sqlite3;
+
+import std;
+import :util;
+
+namespace routemon::sqlite3 {
+
+  class mutex_guard {
+    explicit mutex_guard(::sqlite3_mutex* mut) noexcept : mut_{mut} {
+      ::sqlite3_mutex_enter(mut_);
+    }
+
+    friend auto do_guarded(::sqlite3_mutex* mut, std::invocable<mutex_guard const&> auto f) -> decltype(f(std::declval<mutex_guard const&>()));
+
+  public:
+    mutex_guard(mutex_guard const&) = delete;
+    ~mutex_guard() {
+      ::sqlite3_mutex_leave(mut_);
+    }
+
+  private:
+    ::sqlite3_mutex* mut_;
+  };
+
+  auto do_guarded(::sqlite3_mutex* mut, std::invocable<mutex_guard const&> auto f) -> decltype(f(std::declval<mutex_guard const&>())) {
+    return f(mutex_guard{mut});
+  }
+
+  auto do_guarded(::sqlite3* dbc, std::invocable<mutex_guard const&> auto f) -> decltype(f(std::declval<mutex_guard const&>())) {
+    return do_guarded(::sqlite3_db_mutex(dbc), f);
+  }
+
+  class error : public std::exception {
+    int code_;
+    std::string message_;
+
+  public:
+    explicit error(mutex_guard const&, int code, ::sqlite3* dbc)
+      : code_{code}, message_{::sqlite3_errmsg(dbc)}
+    {}
+
+    explicit error(int code)
+      : code_{code}, message_{::sqlite3_errstr(code)}
+    {}
+
+    [[nodiscard]] auto what() const noexcept -> char const* override {
+      return message_.c_str();
+    }
+
+    [[nodiscard]] auto code() const noexcept -> int {
+      return code_;
+    }
+  };
+
+  template<class T, template<class U> concept C>
+  concept optional_of = requires {
+    typename T::value_type;
+    requires std::same_as<T, std::optional<typename T::value_type>>;
+    requires C<typename T::value_type>;
+  };
+
+  template<class T>
+  concept scannable_prim =
+    std::same_as<T, std::string> ||
+    std::same_as<T, double> ||
+    std::same_as<T, std::int64_t>;
+
+  template<class T>
+  concept scannable = scannable_prim<T> || optional_of<T, scannable_prim>;
+
+  class statement {
+    ::sqlite3_stmt* stmt_;
+
+  public:
+    explicit statement(::sqlite3_stmt* stmt) : stmt_{stmt} {}
+    statement(statement const&) = delete;
+    statement(statement&& s) noexcept {
+      stmt_ = s.stmt_;
+      s.stmt_ = nullptr;
+    }
+    ~statement() {
+      ::sqlite3_finalize(stmt_);
+    }
+    auto get() -> ::sqlite3_stmt* {
+      return stmt_;
+    }
+  };
+
+  class row_reader {
+    statement stmt_;
+
+    explicit row_reader(statement stmt) : stmt_{std::move(stmt)} {}
+
+    friend class connection;
+
+    void scan(int col, std::string& s) {
+      if (::sqlite3_column_type(stmt_.get(), col) != SQLITE_TEXT)
+        throw std::invalid_argument{"invalid type for scan"};
+      unsigned char const* chs = ::sqlite3_column_text(stmt_.get(), col);
+      auto size = util::size_from_int(::sqlite3_column_bytes(stmt_.get(), col));
+      if (!size.has_value())
+        throw std::logic_error{"unexpected negative amount of bytes in column"};
+      s = std::string{reinterpret_cast<char const*>(chs), *size};
+    }
+
+    void scan(int col, double& v) {
+      if (::sqlite3_column_type(stmt_.get(), col) != SQLITE_FLOAT)
+        throw std::invalid_argument{"invalid type for scan"};
+      v = ::sqlite3_column_double(stmt_.get(), col);
+    }
+
+    void scan(int col, std::int64_t& v) {
+      if (::sqlite3_column_type(stmt_.get(), col) != SQLITE_INTEGER)
+        throw std::invalid_argument{"invalid type for scan"};
+      v = ::sqlite3_column_int64(stmt_.get(), col);
+    }
+
+    void scan(int col, optional_of<scannable> auto& v) {
+      if (::sqlite3_column_type(stmt_.get(), col) == SQLITE_NULL) {
+        v.reset();
+      } else {
+        typename std::remove_cvref_t<decltype(v)>::value_type tmp;
+        scan(col, tmp);
+        v = std::move(tmp);
+      }
+    }
+
+  public:
+    auto next() -> bool {
+      ::sqlite3* dbc = ::sqlite3_db_handle(stmt_.get());
+      return do_guarded(dbc, [&](auto const& guard) -> bool {
+        auto const s = ::sqlite3_step(stmt_.get());
+        if (s == SQLITE_ROW)
+          return true;
+        if (s == SQLITE_DONE)
+          return false;
+        throw error{guard, s, dbc};
+      });
+    }
+
+    auto scan(scannable auto&... args) -> void {
+      auto const ncols = util::size_from_int(::sqlite3_data_count(stmt_.get()));
+      if (!ncols.has_value())
+        throw std::logic_error{"got unexpected negative amount of columns"};
+      if (sizeof...(args) > *ncols)
+        throw std::invalid_argument{"more scanning arguments provided than columns in result set"};
+      auto col = 0; (..., scan(col++, args));
+    }
+
+    auto scan_single(scannable auto&... args) -> void {
+      if (!next())
+        throw std::logic_error{"no row in result set"};
+      scan(args...);
+      if (next()) {
+        throw std::logic_error{"more than one row in result set"};
+      }
+    }
+  };
+
+  class binder {
+    statement& stmt_;
+
+    explicit binder(statement& stmt) : stmt_{stmt} {}
+
+    friend class connection;
+
+  public:
+    auto text(std::string const& param_name, std::string_view str) -> void {
+      int const i = ::sqlite3_bind_parameter_index(stmt_.get(), param_name.c_str());
+      if (i == 0)
+        throw std::invalid_argument{std::format("bind: no parameter with name {} found", param_name)};
+      auto str_size = util::int_from_size(str.size());
+      if (!str_size.has_value())
+        throw std::invalid_argument{"bind: provided text is too long"};
+      if (auto s = ::sqlite3_bind_text(stmt_.get(), i, str.data(), *str_size, SQLITE_TRANSIENT); s != SQLITE_OK) {
+        throw error{s};
+      }
+    }
+
+    static auto noop(binder&) -> void {}
+  };
+
+  export class connection {
+    ::sqlite3* dbc_;
+    ::sqlite3_mutex* mut_;
+
+    explicit connection(::sqlite3* dbc) : dbc_{dbc}, mut_{::sqlite3_db_mutex(dbc)} {}
+
+    friend auto open(std::string const& filename) -> connection;
+
+  public:
+    connection(connection const&) = delete;
+    connection(connection&& c) noexcept {
+      dbc_ = c.dbc_;
+      mut_ = c.mut_;
+      c.dbc_ = nullptr;
+      c.mut_ = nullptr;
+    }
+
+    [[nodiscard]] auto query(std::string const& sql, std::function<void(binder&)> const& bf = binder::noop) -> row_reader {
+      ::sqlite3_stmt* pstmt = nullptr;
+      char const* sql_tail = nullptr;
+      auto sql_size = util::int_from_size(sql.size());
+      if (!sql_size.has_value() || *sql_size >= std::numeric_limits<int>::max() - 1)
+        throw std::invalid_argument{"provided input text too large"};
+      do_guarded(mut_, [&](auto const& guard) -> void {
+        if (auto s = ::sqlite3_prepare_v2(dbc_, sql.data(), *sql_size + 1, &pstmt, &sql_tail); s != SQLITE_OK) {
+          if (pstmt != nullptr) {
+            // Use contract_assert when having a compiler with contracts available
+            ::sqlite3_finalize(pstmt);
+            throw std::logic_error{"expected stmt to be null after failed preparation"};
+          }
+          throw error{guard, s, dbc_};
+        }
+      });
+      if (!pstmt)
+        throw std::invalid_argument{"provided input text contains no SQL"};
+      auto stmt = statement{pstmt};
+      if (sql_tail && std::strlen(sql_tail) > 0)
+        throw std::invalid_argument{"provided input text contains more than one SQL statement"};
+      auto b = binder{stmt}; bf(b);
+      return row_reader{std::move(stmt)};
+    }
+
+    auto exec(std::string const& sql, std::function<void(binder&)> const& bf = binder::noop) -> void {
+      auto reader = query(sql, bf);
+      while (reader.next());
+    }
+
+    ~connection() {
+      std::ignore = ::sqlite3_close(std::exchange(dbc_, nullptr));
+    }
+  };
+
+  export auto open(std::string const& filename) -> connection {
+    ::sqlite3* dbc = nullptr;
+    auto s = ::sqlite3_open_v2(filename.c_str(), &dbc,
+                              SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE |
+                              SQLITE_OPEN_FULLMUTEX | SQLITE_OPEN_EXRESCODE,
+                              nullptr);
+    if (s != SQLITE_OK) {
+      if (dbc) {
+        do_guarded(dbc, [&](auto const& guard) -> void {
+          throw error{guard, s, dbc};
+        });
+      } else {
+        throw error{s};
+      }
+    }
+    return connection{dbc};
+  }
+
+} // namespace routemon::sqlite3