-- Lua-side of the sqlite module.
-- The connection methods execute/query/queryOne/lastInsertRowid/changes/close
-- are provided by Rust. This file adds the transaction helpers on top of the
-- same connection so users can write con:transaction(fn), con:begin(), etc.
--
-- Rust passes in `Connection`: the shared method table that every connection's
-- metatable indexes into (mlua hides the metatable itself from Lua).

return function(Connection)
    --- Begin a transaction.
    function Connection:begin()
        self:execute("BEGIN")
    end

    --- Commit the current transaction.
    function Connection:commit()
        self:execute("COMMIT")
    end

    --- Roll back the current transaction.
    function Connection:rollback()
        self:execute("ROLLBACK")
    end

    --- Run `fn` inside a transaction: commit on success, roll back and re-raise
    --- on error. The original error is re-raised unchanged (level 0), and fn's
    --- return values are passed through on success.
    function Connection:transaction(fn)
        if type(fn) ~= "function" then
            error("sqlite: transaction requires a function argument (got " .. type(fn) .. ")", 2)
        end
        self:begin()
        local results = table.pack(pcall(fn))
        if results[1] then
            self:commit()
            return table.unpack(results, 2, results.n)
        end
        -- On failure, roll back but never let a rollback error mask the original
        -- one (the connection may already be closed, or no transaction active).
        pcall(self.rollback, self)
        error(results[2], 0)
    end
end