fix: adds a preset name to a scope when caching highlight name and in…

…troduces restrictions to a preset name. Fixes #14

Now preset name should be validated through this regexp: [a-zA-Z0-9_-]
It had to be introduced before because it was initially planned to put a
preset name into a highlight group value.

lua/reactive/snapshot.lua

@@ -284,7 +284,10 @@ local merge_handlers = {
 ---@param scope string
 ---@param constraints TriggerConstraints
 function M:form_snapshot(preset_name, highlights, scope, constraints)
-  local opts = { scope = scope, preset_name = preset_name }
+  local opts = {
+    scope = string.format('@preset.%s.%s', preset_name, scope),
+    preset_name = preset_name,
+  }
 
   Util.each(merge_handlers, function(value)
     if not highlights[value] or constraints and constraints[value] then

lua/reactive/state.lua

@@ -70,12 +70,29 @@ end
 
 ---@param preset Reactive.Preset
 function M:add_preset(preset)
-  vim.validate { name = { preset.name, 'string' } }
+  vim.validate {
+    name = {
+      preset.name,
+      function(value)
+        if type(value) ~= 'string' then
+          return false, 'preset name has to be a string'
+        end
 
-  if preset.name:find ' ' then
-    vim.notify('reactive.nvim: whitespaces are not allowed in a preset name', vim.log.levels.ERROR)
-    return
-  end
+        local invalid_chars = value:match '[^a-zA-Z0-9_-]+'
+
+        if invalid_chars ~= nil then
+          return false,
+            [[You've used an invalid character(s) in a preset name.
+              Allowed: a-z A-Z 0-9 _ -
+              Whitespace is not allowed as well.
+              Your invalid characters:]] .. invalid_chars
+        end
+
+        return true
+      end,
+      'a valid string',
+    },
+  }
 
   preset = Preset:parse(preset)