3 files changed, 87 insertions, 0 deletions
diff --git a/lua/clever_f/capabilities.lua b/lua/clever_f/capabilities.lua
index 23da397..194de0b 100644
--- a/lua/clever_f/capabilities.lua
+++ b/lua/clever_f/capabilities.lua
@@ -11,6 +11,7 @@ M.read_methods = {
   macro_state = { "read_macro_state" },
   fold_state = { "read_fold_state" },
   time = { "read_time_ms" },
+  highlight_groups = { "read_highlight_group" },
 }
 
 M.effect_methods = {
diff --git a/lua/clever_f/feedback_service.lua b/lua/clever_f/feedback_service.lua
index 0b9c8cd..f7e1dd6 100644
--- a/lua/clever_f/feedback_service.lua
+++ b/lua/clever_f/feedback_service.lua
@@ -1,4 +1,11 @@
 local M = {}
+local FeedbackService = {}
+FeedbackService.__index = FeedbackService
+M.FeedbackService = FeedbackService
+
+M.DEFAULT_LABEL_GROUP = "CleverFDefaultLabel"
+
+local service_records = setmetatable({}, { __mode = "k" })
 
 local DEFAULT_LABEL_DEFINITION = {
   guifg = "red",
@@ -30,4 +37,66 @@ function M.default_label_definition()
   return copy(DEFAULT_LABEL_DEFINITION)
 end
 
+local function fail(message, level)
+  error(message, (level or 1) + 1)
+end
+
+local function normalize_options(options)
+  if type(options) ~= "table" then
+    fail("FeedbackService options must be a table", 3)
+  end
+  if options.host == nil then
+    return { host = options }
+  end
+  return options
+end
+
+local function require_host(host)
+  if type(host) ~= "table" or type(host.read_highlight_group) ~= "function" then
+    fail("FeedbackService host must provide highlight groups", 3)
+  end
+  return host
+end
+
+function FeedbackService.new(options)
+  if FeedbackService.is(options) then
+    return options
+  end
+  options = normalize_options(options)
+  local service = setmetatable({}, FeedbackService)
+  service_records[service] = {
+    host = require_host(options.host),
+  }
+  return service
+end
+
+function FeedbackService.is(value)
+  return type(value) == "table" and service_records[value] ~= nil
+end
+
+function FeedbackService:ensure_default_label()
+  local existing = service_records[self].host:read_highlight_group(
+    M.DEFAULT_LABEL_GROUP
+  )
+  if existing ~= nil then
+    return {
+      group = M.DEFAULT_LABEL_GROUP,
+      definition = existing,
+      source = "colorscheme",
+      applied = false,
+    }
+  end
+  return nil
+end
+
+function M.new(options)
+  return FeedbackService.new(options)
+end
+
+setmetatable(M, {
+  __call = function(_, options)
+    return FeedbackService.new(options)
+  end,
+})
+
 return M
diff --git a/lua/clever_f/testing/memory_host.lua b/lua/clever_f/testing/memory_host.lua
index 42dab71..459c9a8 100644
--- a/lua/clever_f/testing/memory_host.lua
+++ b/lua/clever_f/testing/memory_host.lua
@@ -163,6 +163,7 @@ function MemoryHost.new(options)
     _prompts = {},
     _redraws = {},
     _diagnostics = {},
+    _highlight_groups = copy(options.highlight_groups or {}),
     _highlights = {},
     _timers = {},
     _event_registrations = {},
@@ -646,6 +647,22 @@ function MemoryHost:diagnostics()
   return copy(self._diagnostics)
 end
 
+function MemoryHost:read_highlight_group(name)
+  if type(name) ~= "string" or name == "" then
+    error("highlight group name must be a nonempty string", 2)
+  end
+  local definition = self._highlight_groups[name]
+  self:_record("read_highlight_group", {
+    name = name,
+    defined = definition ~= nil,
+  })
+  return copy(definition)
+end
+
+function MemoryHost:highlight_groups()
+  return copy(self._highlight_groups)
+end
+
 function MemoryHost:create_highlight(specification)
   if type(specification) ~= "table" then
     error("highlight specification must be a table", 2)