feat: adds callbacks for modes

Now callbacks for each mode can be used:
from - triggered when switching from a mode
to - triggered when switching to a mode
on - triggered when switching from or to a mode

lua/reactive/commands.lua

@@ -59,7 +59,7 @@ function M:init()
 
         Snapshot:set_modes(from, to)
 
-        Highlight:apply(Snapshot:gen())
+        Highlight:apply(Snapshot:gen { callbacks = true })
       end,
     })
 
@@ -77,7 +77,7 @@ function M:init()
       group = group,
       desc = 'Reactive: applies inactive window highlights',
       callback = function()
-        Highlight:apply(Snapshot:gen(true))
+        Highlight:apply(Snapshot:gen { inactive_win = true })
       end,
     })
   end

lua/reactive/snapshot.lua

@@ -31,19 +31,23 @@ function M:set_opfunc(opfunc)
   self.current_opfunc = opfunc
 end
 
----@param inactive? boolean
+---@param opts? { inactive_win?: boolean, callbacks?: boolean }
 ---@return table<any>
-function M:gen(inactive)
+function M:gen(opts)
   local State = require 'reactive.state'
 
   self.snapshot = { winhl = {}, hl = {} }
 
   -- if we're leaving a window, then we just color that window with `inactive` colors, if present
-  if inactive then
+  if opts and opts.inactive_win then
     State:iterate_presets(function(preset)
       local constraints = {}
 
-      if preset.static and not vim.tbl_isempty(preset.static) and not self:process_skip(preset.skip, constraints) then
+      if
+        preset.static
+        and not vim.tbl_isempty(preset.static)
+        and not self:process_constraints(preset.skip, constraints)
+      then
         self:form_snapshot(preset.name, {
           winhl = preset.static.winhl and preset.static.winhl.inactive,
           hl = preset.static.hl,
@@ -94,7 +98,7 @@ function M:gen(inactive)
         end
 
         -- we check `skip` method/table only on a first iteration
-        if self:process_skip(preset.skip, scope[preset.name].constraints) then
+        if self:process_constraints(preset.skip, scope[preset.name].constraints) then
           dropped_presets[preset.name] = true
 
           return
@@ -159,14 +163,44 @@ function M:gen(inactive)
     end)
   end)
 
-  if has_static then
+  if has_static or (opts and opts.callbacks) then
     State:iterate_presets(function(preset)
       if preset.static and not vim.tbl_isempty(preset.static) then
         self:form_snapshot(preset.name, {
           winhl = preset.static.winhl and preset.static.winhl.active,
           hl = preset.static.hl,
         }, '@static.active', scope[preset.name].constraints)
       end
+
+      if
+        not opts
+        or not opts.callbacks
+        or not preset.modes
+        or scope[preset.name].constraints.callbacks
+        or dropped_presets[preset.name]
+      then
+        return
+      end
+
+      if preset.modes[self.from] then
+        if preset.modes[self.from].from then
+          preset.modes[self.from].from(self.from, self.to)
+        end
+
+        if preset.modes[self.from].on then
+          preset.modes[self.from].on(self.from, self.to)
+        end
+      end
+
+      if preset.modes[self.to] then
+        if preset.modes[self.to].to then
+          preset.modes[self.to].to(self.from, self.to)
+        end
+
+        if preset.modes[self.to].on then
+          preset.modes[self.to].on(self.from, self.to)
+        end
+      end
     end)
   end
 
@@ -262,7 +296,7 @@ end
 ---@param skip table | fun(): boolean
 ---@param constraints? table<string, boolean>
 ---@return boolean is_dropped
-function M:process_skip(skip, constraints)
+function M:process_constraints(skip, constraints)
   if type(skip) == 'function' then
     return skip()
   end
@@ -273,7 +307,7 @@ function M:process_skip(skip, constraints)
 
   local escaped = true
 
-  for _, field in ipairs(shape_fields) do
+  for _, field in ipairs { 'winhl', 'hl', 'callbacks' } do
     if skip[field] and skip[field]() then
       if constraints then
         constraints[field] = true

lua/reactive/state.lua

@@ -1,7 +1,7 @@
 local Preset = require 'reactive.preset'
 local Util = require 'reactive.util'
 
----@class TriggerConstraints<V>: { winhl?: V, hl?: V }
+---@class TriggerConstraints<V>: { winhl?: V, hl?: V, callbacks?: V }
 
 ---@class Reactive.TriggerConfig
 ---@field winhl? table<string, string | table<string, any>>
@@ -10,6 +10,9 @@ local Util = require 'reactive.util'
 ---@field opfuncs? table<string, Reactive.TriggerConfig>
 ---@field exact? boolean | TriggerConstraints<boolean>
 ---@field frozen? boolean | TriggerConstraints<boolean>
+---@field from? fun(from: string, to: string)
+---@field to? fun(from: string, to: string)
+---@field on? fun(from: string, to: string)
 
 ---@class Reactive.Preset
 ---@field name string