feat: listeners for list actions

one thing to consider is if we want to add filtering to the listeners by
list?  or should we move the listeners to the list?

lua/harpoon2/config.lua

@@ -1,4 +1,6 @@
-local utils = require("harpoon2.utils")
+local Listeners = require("harpoon2.listeners")
+local listeners = Listeners.listeners
+
 local M = {}
 
 ---@alias HarpoonListItem {value: any, context: any}
@@ -19,7 +21,6 @@ local M = {}
 ---@field width number
 ---@field height number
 
-
 ---notehunthoeunthoeunthoeunthoeunthoeunth
 ---@class HarpoonSettings
 ---@field save_on_toggle boolean defaults to true
@@ -31,7 +32,6 @@ local M = {}
 ---@field jump_to_file_location? boolean
 ---@field key? (fun(): string)
 
-
 ---@class HarpoonConfig
 ---@field default HarpoonPartialConfigItem
 ---@field settings HarpoonSettings

lua/harpoon2/init.lua

@@ -2,6 +2,7 @@ local Ui = require("harpoon2.ui")
 local Data = require("harpoon2.data")
 local Config = require("harpoon2.config")
 local List = require("harpoon2.list")
+local Listeners = require("harpoon2.listeners")
 
 -- setup
 -- read from a config file
@@ -14,6 +15,7 @@ local DEFAULT_LIST = "__harpoon_files"
 ---@class Harpoon
 ---@field config HarpoonConfig
 ---@field ui HarpoonUI
+---@field listeners HarpoonListeners
 ---@field data HarpoonData
 ---@field lists {[string]: {[string]: HarpoonList}}
 ---@field hooks_setup boolean
@@ -29,6 +31,7 @@ function Harpoon:new()
         config = config,
         data = Data.Data:new(),
         ui = Ui:new(config.settings),
+        listeners = Listeners.listeners,
         lists = {},
         hooks_setup = false,
     }, self)

lua/harpoon2/list.lua

@@ -1,3 +1,5 @@
+local Listeners = require("harpoon2.listeners")
+
 local function index_of(items, element, config)
     local equals = config and config.equals or function(a, b) return a == b end
     local index = -1
@@ -43,6 +45,7 @@ function HarpoonList:append(item)
 
     local index = index_of(self.items, item, self.config)
     if index == -1 then
+        Listeners.listeners:emit(Listeners.event_names.ADD, {list = self, item = item, idx = #self.items + 1})
         table.insert(self.items, item)
     end
 
@@ -54,6 +57,7 @@ function HarpoonList:prepend(item)
     item = item or self.config.add()
     local index = index_of(self.items, item, self.config)
     if index == -1 then
+        Listeners.listeners:emit(Listeners.event_names.ADD, {list = self, item = item, idx = 1})
         table.insert(self.items, 1, item)
     end
 
@@ -64,6 +68,7 @@ end
 function HarpoonList:remove(item)
     for i, v in ipairs(self.items) do
         if self.config.equals(v, item) then
+            Listeners.listeners:emit(Listeners.event_names.REMOVE, {list = self, item = item, idx = i})
             table.remove(self.items, i)
             break
         end
@@ -73,6 +78,7 @@ end
 
 ---@return HarpoonList
 function HarpoonList:removeAt(index)
+    Listeners.listeners:emit(Listeners.event_names.REMOVE, {list = self, item = self.items[index], idx = index})
     table.remove(self.items, index)
     return self
 end
@@ -97,17 +103,25 @@ function HarpoonList:resolve_displayed(displayed)
     local new_list = {}
 
     local list_displayed = self:display()
+
+    for i, v in ipairs(list_displayed) do
+        local index = index_of(list_displayed, v)
+        if index == -1 then
+            Listeners.listeners:emit(Listeners.event_names.REMOVE, {list = self, item = v, idx = i})
+        end
+    end
+
     for i, v in ipairs(displayed) do
         local index = index_of(list_displayed, v)
         if index == -1 then
-            table.insert(new_list, self.config.add(v))
+            Listeners.listeners:emit(Listeners.event_names.ADD, {list = self, item = v, idx = i})
+            new_list[i] = self.config.add(v)
         else
             local index_in_new_list = index_of(new_list, self.items[index], self.config)
             if index_in_new_list == -1 then
-                table.insert(new_list, self.items[index])
+                new_list[i] = self.items[index]
             end
         end
-
     end
 
     self.items = new_list
@@ -116,6 +130,7 @@ end
 function HarpoonList:select(index, options)
     local item = self.items[index]
     if item then
+        Listeners.listeners:emit(Listeners.event_names.SELECT, {list = self, item = item, idx = index})
         self.config.select(item, options)
     end
 end

lua/harpoon2/listeners.lua

@@ -0,0 +1,57 @@
+
+---@alias HarpoonListener fun(type: string, args: any[] | any | nil): nil
+
+---@class HarpoonListeners
+---@field listeners (HarpoonListener)[]
+---@field listenersByType (table<string, HarpoonListener>)[]
+local HarpoonListeners = {}
+
+HarpoonListeners.__index = HarpoonListeners
+
+function HarpoonListeners:new()
+    return setmetatable({
+        listeners = {},
+        listenersByType = {}
+    }, self)
+end
+
+---@param cbOrType HarpoonListener | string
+---@param cbOrNil HarpoonListener | string
+function HarpoonListeners:add_listener(cbOrType, cbOrNil)
+    if (type(cbOrType) == "string") then
+        if not self.listenersByType[cbOrType] then
+            self.listenersByType[cbOrType] = {}
+        end
+        table.insert(self.listenersByType[cbOrType], cbOrNil)
+    else
+        table.insert(self.listeners, cbOrType)
+    end
+end
+
+function HarpoonListeners:clear_listeners()
+    self.listeners = {}
+end
+
+---@param type string
+---@param args any[] | any | nil
+function HarpoonListeners:emit(type, args)
+    for _, cb in ipairs(self.listeners) do
+        cb(type, args)
+    end
+
+    local listeners = self.listenersByType[type]
+    if listeners ~= nil then
+        for _, cb in ipairs(listeners) do
+            cb(type, args)
+        end
+    end
+end
+
+return {
+    listeners = HarpoonListeners:new(),
+    event_names = {
+        ADD = "ADD",
+        SELECT = "SELECT",
+        REMOVE = "REMOVE",
+    },
+}

lua/harpoon2/test/ui_spec.lua

@@ -13,6 +13,9 @@ describe("harpoon", function()
         local bufnr = harpoon.ui.bufnr
         local win_id = harpoon.ui.win_id
 
+        eq(vim.api.nvim_buf_is_valid(bufnr), true)
+        eq(vim.api.nvim_win_is_valid(win_id), true)
+
         harpoon.ui:toggle_quick_menu()
 
         eq(vim.api.nvim_buf_is_valid(bufnr), false)
@@ -20,7 +23,6 @@ describe("harpoon", function()
         eq(harpoon.ui.bufnr, nil)
         eq(harpoon.ui.win_id, nil)
     end)
-
 end)