local Config = require("lazy.core.config")
local Util = require("lazy.util")
local Plugin = require("lazy.core.plugin")
local Loader = require("lazy.core.loader")

local M = {}

---@type table<string, uv.aliases.fs_stat_table>
M.files = {}

---@type uv_timer_t
M.timer = nil

function M.enable()
  if M.timer then
    M.timer:stop()
  end
  if #Config.spec.modules > 0 then
    M.timer = assert(vim.loop.new_timer())
    M.check(true)
    M.timer:start(2000, 2000, M.check)
  end
end

function M.disable()
  if M.timer then
    M.timer:stop()
    M.timer = nil
  end
end

---@param h1 uv.aliases.fs_stat_table
---@param h2 uv.aliases.fs_stat_table
function M.eq(h1, h2)
  return h1 and h2 and h1.size == h2.size and h1.mtime.sec == h2.mtime.sec and h1.mtime.nsec == h2.mtime.nsec
end

function M.check(start)
  ---@type table<string,true>
  local checked = {}
  ---@type {file:string, what:string}[]
  local changes = {}

  -- spec is a module
  local function check(_, modpath)
    checked[modpath] = true
    local hash = vim.loop.fs_stat(modpath)
    if hash then
      if M.files[modpath] then
        if not M.eq(M.files[modpath], hash) then
          M.files[modpath] = hash
          table.insert(changes, { file = modpath, what = "changed" })
        end
      else
        M.files[modpath] = hash
        table.insert(changes, { file = modpath, what = "added" })
      end
    end
  end

  for _, modname in ipairs(Config.spec.modules) do
    Util.lsmod(modname, check)
  end

  for file in pairs(M.files) do
    if not checked[file] then
      table.insert(changes, { file = file, what = "deleted" })
      M.files[file] = nil
    end
  end

  if Loader.init_done and Config.mapleader ~= vim.g.mapleader then
    vim.schedule(function()
      require("lazy.core.util").warn("You need to set `vim.g.mapleader` **BEFORE** loading lazy")
    end)
    Config.mapleader = vim.g.mapleader
  end

  if not (start or #changes == 0) then
    vim.schedule(function()
      if Config.options.change_detection.notify and not Config.headless() then
        local lines = { "# Config Change Detected. Reloading...", "" }
        for _, change in ipairs(changes) do
          table.insert(lines, "- **" .. change.what .. "**: `" .. vim.fn.fnamemodify(change.file, ":p:~:.") .. "`")
        end
        Util.warn(lines)
      end
      Plugin.load()
      vim.api.nvim_exec_autocmds("User", { pattern = "LazyRender", modeline = false })
      vim.api.nvim_exec_autocmds("User", { pattern = "LazyReload", modeline = false })
    end)
  end
end

return M