feat: replace npm live-server with pure-Lua HTTP server (#29)

## Problem

The plugin requires users to install Node.js and the `live-server` npm
package globally. This is a heavyweight external dependency for what
amounts to a simple local dev-server workflow, and it creates friction
for users who don't otherwise need Node.js.

## Solution

Replace the npm shell-out with a pure-Lua HTTP server built on `vim.uv`
(libuv bindings), eliminating all external dependencies. The new server
supports static file serving, SSE-based live reload, CSS hot-swap
without full page reload, directory listings, and recursive file
watching with configurable debounce.

Minimum Neovim version is bumped to 0.10 for `vim.uv` and `vim.ui.open`.
The old `args`-based config is automatically migrated with a deprecation
warning.

Closes #28.

lua/live-server/init.lua

@@ -0,0 +1,238 @@
+local server = require('live-server.server')
+
+local M = {}
+
+---@type boolean
+local initialized = false
+
+---@type table<string, live_server.Instance>
+local instances = {}
+
+---@class live_server.Config
+---@field port? integer
+---@field browser? boolean
+---@field debounce? integer
+---@field ignore? string[]
+---@field css_inject? boolean
+---@field debug? boolean
+
+---@type live_server.Config
+local defaults = {
+  port = 5500,
+  browser = true,
+  debounce = 120,
+  ignore = {},
+  css_inject = true,
+  debug = false,
+}
+
+---@type live_server.Config
+local config = vim.deepcopy(defaults)
+
+---@param message string
+---@param level string
+local function log(message, level)
+  vim.notify(('live-server.nvim: %s'):format(message), vim.log.levels[level])
+end
+
+---@type table<string, boolean>
+local UNSUPPORTED_FLAGS = {
+  ['--host'] = true,
+  ['--open'] = true,
+  ['--browser'] = true,
+  ['--quiet'] = true,
+  ['--entry-file'] = true,
+  ['--spa'] = true,
+  ['--mount'] = true,
+  ['--proxy'] = true,
+  ['--htpasswd'] = true,
+  ['--cors'] = true,
+  ['--https'] = true,
+  ['--https-module'] = true,
+  ['--middleware'] = true,
+  ['--ignorePattern'] = true,
+}
+
+---@param user_config table
+---@return table
+local function migrate_args(user_config)
+  if not user_config.args then
+    return user_config
+  end
+
+  vim.deprecate(
+    '`vim.g.live_server.args`',
+    '`:h live-server-config`',
+    'v0.2.0',
+    'live-server.nvim',
+    false
+  )
+
+  local migrated = {}
+  for k, v in pairs(user_config) do
+    if k ~= 'args' then
+      migrated[k] = v
+    end
+  end
+
+  for _, arg in ipairs(user_config.args) do
+    local port = arg:match('%-%-port=(%d+)')
+    if port then
+      migrated.port = tonumber(port)
+    elseif arg == '--no-browser' then
+      migrated.browser = false
+    elseif arg == '--no-css-inject' then
+      migrated.css_inject = false
+    else
+      local wait = arg:match('%-%-wait=(%d+)')
+      if wait then
+        migrated.debounce = tonumber(wait)
+      else
+        local ignore_val = arg:match('%-%-ignore=(.*)')
+        if ignore_val then
+          migrated.ignore = migrated.ignore or {}
+          for pattern in ignore_val:gmatch('[^,]+') do
+            migrated.ignore[#migrated.ignore + 1] = vim.trim(pattern)
+          end
+        else
+          local flag = arg:match('^(%-%-[%w-]+)')
+          if flag and UNSUPPORTED_FLAGS[flag] then
+            log(('flag `%s` is not supported and will be ignored'):format(arg), 'WARN')
+          end
+        end
+      end
+    end
+  end
+
+  return migrated
+end
+
+local function init()
+  if initialized then
+    return
+  end
+
+  local user_config = vim.g.live_server or {}
+  user_config = migrate_args(user_config)
+  config = vim.tbl_deep_extend('force', defaults, user_config)
+
+  vim.api.nvim_create_autocmd('VimLeavePre', {
+    callback = function()
+      for dir, inst in pairs(instances) do
+        server.stop(inst)
+        instances[dir] = nil
+      end
+    end,
+  })
+
+  initialized = true
+end
+
+---@param dir? string
+---@return string?
+local function find_cached_dir(dir)
+  if not dir then
+    return nil
+  end
+
+  local cur = dir
+  while not instances[cur] do
+    if cur == '/' or cur:match('^[A-Z]:\\$') then
+      return nil
+    end
+    cur = vim.fn.fnamemodify(cur, ':h')
+  end
+  return cur
+end
+
+---@param dir string
+---@return live_server.Instance?
+local function is_running(dir)
+  local cached_dir = find_cached_dir(dir)
+  return cached_dir and instances[cached_dir]
+end
+
+---@param dir? string
+---@return string
+local function resolve_dir(dir)
+  if not dir or dir == '' then
+    dir = '%:p:h'
+  end
+  return vim.fn.expand(vim.fn.fnamemodify(vim.fn.expand(dir), ':p'))
+end
+
+---@param dir? string
+function M.start(dir)
+  init()
+
+  dir = resolve_dir(dir)
+
+  if is_running(dir) then
+    log('already running', 'INFO')
+    return
+  end
+
+  local root_real = vim.uv.fs_realpath(dir)
+  if not root_real then
+    log(('directory does not exist: %s'):format(dir), 'ERROR')
+    return
+  end
+
+  local inst = server.start({
+    port = config.port,
+    root_real = root_real,
+    debounce = config.debounce,
+    ignore = config.ignore,
+    css_inject = config.css_inject,
+    debug = config.debug,
+  })
+
+  instances[dir] = inst
+  log(('started on 127.0.0.1:%d'):format(config.port), 'INFO')
+
+  if config.browser then
+    vim.ui.open(('http://127.0.0.1:%d/'):format(config.port))
+  end
+end
+
+---@param dir? string
+function M.stop(dir)
+  dir = resolve_dir(dir)
+  local cached_dir = find_cached_dir(dir)
+  if cached_dir and instances[cached_dir] then
+    server.stop(instances[cached_dir])
+    instances[cached_dir] = nil
+    log('stopped', 'INFO')
+  end
+end
+
+---@param dir? string
+function M.toggle(dir)
+  dir = resolve_dir(dir)
+  if is_running(dir) then
+    M.stop(dir)
+  else
+    M.start(dir)
+  end
+end
+
+---@deprecated Use `vim.g.live_server` instead
+---@param user_config? live_server.Config
+function M.setup(user_config)
+  vim.deprecate(
+    '`require("live-server").setup()`',
+    '`vim.g.live_server`',
+    'v0.1.0',
+    'live-server.nvim',
+    false
+  )
+
+  if user_config then
+    vim.g.live_server = vim.tbl_deep_extend('force', vim.g.live_server or {}, user_config)
+  end
+
+  initialized = false
+  init()
+end
+
+return M