---@class RuntimeI18n
local i18n = {}

local default_locale = "zh-Hans"
local current_locale = default_locale

local messages = {
  ["zh-Hans"] = {
    title = "Lua 飞行棋",
    roll_button = "掷骰子",
    dice_empty = "骰子: -",
    dice_value = "骰子: {value}",
    current_player = "当前玩家: {player}",
    ["player.red"] = "红方",
    ["player.blue"] = "蓝方",
    ["toast.move_first"] = "请先移动棋子",
    ["toast.no_movable_piece"] = "无可移动棋子",
    ["toast.invalid_piece"] = "该棋子不能移动"
  },
  en = {
    title = "Lua Ludo",
    roll_button = "Roll",
    dice_empty = "Dice: -",
    dice_value = "Dice: {value}",
    current_player = "Current player: {player}",
    ["player.red"] = "Red",
    ["player.blue"] = "Blue",
    ["toast.move_first"] = "Move a piece first",
    ["toast.no_movable_piece"] = "No movable pieces",
    ["toast.invalid_piece"] = "This piece cannot move"
  }
}

---@param locale? string
---@return string
local function normalize_locale(locale)
  if type(locale) ~= "string" or locale == "" then
    return default_locale
  end
  locale = string.gsub(locale, "_", "-")
  if messages[locale] ~= nil then
    return locale
  end

  local language = string.match(locale, "^([A-Za-z]+)")
  if language ~= nil and messages[language] ~= nil then
    return language
  end
  return default_locale
end

---@param value string
---@return string
local function escape_pattern(value)
  return string.gsub(value, "([%(%)%.%%%+%-%*%?%[%]%^%$])", "%%%1")
end

---@param template string
---@param vars? table<string, string|number>
---@return string
local function interpolate(template, vars)
  if vars == nil then
    return template
  end

  local result = template
  for key, value in pairs(vars) do
    result = string.gsub(result, "{" .. escape_pattern(key) .. "}", tostring(value))
  end
  return result
end

---@param ctx? RuntimeContext
function i18n.configure(ctx)
  local locale = nil
  if ctx ~= nil and ctx.locale ~= nil then
    locale = ctx.locale.resolved or ctx.locale.requested or ctx.locale.default
  end
  current_locale = normalize_locale(locale)
end

---@return string
function i18n.locale()
  return current_locale
end

---@param key string
---@param vars? table<string, string|number>
---@return string
function i18n.t(key, vars)
  local bundle = messages[current_locale] or messages[default_locale]
  local fallback = messages[default_locale]
  local value = bundle[key] or fallback[key] or key
  return interpolate(value, vars)
end

---@param color PlayerColor
---@return string
function i18n.player(color)
  return i18n.t("player." .. color)
end

return i18n