local M = {}

---@class N8nConfig
M.config = {
  transparent = false,       -- enable transparent background
  terminal_colors = true,    -- set terminal colors
  dim_inactive = false,      -- dim inactive windows
  styles = {
    comments = { italic = true },
    keywords = {},
    functions = {},
    strings = {},
    variables = {},
  },
  ---@type table<string, vim.api.keyset.highlight>
  on_highlights = function(highlights, colors) end,
  ---@type fun(colors: table): table
  on_colors = function(colors) return colors end,
}

---@param opts? N8nConfig
function M.setup(opts)
  M.config = vim.tbl_deep_extend("force", M.config, opts or {})
end

function M.load()
  if vim.g.colors_name then
    vim.cmd("hi clear")
  end
  if vim.fn.exists("syntax_on") then
    vim.cmd("syntax reset")
  end

  vim.o.termguicolors = true
  vim.g.colors_name = "n8n"
  vim.o.background = "dark"

  local theme = require("n8n.theme")
  local groups_mod = require("n8n.groups")
  local c = theme.colors()

  -- Let user modify colors
  if type(M.config.on_colors) == "function" then
    local custom = M.config.on_colors(c)
    if custom then
      c = vim.tbl_deep_extend("force", c, custom)
    end
  end

  -- Handle transparent mode
  if M.config.transparent then
    c.bg = "NONE"
    c.bg_sidebar = "NONE"
    c.bg_float = "NONE"
  end

  local groups = groups_mod.setup({ colors = c })

  -- Apply style overrides
  if M.config.styles.comments then
    groups.Comment = vim.tbl_extend("force", groups.Comment or {}, M.config.styles.comments)
    groups["@comment"] = vim.tbl_extend("force", groups["@comment"] or {}, M.config.styles.comments)
  end
  if M.config.styles.keywords then
    for _, key in ipairs({ "Keyword", "Statement", "Conditional", "Repeat", "@keyword" }) do
      if groups[key] then
        groups[key] = vim.tbl_extend("force", groups[key], M.config.styles.keywords)
      end
    end
  end
  if M.config.styles.functions then
    for _, key in ipairs({ "Function", "@function", "@function.call" }) do
      if groups[key] then
        groups[key] = vim.tbl_extend("force", groups[key], M.config.styles.functions)
      end
    end
  end
  if M.config.styles.strings then
    for _, key in ipairs({ "String", "@string" }) do
      if groups[key] then
        groups[key] = vim.tbl_extend("force", groups[key], M.config.styles.strings)
      end
    end
  end
  if M.config.styles.variables then
    for _, key in ipairs({ "Identifier", "@variable" }) do
      if groups[key] then
        groups[key] = vim.tbl_extend("force", groups[key], M.config.styles.variables)
      end
    end
  end

  -- Dim inactive windows
  if M.config.dim_inactive then
    groups.NormalNC = { fg = c.fg_dark, bg = c.bg_dark }
  end

  -- Let user modify highlights
  if type(M.config.on_highlights) == "function" then
    M.config.on_highlights(groups, c)
  end

  -- Apply all highlight groups
  for group, hl in pairs(groups) do
    vim.api.nvim_set_hl(0, group, hl)
  end

  -- Set terminal colors
  if M.config.terminal_colors then
    local t = theme.colors().terminal
    vim.g.terminal_color_0  = t.black
    vim.g.terminal_color_1  = t.red
    vim.g.terminal_color_2  = t.green
    vim.g.terminal_color_3  = t.yellow
    vim.g.terminal_color_4  = t.blue
    vim.g.terminal_color_5  = t.magenta
    vim.g.terminal_color_6  = t.cyan
    vim.g.terminal_color_7  = t.white
    vim.g.terminal_color_8  = t.bright_black
    vim.g.terminal_color_9  = t.bright_red
    vim.g.terminal_color_10 = t.bright_green
    vim.g.terminal_color_11 = t.bright_yellow
    vim.g.terminal_color_12 = t.bright_blue
    vim.g.terminal_color_13 = t.bright_magenta
    vim.g.terminal_color_14 = t.bright_cyan
    vim.g.terminal_color_15 = t.bright_white
  end
end

return M