Different highlights for each statusline

Neovim
1

I’m writing a plugin where I’m trying to colorize the statuslines with different colors depending on the file name. However, I’m having troubles setting the highlights. So far I’ve been trying to use nvim_win_set_hl_ns and used User1…9. Is there a better way? Is it even possible?

I’ve provided a repro-script below. You can run it with nvim --clean -u repro_script.lua. I want the two status-lines to have red and green text. None of them should have blue.

local function get_line(buf_nbr)
  if buf_nbr == 1 then
    return "%9*I should be green";
  end
  if buf_nbr == 2 then
    return "%9*I should be red";
  end
  return "%9*I should be blue";
end

function Status_Line()
  local buf_nbr = vim.fn.winbufnr(vim.g.statusline_winid);
  return table.concat {
    get_line(buf_nbr),
    " | buf_nr: " .. buf_nbr
  }
end

vim.o.statusline = "%!luaeval('Status_Line()')"

local ns_1_id = vim.api.nvim_create_namespace("one");
local ns_2_id = vim.api.nvim_create_namespace("two");
local ns_3_id = vim.api.nvim_create_namespace("three");

vim.api.nvim_set_hl(ns_1_id, "User9", { ctermfg = "green" });
vim.api.nvim_set_hl(ns_2_id, "User9", { ctermfg = "red" });
vim.api.nvim_set_hl(ns_3_id, "User9", { ctermfg = "blue" });

vim.api.nvim_set_hl_ns(ns_3_id);

local win_1 = vim.api.nvim_get_current_win()
vim.api.nvim_command('botright vnew')
local win_2 = vim.api.nvim_get_current_win()
vim.api.nvim_win_set_hl_ns(win_1, ns_1_id);
vim.api.nvim_win_set_hl_ns(win_2, ns_2_id);