-- Neovim preview for Luma files.
--
-- Set LUMA_MARKDOWN_BIN to the path of the generated executable, or make
-- luma_markdown available on PATH:
--   export LUMA_MARKDOWN_BIN="$PWD/luma_markdown"

local preview_buf = nil
local preview_win = nil

local function update_luma_preview()
  local src_buf = vim.api.nvim_get_current_buf()
  local lines = vim.api.nvim_buf_get_lines(src_buf, 0, -1, false)
  local cmd = vim.env.LUMA_MARKDOWN_BIN or "luma_markdown"
  local output = vim.fn.systemlist(cmd, lines)

  if not preview_buf or not vim.api.nvim_buf_is_valid(preview_buf) then
    preview_buf = vim.api.nvim_create_buf(false, true)
    vim.api.nvim_buf_set_option(preview_buf, "buftype", "nofile")
    vim.api.nvim_buf_set_option(preview_buf, "bufhidden", "hide")
    vim.api.nvim_buf_set_option(preview_buf, "swapfile", false)
    vim.api.nvim_buf_set_option(preview_buf, "filetype", "markdown")
  end

  vim.api.nvim_buf_set_lines(preview_buf, 0, -1, false, output)

  if not preview_win or not vim.api.nvim_win_is_valid(preview_win) then
    vim.cmd "rightbelow vsplit"
    preview_win = vim.api.nvim_get_current_win()
    vim.api.nvim_win_set_buf(preview_win, preview_buf)

    local src_win = vim.fn.bufwinid(src_buf)
    if src_win ~= -1 then vim.api.nvim_set_current_win(src_win) end
  end
end

vim.api.nvim_create_autocmd("BufWritePost", {
  pattern = "*.luma",
  callback = update_luma_preview,
})

vim.api.nvim_create_user_command("LumaPreview", update_luma_preview, {})

local timer = nil
local function debounced_update()
  if timer then timer:stop() end
  timer = vim.defer_fn(update_luma_preview, 150)
end

vim.api.nvim_create_autocmd({ "TextChanged", "TextChangedI" }, {
  pattern = "*.luma",
  callback = debounced_update,
})