local M = {}

local reference_filename = "KEYMAPS.md"
local reference_path = vim.fn.stdpath("config") .. "/" .. reference_filename

local function read_reference()
  local lines = {}
  local fd = io.open(reference_path, "r")
  if not fd then
    return {
      ("Keymap reference file not found: %s"):format(reference_path),
      "Create KEYMAPS.md to document mappings.",
    }
  end

  for line in fd:lines() do
    table.insert(lines, line)
  end
  fd:close()

  if #lines == 0 then
    lines = { "KEYMAPS.md is empty." }
  end

  return lines
end

local function open_float(lines)
  local buf = vim.api.nvim_create_buf(false, true)
  vim.api.nvim_buf_set_lines(buf, 0, -1, false, lines)

  vim.bo[buf].buftype = "nofile"
  vim.bo[buf].bufhidden = "wipe"
  vim.bo[buf].filetype = "markdown"
  vim.bo[buf].swapfile = false
  vim.bo[buf].modifiable = false

  local width = 0
  for _, line in ipairs(lines) do
    width = math.max(width, vim.fn.strdisplaywidth(line))
  end
  width = math.min(math.max(width + 4, 60), math.floor(vim.o.columns * 0.9))

  local height = math.min(#lines, math.floor(vim.o.lines * 0.9))
  if height < 10 then
    height = math.min(10, vim.o.lines - 2)
  end

  local win_opts = {
    relative = "editor",
    width = width,
    height = height,
    row = math.floor((vim.o.lines - height) / 2),
    col = math.floor((vim.o.columns - width) / 2),
    style = "minimal",
    border = "rounded",
  }

  local win = vim.api.nvim_open_win(buf, true, win_opts)
  vim.keymap.set("n", "q", "<cmd>close<cr>", { buffer = buf, silent = true })
  vim.keymap.set("n", "<Esc>", "<cmd>close<cr>", { buffer = buf, silent = true })
  return win
end

function M.open_reference()
  local lines = read_reference()
  open_float(lines)
end

vim.api.nvim_create_user_command("KeymapsGuide", function()
  M.open_reference()
end, { desc = "Show KEYMAPS.md in a floating window" })

return M