if not pcall(require, "lspconfig") then
  return
end

local M = {}

local _winopts = { border = "rounded" }
local _float_win = nil

function M.preview_location(loc, _, _)
  -- location may be LocationLink or Location
  local uri = loc.targetUri or loc.uri
  if uri == nil then return end
  local bufnr = vim.uri_to_bufnr(uri)
  if not vim.api.nvim_buf_is_loaded(bufnr) then
    vim.fn.bufload(bufnr)
  end
  local range = loc.targetRange or loc.range
  local before, after = math.min(5, range.start.line), 10
  local lines = vim.api.nvim_buf_get_lines(bufnr,
    (range.start.line - before),
    -- end is reserved, can't use 'range.end'
    (range["end"].line + after + 1),
    false)
  -- empty lines at the start don't count
  for _, l in ipairs(lines) do
    if #l > 0 then break end
    before = before - 1
  end
  local ft = vim.api.nvim_buf_get_option(bufnr, "filetype")
  local buf, win = vim.lsp.util.open_floating_preview(lines, ft, {})
  vim.api.nvim_win_set_config(win, _winopts)
  vim.api.nvim_buf_set_option(buf, "bufhidden", "wipe")
  vim.api.nvim_buf_set_option(buf, "modifiable", false)
  vim.api.nvim_buf_set_option(buf, "filetype", ft)
  vim.api.nvim_win_set_option(win, "winhighlight", "Normal:NormalFloat,FloatBorder:FloatBorder")
  vim.api.nvim_win_set_option(win, "cursorline", true)
  -- partial data, numbers make no sense
  vim.api.nvim_win_set_option(win, "number", false)
  vim.api.nvim_win_set_cursor(win, { before + 1, 1 })
  local pos = range.start.line == range["end"].line and
      { before + 1, range.start.character + 1, range["end"].character - range.start.character } or
      { before + 1 }
  vim.api.nvim_win_call(win, function()
    vim.fn.matchaddpos("IncSearch", { pos })
  end)
  return buf, win
end

function M.preview_location_callback(err, res, ctx, cfg)
  if err then
    vim.notify(("Error running LSP query '%s'"):format(cfg.method), vim.log.levels.ERROR)
    return nil
  end
  if res == nil or vim.tbl_isempty(res) then
    vim.notify("Unable to find code location.", vim.log.levels.WARN)
    return nil
  end
  _, _float_win = M.preview_location(vim.tbl_islist(res) and res[1] or res, ctx, cfg)
end

function M.peek_definition()
  -- workaround for subsequent calls with the popup visuble
  if _float_win ~= nil then
    pcall(vim.api.nvim_win_hide, _float_win)
  end
  if vim.tbl_contains(vim.api.nvim_list_wins(), _float_win) then
    vim.api.nvim_set_current_win(_float_win)
  else
    local params = vim.lsp.util.make_position_params()
    return vim.lsp.buf_request(0, "textDocument/definition", params, M.preview_location_callback)
  end
end

return M