local util = require 'lspconfig.util'

-- https://clangd.llvm.org/extensions.html#switch-between-sourceheader
local function switch_source_header(bufnr)
  bufnr = util.validate_bufnr(bufnr)
  local clangd_client = util.get_active_client_by_name(bufnr, 'clangd')
  local params = { uri = vim.uri_from_bufnr(bufnr) }
  if clangd_client then
    clangd_client.request(
      'textDocument/switchSourceHeader',
      params,
      util.compat_handler(function(err, result)
        if err then
          error(tostring(err))
        end
        if not result then
          print 'Corresponding file cannot be determined'
          return
        end
        vim.api.nvim_command('edit ' .. vim.uri_to_fname(result))
      end),
      bufnr
    )
  else
    print 'method textDocument/switchSourceHeader is not supported by any servers active on the current buffer'
  end
end

local root_pattern = util.root_pattern('compile_commands.json', 'compile_flags.txt', '.git')

local default_capabilities = vim.tbl_deep_extend(
  'force',
  util.default_config.capabilities or vim.lsp.protocol.make_client_capabilities(),
  {
    textDocument = {
      completion = {
        editsNearCursor = true,
      },
    },
    offsetEncoding = { 'utf-8', 'utf-16' },
  }
)

return {
  default_config = {
    cmd = { 'clangd', '--background-index' },
    filetypes = { 'c', 'cpp', 'objc', 'objcpp' },
    root_dir = function(fname)
      local filename = util.path.is_absolute(fname) and fname or util.path.join(vim.loop.cwd(), fname)
      return root_pattern(filename)
    end,
    single_file_support = true,
    capabilities = default_capabilities,
  },
  commands = {
    ClangdSwitchSourceHeader = {
      function()
        switch_source_header(0)
      end,
      description = 'Switch between source/header',
    },
  },
  docs = {
    description = [[
https://clangd.llvm.org/installation.html

**NOTE:** Clang >= 9 is recommended! See [this issue for more](https://github.com/neovim/nvim-lsp/issues/23).

clangd relies on a [JSON compilation database](https://clang.llvm.org/docs/JSONCompilationDatabase.html) specified
as compile_commands.json or, for simpler projects, a compile_flags.txt.
For details on how to automatically generate one using CMake look [here](https://cmake.org/cmake/help/latest/variable/CMAKE_EXPORT_COMPILE_COMMANDS.html). Alternatively, you can use [Bear](https://github.com/rizsotto/Bear).
]],
    default_config = {
      root_dir = [[root_pattern("compile_commands.json", "compile_flags.txt", ".git") or dirname]],
      capabilities = [[default capabilities, with offsetEncoding utf-8]],
    },
  },
}
