local servers = {
  omnisharp = {
    cmd = { vim.fn.expand '~/omnisharp/OmniSharp' },
  },
}

local filetypes = {
  cs = function(client, bufnr)
    client.server_capabilities.semanticTokensProvider = nil
  end,
}

local on_attach = function(client, bufnr)
  vim.bo.omnifunc = 'v:lua.vim.lsp.omnifunc'  -- do completion with <c-x><c-o>

  local map = vim.keymap.set
  local opts = { buffer = bufnr }

  map('n', '<space>ca',   vim.lsp.buf.code_action,                opts)
  map('n', '<space>cf',   vim.lsp.buf.format,                     opts)
  map('n', 'gD',          vim.lsp.buf.declaration,                opts)
  map('n', 'gd',          vim.lsp.buf.definition,                 opts)
  map('n', 'K',           vim.lsp.buf.hover,                      opts)
  map('n', 'gi',          vim.lsp.buf.implementation,             opts)
  map('n', 'grr',         vim.lsp.buf.rename,                     opts)
  map('n', 'gt',          vim.lsp.buf.type_definition,            opts)

  filetype_attach = filetypes[vim.bo.filetype]
  if filetype_attach then filetype_attach(client, bufnr) end
end

local config = function()
  local capabilities = vim.lsp.protocol.make_client_capabilities()
  local has_cmp, cmp = pcall(require, 'cmp_nvim_lsp')
  if has_cmp then
    vim.tbl_deep_extend('force', capabilities, cmp.default_capabilities())
  end

  lsp = require('lspconfig')
  for server, opts in pairs(servers) do
    opts = vim.tbl_deep_extend('keep', opts, {
      on_attach = on_attach,
      capabilities = capabilities,
    })
    lsp[server].setup(opts)
  end
end

return {
  'neovim/nvim-lspconfig',
  config = config,
}