nvim/lua/plugins/completions.lua

return {
  'neovim/nvim-lspconfig',

  dependencies = {
    -- Language server management plugins
    'williamboman/mason.nvim',
    'williamboman/mason-lspconfig.nvim',

    -- Completion plugins
    'hrsh7th/cmp-nvim-lsp', -- Source for built-in language server client
    'hrsh7th/cmp-buffer',   -- Source for buffer words
    'hrsh7th/cmp-path',     -- Source for filesystem paths
    'hrsh7th/cmp-cmdline',  -- Source for command-line
    'hrsh7th/nvim-cmp',     -- Completion engine combines and use the above

    -- LSP UI plugins
    'aznhe21/actions-preview.nvim',

    -- Lue vim module support in lua language server
    'folke/neodev.nvim',

    -- Snippet pluggins
    'L3MON4D3/LuaSnip',
    'saadparwaiz1/cmp_luasnip',

    -- TODO: https://github.com/j-hui/fidget.nvim

    -- TODO: https://github.com/nvimtools/none-ls.nvim

    -- TODO: https://github.com/mfussenegger/nvim-dap
    -- TODO: https://github.com/rcarriga/nvim-dap-ui
  },

  config = function()
    require('mason').setup()
    require('mason-lspconfig').setup({
      ensure_installed = {
        'clangd',
        'cmake',
        'jsonls',
        'lua_ls',
        'lemminx',
        'vimls',
        'yamlls',
      },
      automatic_installation = false,
      handlers = {
        -- Default handler, sets up everything unless a custom language server
        -- setup handler is defined below
        function(server_name)
          require('lspconfig')[server_name].setup({})
        end,

        ['lua_ls'] = function()
          require('neodev').setup()
          local lspconfig = require('lspconfig')
          lspconfig.lua_ls.setup({
            settings = {
              Lua = {
                diagnostics = {
                  disable = { 'missing-fields', },
                  globals = { 'vim', },
                }
              }
            }
          })
        end
      },
    })

    local cmp = require('cmp')
    cmp.setup({
      snippet = {
        expand = function(args)
          require('luasnip').lsp_expand(args.body)
        end
      },
      mapping = cmp.mapping.preset.insert({
        ['<C-p>'] = cmp.mapping.select_prev_item(),
        ['<C-n>'] = cmp.mapping.select_next_item(),
        ['<C-l>'] = cmp.mapping.confirm({ select = true }),
      }),
      sources = {
        { name = 'luasnip' },
        { name = 'nvim_lsp' },
        -- { name = 'buffer' },
        { name = 'path' },
        -- { name = 'cmdline' },
      },
    })

    -- Disable displaying diagnostics as virtual text
    vim.diagnostic.config({ virtual_text = false })

    -- Diagnostic mappings
    -- TODO: trouble.nvim mappings instead? https://youtu.be/MuUrCcvE-Yw?t=631
    vim.keymap.set('n', '<C-n>', vim.diagnostic.goto_next, { noremap = true })
    vim.keymap.set('n', '<C-p>', vim.diagnostic.goto_prev, { noremap = true })
    vim.keymap.set('n', '<leader>sd', vim.diagnostic.open_float, { noremap = true })

    -- LSP mappings created when attached to a buffer
    local augroup = vim.api.nvim_create_augroup('lsp', { clear = true })
    vim.api.nvim_create_autocmd('LspAttach', {
      pattern = '*',
      group = augroup,
      callback = function(ev)
        local opts = { noremap = true, buffer = ev.buf }

        -- TODO: inoremap <silent><expr> <TAB> coc#pum#visible() ? coc#pum#confirm() : "\<TAB>"
        -- Should I drop this? It's only for expanding snippets because
        -- coc.nvim was being weird about it

        -- Fixit mapping, or close enough, actually any code action
        vim.keymap.set('n', '<leader>fi',
          require("actions-preview").code_actions, opts)

        -- Goto definition mapping
        vim.keymap.set('n', 'gd', vim.lsp.buf.definition, opts)
        -- TODO: nnoremap <silent> <leader>gt <Plug>(coc-type-definition)
        -- TODO: nnoremap <silent> <leader>gu <Plug>(coc-references-used)

        -- Get references to symbol under cursor, store in quickfix window
        vim.keymap.set('n', '<leader>gr', vim.lsp.buf.references, opts)

        -- Refactoring mappings
        vim.keymap.set('n', '<leader>rn', vim.lsp.buf.rename, opts)

        -- Format whole buffer mapping
        vim.keymap.set('n', '<leader>gq', vim.lsp.buf.format, opts)

        -- Help mappings
        vim.keymap.set('n', 'K', vim.lsp.buf.hover, opts)
        vim.keymap.set('i', '<C-h>', vim.lsp.buf.signature_help, opts)
      end
    })

    -- Snippet mappings
    local luasnip = require('luasnip')
    luasnip.setup({})
    vim.keymap.set({ 'i', 's' }, '<C-j>', function()
      if luasnip.expand_or_jumpable() then
        luasnip.expand_or_jump()
      end
    end, { silent = true })
    vim.keymap.set({ 'i', 's' }, '<C-K>', function()
      if luasnip.jumpable(-1) then
        luasnip.jump(-1)
      end
    end, { silent = true })

    -- Load snippets
    local opts = { paths = vim.fn.stdpath('config') .. '/snippets' }
    require('luasnip.loaders.from_snipmate').lazy_load(opts)
    require('luasnip.loaders.from_lua').lazy_load(opts)
  end
}