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',
    'j-hui/fidget.nvim',
    'folke/trouble.nvim',
    'nvim-tree/nvim-web-devicons',

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

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

    -- 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({
      automatic_installation = false,
      ensure_installed = {
        'ansiblels',                       -- Ansible
        'bashls',                          -- Bash
        'clangd',                          -- C/C++
        'cmake',                           -- Cmake
        'docker_compose_language_service', -- Docker Compose
        'dockerls',                        -- Dockerfile
        'esbonio',                         -- Sphinx
        'html',                            -- HTML
        'jsonls',                          -- JSON
        'lemminx',                         -- XML
        'lua_ls',                          -- Lua
        'opencl_ls',                       -- OpenCL
        'powershell_es',                   -- Powershell
        'pyright',                         -- Python
        'ruff_lsp',                        -- Python
        'vimls',                           -- VimScript
        'yamlls',                          -- YAML
      },

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

        ['pyright'] = function()
          require('lspconfig').pyright.setup({
            settings = {
              pyright = {
                -- Using Ruff's import organizer
                disableOrganizeImports = true,
              },
            }
          })
        end,

      },
    })

    local cmp = require('cmp')
    cmp.setup({
      snippet = {
        expand = function(args)
          require('luasnip').lsp_expand(args.body)
        end
      },

      mapping = cmp.mapping.preset.insert({
        -- Open completion menu/confirm completion
        ['<C-Space>'] = cmp.mapping.complete(),
        ['<C-l>'] = cmp.mapping.confirm({ select = true }),
        -- Select completion from menu
        ['<C-n>'] = cmp.mapping.select_next_item(),
        ['<C-p>'] = cmp.mapping.select_prev_item(),
        -- Scroll documentation of selected completion item
        ['<C-d>'] = cmp.mapping.scroll_docs(4),
        ['<C-u>'] = cmp.mapping.scroll_docs(-4),
      }),

      sources = {
        { name = 'nvim_lsp' },
        { name = 'luasnip' },
        -- { name = 'buffer' },
        { name = 'path' },
        -- { name = 'cmdline' },
      },

      window = {
        completion = cmp.config.window.bordered(),
        documentation = cmp.config.window.bordered(),
      },
    })

    -- Customise LSP UI
    vim.lsp.handlers['textDocument/hover'] = vim.lsp.with(
      vim.lsp.handlers.hover, {
        border = 'rounded',
        title = 'Hover',
      }
    )
    vim.lsp.handlers["textDocument/signatureHelp"] = vim.lsp.with(
      vim.lsp.handlers.signature_help, {
        border = 'rounded',
        title = 'Signature Help'
      }
    )

    -- Customise diagnostics UI
    vim.diagnostic.config({
      float = {
        border = 'rounded', -- Enable rounded border on floats
      },
      virtual_text = false, -- Disable trailing virtual text
    })

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

    -- 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 }

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

        -- Goto mappings
        vim.keymap.set('n', 'gD', vim.lsp.buf.declaration, opts)
        vim.keymap.set('n', 'gd', vim.lsp.buf.definition, opts)
        vim.keymap.set('n', 'gi', vim.lsp.buf.implementation, opts)
        vim.keymap.set('n', '<leader>D', vim.lsp.buf.type_definition, opts)

        -- Get references to symbol under cursor, store in quickfix window
        vim.keymap.set('n', '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)

    -- LSP UI plugins
    require('fidget').setup({})
    require('trouble').setup({})
    vim.keymap.set('n', '<leader>t', function()
      require('trouble').toggle()
    end, { remap = false })
  end
}