-- LSP stack:
--   mason        → installs language servers automatically
--   lspconfig    → configures them
--   nvim-cmp     → completion popup
--   LuaSnip      → snippet engine (required by cmp)
--
-- LSP keymaps (active when a file has an attached language server):
--   K           → hover documentation
--   gd          → go to definition
--   gr          → list references
--   <leader>rn  → rename symbol
--   <leader>ca  → code actions (quick fixes, imports, etc.)
--   <leader>d   → show line diagnostics
--   [d / ]d     → jump to prev/next diagnostic
return {

  -- ── Mason: auto-installs language servers ──────────────────────────────────
  {
    "williamboman/mason.nvim",
    config = function()
      require("mason").setup()
    end,
  },
  {
    "williamboman/mason-lspconfig.nvim",
    dependencies = { "williamboman/mason.nvim" },
    config = function()
      require("mason-lspconfig").setup({
        ensure_installed = {
          "bashls",     -- Bash
          "pyright",    -- Python
          "omnisharp",  -- C#
        },
        automatic_installation = true,
      })
    end,
  },

  -- ── Completion ─────────────────────────────────────────────────────────────
  {
    "hrsh7th/nvim-cmp",
    dependencies = {
      "hrsh7th/cmp-nvim-lsp",    -- LSP completions
      "hrsh7th/cmp-buffer",      -- words from current buffer
      "hrsh7th/cmp-path",        -- file paths
      "L3MON4D3/LuaSnip",        -- snippet engine
      "saadparwaiz1/cmp_luasnip",
    },
    config = function()
      local cmp     = require("cmp")
      local luasnip = require("luasnip")

      cmp.setup({
        snippet = {
          expand = function(args) luasnip.lsp_expand(args.body) end,
        },
        mapping = cmp.mapping.preset.insert({
          ["<C-Space>"] = cmp.mapping.complete(),
          ["<CR>"]      = cmp.mapping.confirm({ select = true }),
          ["<Tab>"] = cmp.mapping(function(fallback)
            if cmp.visible() then
              cmp.select_next_item()
            elseif luasnip.expand_or_jumpable() then
              luasnip.expand_or_jump()
            else
              fallback()
            end
          end, { "i", "s" }),
          ["<S-Tab>"] = cmp.mapping(function(fallback)
            if cmp.visible() then
              cmp.select_prev_item()
            elseif luasnip.jumpable(-1) then
              luasnip.jump(-1)
            else
              fallback()
            end
          end, { "i", "s" }),
        }),
        sources = cmp.config.sources({
          { name = "nvim_lsp" },
          { name = "luasnip" },
        }, {
          { name = "buffer" },
          { name = "path" },
        }),
      })
    end,
  },

  -- ── LSP config ─────────────────────────────────────────────────────────────
  {
    "neovim/nvim-lspconfig",
    dependencies = {
      "williamboman/mason-lspconfig.nvim",
      "hrsh7th/cmp-nvim-lsp",
    },
    config = function()
      local lspconfig    = require("lspconfig")
      local capabilities = require("cmp_nvim_lsp").default_capabilities()

      -- Keymaps applied whenever an LSP attaches to a buffer
      vim.api.nvim_create_autocmd("LspAttach", {
        callback = function(ev)
          local map  = vim.keymap.set
          local opts = function(desc) return { buffer = ev.buf, desc = desc } end

          map("n", "K",           vim.lsp.buf.hover,          opts("Hover docs"))
          map("n", "gd",          vim.lsp.buf.definition,     opts("Go to definition"))
          map("n", "gr",          vim.lsp.buf.references,     opts("References"))
          map("n", "<leader>rn",  vim.lsp.buf.rename,         opts("Rename symbol"))
          map("n", "<leader>ca",  vim.lsp.buf.code_action,    opts("Code action"))
          map("n", "<leader>d",   vim.diagnostic.open_float,  opts("Line diagnostics"))
          map("n", "[d",          vim.diagnostic.goto_prev,   opts("Prev diagnostic"))
          map("n", "]d",          vim.diagnostic.goto_next,   opts("Next diagnostic"))
        end,
      })

      lspconfig.bashls.setup({ capabilities = capabilities })
      lspconfig.pyright.setup({ capabilities = capabilities })
      lspconfig.omnisharp.setup({ capabilities = capabilities })
    end,
  },
}