init.lua/after/plugin/lsp.lua

-- settings erro signs
local function sign_define(args)
	vim.fn.sign_define(args.name, {
		texthl = args.name,
		text = args.text,
		numhl = "",
	})
end

sign_define({ name = "DiagnosticSignError", text = "E" })
sign_define({ name = "DiagnosticSignWarn", text = "W" })
sign_define({ name = "DiagnosticSignHint", text = "H" })
sign_define({ name = "DiagnosticSignInfo", text = "I" })

-- diagnostic's aren't lsp dependent
vim.keymap.set("n", "<leader>vd", function()
	vim.diagnostic.open_float()
end)
vim.keymap.set("n", "[d", function()
	vim.diagnostic.goto_next()
end)
vim.keymap.set("n", "]d", function()
	vim.diagnostic.goto_prev()
end)

-- lsp capabilites enabler
vim.api.nvim_create_autocmd("LspAttach", {
	desc = "LSP Actions",
	callback = function(event)
		-- Enable omnifunc
		vim.bo[event.buf].omnifunc = "v:lua.MiniCompletion.completefunc_lsp"

		-- Buffer local mappings
		local opts = { buffer = event.buf }
		vim.keymap.set("n", "K", function()
			vim.lsp.buf.hover()
		end, opts)
		vim.keymap.set("n", "gd", function()
			vim.lsp.buf.definition()
		end, opts)
		vim.keymap.set("n", "gD", function()
			vim.lsp.buf.declaration()
		end, opts)
		vim.keymap.set("n", "gi", function()
			vim.lsp.buf.implementation()
		end, opts)
		vim.keymap.set("n", "<leader>lca", function()
			vim.lsp.buf.code_action()
		end, opts)
		vim.keymap.set("n", "<leader>lrn", function()
			vim.lsp.buf.rename()
		end, opts)
		vim.keymap.set("i", "<C-h>", function()
			vim.lsp.buf.signature_help()
		end, opts)
	end,
})

-- setup mason and automatically install some language server's
require("mason").setup({})
require("mason-lspconfig").setup({
	ensure_installed = { "lua_ls", "jsonls", "bashls", "pyright", "marksman", "gopls", "clangd" },
})

-- automatically setup already installed lsp's
require("mason-lspconfig").setup_handlers({
	function(server_name)
		require("lspconfig")[server_name].setup({})
	end,
})

-- setup haskell language server manually cause it doesn't work with mason for xmonad
require("lspconfig").hls.setup({})

-- autocompletion using mini.completion
require("mini.completion").setup({
	lsp_completion = {
		source_func = "omnifunc",
		auto_setup = false,
	},
	fallback_action = "<C-x><C-n>",
})

-- bind ctrl j and k to move beetwen completion items
vim.keymap.set("i", "<C-j>", [[pumvisible() ? "\<C-n>" : "\<C-j>"]], { expr = true })
vim.keymap.set("i", "<C-k>", [[pumvisible() ? "\<C-p>" : "\<C-k>"]], { expr = true })