dotfiles/config/nvim/init.lua

local MAP     = vim.keymap.set
local AUTOCMD = vim.api.nvim_create_autocmd

vim.cmd("colorscheme scheme")
vim.cmd("filetype indent on")

-- Language people you have more important things to do than police the code style, if people
-- want consistent styling it should be done at a project level using a linter or .editorconfig
vim.g.rust_recommended_style     = false
vim.g.python_recommended_style   = false
vim.g.go_recommended_style       = false
vim.g.zig_recommended_style      = false
vim.g.markdown_recommended_style = false
vim.g.arduino_recommended_style  = false
vim.g.gdscript_recommended_style = false
vim.g.yaml_recommended_style     = false

-- Basic options
vim.o.tabstop        = 2
vim.o.shiftwidth     = 0
vim.o.expandtab      = false
vim.o.list           = true
vim.o.clipboard      = "unnamedplus"
vim.o.ff             = "unix"
vim.o.ffs            = "unix,dos"
vim.o.switchbuf      = "useopen,uselast"
vim.o.textwidth      = 95
vim.o.wrapmargin     = 5
vim.o.number         = true
vim.o.relativenumber = true
vim.o.splitbelow     = true
vim.o.splitright     = true
vim.o.autoread       = true
vim.o.lazyredraw     = true
vim.o.cursorline     = true
vim.o.ignorecase     = true
vim.o.wrap           = false
vim.o.wildmenu       = false
vim.o.termguicolors  = true
vim.o.cindent        = true
vim.o.timeoutlen     = 1500
vim.o.completeopt    = "preview"
vim.o.wildmode       = "full"
vim.o.cinoptions     = "l1,b-s"
vim.o.statusline     = "%#LineNr# [%n] %#Default# %f%m%r %= %#StatusLineNC# %w[%{&ft == '' ? 'None' : ''}%Y] %#LineNr# Line: %l Column: %c "

vim.opt.errorformat = {
	"%f:%l:%c: fatal %trror: %m", -- gcc/clang fatal error
	"%f:%l:%c: %trror: %m",       -- gcc/clang error
	"%f:%l:%c: %tarning: %m",     -- gcc/clang warning
	"%-G%m"                       -- Ignore anything else
}

vim.opt.formatoptions:append("/")
vim.opt.cinkeys:append("0=break")
vim.opt.listchars:append({ lead = "." })

--------------------------------------------------------------------------------
-- Functions
--------------------------------------------------------------------------------

-- Building & Errors

-- Diagnostics configuration
vim.diagnostic.config({
	signs = {
		text = {
			[vim.diagnostic.severity.ERROR] = "",
			[vim.diagnostic.severity.WARN]  = ""
		},
		linehl = {
			[vim.diagnostic.severity.ERROR] = "DiagnosticLineError",
			[vim.diagnostic.severity.WARN]  = "DiagnosticLineWarn"
		},
	},
	virtual_text = {
		virt_text_pos = "eol_right_align",
		prefix =
			function(d, i, total)
				return d.severity == vim.diagnostic.severity.ERROR and "!" or "#"
			end
	},
	underline     = false,
	severity_sort = true
})

local _last_build = ""
local _quickfix   = {}
local _namespace  = vim.api.nvim_create_namespace("__qf.buffer.errors")

local function LoadDiagnostics(args)
	local bufnr = args.buf

	if _quickfix[bufnr] then
		vim.diagnostic.set(_namespace, bufnr, _quickfix[bufnr])
	end
end

local function ExecuteBuild()
	vim.cmd("silent make")

	-- Reset currently displayed diagnostics
	_quickfix = {}
	vim.diagnostic.reset()

	local entries = vim.fn.getqflist()
	if #entries ~= 0 then
		-- Group diagnostics by buffer number
		local diagnostics = vim.diagnostic.fromqflist(entries)
		for _, d in ipairs(diagnostics) do
			if not _quickfix[d.bufnr] then
				_quickfix[d.bufnr] = {}
			end

			table.insert(_quickfix[d.bufnr], d)
		end

		-- Display the new diagnostics
		for it, v in pairs(_quickfix) do
			vim.diagnostic.set(_namespace, it, v)
		end
	end
end

local function PromptBuild()
	vim.ui.input(
		{
			prompt     = "Compile: ",
			completion = "shellcmdline",
			default    = _last_build
		},
		function(input)
			if input ~= nil then
				local makeprg = vim.o.makeprg
				vim.o.makeprg = input

				ExecuteBuild()

				_last_build   = input
				vim.o.makeprg = makeprg
			end
		end
	)
end

-- Buffers

local function BufferComplete()
	local pos   = vim.api.nvim_win_get_cursor(0)
	local line  = vim.fn.getline('.')
	local ident = line:sub(1, pos[2]):match("[^ \t]*$")

	return #ident ~= 0 and "<C-P>" or "<Tab>"
end

local function TrimBuffer()
	local view = vim.fn.winsaveview()
	vim.cmd("%s/\\s\\+$//e")
	vim.fn.winrestview(view)
end

local function MakeScratch()
	local bufnr = vim.api.nvim_create_buf(true, true)

	vim.api.nvim_buf_set_option(bufnr, "buftype",   "nofile")
	vim.api.nvim_buf_set_option(bufnr, "bufhidden", "hide")
	vim.api.nvim_buf_set_option(bufnr, "swapfile",  false)
	vim.api.nvim_buf_set_option(bufnr, "modified",  false)

	vim.api.nvim_buf_set_name(bufnr, "scratch")

	vim.api.nvim_buf_set_text(bufnr, 0, 0, 0, -1, { "-*- Scratch Buffer -*-" })

	-- @Hack: There isn't really any way to get the fullscreen size, 150 greater than the
	-- half-screen width on all of my devices as we don't want to split in that case
	if vim.o.columns > 150 then
		vim.cmd(string.format("vsplit #%d", bufnr))
		vim.cmd("wincmd p")
	end
end

-- Windowing

local _is_help = { help = true, man = true, qf = true }

function ManageSplit()
	local windows  = vim.api.nvim_tabpage_list_wins(0)
	local bufnr    = vim.api.nvim_win_get_buf(windows[#windows])
	local filetype = vim.bo[bufnr].filetype

	local target_count = _is_help[filetype] and 3 or 2

	if #windows == target_count then
		-- We already have the target number of windows open so we should close our split window,
		-- always close 2 because that is the right-most split. The third window if it exists is
		-- the bottom most window and is a "help" window
		vim.api.nvim_win_close(windows[2], false)
	else
		-- We have less than the required windows open so split the first window, we open the
		-- "scratch" buffer in this new window, if it is still open. Otherwise the same buffer in
		-- the first window is opened.
		local scratch = vim.fn.bufnr("scratch")
		local first   = vim.api.nvim_win_get_buf(windows[1])

		bufnr = vim.api.nvim_buf_is_loaded(scratch) and scratch or first
		vim.api.nvim_open_win(bufnr, true, { split = "right", win = windows[1] })
	end
end

local function ProjectSearch()
	local input = vim.fn.input("Search: ")

	if input and input ~= "" then
		vim.cmd("silent lgrep! \"" .. input .. "\" **")
		vim.cmd("lopen | lfirst | wincmd p")
	end
end

local function ExpandHelp(a)
	local winid    = vim.api.nvim_get_current_win()
	local filetype = vim.bo[vim.api.nvim_win_get_buf(winid)].filetype
	local height   = a.event == "WinEnter" and math.floor(0.8 * vim.o.lines) or 5

	if _is_help[filetype] then
		vim.api.nvim_win_set_height(winid, height)
	end
end

local function LayoutHelp(a)
	if _is_help[vim.bo.filetype] then
		local winid   = vim.api.nvim_get_current_win()
		local windows = vim.api.nvim_tabpage_list_wins(0)

		-- We need to close other "help" windows that may be open so search through the open
		-- windows. There *should* only ever be 3 windows open if my window handling is working
		-- correctly
		for _, w in ipairs(windows) do
			if w ~= winid then
				local bufnr = vim.api.nvim_win_get_buf(w)
				if _is_help[vim.bo[bufnr].filetype] then
					vim.api.nvim_win_close(wi.winid, true)
				end
			end
		end

		-- Force the new window to the bottom and expand it to be 80% of the height
		vim.cmd("wincmd J")
		vim.cmd(string.format("resize %d", math.floor(0.8 * vim.o.lines)))
	end
end

--------------------------------------------------------------------------------
-- Input mappings
--------------------------------------------------------------------------------

vim.g.mapleader = " "

MAP("n", "<A-j>",     "mz:m+<CR>")
MAP("n", "<A-k>",     "mz:m-2<CR>")
MAP("n", "<Esc>",     ":nohl<CR>")
MAP("n", "<Leader>n", ":cnext<CR>")
MAP("n", "<Leader>N", ":cprev<CR>")
MAP("n", "J",         "}")
MAP("v", "J",         "}")
MAP("n", "K",         "{")
MAP("v", "K",         "{")
MAP("n", "<Leader>k", ":Man<CR>")
MAP("i", "<S-Tab>",   "<C-o><<")
MAP("i", "<Tab>",     BufferComplete, { expr = true })
MAP("n", "<Leader>s", ManageSplit)
MAP("n", "<Leader>f", ProjectSearch)
MAP("n", "<Leader>m", PromptBuild)

--------------------------------------------------------------------------------
-- Autocommands
--------------------------------------------------------------------------------

AUTOCMD('BufEnter',    { command = "let b:man_default_sects=\"2,3\"", pattern = "*.c"      })
AUTOCMD('BufReadPost', { command = "setlocal nornu",                  pattern = "quickfix" })

AUTOCMD('BufWritePre', { callback = TrimBuffer,      pattern = "*" })
AUTOCMD('VimEnter',    { callback = MakeScratch,     pattern = "*" })
AUTOCMD('BufWinEnter', { callback = LayoutHelp,      pattern = "*" })
AUTOCMD('WinEnter',    { callback = ExpandHelp,      pattern = "*" })
AUTOCMD('WinLeave',    { callback = ExpandHelp,      pattern = "*" })
AUTOCMD('BufRead',     { callback = LoadDiagnostics, pattern = "*" })