path: root/plugin/50-color.lua

--
-- 50-color.lua
--
-- * Highlight tweaks for the solarized colorscheme, plus popup-menu and tabpage-title styling.
-- * The lualine statusline (https://github.com/nvim-lualine/lualine.nvim), themed to match.
-- * Registers both into dotfiles.color, which re-applies them on colorscheme / 'background' changes
--   and once after startup.
-- * Sets the default colorscheme (solarized) and background (dark).
--
-- User commands:
--   `ColorsBgToggle`: toggle light/dark background
--   `TabRename`: rename current tab
--   `TabRenameFileName`: rename current tab to the active buffer's file name
--   `LualineConfig`: show the resolved lualine configuration
--

local color = require("dotfiles.color")
local lualine = require("lualine")

local solarized = { blue = "#268bd2" }

----------------------------------------------------------------------------------------------------
-- Highlights
----------------------------------------------------------------------------------------------------

-- Highlight applier: adjust the solarized groups to fit my personal tastes. No-ops unless solarized
-- is the active colorscheme.
local function apply_solarized_highlights()
	if vim.g.colors_name ~= "solarized" then
		return
	end
	-- Window bar style
	vim.api.nvim_set_hl(0, "WinBarCwd", { fg = solarized.blue, italic = true })
	vim.api.nvim_set_hl(0, "WinBarFilePath", { italic = true })
	-- Matching delimiter
	vim.api.nvim_set_hl(0, "MatchParen", { link = "CurSearch" })
	-- Floating windows and popup menu windows follow the editor background, their borders too so
	-- that the popup menu border draws a clean separation.
	vim.opt.pumborder = "rounded"
	vim.opt.pumwidth = 25 -- Minimum popup menu width
	vim.api.nvim_set_hl(0, "NormalFloat", { link = "Normal" })
	local normal_bg = vim.api.nvim_get_hl(0, { name = "Normal", link = false }).bg
	vim.api.nvim_set_hl(0, "FloatBorder", { bg = normal_bg, update = true })
	vim.api.nvim_set_hl(0, "Pmenu", { bg = normal_bg, update = true })
	vim.api.nvim_set_hl(0, "PmenuSbar", { bg = normal_bg, update = true })
	-- Currently selected tabpage
	vim.api.nvim_set_hl(0, "TabLineSel", { bold = true, italic = true, update = true })
	-- Todo hl group
	vim.api.nvim_set_hl(0, "Todo", { bg = "Yellow", fg = "Black", bold = true })
	-- Fold lines being the same color as the cursor line (default) make unfocused windows unreadable
	-- Their background is set to blend in, the folds are visible enough with their dotted lines
	vim.api.nvim_set_hl(0, "Folded", { bg = normal_bg, underline = true, update = true })
end

-- Highlight applier: create custom highlight groups for styling the tabpage title bars:
-- * TabLineWinCount: number of open windows in the tabpage
-- * TabLineSelWinCount: number of open windows in the currently active tabpage
local function apply_tabpage_title_highlights()
	local normal = vim.api.nvim_get_hl(0, { name = "Normal", link = false })
	local tabline = vim.api.nvim_get_hl(0, { name = "TabLine", link = false })
	local tablinesel = vim.api.nvim_get_hl(0, { name = "TabLineSel", link = false })
	vim.api.nvim_set_hl(0, "TabLineSel", { fg = normal.fg, update = true })
	vim.api.nvim_set_hl(0, "TabLineWinCount", { fg = solarized.blue, bg = tabline.bg })
	vim.api.nvim_set_hl(
		0,
		"TabLineSelWinCount",
		{ fg = solarized.blue, bg = tablinesel.bg, bold = true }
	)
end

----------------------------------------------------------------------------------------------------
-- Statusline
----------------------------------------------------------------------------------------------------

-- Spell flag: which spell languages are enabled, or nil when 'spelllang' matches none of these.
local function spell_status()
	if vim.o.spelllang == "fr" then
		return "+S(fr)"
	elseif vim.o.spelllang == "en_us" then
		return "+S(en)"
	elseif vim.o.spelllang == "en_us,fr" then
		return "+S(en,fr)"
	end
end

-- Custom status flags: "+F" when formatting is on for the buffer, "+H" when LSP inlay hints are on,
-- followed by the spell flag.
local function statuses()
	return (vim.b.format and "+F" or "")
		.. (vim.lsp.inlay_hint.is_enabled({ bufnr = 0 }) and "+H" or "")
		.. (vim.o.spell and spell_status() or "")
end

-- lualine builds its own section-b-backed highlights for the diff/diagnostics components
-- (lualine_b_diff_added_normal, lualine_b_diagnostics_error_normal, ...). Stamp bold onto them with
-- update=true so only the bold attribute changes — fg and section b's background are left untouched.
-- Must run after lualine (re)creates the groups: initial setup, theme switch, colorscheme.
local function bold_diff_diag()
	for name in pairs(vim.api.nvim_get_hl(0, {})) do
		if name:find("^lualine_b_diff") or name:find("^lualine_b_diagnostics") then
			vim.api.nvim_set_hl(0, name, { bold = true, update = true })
		end
	end
end

local lualine_sections = {
	lualine_c = { statuses },
	lualine_x = { "encoding", "fileformat", "filetype", "lsp_status" },
}

local lualine_options = {
	disabled_filetypes = { "netrw", "qf" },
	component_separators = { left = "|", right = "|" },
	section_separators = { left = "", right = "" },
}

-- Pick the lualine theme from 'background' and (re)apply the configuration.
local function configure_lualine()
	lualine_options.theme = vim.o.background == "light" and "solarized_light" or "solarized_dark"
	lualine.setup({ options = lualine_options, sections = lualine_sections })
end

-- Statusline applier: re-pick the lualine theme for the current 'background', then re-bold the
-- diff/diagnostics groups once lualine has rebuilt them.
local function apply_statusline_highlights()
	configure_lualine()
	vim.schedule(bold_diff_diag)
end

----------------------------------------------------------------------------------------------------
-- Tabline
----------------------------------------------------------------------------------------------------

-- Builds the window-count segment of a tabpage label, e.g. ` (2)[+] ` (no styling).
-- `is_modified` appends the `[+]` marker when any window in the tab has pending changes.
local function make_tab_info_label(win_count, is_modified)
	local tab_win_count = "(" .. (win_count >= 10 and ">9" or tostring(win_count)) .. ")"
	local tab_win_count_suffix = is_modified and "[+] " or " "
	return " " .. tab_win_count .. tab_win_count_suffix
end

-- Builds the title segment of a tabpage label, padded or truncated to `width` (no styling).
-- Uses the tab's `tabname` if set, else the active buffer's file name, else `[No Name]`, prefixed
-- with `*` for the current tab and `-` for the last-accessed tab.
local function make_tab_label(id, is_current, width)
	local is_last_accessed = vim.api.nvim_tabpage_get_number(id) == vim.fn.tabpagenr("#")
	local tab_label_prefix = (is_current and "*" or "") .. (is_last_accessed and "-" or "")
	local tab_label = vim.t[id].tabname
	if tab_label == nil or tab_label == "" then
		local win = vim.api.nvim_tabpage_get_win(id)
		local bufname = vim.api.nvim_buf_get_name(vim.api.nvim_win_get_buf(win))
		tab_label = vim.fn.fnamemodify(bufname, ":t")
	end
	if tab_label == "" then
		tab_label = "[No Name]"
	end
	tab_label = tab_label_prefix .. tab_label
	local display_width = vim.fn.strdisplaywidth(tab_label)
	return (display_width > width) and (vim.fn.strcharpart(tab_label, 0, width - 1) .. "…")
		or (tab_label .. string.rep(" ", width - display_width))
end

-- Returns a string compatible with the 'tabline' option, used to set the tabline content and style.
-- Declared as a global function to be available as `v:lua.GetTabLine` in the Vimscript engine for
-- the 'tabline' option. See `:help 'statusline'`.
function GetTabLine()
	local max_tab_label_width = 30
	local s = ""
	for _, id in pairs(vim.api.nvim_list_tabpages()) do
		local is_current = id == vim.api.nvim_get_current_tabpage()
		local is_modified = false
		local wins = vim.api.nvim_tabpage_list_wins(id)
		for _, win in ipairs(wins) do
			if vim.bo[vim.api.nvim_win_get_buf(win)].modified then
				is_modified = true
				break
			end
		end

		-- Define start of tabpage label (marks where clickage region begins)
		s = s .. "%" .. vim.api.nvim_tabpage_get_number(id) .. "T"

		local tab_info_label = make_tab_info_label(#wins, is_modified)
		local tab_label_width = max_tab_label_width - vim.fn.strdisplaywidth(tab_info_label)
		local tab_label = make_tab_label(id, is_current, tab_label_width)

		s = s .. (is_current and "%#TabLineSelWinCount#" or "%#TabLineWinCount#") .. tab_info_label
		s = s .. (is_current and "%#TabLineSel#" or "%#TabLine#") .. tab_label
	end
	return s .. "%#TabLineFill#"
end

-- Name the current tab from the command argument.
local function rename_tab(opts)
	vim.t.tabname = opts.args
	vim.cmd.redrawtabline()
end

-- Name the current tab after the active buffer's file name (without extension).
local function rename_tab_to_cur_filename()
	vim.t.tabname = vim.fn.expand("%:t:r")
	vim.cmd.redrawtabline()
end

----------------------------------------------------------------------------------------------------
-- Commands & init
----------------------------------------------------------------------------------------------------

-- Flip between the light and dark backgrounds (the colorscheme reloads, OptionSet re-themes).
local function toggle_theme()
	vim.opt.background = vim.o.background == "light" and "dark" or "light"
	vim.notify("Color theme set to " .. vim.o.background)
end

-- Show the resolved lualine configuration.
local function show_lualine_config()
	vim.notify(vim.inspect(lualine.get_config()))
end

color.register(apply_solarized_highlights)
color.register(apply_tabpage_title_highlights)
color.register(apply_statusline_highlights)

vim.api.nvim_create_user_command(
	"ColorsBgToggle",
	toggle_theme,
	{ desc = "Toggle light/dark theme" }
)
vim.api.nvim_create_user_command("TabRename", rename_tab, { nargs = 1 })
vim.api.nvim_create_user_command("TabRenameFileName", rename_tab_to_cur_filename, { nargs = 0 })
vim.api.nvim_create_user_command(
	"LualineConfig",
	show_lualine_config,
	{ desc = "Show lualine configuration" }
)

-- See `:help stl-%!`
vim.o.tabline = "%!v:lua.GetTabLine()"
vim.cmd.colorscheme("solarized")
vim.opt.background = "dark"