/**
 * Terminal capability detection via environment variables.
 *
 * Computed once at import time — terminal capabilities don't change mid-session.
 * No async queries (DECRQM, DA) needed; env vars cover the common terminals.
 */

const env = process.env;
const termProgram = env.TERM_PROGRAM ?? "";
const termVar = env.TERM ?? "";

/** Detected terminal capabilities. */
export interface TerminalCaps {
	/** OSC 8 hyperlinks supported */
	hyperlinks: boolean;
	/** Kitty keyboard protocol (CSI u) supported */
	kittyKeyboard: boolean;
	/** SGR mouse reporting supported */
	mouse: boolean;
	/** Synchronized output (DEC 2026) supported */
	syncOutput: boolean;
	/** Terminal name (best guess) */
	terminal: string;
	/** 24-bit true color supported */
	trueColor: boolean;
}

// --- Shared terminal sets ---

const SYNC_TERM_PROGRAMS = new Set([
	"iTerm.app",
	"WezTerm",
	"WarpTerminal",
	"ghostty",
	"contour",
	"vscode",
	"alacritty",
	"zed",
]);

const TRUECOLOR_TERM_PROGRAMS = new Set([
	"iTerm.app",
	"WezTerm",
	"WarpTerminal",
	"ghostty",
	"vscode",
	"alacritty",
	"Hyper",
	"zed",
]);

const HYPERLINK_TERM_PROGRAMS = new Set([
	"iTerm.app",
	"WezTerm",
	"ghostty",
	"alacritty",
	"Hyper",
	"vscode",
	"zed",
]);

const KITTY_KEYBOARD_TERM_PROGRAMS = new Set([
	"iTerm.app",
	"WezTerm",
	"ghostty",
	"zed",
]);

const KITTY_TERM_VARS = new Set([
	"kitty",
	"xterm-ghostty",
	"foot",
	"alacritty",
]);

function getVteVersion(): number {
	const raw = env.VTE_VERSION;
	if (!raw) return 0;
	const v = Number.parseInt(raw, 10);
	return Number.isNaN(v) ? 0 : v;
}

function isKittyEnv(): boolean {
	return !!env.KITTY_WINDOW_ID;
}

// --- Detectors ---

function detectTerminal(): string {
	if (env.TERM_PROGRAM) return env.TERM_PROGRAM;
	if (env.KITTY_WINDOW_ID) return "kitty";
	if (env.WT_SESSION) return "windows-terminal";
	if (env.ZED_TERM) return "zed";
	if (env.TERM) return env.TERM;
	return "unknown";
}

function detectSyncOutput(): boolean {
	if (env.TMUX) return false;
	if (SYNC_TERM_PROGRAMS.has(termProgram)) return true;
	if (KITTY_TERM_VARS.has(termVar)) return true;
	if (isKittyEnv()) return true;
	if (env.ZED_TERM) return true;
	if (env.WT_SESSION) return true;
	if (getVteVersion() >= 6800) return true;
	return false;
}

function detectTrueColor(): boolean {
	if (env.COLORTERM === "truecolor" || env.COLORTERM === "24bit") return true;
	if (TRUECOLOR_TERM_PROGRAMS.has(termProgram)) return true;
	if (KITTY_TERM_VARS.has(termVar)) return true;
	if (isKittyEnv()) return true;
	if (env.WT_SESSION) return true;
	return false;
}

function detectKittyKeyboard(): boolean {
	if (KITTY_KEYBOARD_TERM_PROGRAMS.has(termProgram)) return true;
	if (KITTY_TERM_VARS.has(termVar)) return true;
	if (isKittyEnv()) return true;
	if (env.TMUX) return true;
	return false;
}

function detectHyperlinks(): boolean {
	if (env.TMUX) return false;
	if (HYPERLINK_TERM_PROGRAMS.has(termProgram)) return true;
	if (KITTY_TERM_VARS.has(termVar)) return true;
	if (isKittyEnv()) return true;
	if (env.WT_SESSION) return true;
	if (getVteVersion() >= 5000) return true;
	return false;
}

function detectMouse(): boolean {
	return process.stdout.isTTY === true;
}

/** Cached terminal capabilities — computed once at import time. */
export const terminalCaps: TerminalCaps = {
	terminal: detectTerminal(),
	syncOutput: detectSyncOutput(),
	trueColor: detectTrueColor(),
	kittyKeyboard: detectKittyKeyboard(),
	hyperlinks: detectHyperlinks(),
	mouse: detectMouse(),
};