import fs from "node:fs";
import os from "node:os";
import path from "node:path";
import type { HudConfig, HudElement } from "./types.js";

export const CONFIG_PATH = path.join(os.homedir(), ".pi", "agent", "state", "universal-hud.json");

export const DEFAULT_ELEMENT_ORDER: HudElement[] = [
	"project",
	"identity",
	"usage",
	"tools",
	"agents",
	"session",
];

export const DEFAULT_CONFIG: HudConfig = {
	enabled: true,
	surface: "statusline",
	lineLayout: "expanded",
	showSeparators: false,
	pathLevels: 1,
	elementOrder: [...DEFAULT_ELEMENT_ORDER],
	display: {
		showProject: true,
		showContextBar: true,
		showUsage: true,
		showLimits: true,
		showTools: true,
		showAgents: true,
		showSession: true,
		showSessionTokens: true,
		showSpeed: true,
		showCost: true,
	},
};

export function loadConfig(): HudConfig {
	try {
		const raw = fs.readFileSync(CONFIG_PATH, "utf8");
		return normalizeConfig(JSON.parse(raw));
	} catch {
		return normalizeConfig(DEFAULT_CONFIG);
	}
}

export function saveConfig(next: HudConfig): void {
	try {
		fs.mkdirSync(path.dirname(CONFIG_PATH), { recursive: true });
		fs.writeFileSync(CONFIG_PATH, `${JSON.stringify(next, null, 2)}\n`, "utf8");
	} catch {
		// UI config persistence is best-effort.
	}
}

export function normalizeConfig(input: unknown): HudConfig {
	const raw = input && typeof input === "object" ? input as Partial<HudConfig> : {};
	const display: Record<string, unknown> = raw.display && typeof raw.display === "object" ? raw.display as Record<string, unknown> : {};
	const elementOrder = Array.isArray(raw.elementOrder)
		? raw.elementOrder.filter((item): item is HudElement => typeof item === "string" && DEFAULT_ELEMENT_ORDER.includes(item as HudElement))
		: DEFAULT_ELEMENT_ORDER;
	return {
		enabled: typeof raw.enabled === "boolean" ? raw.enabled : DEFAULT_CONFIG.enabled,
		surface: raw.surface === "footer" ? "footer" : "statusline",
		lineLayout: raw.lineLayout === "compact" ? "compact" : "expanded",
		showSeparators: typeof raw.showSeparators === "boolean" ? raw.showSeparators : DEFAULT_CONFIG.showSeparators,
		pathLevels: raw.pathLevels === 1 || raw.pathLevels === 2 || raw.pathLevels === 3 ? raw.pathLevels : DEFAULT_CONFIG.pathLevels,
		elementOrder: elementOrder.length > 0 ? dedupeElements(elementOrder) : [...DEFAULT_ELEMENT_ORDER],
		display: {
			showProject: booleanValue(display.showProject, true),
			showContextBar: booleanValue(display.showContextBar, true),
			showUsage: booleanValue(display.showUsage, true),
			showLimits: booleanValue(display.showLimits, true),
			showTools: booleanValue(display.showTools, true),
			showAgents: booleanValue(display.showAgents, true),
			showSession: booleanValue(display.showSession, true),
			showSessionTokens: booleanValue(display.showSessionTokens, true),
			showSpeed: booleanValue(display.showSpeed, true),
			showCost: booleanValue(display.showCost, true),
		},
	};
}

function dedupeElements(elements: HudElement[]): HudElement[] {
	const seen = new Set<HudElement>();
	const result: HudElement[] = [];
	for (const element of elements) {
		if (seen.has(element)) continue;
		seen.add(element);
		result.push(element);
	}
	return result;
}

function booleanValue(value: unknown, fallback: boolean): boolean {
	return typeof value === "boolean" ? value : fallback;
}