/**
 * Next.js Analyzer (RFC-0062)
 *
 * Deep analysis of Next.js workspaces via filesystem inspection.
 * Does NOT evaluate code or connect to the network.
 */

import { existsSync } from "node:fs";
import { readdir, readFile } from "node:fs/promises";
import { join } from "node:path";
import type { NextJsAnalysis, AppRoute, ConfigFile } from "./types.js";

// ─── Detection ───────────────────────────────────────────────────────────────

function isNextJsWorkspace(root: string): boolean {
	return (
		existsSync(join(root, "next.config.js")) ||
		existsSync(join(root, "next.config.mjs")) ||
		existsSync(join(root, "next.config.ts")) ||
		existsSync(join(root, "app")) ||
		existsSync(join(root, "pages"))
	);
}

// ─── Version Detection ───────────────────────────────────────────────────────

async function detectVersion(root: string): Promise<string | undefined> {
	try {
		const pkg = JSON.parse(await readFile(join(root, "package.json"), "utf-8"));
		return pkg.dependencies?.next
			? pkg.dependencies.next.replace(/[\^~>=<]/, "")
			: pkg.devDependencies?.next
				? pkg.devDependencies.next.replace(/[\^~>=<]/, "")
				: undefined;
	} catch {
		return undefined;
	}
}

// ─── Router Detection ───────────────────────────────────────────────────────

async function detectRouters(root: string): Promise<{
	usingAppRouter: boolean;
	usingPagesRouter: boolean;
}> {
	const hasApp = existsSync(join(root, "app"));
	const hasPages = existsSync(join(root, "pages"));
	return { usingAppRouter: hasApp, usingPagesRouter: hasPages };
}

// ─── Config Files ────────────────────────────────────────────────────────────

async function findConfigFiles(root: string): Promise<ConfigFile[]> {
	const configFiles = [
		{ name: "next.config.js", path: join(root, "next.config.js") },
		{ name: "next.config.mjs", path: join(root, "next.config.mjs") },
		{ name: "next.config.ts", path: join(root, "next.config.ts") },
	];
	const configs: ConfigFile[] = [];
	for (const cfg of configFiles) {
		if (existsSync(cfg.path)) {
			configs.push({ name: cfg.name, path: cfg.path });
		}
	}
	return configs;
}

// ─── App Router Routes ─────────────────────────────────────────────────────

async function walkAppRouter(
	dir: string,
	base: string = "",
): Promise<AppRoute[]> {
	const routes: AppRoute[] = [];
	try {
		const entries = await readdir(dir, { withFileTypes: true });
		for (const entry of entries) {
			if (entry.name.startsWith("_") || entry.name.startsWith(".")) continue;

			const rel = base ? `${base}/${entry.name}` : entry.name;

			if (entry.isDirectory()) {
				// Dynamic segment: [param] or (group)
				const isDynamic =
					entry.name.startsWith("[") && entry.name.endsWith("]");
				const isGroup = entry.name.startsWith("(") && entry.name.endsWith(")");
				if (!isGroup) {
					routes.push({
						path: rel,
						method: "GET",
						isDynamic,
						file: rel,
					});
				}
				const sub = await walkAppRouter(join(dir, entry.name), rel);
				routes.push(...sub);
			} else if (entry.name === "page.tsx" || entry.name === "page.ts") {
				routes.push({
					path: rel.replace(/page\.(tsx?|jsx?)$/, ""),
					method: "GET",
					isDynamic: base.includes("["),
					file: rel,
				});
			} else if (entry.name === "route.ts" || entry.name === "route.js") {
				// HTTP method detection from siblings
				routes.push({
					path: rel.replace(/\/route\.(ts|js)$/, ""),
					method: "ALL",
					isDynamic: base.includes("["),
					file: rel,
				});
			}
		}
	} catch {
		// ignore
	}
	return routes;
}

// ─── Pages Router API Routes ─────────────────────────────────────────────────

async function walkApiRoutes(
	dir: string,
	base: string = "",
): Promise<string[]> {
	const routes: string[] = [];
	try {
		const entries = await readdir(dir, { withFileTypes: true });
		for (const entry of entries) {
			if (entry.name.startsWith("_") || entry.name.startsWith(".")) continue;
			const rel = base ? `${base}/${entry.name}` : entry.name;
			if (entry.isDirectory()) {
				routes.push(...(await walkApiRoutes(join(dir, entry.name), rel)));
			} else if (entry.name.endsWith(".ts") || entry.name.endsWith(".js")) {
				const normalized = rel.replace(/\.(ts|js)$/, "").replace(/index$/, "");
				if (!routes.includes(normalized)) {
					routes.push(normalized);
				}
			}
		}
	} catch {
		// ignore
	}
	return routes;
}

// ─── Middleware ─────────────────────────────────────────────────────────────

async function findMiddleware(root: string): Promise<string | undefined> {
	const candidates = [
		join(root, "middleware.ts"),
		join(root, "middleware.js"),
		join(root, "middleware.tsx"),
		join(root, "middleware.jsx"),
	];
	for (const p of candidates) {
		if (existsSync(p)) return p;
	}
	return undefined;
}

// ─── Environment Variables ─────────────────────────────────────────────────

async function findEnvVars(root: string): Promise<string[]> {
	const candidates = [
		join(root, ".env.example"),
		join(root, ".env.local"),
		join(root, ".env.development"),
		join(root, ".env.production"),
	];
	const vars: string[] = [];
	const seen = new Set<string>();
	for (const p of candidates) {
		if (existsSync(p)) {
			try {
				const content = await readFile(p, "utf-8");
				for (const line of content.split("\n")) {
					const trimmed = line.trim();
					if (trimmed && !trimmed.startsWith("#") && trimmed.includes("=")) {
						const key = trimmed.split("=")[0].trim();
						if (key && !seen.has(key)) {
							seen.add(key);
							vars.push(key);
						}
					}
				}
			} catch {
				// ignore
			}
		}
	}
	return vars;
}

// ─── Main Analyzer ─────────────────────────────────────────────────────────

/**
 * Analyze a Next.js workspace (RFC-0062)
 */
export async function analyzeNextJs(
	root: string,
): Promise<NextJsAnalysis | null> {
	if (!isNextJsWorkspace(root)) {
		return null;
	}

	const [version, routers, configs] = await Promise.all([
		detectVersion(root),
		detectRouters(root),
		findConfigFiles(root),
	]);

	const appRoutes: AppRoute[] = [];
	if (routers.usingAppRouter) {
		appRoutes.push(...(await walkAppRouter(join(root, "app"))));
	}

	const apiRoutes: string[] = [];
	if (routers.usingPagesRouter) {
		const apiDir = join(root, "pages", "api");
		if (existsSync(apiDir)) {
			apiRoutes.push(...(await walkApiRoutes(apiDir)));
		}
	}

	const [middleware, environmentVars] = await Promise.all([
		findMiddleware(root),
		findEnvVars(root),
	]);

	return {
		framework: {
			id: "nextjs",
			name: "Next.js",
			category: "fullstack",
			description: "The React Framework for Production",
			tags: ["react", "ssr", "fullstack", "typescript"],
		},
		version,
		...routers,
		apiRoutes,
		appRoutes,
		middleware,
		environmentVars,
		configs,
	};
}