import { isProKey } from "../services/keys.js";
import fs from "fs/promises";
import path from "path";

const USAGE_FILE = "/app/data/usage.json";
let usage = new Map<string, { count: number; monthKey: string }>();
const FREE_TIER_LIMIT = 100;

function getMonthKey(): string {
  const d = new Date();
  return `${d.getFullYear()}-${String(d.getMonth() + 1).padStart(2, "0")}`;
}

// Load usage data from file on startup
async function loadUsageData(): Promise<void> {
  try {
    const data = await fs.readFile(USAGE_FILE, "utf8");
    const usageObj = JSON.parse(data);
    
    usage = new Map();
    for (const [key, record] of Object.entries(usageObj)) {
      usage.set(key, record as { count: number; monthKey: string });
    }
    
    console.log(`Loaded usage data for ${usage.size} keys`);
  } catch (error) {
    // File doesn't exist or invalid JSON - start fresh
    console.log("No existing usage data found, starting fresh");
    usage = new Map();
  }
}

// Save usage data to file
async function saveUsageData(): Promise<void> {
  try {
    const usageObj: Record<string, { count: number; monthKey: string }> = {};
    for (const [key, record] of usage) {
      usageObj[key] = record;
    }
    
    // Ensure directory exists
    await fs.mkdir(path.dirname(USAGE_FILE), { recursive: true });
    await fs.writeFile(USAGE_FILE, JSON.stringify(usageObj, null, 2));
  } catch (error) {
    console.error("Failed to save usage data:", error);
  }
}

// Initialize usage data loading
loadUsageData().catch(console.error);

export function usageMiddleware(req: any, res: any, next: any): void {
  const key = req.headers.authorization?.slice(7) || "unknown";
  const monthKey = getMonthKey();

  // Pro keys have no limit
  if (isProKey(key)) {
    trackUsage(key, monthKey);
    next();
    return;
  }

  // Free tier limit check
  const record = usage.get(key);
  if (record && record.monthKey === monthKey && record.count >= FREE_TIER_LIMIT) {
    res.status(429).json({
      error: "Free tier limit reached",
      limit: FREE_TIER_LIMIT,
      used: record.count,
      upgrade: "Upgrade to Pro for unlimited conversions: https://docfast.dev/pricing",
    });
    return;
  }

  trackUsage(key, monthKey);
  next();
}

function trackUsage(key: string, monthKey: string): void {
  const record = usage.get(key);
  if (!record || record.monthKey !== monthKey) {
    usage.set(key, { count: 1, monthKey });
  } else {
    record.count++;
  }
  
  // Save to file after each update (simple approach)
  saveUsageData().catch(console.error);
}

export function getUsageStats(): Record<string, { count: number; month: string }> {
  const stats: Record<string, { count: number; month: string }> = {};
  for (const [key, record] of usage) {
    const masked = key.slice(0, 8) + "...";
    stats[masked] = { count: record.count, month: record.monthKey };
  }
  return stats;
}