interface RateLimitEntry {
  count: number
  resetAt: number
}

const store = new Map<string, RateLimitEntry>()

// Cleanup stale entries every 60 seconds
setInterval(() => {
  const now = Date.now()
  for (const [key, entry] of store) {
    if (entry.resetAt <= now) store.delete(key)
  }
}, 60_000)

export interface RateLimitConfig {
  /** Max requests in the window */
  limit: number
  /** Window size in seconds */
  windowSec: number
}

export interface RateLimitResult {
  allowed: boolean
  remaining: number
  resetAt: number
}

export function checkRateLimit(key: string, config: RateLimitConfig): RateLimitResult {
  const now = Date.now()
  const entry = store.get(key)

  if (!entry || entry.resetAt <= now) {
    store.set(key, { count: 1, resetAt: now + config.windowSec * 1000 })
    return { allowed: true, remaining: config.limit - 1, resetAt: now + config.windowSec * 1000 }
  }

  if (entry.count >= config.limit) {
    return { allowed: false, remaining: 0, resetAt: entry.resetAt }
  }

  entry.count++
  return { allowed: true, remaining: config.limit - entry.count, resetAt: entry.resetAt }
}

// Preset configurations
export const RATE_LIMITS = {
  magicLink: { limit: 3, windowSec: 3600 } as RateLimitConfig,        // 3 per email per hour
  authVerify: { limit: 10, windowSec: 900 } as RateLimitConfig,       // 10 per IP per 15min
  api: { limit: 60, windowSec: 60 } as RateLimitConfig,               // 60 per session per minute
  chat: { limit: 20, windowSec: 60 } as RateLimitConfig,              // 20 per session per minute
} as const