/**
 * Server-only: read/write delivery rate overrides from data/delivery-rates.json.
 * Do NOT import this file from client components.
 */
import { readFileSync, existsSync } from 'fs'
import path from 'path'
import { atomicWriteJSON } from './file-utils'
import { RATES, type DeliveryRatesConfig, type DeliveryTier } from './delivery'

const RATES_PATH = path.join(process.cwd(), 'data', 'delivery-rates.json')

const TIERS: DeliveryTier[] = ['dropoff', 'classic', 'organic']

export function readDeliveryRates(): DeliveryRatesConfig {
  const defaults: DeliveryRatesConfig = {
    dropoff: { ...RATES.dropoff },
    classic: { ...RATES.classic },
    organic: { ...RATES.organic },
  }
  if (!existsSync(RATES_PATH)) return defaults
  try {
    const stored = JSON.parse(readFileSync(RATES_PATH, 'utf-8')) as Partial<DeliveryRatesConfig>
    const merged = { ...defaults }
    for (const tier of TIERS) {
      if (stored[tier]) merged[tier] = { ...defaults[tier], ...stored[tier] }
    }
    return merged
  } catch {
    return defaults
  }
}

export function writeDeliveryRates(config: DeliveryRatesConfig): void {
  atomicWriteJSON(RATES_PATH, config)
}