fullstack-starter/src/server/prediction/client.ts

import { LRUCache } from 'lru-cache'
import { z } from 'zod'
import {
  type BatteryInfo,
  type BatteryPrediction,
  POWER_STATUS,
  type PowerStatus,
  toMysqlBoolean,
} from '@/domain/battery'
import { env } from '@/env'
import { getLogger } from '@/server/logger'

export const sohPredictionSchema = z.object({
  batteryId: z.number().int(),
  mac: z.string(),
  nowSoh: z.number(),
  monthSoh: z.number(),
  trmonthSoh: z.number(),
  riskScore: z.number().nullable(),
  riskLevel: z.string().nullable(),
  status: z.string().nullable(),
  modelName: z.string().nullable(),
  cyclesUsed: z.number().int().nullable(),
  updatedAt: z.string().nullable(),
})
export type SohPrediction = BatteryPrediction & z.infer<typeof sohPredictionSchema>

type PredictionHistoryItem = {
  cycle: number
  charge_capacity_ah: number
  discharge_capacity_ah: number
  charge_energy_wh: number
  discharge_energy_wh: number
  charge_time: string
  discharge_time: string
  coulombic_efficiency_pct: number
  timestamp: string
}

type PredictionRequest = {
  battery: {
    id: number
    user_id: number
    mac: string
    dev_model: string
    dev_name: string
    is_low_power: string
    power_status: PowerStatus
    power: number
    create_time: string
    remark: string
  }
  history: PredictionHistoryItem[]
}

const predictionResponseSchema = z.object({
  now_soh: z.number(),
  month_soh: z.number(),
  trmonth_soh: z.number(),
  risk_score: z.number().nullable().optional(),
  risk_level: z.string().nullable().optional(),
  status: z.string().nullable().optional(),
  battery_id: z.number().int(),
  mac: z.string(),
  model_name: z.string().nullable().optional(),
  cycles_used: z.number().int().nullable().optional(),
  updated_at: z.string().nullable().optional(),
})

const logger = getLogger(['prediction'])
const cache = new LRUCache<string, SohPrediction>({
  max: 5_000,
  ttl: env.SOH_PREDICTION_CACHE_TTL_SECONDS * 1000,
})
const inFlightRequests = new Map<string, Promise<SohPrediction | null>>()

const round2 = (value: number) => Math.round(value * 100) / 100

function normalizeMysqlDateTime(value: string) {
  if (!value.includes('T')) return value

  return value.slice(0, 19).replace('T', ' ')
}

function createCacheKey(battery: BatteryInfo, history: BatteryInfo[]) {
  const latestHistory = history.at(-1)
  const latestId = latestHistory?.id ?? battery.id
  const latestTime = latestHistory?.createTime ?? battery.createTime

  return `${battery.mac}:${latestId}:${latestTime}`
}

function createHistoryItem(item: BatteryInfo, index: number): PredictionHistoryItem {
  const sohRatio = Math.max(0.5, Math.min(1, item.power / 100))
  const chargeCapacity = round2(3.2 * sohRatio)
  const efficiency = round2(Math.max(80, Math.min(99, 92 + item.power / 12 - (item.isLowPower ? 4 : 0))))
  const dischargeCapacity = round2(chargeCapacity * (efficiency / 100))
  const chargeEnergy = round2(chargeCapacity * 3.75)
  const dischargeEnergy = round2(dischargeCapacity * 3.7)

  return {
    cycle: index + 1,
    charge_capacity_ah: chargeCapacity,
    discharge_capacity_ah: dischargeCapacity,
    charge_energy_wh: chargeEnergy,
    discharge_energy_wh: dischargeEnergy,
    charge_time: item.powerStatus === POWER_STATUS.CHARGING ? '01:20:00' : '01:18:00',
    discharge_time: item.isLowPower ? '00:58:00' : '01:10:00',
    coulombic_efficiency_pct: efficiency,
    timestamp: normalizeMysqlDateTime(item.createTime),
  }
}

export function createPredictionRequest(battery: BatteryInfo, history: BatteryInfo[]): PredictionRequest | null {
  const sourceHistory = history.length > 0 ? history : [battery]

  if (sourceHistory.length < 5) return null

  return {
    battery: {
      id: battery.id,
      user_id: battery.userId,
      mac: battery.mac,
      dev_model: battery.devModel,
      dev_name: battery.devName,
      is_low_power: toMysqlBoolean(battery.isLowPower),
      power_status: battery.powerStatus,
      power: battery.power,
      create_time: normalizeMysqlDateTime(battery.createTime),
      remark: battery.remark ?? '',
    },
    history: sourceHistory.map(createHistoryItem),
  }
}

function normalizePrediction(response: z.infer<typeof predictionResponseSchema>): SohPrediction {
  return {
    batteryId: response.battery_id,
    mac: response.mac,
    nowSoh: response.now_soh,
    monthSoh: response.month_soh,
    trmonthSoh: response.trmonth_soh,
    riskScore: response.risk_score ?? null,
    riskLevel: response.risk_level ?? null,
    status: response.status ?? null,
    modelName: response.model_name ?? null,
    cyclesUsed: response.cycles_used ?? null,
    updatedAt: response.updated_at ?? null,
  }
}

export function isPredictionEnabled() {
  return true
}

export async function predictSoh(battery: BatteryInfo, history: BatteryInfo[]): Promise<SohPrediction | null> {
  const request = createPredictionRequest(battery, history)
  if (!request) return null

  const cacheKey = createCacheKey(battery, history)
  const cached = cache.get(cacheKey)
  if (cached) return cached
  const pendingRequest = inFlightRequests.get(cacheKey)
  if (pendingRequest) return pendingRequest

  const requestPromise = requestPrediction(cacheKey, battery, request)
  inFlightRequests.set(cacheKey, requestPromise)

  return requestPromise
}

async function requestPrediction(
  cacheKey: string,
  battery: BatteryInfo,
  request: PredictionRequest,
): Promise<SohPrediction | null> {
  const controller = new AbortController()
  const timeout = setTimeout(() => controller.abort(), env.SOH_PREDICTION_TIMEOUT_MS)
  const baseUrl = env.SOH_PREDICTION_API_BASE_URL.endsWith('/')
    ? env.SOH_PREDICTION_API_BASE_URL
    : `${env.SOH_PREDICTION_API_BASE_URL}/`
  const endpoint = new URL('predict', baseUrl)

  try {
    const response = await fetch(endpoint, {
      method: 'POST',
      headers: { 'content-type': 'application/json' },
      body: JSON.stringify(request),
      signal: controller.signal,
    })

    if (!response.ok) {
      logger.warn('SOH prediction request failed', { mac: battery.mac, status: response.status })
      return null
    }

    const json = await response.json()
    const prediction = normalizePrediction(predictionResponseSchema.parse(json))
    cache.set(cacheKey, prediction)

    return prediction
  } catch (error) {
    logger.warn('SOH prediction request errored', { mac: battery.mac, error })
    return null
  } finally {
    clearTimeout(timeout)
    inFlightRequests.delete(cacheKey)
  }
}

export function clearPredictionCache() {
  cache.clear()
  inFlightRequests.clear()
}