import { createWriteStream, existsSync, mkdirSync } from 'fs'
import { resolve, dirname } from 'path'
import { fileURLToPath } from 'url'
import { pipeline } from 'stream/promises'

const DIR      = dirname(fileURLToPath(import.meta.url))
const ICON_DIR = resolve(DIR, 'public', 'icons')
const CACHE    = {}
const CACHE_MS = 15 * 60 * 1000

if (!existsSync(ICON_DIR)) mkdirSync(ICON_DIR, { recursive: true })

const WMO = {
  0:  'Clear Sky',
  1:  'Mainly Clear',
  2:  'Partly Cloudy',
  3:  'Overcast',
  45: 'Fog',
  48: 'Icy Fog',
  51: 'Light Drizzle',
  53: 'Drizzle',
  55: 'Heavy Drizzle',
  61: 'Light Rain',
  63: 'Rain',
  65: 'Heavy Rain',
  71: 'Light Snow',
  73: 'Snow',
  75: 'Heavy Snow',
  77: 'Snow Grains',
  80: 'Light Showers',
  81: 'Showers',
  82: 'Heavy Showers',
  85: 'Snow Showers',
  86: 'Heavy Snow Showers',
  95: 'Thunderstorm',
  96: 'Thunderstorm w/ Hail',
  99: 'Thunderstorm w/ Heavy Hail',
}

const OWM_ICONS = {
  0:  '01d', 1:  '01d', 2:  '02d', 3:  '04d',
  45: '50d', 48: '50d',
  51: '09d', 53: '09d', 55: '09d',
  61: '10d', 63: '10d', 65: '10d',
  71: '13d', 73: '13d', 75: '13d', 77: '13d',
  80: '09d', 81: '09d', 82: '09d',
  85: '13d', 86: '13d',
  95: '11d', 96: '11d', 99: '11d',
}

async function ensureIcon(code) {
  const owmCode  = OWM_ICONS[code] || '01d'
  const filename = `${owmCode}.png`
  const filepath = resolve(ICON_DIR, filename)
  if (!existsSync(filepath)) {
    const res = await fetch(`https://openweathermap.org/img/wn/${owmCode}@2x.png`)
    await pipeline(res.body, createWriteStream(filepath))
  }
  return `/icons/${filename}`
}

async function cachedFetch(key, url) {
  const now = Date.now()
  if (CACHE[key] && now - CACHE[key].ts < CACHE_MS) return CACHE[key].data
  const res  = await fetch(url)
  const data = await res.json()
  CACHE[key] = { ts: now, data }
  return data
}

const DAILY_FIELDS = [
  'temperature_2m_max', 'temperature_2m_min',
  'precipitation_sum', 'precipitation_probability_max',
  'windspeed_10m_max', 'windgusts_10m_max', 'winddirection_10m_dominant',
  'weathercode', 'sunrise', 'sunset',
  'uv_index_max', 'shortwave_radiation_sum',
].join(',')

// start & end are Date objects
export async function getOpenMeteo(lat, lon, start, end) {
  const startStr = start.toISOString().slice(0, 10)
  const endStr   = end.toISOString().slice(0, 10)

  console.log('[meteo] startStr :', startStr)
  console.log('[meteo] endStr   :', endStr)
  console.log('[meteo] url      :', url)

  const url = `https://api.open-meteo.com/v1/forecast?latitude=${lat}&longitude=${lon}` +
      `&daily=${DAILY_FIELDS}&timezone=auto&start_date=${startStr}&end_date=${endStr}`

  const data = await cachedFetch(`daily_${lat}_${lon}_${startStr}_${endStr}`, url)

  if (!data?.daily?.time) return []

  return Promise.all(data.daily.time.map(async (time, i) => {
    const code = data.daily.weathercode[i]
    const icon = await ensureIcon(code).catch(() => null)
    return {
      time,
      label:                          WMO[code] || 'Unknown',
      icon,
      forecast_weathercode:           code,
      temperature:                    data.daily.temperature_2m_max[i],
      env_temp_max_c:                 data.daily.temperature_2m_max[i],
      env_temp_min_c:                 data.daily.temperature_2m_min[i],
      precipitation:                  data.daily.precipitation_sum[i],
      forecast_precipitation_probability: data.daily.precipitation_probability_max[i],
      wind_speed:                     data.daily.windspeed_10m_max[i],
      wind_gusts:                     data.daily.windgusts_10m_max[i],
      wind_direction:                 data.daily.winddirection_10m_dominant[i],
      uv_index:                       data.daily.uv_index_max[i],
      solar_wm2:                      data.daily.shortwave_radiation_sum[i],
      sunrise:                        data.daily.sunrise[i],
      sunset:                         data.daily.sunset[i],
    }
  }))
}