import fs from 'fs';
import path from 'path';
import axios from 'axios';
import { lakesConfig } from './lakesConfig';

const DATA_DIR = path.resolve(process.cwd(), 'public/data');

async function backfill() {
  console.log('Starting weather backfill for past 7 days...');
  
  for (const lake of lakesConfig) {
    const internalId = lake.id.split('|')[0];
    const filePath = path.join(DATA_DIR, `${internalId}.json`);
    
    if (!fs.existsSync(filePath)) {
      console.log(`Skipping ${internalId}, no data file.`);
      continue;
    }
    
    if (!lake.coords) {
      console.log(`Skipping ${internalId}, no coordinates.`);
      continue;
    }
    
    try {
      const lat = lake.coords[0];
      const lon = lake.coords[1];
      // Fetch maximum past days supported by the forecast API (92 days)
      const url = `https://api.open-meteo.com/v1/forecast?latitude=${lat}&longitude=${lon}&past_days=92&hourly=temperature_2m,precipitation&timezone=GMT`;
      
      const res = await axios.get(url, { timeout: 15000 });
      const hourly = res.data.hourly;
      
      // Build lookup map for O(1) matching: '2026-06-02T04:00' -> { temp, precip }
      const weatherMap = new Map();
      for (let i = 0; i < hourly.time.length; i++) {
        weatherMap.set(hourly.time[i], {
          temperature: hourly.temperature_2m[i],
          precipitation: hourly.precipitation[i]
        });
      }
      
      const data = JSON.parse(fs.readFileSync(filePath, 'utf-8'));
      let updatedCount = 0;
      
      for (const record of data) {
        // record.timestamp is like "2026-06-02T04:10:00.000Z"
        // Open-Meteo time is like "2026-06-02T04:00"
        // Convert to hourly key to match weatherMap
        const hourKey = record.timestamp.substring(0, 13) + ':00';
        
        if (weatherMap.has(hourKey)) {
          const w = weatherMap.get(hourKey);
          if (w.temperature !== null && w.temperature !== undefined) {
            record.temperature = w.temperature;
            updatedCount++;
          }
          if (w.precipitation !== null && w.precipitation !== undefined) {
            record.precipitation = w.precipitation;
          }
        }
      }
      
      fs.writeFileSync(filePath, JSON.stringify(data, null, 2));
      console.log(`[${internalId}] Backfilled ${updatedCount} records with historical Open-Meteo data.`);
      
      // small delay to prevent rate limit
      await new Promise(r => setTimeout(r, 200));
      
    } catch (e: any) {
      console.error(`Error processing ${internalId}:`, e.message);
    }
  }
  
  console.log('Backfill complete!');
}

backfill();