#!/usr/bin/env bun

/**
 * Update COVID-19 Wastewater Data
 *
 * Fetches the latest California statewide wastewater data from CDPH
 * and updates the local CSV dataset.
 */

import { writeFileSync, readFileSync } from 'fs';
import { join } from 'path';

const DATA_URL = 'https://data.chhs.ca.gov/dataset/1184f641-313f-47ee-b126-9e8c42699be5/resource/726752d3-afe6-4733-99bd-ffb9f400348c/download/wastewater.csv';
const CSV_PATH = join(__dirname, 'COVID-Wastewater-California-Statewide-2022-2025.csv');
const UPDATES_PATH = join(__dirname, 'UPDATES.md');

interface RawWastewaterData {
  season: string;
  week_ending_date: string;
  sars_cov2_log10_copies_ml: string;
}

async function fetchLatestData(): Promise<string> {
  console.log('📡 Fetching latest COVID wastewater data from CDPH...\n');

  const response = await fetch(DATA_URL);
  if (!response.ok) {
    throw new Error(`Failed to fetch data: ${response.statusText}`);
  }

  return await response.text();
}

function parseCSV(csvContent: string): RawWastewaterData[] {
  const lines = csvContent.trim().split('\n');
  const headers = lines[0].toLowerCase().split(',');

  return lines.slice(1).map(line => {
    const values = line.split(',');
    return {
      season: values[0],
      week_ending_date: values[1],
      sars_cov2_log10_copies_ml: values[2]
    };
  }).filter(row => row.week_ending_date && row.sars_cov2_log10_copies_ml);
}

function formatDate(dateStr: string): string {
  const date = new Date(dateStr);
  return date.toLocaleDateString('en-US', {
    month: 'short',
    day: 'numeric',
    year: 'numeric'
  });
}

function convertToISO(dateStr: string): string {
  // Convert MM/DD/YYYY to YYYY-MM-DD
  const parts = dateStr.split('/');
  if (parts.length === 3) {
    const [month, day, year] = parts;
    return `${year}-${month.padStart(2, '0')}-${day.padStart(2, '0')}`;
  }
  return dateStr;
}

function processAndSaveData(rawData: RawWastewaterData[]): void {
  // Sort by date (oldest to newest for the file)
  rawData.sort((a, b) => new Date(a.week_ending_date).getTime() - new Date(b.week_ending_date).getTime());

  // Format CSV with proper headers
  const csvLines = [
    'season,week_ending_date,sars_cov2_log10_copies_ml,data_source,region,notes'
  ];

  for (const row of rawData) {
    const isoDate = convertToISO(row.week_ending_date);
    const roundedValue = parseFloat(row.sars_cov2_log10_copies_ml).toFixed(2);
    csvLines.push(
      `${row.season},${isoDate},${roundedValue},CDPH California Wastewater Surveillance,California Statewide,Log10 viral gene copies/mL`
    );
  }

  writeFileSync(CSV_PATH, csvLines.join('\n') + '\n');
  console.log(`✅ Updated dataset: ${rawData.length} records saved\n`);
}

function updateChangelog(latestRecord: RawWastewaterData, recordCount: number): void {
  const now = new Date();
  const updateDate = now.toISOString().split('T')[0];
  const latestDate = convertToISO(latestRecord.week_ending_date);
  const latestValue = parseFloat(latestRecord.sars_cov2_log10_copies_ml).toFixed(2);

  const changelogEntry = `
## ${updateDate} - Automated Data Update

**Data Period**: 2022-07-09 to ${latestDate}
**Source**: CDPH California Wastewater Surveillance
**URL**: ${DATA_URL}

### Changes
- Updated dataset with latest wastewater measurements
- Total records: ${recordCount}

### Latest Value
- **Week Ending**: ${formatDate(latestDate)}
- **SARS-CoV-2**: ${latestValue} log10 copies/mL

---
`;

  try {
    const currentChangelog = readFileSync(UPDATES_PATH, 'utf-8');
    const futureUpdatesMarker = '## Future Updates';
    const parts = currentChangelog.split(futureUpdatesMarker);

    if (parts.length === 2) {
      const updatedChangelog = parts[0] + changelogEntry + futureUpdatesMarker + parts[1];
      writeFileSync(UPDATES_PATH, updatedChangelog);
      console.log('📝 Updated UPDATES.md changelog\n');
    }
  } catch (error) {
    console.log('⚠️  Could not update changelog:', error);
  }
}

try {
  const rawCSV = await fetchLatestData();
  const data = parseCSV(rawCSV);

  if (data.length === 0) {
    console.error('❌ No valid data found in source CSV');
    process.exit(1);
  }

  // Get the latest record (after sorting)
  const latestRecord = data[data.length - 1];

  processAndSaveData(data);
  updateChangelog(latestRecord, data.length);

  console.log('━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━');
  console.log('✅ COVID DATA UPDATE COMPLETE');
  console.log('━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━\n');
  console.log(`📅 Latest data point: ${formatDate(convertToISO(latestRecord.week_ending_date))}`);
  console.log(`📊 Latest viral load: ${parseFloat(latestRecord.sars_cov2_log10_copies_ml).toFixed(2)} log10 copies/mL`);
  console.log(`📈 Total records: ${data.length}\n`);

} catch (error) {
  console.error('❌ Error updating COVID data:', error);
  process.exit(1);
}