import { promises as fs } from 'fs'
import { getCurrentSeasonSlug, validateSeasonSlug } from '../utils/spielplan-data.js'

function normalizeSeasonFilename(season) {
  return `mannschaften_${season}.csv`
}

function isAllowedFilename(filename) {
  return filename === 'mannschaften.csv' || /^mannschaften_\d{2}--\d{2}\.csv$/.test(String(filename || ''))
}

function buildCsvCandidates(cwd, filename) {
  const safeFilename = String(filename || '').trim()
  if (!isAllowedFilename(safeFilename)) {
    throw createError({
      statusCode: 400,
      statusMessage: 'Ungueltiger Dateiname fuer Mannschaften'
    })
  }

  return [
    `${cwd}/server/data/public-data/${safeFilename}`,
    `${cwd}/../server/data/public-data/${safeFilename}`,
    `${cwd}/.output/server/data/${safeFilename}`,
    `${cwd}/server/data/${safeFilename}`,
    `${cwd}/.output/public/data/${safeFilename}`,
    `${cwd}/public/data/${safeFilename}`,
    `${cwd}/../.output/public/data/${safeFilename}`,
    `${cwd}/../public/data/${safeFilename}`
  ]
}

async function exists(p) {
  try {
    await fs.access(p)
    return true
  } catch {
    return false
  }
}

export default defineEventHandler(async (event) => {
  try {
    const cwd = process.cwd()
    const query = getQuery(event)
    const requestedSeason = query.season ? String(query.season).trim() : ''

    if (requestedSeason && !validateSeasonSlug(requestedSeason)) {
      throw createError({
        statusCode: 400,
        statusMessage: 'Ungueltiger Saison-Slug'
      })
    }

    const defaultSeason = getCurrentSeasonSlug()
    const candidateFileNames = requestedSeason
      ? [normalizeSeasonFilename(requestedSeason), 'mannschaften.csv']
      : [normalizeSeasonFilename(defaultSeason), 'mannschaften.csv']

    // Prefer CMS write target first (server/data/public-data),
    // then legacy locations.
    const candidates = []
    for (const filename of candidateFileNames) {
      candidates.push(...buildCsvCandidates(cwd, filename))
    }

    let csvPath = null
    for (const p of candidates) {
       
      if (await exists(p)) {
        csvPath = p
        break
      }
    }

    if (!csvPath) {
      throw createError({
        statusCode: 404,
        statusMessage: 'Mannschaften-Datei nicht gefunden'
      })
    }

    const csv = await fs.readFile(csvPath, 'utf-8')

    setHeader(event, 'Content-Type', 'text/csv; charset=utf-8')
    setHeader(event, 'Cache-Control', 'no-cache, no-store, must-revalidate')
    setHeader(event, 'Pragma', 'no-cache')
    setHeader(event, 'Expires', '0')

    return csv
  } catch (error) {
    if (error?.statusCode) throw error
    console.error('Fehler beim Laden der Mannschaften:', error)
    throw createError({
      statusCode: 500,
      statusMessage: 'Fehler beim Laden der Mannschaften'
    })
  }
})