const admin = require('firebase-admin')
const { FieldValue } = require('firebase-admin/firestore')
const { onSchedule } = require('firebase-functions/v2/scheduler')
const { refList } = require('../index')
const firestore = refList.projects.firestore

function buildMonthContext(referenceDate) {
  const current = referenceDate ? new Date(referenceDate) : new Date()
  current.setHours(0, 0, 0, 0)
  current.setDate(1)

  const target = new Date(current)
  target.setMonth(target.getMonth() - 1)

  const month = target.getMonth()
  const year = target.getFullYear()
  const monthKey = `${year}-${String(month + 1).padStart(2, '0')}`
  const rangeStart = new Date(year, month, 1, 0, 0, 0, 0)
  const rangeEnd = new Date(year, month + 1, 0, 23, 59, 59, 999)

  return {
    year,
    month: month + 1,
    monthKey,
    rangeStart,
    rangeEnd,
  }
}

exports.snapshotMonthlyTopSongs = onSchedule(
  {
    schedule: '5 0 1 * *',
    timeZone: 'Europe/Paris',
  },
  async (event) => {
    const { scheduleTime } = event
    const context = buildMonthContext(scheduleTime ? new Date(scheduleTime) : new Date())

    const topProjectsSnap = await refList.projects.orderBy('views', 'desc').limit(3).get()

    const topProjects = topProjectsSnap.docs.map((doc, index) => {
      const data = doc.data() || {}
      return {
        rank: index + 1,
        projectId: doc.id,
        title: data.title || null,
        userId: data.userId || null,
        userName: data.userName || null,
        coverUrl: data.coverUrl || null,
        songUrl: data.songUrl || null,
        views: data.views || 0,
      }
    })

    const docRef = firestore.collection('monthlyTopSongs').doc(context.monthKey)

    const existingSnapshot = await docRef.get()
    const payload = {
      monthKey: context.monthKey,
      month: context.month,
      year: context.year,
      range: {
        start: admin.firestore.Timestamp.fromDate(context.rangeStart),
        end: admin.firestore.Timestamp.fromDate(context.rangeEnd),
      },
      topProjects,
      totalProjects: topProjects.length,
      updatedAt: FieldValue.serverTimestamp(),
    }

    if (!existingSnapshot.exists) {
      payload.createdAt = FieldValue.serverTimestamp()
    }

    await docRef.set(payload, { merge: true })
  }
)