import { FastifyInstance } from 'fastify'
import { requireAuth } from './authRoutes.js'
import { resolveRipStatusBatch } from '../ripstatus.js'

function countBy(values: string[]): { name: string; count: number }[] {
  const map = new Map<string, number>()
  for (const v of values) {
    if (!v) continue
    map.set(v, (map.get(v) ?? 0) + 1)
  }
  return [...map.entries()].map(([name, count]) => ({ name, count })).sort((a, b) => b.count - a.count)
}

export async function registerStatsRoutes(app: FastifyInstance): Promise<void> {
  app.get('/api/stats', { preHandler: [requireAuth] }, async (request) => {
    const db = request.server.db
    const userId = request.user!.id
    const items = db
      .prepare('SELECT id, title, artist, year, formats, genres, date_added, rip_override FROM collection_items WHERE user_id = ?')
      .all(userId) as {
      id: number
      title: string
      artist: string
      year: number | null
      formats: string
      genres: string
      date_added: string
      rip_override: number | null
    }[]

    const statuses = resolveRipStatusBatch(db, userId, items)
    let ripped = 0
    const formats: string[] = []
    const genres: string[] = []
    const months = new Map<string, number>()
    items.forEach((item, i) => {
      if (statuses[i] === 'ripped') ripped++
      for (const f of JSON.parse(item.formats) as string[]) formats.push(f)
      for (const g of JSON.parse(item.genres) as string[]) genres.push(g)
      const month = (item.date_added ?? '').slice(0, 7)
      if (/^\d{4}-\d{2}$/.test(month)) months.set(month, (months.get(month) ?? 0) + 1)
    })

    const onLoan = (
      db.prepare('SELECT COUNT(*) AS n FROM loans WHERE user_id = ? AND returned_at IS NULL').get(userId) as { n: number }
    ).n

    const addedByMonth: { month: string; count: number }[] = []
    const now = new Date()
    for (let i = 11; i >= 0; i--) {
      const d = new Date(now.getFullYear(), now.getMonth() - i, 1)
      const key = `${d.getFullYear()}-${String(d.getMonth() + 1).padStart(2, '0')}`
      addedByMonth.push({ month: key, count: months.get(key) ?? 0 })
    }

    return {
      totals: { items: items.length, ripped, notRipped: items.length - ripped, onLoan },
      ripRatio: items.length === 0 ? 0 : ripped / items.length,
      formats: countBy(formats),
      decades: countBy(items.map((i) => (i.year ? `${Math.floor(i.year / 10) * 10}s` : ''))),
      topGenres: countBy(genres).slice(0, 10),
      topArtists: countBy(items.map((i) => i.artist)).slice(0, 10),
      addedByMonth,
    }
  })
}