import { withAdmin } from '@/lib/api-handler'
import { apiError } from '@/lib/api-response'
import { PERMS } from '@/lib/permission-slugs'
import { prisma } from '@/lib/prisma'

const VALID_REPORTS = new Set(['registrations', 'online-by-hour', 'economy'])

function csvEscape(value: unknown): string {
  if (value == null) return ''
  const str = String(value)
  if (/[",\n\r]/.test(str)) {
    return `"${str.replace(/"/g, '""')}"`
  }
  return str
}

function csvRow(values: unknown[]): string {
  return `${values.map(csvEscape).join(',')}\n`
}

async function streamRegistrations(): Promise<ReadableStream<Uint8Array>> {
  const rows = await prisma.$queryRaw<{ day: string; cnt: bigint }[]>`
    SELECT FROM_UNIXTIME(account_created, '%Y-%m-%d') AS day, COUNT(*) AS cnt
    FROM users
    WHERE account_created > UNIX_TIMESTAMP(NOW() - INTERVAL 90 DAY)
    GROUP BY day
    ORDER BY day ASC
  `
  const encoder = new TextEncoder()
  return new ReadableStream({
    start(controller) {
      controller.enqueue(encoder.encode(csvRow(['day', 'registrations'])))
      for (const r of rows) {
        controller.enqueue(encoder.encode(csvRow([r.day, Number(r.cnt)])))
      }
      controller.close()
    },
  })
}

async function streamOnlineByHour(): Promise<ReadableStream<Uint8Array>> {
  const rows = await prisma.$queryRaw<{ hour: number; cnt: bigint }[]>`
    SELECT HOUR(FROM_UNIXTIME(last_online)) AS hour, COUNT(*) AS cnt
    FROM users
    WHERE last_online > UNIX_TIMESTAMP(NOW() - INTERVAL 30 DAY)
    GROUP BY hour
    ORDER BY hour ASC
  `
  const encoder = new TextEncoder()
  return new ReadableStream({
    start(controller) {
      controller.enqueue(encoder.encode(csvRow(['hour', 'active_users'])))
      for (const r of rows) {
        controller.enqueue(encoder.encode(csvRow([Number(r.hour), Number(r.cnt)])))
      }
      controller.close()
    },
  })
}

async function streamEconomy(): Promise<ReadableStream<Uint8Array>> {
  const [totals] = await prisma.$queryRaw<{ total_credits: bigint; total_pixels: bigint }[]>`
    SELECT SUM(credits) AS total_credits, SUM(pixels) AS total_pixels FROM users
  `
  const encoder = new TextEncoder()
  return new ReadableStream({
    start(controller) {
      controller.enqueue(encoder.encode(csvRow(['metric', 'value'])))
      controller.enqueue(
        encoder.encode(csvRow(['total_credits', Number(totals?.total_credits ?? 0)])),
      )
      controller.enqueue(
        encoder.encode(csvRow(['total_pixels', Number(totals?.total_pixels ?? 0)])),
      )
      controller.close()
    },
  })
}

export const GET = withAdmin({ permission: PERMS.ANALYTICS_EXPORT }, async (request) => {
  const url = new URL(request.url)
  const report = url.searchParams.get('report') ?? ''
  if (!VALID_REPORTS.has(report)) {
    return apiError(`Unknown report. Use one of: ${[...VALID_REPORTS].join(', ')}`, 400)
  }

  const stream =
    report === 'registrations'
      ? await streamRegistrations()
      : report === 'online-by-hour'
        ? await streamOnlineByHour()
        : await streamEconomy()

  return new Response(stream, {
    headers: {
      'Content-Type': 'text/csv; charset=utf-8',
      'Content-Disposition': `attachment; filename="${report}.csv"`,
      'Cache-Control': 'no-store',
    },
  })
})