import { NextRequest } from 'next/server'
import { z } from 'zod'
import { prisma } from '@/src/lib/prisma'

const ExportSchema = z.object({
  ids: z.array(z.string()).min(1),
  format: z.enum(['csv', 'json']),
})

export async function POST(req: NextRequest) {
  try {
    const body = await req.json()
    const parsed = ExportSchema.safeParse(body)
    if (!parsed.success) return Response.json({ error: 'invalid body' }, { status: 400 })
    const { ids, format } = parsed.data

    const rows = await prisma.recording.findMany({
      where: { id: { in: ids } },
      orderBy: { timestamp: 'asc' },
      // Cast select to any to accommodate freshly added fields before prisma generate
      select: {
        id: true,
        timestamp: true,
        code_data: true,
        fit_a: true,
        fit_b: true,
        sample_count: true,
        duration: true,
        rec_start_ms: true,
        rec_end_ms: true,
      } ,
    })

    if (format === 'json') {
      const payload = rows.map((r) => ({
        id: r.id,
        timestamp: new Date(r.timestamp).toISOString(),
        code: r.code_data,
        fit: r.fit_a != null ? { a: r.fit_a, b: r.fit_b } : undefined,
        sampleCount: r.sample_count,
        duration: r.duration,
      }))
      return new Response(JSON.stringify(payload), {
        headers: {
          'content-type': 'application/json; charset=utf-8',
          'content-disposition': `attachment; filename="export-${Date.now()}.json"`,
        },
      })
    }

    // CSV（去掉 recordId、timestamp，timeSec 改为毫秒单位）
    let csv = 'index,timeMs,code,force\n'
    for (const r of rows) {
      // 以毫秒为单位的步长
      let stepMs = r.sample_count > 0 ? (r.duration * 1000) / r.sample_count : 0
      if (r.rec_start_ms != null && r.rec_end_ms != null && r.sample_count > 0) {
        const dtMs = Number((r.rec_end_ms as bigint) - (r.rec_start_ms as bigint))
        if (Number.isFinite(dtMs) && dtMs > 0) stepMs = dtMs / r.sample_count
      }
      // 采样溢出时强制 1ms 步长（与 16.384s/16384 对齐）
      if (r.sample_count >= 16384) stepMs = 1
      const hasFit = r.fit_a != null
      for (let i = 0; i < r.code_data.length; i++) {
        const t = (i * stepMs).toFixed(3)
        const code = r.code_data[i]
        const force = hasFit ? r.fit_a! * code + (r.fit_b ?? 0) : ''
        csv += `${i},${t},${code},${hasFit ? force : ''}\n`
      }
    }
    return new Response(csv, {
      headers: {
        'content-type': 'text/csv; charset=utf-8',
        'content-disposition': `attachment; filename="export-${Date.now()}.csv"`,
      },
    })
  } catch (err) {
    console.error(err)
    return Response.json({ error: 'internal error' }, { status: 500 })
  }
}