import PDFDocument from 'pdfkit'
import crypto from 'crypto'

const HMAC_SECRET = process.env.HMAC_SECRET || 'newapi-dashboard-default-secret-key-change-in-production'

interface BillingReportData {
  siteName: string
  siteUrl: string
  userId: number
  username: string
  group: string
  startDate: string
  endDate: string
  totalQuota: number
  totalRequests: number
  modelSummary: { model: string; quota: number; count: number }[]
  logs: {
    created_at: number
    model_name: string
    token_name: string
    quota: number
    prompt_tokens: number
    completion_tokens: number
    request_id: string
  }[]
}

export function generateHmacSignature(data: {
  userId: number
  startDate: string
  endDate: string
  totalQuota: number
  totalRecords: number
  generatedAt: string
}): string {
  const signStr = `${data.userId}|${data.startDate}|${data.endDate}|${data.totalQuota}|${data.totalRecords}|${data.generatedAt}`
  return crypto.createHmac('sha256', HMAC_SECRET).update(signStr).digest('hex')
}

export function verifyHmacSignature(data: {
  userId: number
  startDate: string
  endDate: string
  totalQuota: number
  totalRecords: number
  generatedAt: string
  signature: string
}): boolean {
  const expected = generateHmacSignature(data)
  return crypto.timingSafeEqual(Buffer.from(expected), Buffer.from(data.signature))
}

export function generateBillingPDF(data: BillingReportData): Promise<Buffer> {
  return new Promise((resolve, reject) => {
    const doc = new PDFDocument({ size: 'A4', margin: 50 })
    const chunks: Buffer[] = []

    doc.on('data', (chunk: Buffer) => chunks.push(chunk))
    doc.on('end', () => resolve(Buffer.concat(chunks)))
    doc.on('error', reject)

    const generatedAt = new Date().toISOString()
    const reportId = crypto.createHash('md5')
      .update(`${data.userId}-${generatedAt}`)
      .digest('hex')
      .substring(0, 12)
      .toUpperCase()

    // -- Watermark --
    doc.save()
    doc.opacity(0.06)
    doc.fontSize(60)
    doc.rotate(-45, { origin: [300, 400] })
    doc.text(data.siteName, 100, 350, { width: 600 })
    doc.restore()

    // -- Header --
    doc.fontSize(20).text(data.siteName, { align: 'center' })
    doc.fontSize(14).text('API Usage Billing Report', { align: 'center' })
    doc.moveDown(0.5)
    doc.fontSize(9).fillColor('#666')
      .text(`Report ID: RPT-${reportId}`, { align: 'center' })
    doc.moveDown(1)

    // -- Report Info --
    doc.fillColor('#000').fontSize(10)
    doc.text(`Period: ${data.startDate} ~ ${data.endDate}`)
    doc.text(`User ID: ${data.userId}    Username: ${data.username}    Group: ${data.group}`)
    doc.text(`Site: ${data.siteUrl}`)
    doc.moveDown(1)

    // -- Summary --
    doc.fontSize(12).text('Summary', { underline: true })
    doc.moveDown(0.3)
    doc.fontSize(10)
    doc.text(`Total Quota Consumed: ${(data.totalQuota / 500000).toFixed(4)} USD (${data.totalQuota} quota units)`)
    doc.text(`Total Requests: ${data.totalRequests}`)
    doc.moveDown(0.5)

    // Model summary
    if (data.modelSummary.length > 0) {
      doc.fontSize(11).text('By Model:', { underline: true })
      doc.moveDown(0.3)
      doc.fontSize(9)
      for (const m of data.modelSummary) {
        doc.text(`  ${m.model}: ${(m.quota / 500000).toFixed(4)} USD, ${m.count} requests`)
      }
      doc.moveDown(1)
    }

    // -- Detail Table --
    doc.fontSize(12).text('Usage Details', { underline: true })
    doc.moveDown(0.3)

    const tableTop = doc.y
    const col = [50, 150, 280, 370, 460]
    doc.fontSize(8).fillColor('#333')
    doc.text('Time', col[0], tableTop)
    doc.text('Model', col[1], tableTop)
    doc.text('Token', col[2], tableTop)
    doc.text('Cost (USD)', col[3], tableTop)
    doc.text('Request ID', col[4], tableTop)

    doc.moveTo(50, tableTop + 12).lineTo(560, tableTop + 12).stroke('#ccc')

    let y = tableTop + 16
    const maxRows = Math.min(data.logs.length, 200)
    for (let i = 0; i < maxRows; i++) {
      if (y > 750) {
        doc.addPage()
        y = 50
      }
      const log = data.logs[i]
      const time = new Date(log.created_at * 1000).toLocaleString('zh-CN', { timeZone: 'Asia/Shanghai' })
      doc.fontSize(7).fillColor('#000')
      doc.text(time, col[0], y, { width: 95 })
      doc.text(log.model_name || '-', col[1], y, { width: 125 })
      doc.text(log.token_name || '-', col[2], y, { width: 85 })
      doc.text((log.quota / 500000).toFixed(6), col[3], y, { width: 85 })
      doc.text(log.request_id?.substring(0, 12) || '-', col[4], y, { width: 100 })
      y += 14
    }

    if (data.logs.length > maxRows) {
      doc.moveDown(0.5)
      doc.fontSize(8).fillColor('#999')
        .text(`... Total ${data.logs.length} records, showing first ${maxRows}`)
    }

    // -- HMAC Signature --
    const signature = generateHmacSignature({
      userId: data.userId,
      startDate: data.startDate,
      endDate: data.endDate,
      totalQuota: data.totalQuota,
      totalRecords: data.logs.length,
      generatedAt
    })

    doc.addPage()
    doc.fontSize(10).fillColor('#000').text('Report Verification', { underline: true })
    doc.moveDown(0.3)
    doc.fontSize(8).fillColor('#333')
    doc.text(`Generated At: ${generatedAt}`)
    doc.text(`Total Records: ${data.logs.length}`)
    doc.text(`HMAC-SHA256 Signature: ${signature}`)
    doc.moveDown(0.5)
    doc.fontSize(7).fillColor('#999')
    doc.text('This report is system-generated. The signature can be verified through the system verification API.')
    doc.text('Verification endpoint: POST /api/billing/verify')

    doc.end()
  })
}