import 'server-only'
import fs from 'node:fs'
import path from 'node:path'
import crypto from 'node:crypto'
import { fileTypeFromBuffer } from 'file-type'

export type EvidenceStage = 'report' | 'response' | 'investigation' | 'capa' | 'verification'

const ALLOWED_MIME_TYPES = new Set([
  'image/jpeg', 'image/png', 'image/gif', 'image/webp', 'image/heic', 'image/avif',
  'video/mp4', 'video/quicktime', 'video/webm', 'video/x-msvideo',
  'application/pdf',
  'application/msword',
  'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
  'application/vnd.ms-excel',
  'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
])

function evidenceDir(): string {
  const dir = process.env.EVIDENCE_DIR
  if (!dir) throw new Error('EVIDENCE_DIR env var not set')
  return dir
}

function hmacSecret(): string {
  const s = process.env.EVIDENCE_URL_SECRET
  if (!s) throw new Error('EVIDENCE_URL_SECRET env var not set')
  return s
}

export function signEvidencePath(filePath: string): string {
  return crypto.createHmac('sha256', hmacSecret()).update(filePath).digest('hex')
}

export function getEvidenceUrl(filePath: string): string {
  const token = signEvidencePath(filePath)
  return `/api/evidence/${filePath}?token=${token}`
}

export async function uploadEvidenceFile(
  file: File,
  incidentId: string,
  stage: EvidenceStage,
  userId: string,
): Promise<{ path: string; publicUrl: string; hash: string }> {
  const isVideo = file.type.startsWith('video/')
  const maxBytes = isVideo ? 200 * 1024 * 1024 : 10 * 1024 * 1024
  if (file.size > maxBytes) {
    throw new Error(`File too large: max ${isVideo ? '200MB' : '10MB'} for this file type`)
  }

  const buffer = await file.arrayBuffer()
  const detected = await fileTypeFromBuffer(buffer)
  const detectedMime = detected?.mime ?? null
  if (!detectedMime || !ALLOWED_MIME_TYPES.has(detectedMime)) {
    throw new Error(`File type not allowed: ${detectedMime ?? 'unknown'}`)
  }

  const ext = detected?.ext ?? file.name.split('.').pop() ?? 'bin'
  const filename = `${Date.now()}-${crypto.randomBytes(6).toString('hex')}.${ext}`
  const filePath = `${userId}/${incidentId}/${stage}/${filename}`

  const hash = await computeHashFromBuffer(buffer)

  const fullPath = path.join(evidenceDir(), filePath)
  fs.mkdirSync(path.dirname(fullPath), { recursive: true })
  fs.writeFileSync(fullPath, Buffer.from(buffer))

  const publicUrl = getEvidenceUrl(filePath)

  return { path: filePath, publicUrl, hash }
}

async function computeHashFromBuffer(buffer: ArrayBuffer): Promise<string> {
  const hashBuffer = await crypto.subtle.digest('SHA-256', buffer)
  return Array.from(new Uint8Array(hashBuffer))
    .map(b => b.toString(16).padStart(2, '0'))
    .join('')
}