import { NextRequest, NextResponse } from 'next/server'
import { getAuthenticatedUploadUserId } from '@/lib/upload-auth'
import { saveUploadSession } from '@/lib/upload-sessions'
import { getUploadRootDir } from '@/lib/upload-paths'
import {
  ensureSafeDirectoryWithinRoot,
  normalizeSafeFileName,
} from '@/lib/path-security'
import { randomBytes } from 'crypto'
import { rm, statfs, writeFile } from 'fs/promises'
import path from 'path'
import {
  MAX_LOGICAL_UPLOAD_BYTES,
  MAX_UPLOAD_CHUNKS,
  resolveUploadChunkSize,
} from '@/lib/material-upload-chunk-policy'

const MEBIBYTE = 1024 * 1024
const GIBIBYTE = 1024 * MEBIBYTE
const MIN_FREE_SPACE_RESERVE_BYTES = 2 * GIBIBYTE

export async function POST(req: NextRequest) {
  try {
    const userId = await getAuthenticatedUploadUserId(req)
    if (!userId) {
      return NextResponse.json({ error: '请先登录' }, { status: 401 })
    }

    let body
    try {
      body = await req.json()
    } catch (jsonError) {
      console.error('[UploadInit] JSON解析错误:', jsonError)
      return NextResponse.json(
        { error: '请求体格式错误，需要JSON格式' },
        { status: 400 }
      )
    }

    const rawFileName = typeof body?.fileName === 'string' ? body.fileName : ''
    const normalizedFileName = normalizeSafeFileName(rawFileName)
    const normalizedFileSize = Number(body?.fileSize)
    const normalizedTotalChunks = Number(body?.totalChunks)

    if (!rawFileName.trim()) {
      return NextResponse.json({ error: '文件名不能为空' }, { status: 400 })
    }
    if (!normalizedFileName) {
      return NextResponse.json({ error: '文件名包含不安全的路径或字符' }, { status: 400 })
    }

    if (!Number.isSafeInteger(normalizedFileSize) || normalizedFileSize <= 0) {
      return NextResponse.json({ error: '上传文件不能为空' }, { status: 400 })
    }
    if (normalizedFileSize > MAX_LOGICAL_UPLOAD_BYTES) {
      return NextResponse.json(
        { error: '单个源文件不能超过 10GB', code: 'SOURCE_FILE_TOO_LARGE' },
        { status: 413 },
      )
    }

    if (
      !Number.isInteger(normalizedTotalChunks)
      || normalizedTotalChunks <= 0
      || normalizedTotalChunks > MAX_UPLOAD_CHUNKS
    ) {
      return NextResponse.json({ error: '上传分片参数无效' }, { status: 400 })
    }

    const normalizedChunkSize = resolveUploadChunkSize(
      normalizedFileSize,
      normalizedTotalChunks,
      body?.chunkSize,
    )
    if (!normalizedChunkSize) {
      return NextResponse.json(
        { error: '上传分片大小与文件总大小不匹配', code: 'CHUNK_LAYOUT_INVALID' },
        { status: 400 },
      )
    }

    // 生成上传ID
    const uploadId = `upload-${Date.now()}-${randomBytes(16).toString('hex')}`

    // 创建临时目录
    const uploadDir = getUploadRootDir()
    const tempDir = await ensureSafeDirectoryWithinRoot(uploadDir, 'temp', uploadId)
    if (!tempDir) {
      throw new Error('上传临时目录不安全')
    }

    // 分片合并期间会同时保留分片与完整输出，必须为两份源文件再加固定
    // 安全余量预留空间。无法确认剩余空间时保守拒绝，避免写满 uploads/NAS。
    try {
      const disk = await statfs(tempDir, { bigint: true })
      const availableBytes = disk.bavail * disk.bsize
      const requiredBytes = BigInt(normalizedFileSize) * BigInt(2) + BigInt(MIN_FREE_SPACE_RESERVE_BYTES)
      if (availableBytes < requiredBytes) {
        await rm(tempDir, { recursive: true, force: true })
        return NextResponse.json(
          { error: '上传存储空间不足，请联系管理员清理后重试', code: 'UPLOAD_STORAGE_LOW' },
          { status: 507 },
        )
      }
    } catch (diskError) {
      await rm(tempDir, { recursive: true, force: true }).catch(() => undefined)
      console.error('[UploadInit] 无法确认上传盘剩余空间:', diskError)
      return NextResponse.json(
        { error: '暂时无法确认上传存储空间，请稍后重试', code: 'UPLOAD_STORAGE_UNKNOWN' },
        { status: 503 },
      )
    }
    // 写入元数据，方便在Redis丢失时回溯
    const metaPath = path.join(tempDir, 'meta.json')
    const metaPayload = {
      fileName: normalizedFileName,
      fileSize: normalizedFileSize,
      totalChunks: normalizedTotalChunks,
      chunkSize: normalizedChunkSize,
      userId,
      createdAt: Date.now(),
    }
    await writeFile(metaPath, JSON.stringify(metaPayload), 'utf-8')

    // 保存会话（使用统一的接口，自动选择Redis或内存Map）
    const now = Date.now()
    await saveUploadSession(uploadId, {
      fileName: normalizedFileName,
      fileSize: normalizedFileSize,
      totalChunks: normalizedTotalChunks,
      chunkSize: normalizedChunkSize,
      chunks: new Map(),
      createdAt: now,
      lastActivityAt: now,
      uploadedBytes: 0,
      currentSpeed: 0,
      _speedSampleAt: now,
      _speedSampleBytes: 0,
      userId,
    })

    console.log(`[UploadInit] Created upload session: ${uploadId}, chunks: ${normalizedTotalChunks}`)

    return NextResponse.json({ uploadId })
  } catch (error) {
    console.error('[UploadInit] Error:', error)
    return NextResponse.json(
      { error: '初始化上传失败' },
      { status: 500 }
    )
  }
}