'use strict'

const http = require('http')
const fs = require('fs')
const fsp = fs.promises;

function parseBodyHeaders(data) {
  let headers = {}
  let dsplit = data.split('\r\n').filter(p => p.length > 0)
//filter创建一个新数组
  console.log(dsplit);
  let ind
  let k
  for (let d of dsplit) {
    ind = d.indexOf(':')

    if (ind <= 0) continue
    
    k = d.substring(0, ind).toLowerCase()

    headers[k] = d.substring(ind+1).trim()

  }

  let cpd = headers['content-disposition']

  //按照; 分割成数组，第一个元素form-data去掉
  let clist = cpd.split('; ').slice(1)

  let name, filename
  
  for (let a of clist) {
    ind = a.indexOf('filename="')
    if (ind >= 0) {
      filename = a.substring(ind+10, a.length-1)
    } else {
      name = a.substring(6, a.length - 1)
    }
  }

  return {
    headers,
    name,
    filename
  }

}

/**
 * 
 * @param {Buffer} bodyData 原始的Body数据
 * @param {Object} reqHeaders reuqest.headers
 */

function parseBody(bodyData, reqHeaders) {
  
  //content-type: multipart/form-data; boundary=-----34294329
  let ctype = reqHeaders['content-type']

  //拿到分界线boundary
  let bdy = ctype.substring( ctype.indexOf('=')+1 )

  //数据中用于分割文件的分界线
  //let bdy = `--${bdy}\r\n`

  let crlf_bdy = `\r\n--${bdy}`

  //从偏移bdy的长度开始查找下一个分界线的位置
  let data_end_index = bodyData.indexOf(crlf_bdy, crlf_bdy.length)

  //body消息数据中header部分的最后索引
  let header_end_index = bodyData.indexOf('\r\n\r\n', crlf_bdy.length)

  let header_data = bodyData.toString('utf8', 
                                  crlf_bdy.length, 
                                  header_end_index);

  //解析body数据中的消息头
  let hd = parseBodyHeaders(header_data)
  
  let fileinfo = {
    start: header_end_index+4,
    end: data_end_index,
  }

  fileinfo.length = fileinfo.end - fileinfo.start

  return {
    name: hd.name,
    filename: hd.filename,
    headers: hd.headers,
    start: fileinfo.start,
    end: fileinfo.end,
    length: fileinfo.length
  }

}
function parseExtName (filename){
    if(filename.length<2)  return ''

    let namesplit = filename.split('.').filter(p=>p.length>0)
    if(namesplit.length < 2) return '';
    return `.${namesplit[namesplit.length-1]}`

}

let routerTable = {

  GET: {
    '/upload' : async (ctx) => {
        let stm = fs.createReadStream('./upload.html')
        stm.pipe(ctx.res)
        stm.on('end', () => {
          ctx.end()
        })
    }
  },

  POST: {
    '/upload' : async (ctx) => {
      //console.log(request.headers['content-type'])
          let finfo = ctx.files;
          console.log(ctx.files)
          let filename = `${Date.now()}-`
                    + `${parseInt(Math.random()*100000)+100000}`
                    + parseExtName(finfo.filename);
          let fh = await fsp.open(filename,'w+');
          let fret = await fh.write(ctx.rawBody,finfo.start,finfo.length,0)
          //ctx.end(ctx.rawBody);
          fh.close();
          //返回写入的字节数。string或buffer类型，不能是其他类型
          ctx.end(`${fret.bytesWritten}`);
        }
    }
  }
/**   start server */
let serv = http.createServer()

serv.on('request', (request, response) => {
  let rm = routerTable[request.method]
  let usplit = request.url.split('?')
  let pathname = usplit[0]
  let querystring = usplit[1] || ''
  if (!rm ||!rm[ pathname ]) {
    response.statusCode = 404
    response.end('page not found')
    return
  }
  //ctx创建请求上下文对象
  let ctx = {
      req:request,
      res:response,
      method:request.method,
      headers:request.headers,
      end:(data,encoding = 'utf-8')=>{
          response.end(data,encoding)
      },
      write:(data,encoding = 'utf-8')=>{
          response.write(data,encoding)
      },
      path:pathname,
      querystring:querystring,
      rawBody:null,
  }
  let bufferList = []
  let totalLength = 0
  //PD开头，提交请求
  if('PD'.indexOf(request.method[0])>=0){
      request.on('data',chunk=>{
          totalLength += chunk.length
          bufferList.push(chunk)
      })
  }else{
      request.on('data',chunk=>{
          response.statusCode = 400
          response.end()
      })
  }
  request.on('end',()=>{
      if(bufferList.length >0){
          ctx.rawBody = Buffer.concat(bufferList,totalLength)
          bufferList = []
      }
      let ctype = ctx.headers['content-type'] || ''
      if(ctx.rawBody && ctype.indexOf('multipart/form-data') === 0){
          ctx.files = parseBody(ctx.rawBody,ctx.headers);
      }
      rm[ pathname ](ctx)
  })
})

serv.listen(3456)