改进Face/Detect

##改进Face/Detect

现在Face/Detect和Face/Verify将支持将用户提交的结果持久化。我们先考虑下Face/Detect现在的变化，原先我们的流程是：从微信客户端获得mediaID，通过这个mediaID从微信服务器下载图片，然后将这个图片提交给牛津，以获得FaceID

现在我们需要考虑的更周到了：当从微信客户端得到mediaID，我们需要查看下本地文件夹中是否有匹配的文件，在提交给牛津之前我们也需要从Mango数据库中查询是否有匹配的上次的提交结果

我们先改进微信服务的代码，使得只有Mongo没有存储mediaID和对应的文件再从微信的服务器去下载图片

public async Task<string> Get(string mediaid)
{
    var mongo = new MongoDBHelper("weixinImgFile");

    //查询mongo中是否存储了mediaid对应的照片文件
    var doc = await mongo.SelectOneAsync(x => x["mediaid"] == mediaid);
    if (doc != null)
    {
        return doc["filename"].ToString();
    }

    //http://file.api.weixin.qq.com/cgi-bin/media/get?access_token=ACCESS_TOKEN&media_id=MEDIA_ID
    var queryString = HttpUtility.ParseQueryString(string.Empty);
    queryString["access_token"] = await Get();
    queryString["media_id"] = mediaid;

    var uri = "http://file.api.weixin.qq.com/cgi-bin/media/get?" + queryString;

    HttpResponseMessage response;
    response = await client.GetAsync(uri);

    var msg = await response.Content.ReadAsStreamAsync();
    var fileName = response.Content.Headers.ContentDisposition.FileName.Replace("\"", "");

    var helper = new ProjecToxfordClientHelper();

    var content = await FileHelper.ReadAsync(msg);

    FileHelper.SaveFile(content, fileName);

    await mongo.InsertAsync(Newtonsoft.Json.JsonConvert.SerializeObject(
        new {
            Mediaid = mediaid,
            FileName = fileName
        }
        ));

    return fileName;
}

然后我们来改进FaceController的DetectAPI，使得先在Mongo中查询对应照片的分析结果，当没有之前查询的结果，再去牛津进行分析。

[HttpGet]
[Route("face/detect/{weixnmediaid}")]
public async Task<HttpResponseMessage> Detect(string weixnmediaid)
{
    var key = "detect";

    //得到从微信服务器下载的文件名
    var fileName = await new WeixinController().Get(weixnmediaid);

    var mongo = new MongoDBHelper<DetectResultModels>("facedetect");

    //照片之前有没有下载过
    var docArr = await mongo.SelectMoreAsync(x => x.FileName == fileName);
    if (docArr.Count > 0)
    {
        var resultJson = docArr.Select(
            doc => new
            {
                faceId = doc.faceId,
                filename = doc.FileName,
                age = doc.Age,
                gender = doc.Gender,
                smile = doc.Smile
            }
            ).ToJson();

        return client.CreateHttpResponseMessage(
            Request,
            new Models.ProjecToxfordResponseModels(resultJson, HttpStatusCode.OK));
    }
    //如果Mongo中没有该照片对应的Face信息
    var content = await FileHelper.ReadAsync(fileName);

    if (content != null)
    {
        var result = await client.PostAsync(key,
            content,
            new Dictionary<string, string> {
            {"returnFaceId","true"},
            {"returnFaceLandmarks","flase"},
            {"returnFaceAttributes","age,gender,smile"}
            }
            );

        if (result.StatusCode == HttpStatusCode.OK)
        {
            var tmpJArr = Newtonsoft.Json.Linq.JArray.Parse(result.Message);
            //将牛津结果写入数据库
            foreach (var tmp in tmpJArr)
            {
                await mongo.InsertAsync(new DetectResultModels()
                {
                    FileName = fileName,
                    faceId = (string)tmp["faceId"],
                    Age = (double)tmp["faceAttributes"]["age"],
                    Gender = (string)tmp["faceAttributes"]["gender"],
                    Smile = tmp["faceAttributes"]["smile"] != null ? (double)tmp["faceAttributes"]["smile"] : 0
                });
            }
            var resultJson = tmpJArr.Select(x => new
              {
                  faceId = x["faceId"],
                  age = (double)x["faceAttributes"]["age"],
                  gender = (string)x["faceAttributes"]["gender"],
                  smile = x["faceAttributes"]["smile"] != null ? (double)x["faceAttributes"]["smile"] : 0
              }).ToJson();

            return client.CreateHttpResponseMessage(
                Request,
                new Models.ProjecToxfordResponseModels(resultJson, HttpStatusCode.OK));
        }
    }
    throw new HttpResponseException(HttpStatusCode.BadRequest);
}