改進Face/Detect

##改進Face/Detect

現在Face/Detect和Face/Verify將支持將用戶提交的結果持久化。我們先考慮下Face/Detect現在的變化，原先我們的流程是：從微信客戶端獲得mediaID，通過這個mediaID從微信服務器下載圖片，然後將這個圖片提交給牛津，以獲得FaceID

現在我們需要考慮的更周到了：當從微信客戶端得到mediaID，我們需要查看下本地文件夾中是否有匹配的文件，在提交給牛津之前我們也需要從Mango數據庫中查詢是否有匹配的上次的提交結果

我們先改進微信服務的代碼，使得只有Mongo沒有存儲mediaID和對應的文件再從微信的服務器去下載圖片

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

    //查詢mongo中是否存儲了mediaid對應的照片文件
    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;
}

然後我們來改進FaceController的DetectAPI，使得先在Mongo中查詢對應照片的分析結果，當沒有之前查詢的結果，再去牛津進行分析。

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

    //得到從微信服務器下載的文件名
    var fileName = await new WeixinController().Get(weixnmediaid);

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

    //照片之前有沒有下載過
    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中沒有該照片對應的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);
            //將牛津結果寫入數據庫
            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);
}