// ============================================================
//  UapisOcrClient:UApiPro(uapis.cn) 通用文字识别(带位置)
//  · POST https://uapis.cn/api/v1/image/ocr  (multipart/form-data)
//    X-API-Key: {key}(uapis.cn 控制台注册生成,免费积分计费 4积分/次,4QPS)
//    字段:image_base64(纯base64或DataURI) + need_location="true"
//  · 响应 words_result[] { words, location{left,top,width,height},
//    vertexes_location[], score } → 转 OcrItem(坐标为发送图像素)
//  · Key 存 baidu_ocr.json 的 uapis_api_key(OCR设置窗口写)
// ============================================================
using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Net;
using System.Text;
using System.Threading.Tasks;
using System.Web.Script.Serialization;

namespace pdfbt
{
    /// <summary>UApiPro 通用 OCR 客户端(单实例)。</summary>
    internal sealed class UapisOcrClient
    {
        private readonly JavaScriptSerializer _json = new JavaScriptSerializer();
        private string _apiKey;
        private const string BaseUrl = "https://uapis.cn/api/v1/image/ocr";

        /// <summary>状态提示,接 OcrClient.StatusChanged。</summary>
        public event Action<string> StatusChanged;

        public UapisOcrClient()
        {
            try
            {
                ServicePointManager.SecurityProtocol =
                    ServicePointManager.SecurityProtocol | SecurityProtocolType.Tls12;
            }
            catch { }
        }

        public bool IsConfigured
        {
            get { return !string.IsNullOrWhiteSpace(_apiKey); }
        }

        /// <summary>Key 由 OcrClient 从 baidu_ocr.json 的 uapis_api_key 注入(热更新)。</summary>
        public void SetApiKey(string key)
        {
            _apiKey = key == null ? "" : key.Trim();
        }

        /// <summary>识别一块位图 → 文本行列表(带位置)。multipart 上传。</summary>
        public Task<List<OcrItem>> RecognizeAsync(Bitmap crop, int timeoutMs)
        {
            if (crop == null || crop.Width <= 0 || crop.Height <= 0)
                return Task.FromResult(new List<OcrItem>());

            if (!IsConfigured)
            {
                Notify("UApiPro OCR 未配置 API Key(OCR 设置窗口里填 UApiPro Key)");
                var tcs0 = new TaskCompletionSource<List<OcrItem>>();
                tcs0.SetException(new Exception(
                    "UApiPro(uapis.cn) OCR 未配置 API Key。\r\n" +
                    "请到 uapis.cn/console 注册生成 API Key," +
                    "在 OCR 设置窗口选择引擎\"UApiPro 通用OCR\"并填入后保存。"));
                return tcs0.Task;
            }

            return Task.Factory.StartNew(() =>
            {
                var sw = System.Diagnostics.Stopwatch.StartNew();
                var result = RequestAndParse(crop, timeoutMs);
                Notify("UApiPro OCR·" + result.Count + "条 " + sw.ElapsedMilliseconds + "ms");
                return result;
            });
        }

        private List<OcrItem> RequestAndParse(Bitmap crop, int timeoutMs)
        {
            byte[] png;
            using (var ms = new MemoryStream())
            {
                crop.Save(ms, ImageFormat.Png);
                png = ms.ToArray();
            }
            string b64 = Convert.ToBase64String(png);

            // multipart/form-data 手工拼装(net48 无 MultipartFormDataContent)
            string boundary = "----pdfbt" + Guid.NewGuid().ToString("N");
            var body = new MemoryStream();
            Action<string, string> field = (name, value) =>
            {
                byte[] part = Encoding.UTF8.GetBytes(
                    "--" + boundary + "\r\nContent-Disposition: form-data; name=\"" +
                    name + "\"\r\n\r\n" + value + "\r\n");
                body.Write(part, 0, part.Length);
            };
            field("image_base64", b64);
            field("need_location", "true");
            field("enable_cls", "true");   // 文字方向校正(歪扫图抗性)
            byte[] tail = Encoding.UTF8.GetBytes("--" + boundary + "--\r\n");
            body.Write(tail, 0, tail.Length);

            var req = (HttpWebRequest)WebRequest.Create(BaseUrl);
            req.Method = "POST";
            req.ContentType = "multipart/form-data; boundary=" + boundary;
            req.Headers.Add("X-API-Key", _apiKey);
            req.Timeout = timeoutMs;
            req.ReadWriteTimeout = timeoutMs;
            req.Proxy = null;
            byte[] payload = body.ToArray();
            req.ContentLength = payload.Length;
            using (var rs = req.GetRequestStream())
            {
                rs.Write(payload, 0, payload.Length);
            }

            string respText;
            try
            {
                using (var resp = (HttpWebResponse)req.GetResponse())
                using (var sr = new StreamReader(resp.GetResponseStream(), new UTF8Encoding(false)))
                {
                    respText = sr.ReadToEnd();
                }
            }
            catch (WebException wex)
            {
                string detail = "";
                try
                {
                    if (wex.Response != null)
                        using (var sr = new StreamReader(wex.Response.GetResponseStream(), new UTF8Encoding(false)))
                            detail = sr.ReadToEnd();
                }
                catch { }
                string hint = wex.Response == null
                    ? ("网络不可达: " + wex.Message)
                    : ("HTTP " + (int)((HttpWebResponse)wex.Response).StatusCode + " " + detail);
                throw new Exception("UApiPro OCR 请求失败: " + hint);
            }

            return ParseResponse(respText, crop.Width, crop.Height);
        }

        private List<OcrItem> ParseResponse(string respText, int cropW, int cropH)
        {
            var msg = _json.Deserialize<Dictionary<string, object>>(respText);
            if (msg == null) throw new Exception("UApiPro 响应解析失败(空响应)");

            // 业务错误:HTTP 200 但 code 非 200/0;或 HTTP 错误体 {code,message}
            if (msg.ContainsKey("code"))
            {
                string code = Convert.ToString(msg["code"]);
                if (code != "200" && code != "0" && code != "success")
                {
                    string m = msg.ContainsKey("message") ? Convert.ToString(msg["message"]) : respText;
                    throw new Exception("UApiPro OCR 错误 [" + code + "]: " + m);
                }
            }

            var items = new List<OcrItem>();
            var arr = msg.ContainsKey("words_result") ? msg["words_result"] as System.Collections.ArrayList : null;
            if (arr == null)
                throw new Exception("UApiPro 响应没有 words_result(内容: " +
                    (respText.Length > 300 ? respText.Substring(0, 300) : respText) + ")");

            foreach (Dictionary<string, object> w in arr)
            {
                string text = w.ContainsKey("words") ? Convert.ToString(w["words"]) : "";
                if (string.IsNullOrWhiteSpace(text)) continue;

                var loc = w.ContainsKey("location") ? w["location"] as Dictionary<string, object> : null;
                if (loc == null) continue;
                float l = LocF(loc, "left"), t = LocF(loc, "top");
                float wd = LocF(loc, "width"), h = LocF(loc, "height");
                // 裁剪到图内
                l = Math.Max(0, Math.Min(cropW, l));
                t = Math.Max(0, Math.Min(cropH, t));
                wd = Math.Max(2, Math.Min(cropW - l, wd));
                h = Math.Max(2, Math.Min(cropH - t, h));

                float score = 1f;
                if (w.ContainsKey("score"))
                {
                    float sv;
                    if (float.TryParse(Convert.ToString(w["score"]), out sv)) score = sv;
                }

                items.Add(new OcrItem
                {
                    Text = text,
                    Box = new[]
                    {
                        new PointF(l, t),
                        new PointF(l + wd, t),
                        new PointF(l + wd, t + h),
                        new PointF(l, t + h)
                    },
                    Score = score
                });
            }
            return items;
        }

        private static float LocF(Dictionary<string, object> d, string key)
        {
            if (d == null || !d.ContainsKey(key)) return 0f;
            float v;
            if (float.TryParse(Convert.ToString(d[key]), out v)) return v;
            return 0f;
        }

        private void Notify(string s)
        {
            var h = StatusChanged;
            if (h != null) h(s);
        }
    }
}