"""
纯文字 OCR 识别系统 (基于 V4.24 简化)
移除: 公式检测 (MFD) / 公式识别 (MFR)
保留: 文本检测 (DBNet) / 文本识别 (CRNN) / 文本行合并
"""

import cv2
import numpy as np
import onnxruntime as ort
import pyclipper
from shapely.geometry import Polygon
import os
import math


# ==========================================
# 1. 基础工具与后处理 (保持 V4.24 修复版)
# ==========================================
class DBPostProcess:
    """DBNet 后处理"""
    def __init__(self, thresh=0.3, box_thresh=0.6, max_candidates=1000, unclip_ratio=1.5):
        self.thresh = thresh
        self.box_thresh = box_thresh
        self.max_candidates = max_candidates
        self.unclip_ratio = unclip_ratio
        self.min_size = 3

    def __call__(self, pred, shape_list):
        pred = pred[0, 0, :, :]
        segmentation = pred > self.thresh
        boxes_batch = []
        scores_batch = []
        mask = (segmentation * 255).astype(np.uint8)
        contours, _ = cv2.findContours(mask, cv2.RETR_LIST, cv2.CHAIN_APPROX_SIMPLE)
        src_h, src_w, ratio_h, ratio_w = shape_list
        
        for contour in contours:
            if len(contour) < 2: continue
            
            # 第一次调用 get_mini_boxes
            box, sside = self.get_mini_boxes(contour)
            if sside < self.min_size: continue
            
            points = np.array(box)
            score = self.box_score_fast(pred, points)
            if score < self.box_thresh: continue
            
            # unclip 返回的是列表 (list of points)
            box = self.unclip(points)
            if box is None: continue
            
            # 第二次调用 get_mini_boxes
            box, sside = self.get_mini_boxes(box)
            if sside < self.min_size + 2: continue
            
            box = np.array(box)
            box[:, 0] = np.clip(np.round(box[:, 0] / ratio_w), 0, src_w)
            box[:, 1] = np.clip(np.round(box[:, 1] / ratio_h), 0, src_h)
            boxes_batch.append(box.astype(np.int32))
            scores_batch.append(score)
        return boxes_batch, scores_batch

    def unclip(self, box):
        poly = Polygon(box)
        if poly.length == 0: return None
        distance = poly.area * self.unclip_ratio / poly.length
        offset = pyclipper.PyclipperOffset()
        offset.AddPath(box, pyclipper.JT_ROUND, pyclipper.ET_CLOSEDPOLYGON)
        expanded = offset.Execute(distance)
        return expanded[0] if len(expanded) > 0 else None

    def get_mini_boxes(self, contour):
        # 强制转换为 numpy array (修复 OpenCV 报错)
        if not isinstance(contour, np.ndarray):
            contour = np.array(contour, dtype=np.float32)
        
        bounding_box = cv2.minAreaRect(contour)
        points = sorted(list(cv2.boxPoints(bounding_box)), key=lambda x: x[0])
        
        index_1, index_2, index_3, index_4 = 0, 1, 2, 3
        if points[1][1] > points[0][1]: index_1, index_4 = 0, 1
        else: index_1, index_4 = 1, 0
        if points[3][1] > points[2][1]: index_2, index_3 = 2, 3
        else: index_2, index_3 = 3, 2
        
        box = [points[index_1], points[index_2], points[index_3], points[index_4]]
        return box, min(bounding_box[1])

    def box_score_fast(self, bitmap, _box):
        h, w = bitmap.shape[:2]
        box = _box.copy()
        xmin = np.clip(np.floor(box[:, 0].min()).astype(int), 0, w - 1)
        xmax = np.clip(np.ceil(box[:, 0].max()).astype(int), 0, w - 1)
        ymin = np.clip(np.floor(box[:, 1].min()).astype(int), 0, h - 1)
        ymax = np.clip(np.ceil(box[:, 1].max()).astype(int), 0, h - 1)
        
        if xmax <= xmin or ymax <= ymin: return 0
        
        mask = np.zeros((ymax - ymin + 1, xmax - xmin + 1), dtype=np.uint8)
        box[:, 0] = box[:, 0] - xmin
        box[:, 1] = box[:, 1] - ymin
        cv2.fillPoly(mask, box.reshape(1, -1, 2).astype(np.int32), 1)
        return cv2.mean(bitmap[ymin:ymax + 1, xmin:xmax + 1], mask)[0]


def get_rotate_crop_image(img, points):
    points = np.array(points, dtype=np.float32)
    width = int(max(np.linalg.norm(points[0] - points[1]), np.linalg.norm(points[2] - points[3])))
    height = int(max(np.linalg.norm(points[0] - points[3]), np.linalg.norm(points[1] - points[2])))
    pts_std = np.float32([[0, 0], [width, 0], [width, height], [0, height]])
    M = cv2.getPerspectiveTransform(points, pts_std)
    dst_img = cv2.warpPerspective(img, M, (width, height), borderMode=cv2.BORDER_REPLICATE, flags=cv2.INTER_CUBIC)
    if dst_img.shape[0] * 1.0 / dst_img.shape[1] >= 1.5: 
        dst_img = np.rot90(dst_img)
    return dst_img


# ==========================================
# 2. 文本检测器 (DBNet)
# ==========================================
class TextDetector:
    def __init__(self, model_path, use_gpu=True):
        print(f"Loading DBNet model from: {model_path}")
        providers = ['CUDAExecutionProvider', 'CPUExecutionProvider'] if use_gpu else ['CPUExecutionProvider']
        self.session = ort.InferenceSession(model_path, providers=providers)
        self.input_name = self.session.get_inputs()[0].name
        self.post_process = DBPostProcess(thresh=0.3, box_thresh=0.5, unclip_ratio=1.5)

    def predict(self, img, limit_side_len=1280):
        h, w = img.shape[:2]
        ratio = 1.0
        if max(h, w) > limit_side_len:
            ratio = float(limit_side_len) / max(h, w)
        resize_h = int(h * ratio)
        resize_w = int(w * ratio)
        resize_h = max(int(round(resize_h / 32) * 32), 32)
        resize_w = max(int(round(resize_w / 32) * 32), 32)
        ratio_h = resize_h / float(h)
        ratio_w = resize_w / float(w)
        
        img_resized = cv2.resize(img, (resize_w, resize_h))
        
        # 显式 float32 运算
        img_norm = img_resized.astype(np.float32) / 255.0
        img_norm -= np.array([0.485, 0.456, 0.406], dtype=np.float32)
        img_norm /= np.array([0.229, 0.224, 0.225], dtype=np.float32)
        
        img_input = img_norm.transpose((2, 0, 1))[np.newaxis, :]
        img_input = img_input.astype(np.float32)
        
        outputs = self.session.run(None, {self.input_name: img_input})
        boxes, scores = self.post_process(outputs[0], [h, w, ratio_h, ratio_w])
        return boxes, scores


# ==========================================
# 3. 文本识别器 (CRNN)
# ==========================================
class TextRecognizer:
    def __init__(self, model_path, label_path, use_gpu=True):
        print(f"Loading CRNN model from: {model_path}")
        providers = ['CUDAExecutionProvider', 'CPUExecutionProvider'] if use_gpu else ['CPUExecutionProvider']
        self.session = ort.InferenceSession(model_path, providers=providers)
        self.input_name = self.session.get_inputs()[0].name
        self.character = self.load_dict(label_path)
        self.rec_image_height = 48

    def load_dict(self, label_path):
        with open(label_path, 'r', encoding='utf-8') as f:
            character = [line.strip('\n') for line in f.readlines()]
        return ['blank'] + character + [' '] 

    def predict(self, img_list):
        if len(img_list) == 0: return []
        imgH = self.rec_image_height
        max_wh_ratio = max([w / h for h, w in [img.shape[:2] for img in img_list]] + [320.0 / imgH])
        
        batch_input = []
        for img in img_list:
            h, w = img.shape[:2]
            imgW = int(imgH * max_wh_ratio)
            ratio = w / float(h)
            resized_w = int(math.ceil(imgH * ratio)) if math.ceil(imgH * ratio) <= imgW else imgW
            resized_image = cv2.resize(img, (resized_w, imgH)).astype(np.float32)
            resized_image = (resized_image.transpose((2, 0, 1)) / 255.0 - 0.5) / 0.5
            padding_im = np.zeros((3, imgH, imgW), dtype=np.float32)
            padding_im[:, :, 0:resized_w] = resized_image
            batch_input.append(padding_im[np.newaxis, :])
            
        input_tensor = np.concatenate(batch_input, axis=0)
        outputs = self.session.run(None, {self.input_name: input_tensor})[0]
        preds_idx = outputs.argmax(axis=2)
        
        results = []
        for idxs in preds_idx:
            res = ""
            last = 0
            for idx in idxs:
                if idx != last and idx != 0 and idx < len(self.character):
                    res += self.character[idx]
                last = idx
            results.append(res)
        return results


# ==========================================
# 4. 文本行合并器 (TextMerger) - 优化版
# ==========================================
class TextMerger:
    def __init__(self, y_thresh=20):
        self.y_thresh = y_thresh

    def merge(self, text_results):
        """
        优化合并逻辑：确保严格的'从左到右，从上到下'顺序
        使用基于重叠度的行聚类，而非简单的线性阈值
        """
        if not text_results: return []

        # 1. 预计算几何信息
        for item in text_results:
            box = item['box']
            y_min, y_max = np.min(box[:, 1]), np.max(box[:, 1])
            x_min = np.min(box[:, 0])
            item['y_min'] = y_min
            item['y_max'] = y_max
            item['y_center'] = (y_min + y_max) / 2
            item['x_min'] = x_min
            item['height'] = y_max - y_min

        # 2. 初始按 y_min 排序，作为基准选择顺序
        text_results.sort(key=lambda x: x['y_min'])
        
        lines = []
        
        # 3. 迭代聚类
        while len(text_results) > 0:
            # 取出当前最顶部的框作为"行基准"
            base = text_results.pop(0)
            current_line = [base]
            
            remains = []
            base_y_center = base['y_center']
            base_height = base['height']
            
            for item in text_results:
                # 判定同行：中心点 Y 轴距离小于一定阈值
                avg_height = (base_height + item['height']) / 2
                dynamic_thresh = max(self.y_thresh, avg_height * 0.5)
                
                y_diff = abs(item['y_center'] - base_y_center)
                
                if y_diff < dynamic_thresh:
                    current_line.append(item)
                else:
                    remains.append(item)
            
            text_results = remains
            
            # 4. 行内排序：严格按 X 轴 (从左到右)
            current_line.sort(key=lambda x: x['x_min'])
            lines.append(current_line)

        # 5. 行间排序：虽已大致有序，可再按每行第一个元素的 Y 重新微调
        lines.sort(key=lambda line: line[0]['y_min'])

        # 6. 拼接输出
        final_output = []
        for line in lines:
            # 简单空格连接
            line_text = " ".join([x['content'] for x in line])
            # 清理多余空格
            line_text = " ".join(line_text.split())
            final_output.append(line_text)

        return final_output


# ==========================================
# 5. 主处理器 (PureOCRSystem)
# ==========================================
class PureOCRSystem:
    def __init__(self, det_path, rec_path, key_path, use_gpu=True):
        print("\n" + "="*50)
        print("初始化纯文字识别系统 (无公式)")
        print("="*50)
        
        self.detector = TextDetector(det_path, use_gpu=use_gpu)
        self.recognizer = TextRecognizer(rec_path, key_path, use_gpu=use_gpu)
        self.merger = TextMerger(y_thresh=20) 

    def process(self, img_path):
        """处理本地图片文件"""
        img = cv2.imdecode(np.fromfile(img_path, dtype=np.uint8), cv2.IMREAD_COLOR)
        if img is None: 
            print(f"❌ 无法读取图像: {img_path}")
            return None
        
        return self._process_image(img)

    def process_image(self, img):
        """处理 numpy 数组格式的图片（FastAPI 使用）"""
        return self._process_image(img)

    def _process_image(self, img):
        """内部处理函数"""
        # 1. 文本检测 (直接在原图上进行)
        print("Step 1: 检测文本...")
        text_boxes, scores = self.detector.predict(img)
        
        print(f"   找到 {len(text_boxes)} 个文本框")
        
        # 2. 文本识别
        print("Step 2: 识别文本...")
        text_results = []
        if len(text_boxes) > 0:
            # 简单按Y坐标初排，方便批量处理
            sorted_indices = np.argsort(np.array(text_boxes)[:, 0, 1])
            text_boxes = [text_boxes[i] for i in sorted_indices]
            
            crop_list = []
            for box in text_boxes:
                crop = get_rotate_crop_image(img, box)
                crop_list.append(crop)
            
            raw_texts = self.recognizer.predict(crop_list)
            
            for i, box in enumerate(text_boxes):
                text_results.append({
                    'box': box.astype(float),
                    'content': raw_texts[i],
                    'type': 'text'
                })
        
        # 3. 行合并
        print("Step 3: 结果合并 (从左到右，从上到下)...")
        final_lines = self.merger.merge(text_results)
        
        return final_lines