import json
from collections.abc import Generator
from io import BytesIO
from typing import Any

import fitz  # PyMuPDF 核心库
from dify_plugin import Tool
from dify_plugin.entities.tool import ToolInvokeMessage


class PdfSinglePageTool(Tool):
    def _invoke(self, tool_parameters: dict[str, Any]) -> Generator[ToolInvokeMessage]:
        file = tool_parameters.get("file")
        page = tool_parameters.get("page", 0)

        if not file:
            yield self.create_text_message("Error: file is required")
            return

        # 从字节流加载 PDF（替换 PyPDF2 的 PdfReader）
        pdf_bytes = file.blob
        doc = fitz.open(stream=pdf_bytes, filetype="pdf")  # 字节流方式打开
        num_pages = len(doc)

        # 页码边界处理（逻辑与原代码一致）
        page_index = int(page)
        if page_index < 0:
            page_index = 0
        if page_index >= num_pages:
            page_index = num_pages - 1

        # 提取指定页面文本（PyMuPDF 方式）
        selected_page = doc[page_index]
        text = selected_page.get_text() or ""  # get_text() 提取文本，比 PyPDF2 更精准

        # 关闭文档释放资源
        doc.close()

        result = {
            "start": page_index,
            "end": page_index,
            "pages": [text]
        }
        yield self.create_text_message(json.dumps(result, ensure_ascii=False))
        yield self.create_json_message(result)