main.py

import os
import io
import re
import PIL.Image
import uvicorn
from collections import defaultdict
from fastapi import FastAPI, Request, Header, BackgroundTasks, HTTPException
from fastapi.middleware.cors import CORSMiddleware
from fastapi.staticfiles import StaticFiles

# Google GenAI SDK
from google import genai
from google.genai import types

# Line Bot
from linebot import LineBotApi, WebhookHandler
from linebot.exceptions import InvalidSignatureError
from linebot.models import (
    MessageEvent, TextMessage, TextSendMessage, ImageSendMessage, ImageMessage,
)

# LangChain imports (修正後)
from langchain_core.prompts import ChatPromptTemplate, MessagesPlaceholder
from langchain_core.tools import tool
from langchain_google_genai import ChatGoogleGenerativeAI
# 直接使用標準路徑，不再使用 try-except
# 從具體路徑匯入 AgentExecutor
from langchain.agents.agent import AgentExecutor
from langchain.agents import create_tool_calling_agent

# ==========================
#  環境設定與工具函式
# ==========================
google_api = os.environ.get("GOOGLE_API_KEY")
genai_client = genai.Client(api_key=google_api)

line_bot_api = LineBotApi(os.environ.get("CHANNEL_ACCESS_TOKEN"))
line_handler = WebhookHandler(os.environ.get("CHANNEL_SECRET"))

user_message_history = defaultdict(list)
app = FastAPI()

if not os.path.exists("static"):
    os.makedirs("static")
app.mount("/static", StaticFiles(directory="static"), name="static")

app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

def get_image_url_from_line(message_id):
    try:
        message_content = line_bot_api.get_message_content(message_id)
        file_path = f"static/{message_id}.png"
        with open(file_path, "wb") as f:
            for chunk in message_content.iter_content():
                f.write(chunk)
        return file_path
    except Exception as e:
        print(f"❌ 圖片取得失敗：{e}")
        return None

def store_user_message(user_id, message_type, message_content):
    user_message_history[user_id].append({"type": message_type, "content": message_content})

def get_previous_message(user_id):
    if user_id in user_message_history and len(user_message_history[user_id]) > 0:
        return user_message_history[user_id][-1]
    return {"type": "text", "content": "No message!"}

# ==========================
#  LangChain 工具定義
# ==========================

@tool
def generate_and_upload_image(prompt: str) -> str:
    """根據文字提示生成圖片。"""
    try:
        # 修正：2026 年請使用實質存在的模型 imagen-3.0
        response = genai_client.models.generate_content(
            model="gemini-2.5-flash-image", 
            contents=prompt,
            config=types.GenerateContentConfig(response_modalities=['IMAGE'])
        )
        
        image_binary = None
        for part in response.candidates[0].content.parts:
            if part.inline_data:
                image_binary = part.inline_data.data
                break
        
        if image_binary:
            image = PIL.Image.open(io.BytesIO(image_binary))
            file_name = f"static/{os.urandom(8).hex()}.png"
            image.save(file_name, format="PNG")
            
            base_url = os.getenv("HF_SPACE", "http://localhost:7860").rstrip("/")
            return f"{base_url}/{file_name}"
        return "圖片生成失敗：模型未回傳數據。"
    except Exception as e:
        return f"圖片生成失敗: {e}"

@tool
def analyze_image_with_text(image_path: str, user_text: str) -> str:
    """根據圖片路徑和文字提問進行分析。"""
    try:
        if not os.path.exists(image_path):
            return "錯誤：找不到該圖片檔案。"
        img_user = PIL.Image.open(image_path)
        # 修正模型：gemini-1.5-flash 或 2.0-flash
        response = genai_client.models.generate_content(
            model="gemini-2.5-flash",
            contents=[img_user, user_text]
        )
        return response.text if response.text else "Gemini 沒答案！"
    except Exception as e:
        return f"分析出錯: {e}"

# ==========================
#  LangChain 代理人設定
# ==========================
tools = [generate_and_upload_image, analyze_image_with_text]
# 修正模型：gemini-3-flash-preview 目前在正式 API 中通常不可用
llm = ChatGoogleGenerativeAI(model="gemini-2.5-flash", temperature=0.4)

prompt_template = ChatPromptTemplate.from_messages([
    ("system", "你是一個強大的助理。在使用工具之前，請務必先說明你的思考步驟。如果生成了圖片，請直接給出 URL。"),
    ("user", "{input}"),
    MessagesPlaceholder(variable_name="agent_scratchpad"),
])

agent = create_tool_calling_agent(llm, tools, prompt_template)
agent_executor = AgentExecutor(agent=agent, tools=tools, verbose=False, handle_parsing_errors=True)

# ==========================
#  FastAPI 路由
# ==========================

@app.get("/")
def root():
    return {"status": "running"}

@app.post("/webhook")
async def webhook(request: Request, background_tasks: BackgroundTasks, x_line_signature=Header(None)):
    body = await request.body()
    try:
        background_tasks.add_task(line_handler.handle, body.decode("utf-8"), x_line_signature)
    except InvalidSignatureError:
        raise HTTPException(status_code=400)
    return "ok"

@line_handler.add(MessageEvent, message=(ImageMessage, TextMessage))
def handle_message(event):
    user_id = event.source.user_id
    
    # 1. 處理圖片訊息
    if isinstance(event.message, ImageMessage):
        image_path = get_image_url_from_line(event.message.id)
        if image_path:
            store_user_message(user_id, "image", image_path)
            line_bot_api.reply_message(event.reply_token, TextSendMessage(text="收到圖片了！請問你想對這張圖做什麼分析？"))
    
    # 2. 處理文字訊息 (修正縮進，確保它與上面的 if 對齊)
    elif isinstance(event.message, TextMessage):
        user_text = event.message.text
        previous_message = get_previous_message(user_id)
        
        if previous_message["type"] == "image":
            image_path = previous_message["content"]
            agent_input = {"input": f"請分析這張圖片 {image_path}，問題是：{user_text}"}
            user_message_history[user_id].pop()
        else:
            agent_input = {"input": user_text}
        
        try:
            response = agent_executor.invoke(agent_input)
            out = response["output"]
            
            # 搜尋 URL 邏輯
            urls = re.findall(r'https?://[^\s<>"]+|www\.[^\s<>"]+', out)
            image_url = next((u for u in urls if any(ext in u.lower() for ext in ['.png', '.jpg'])), None)
            
            if image_url:
                line_bot_api.reply_message(
                    event.reply_token,
                    [
                        TextSendMessage(text="這是我為你生成的圖片："),
                        ImageSendMessage(original_content_url=image_url, preview_image_url=image_url)
                    ]
                )
            else:
                line_bot_api.reply_message(event.reply_token, TextSendMessage(text=out))
        except Exception as e:
            print(f"Agent Error: {e}")
            line_bot_api.reply_message(event.reply_token, TextSendMessage(text="抱歉，我現在無法處理這個請求。"))

if __name__ == "__main__":
    uvicorn.run(app, host="0.0.0.0", port=7860)