import os
import re
from dotenv import load_dotenv
from fastapi import FastAPI, Request, HTTPException
from linebot.v3 import WebhookHandler
from linebot.v3.messaging import (
    Configuration,
    ApiClient,
    MessagingApi,
    ReplyMessageRequest,
    TextMessage,
)
from linebot.v3.webhooks import MessageEvent, TextMessageContent, FollowEvent
from linebot.v3.exceptions import InvalidSignatureError
from sqlalchemy import create_engine, Column, Integer, String, Float, DateTime, text
from sqlalchemy.orm import declarative_base, sessionmaker
from datetime import datetime


load_dotenv()

app = FastAPI()

# LINE 設定
configuration = Configuration(access_token=os.getenv("LINE_CHANNEL_ACCESS_TOKEN"))
handler = WebhookHandler(os.getenv("LINE_CHANNEL_SECRET"))

# DB 設定
DATABASE_URL = os.getenv("DATABASE_URL")
engine = create_engine(DATABASE_URL)
SessionLocal = sessionmaker(bind=engine)
Base = declarative_base()

# 資料表
class Transaction(Base):
    __tablename__ = "transactions"
    id = Column(Integer, primary_key=True, index=True)
    user_id = Column(String)
    category = Column(String)
    amount = Column(Float)
    note = Column(String, nullable=True)
    created_at = Column(DateTime, default=datetime.now)

Base.metadata.create_all(bind=engine)

# Webhook endpoint
@app.post("/webhook")
async def webhook(request: Request):
    signature = request.headers.get("X-Line-Signature", "")
    body = await request.body()
    try:
        handler.handle(body.decode(), signature)
    except InvalidSignatureError:
        raise HTTPException(status_code=400, detail="Invalid signature")
    return "OK"

@handler.add(MessageEvent, message=TextMessageContent)
def handle_message(event):
    user_id = event.source.user_id
    text = event.message.text.strip()
    reply = parse_and_save(user_id, text)

    with ApiClient(configuration) as api_client:
        line_bot_api = MessagingApi(api_client)
        line_bot_api.reply_message(
            ReplyMessageRequest(
                reply_token=event.reply_token,
                messages=[TextMessage(text=reply)]
            )
        )

@handler.add(FollowEvent)
def handle_follow(event):
    with ApiClient(configuration) as api_client:
        line_bot_api = MessagingApi(api_client)
        line_bot_api.reply_message(
            ReplyMessageRequest(
                reply_token=event.reply_token,
                messages=[TextMessage(text=(
                    "👋 歡迎使用 Myfinance 記帳 Bot！\n\n"
                    "📝 記帳格式：\n"
                    "類別 金額\n"
                    "類別 金額 備註\n\n"
                    "範例：\n"
                    "早餐 80\n"
                    "午餐 120 便當\n"
                    "交通 50 捷運\n\n"
                    "📊 查詢指令：\n"
                    "查今天 → 今日明細\n"
                    "查本月 → 本月統計\n\n"
                    "開始記帳吧！💪"
                ))]
            )
        )

def parse_and_save(user_id: str, text: str) -> str:
    # 查詢指令
    if text == "查今天":
        return query_today(user_id)
    if text == "查本月":
        return query_month(user_id)
    if text == "記帳說明":
        return (
            "📝 記帳格式：\n"
            "類別 金額\n"
            "類別 金額 備註\n\n"
            "範例：\n"
            "早餐 80\n"
            "午餐 120 便當\n"
            "交通 50 捷運\n\n"
            "輸入後 Bot 會自動記錄 ✅"
        )
    # 刪除指令：刪除 1 或 刪除 早餐
    if text.startswith("刪除 "):
        target = text[3:].strip()
        return delete_transaction(user_id, target)

    # 記帳格式：「早餐 80」或「早餐 80 備註」
    match = re.match(r"^(\S+)\s+(\d+(?:\.\d+)?)(?:\s+(.+))?$", text)
    if match:
        category = match.group(1)
        amount = float(match.group(2))
        note = match.group(3)
        save_transaction(user_id, category, amount, note)
        return f"✅ 已記錄：{category} ${amount:.0f}" + (f"（{note}）" if note else "")

    return "格式錯誤 😅\n記帳請輸入：類別 金額\n例如：早餐 80\n\n查詢請輸入：查今天 / 查本月"

def save_transaction(user_id, category, amount, note):
    db = SessionLocal()
    try:
        db.add(Transaction(user_id=user_id, category=category, amount=amount, note=note))
        db.commit()
    finally:
        db.close()

def delete_transaction(user_id: str, target: str) -> str:
    db = SessionLocal()
    try:
        today = datetime.now().date()
        rows = db.query(Transaction).filter(
            Transaction.user_id == user_id,
            text("DATE(created_at) = :today")
        ).params(today=today).all()

        if not rows:
            return "今天還沒有記錄 📭"

        # 用編號刪除
        if target.isdigit():
            idx = int(target) - 1
            if idx < 0 or idx >= len(rows):
                return f"沒有第 {target} 筆記錄，請先輸入「查今天」確認編號"
            row = rows[idx]
            db.delete(row)
            db.commit()
            return f"✅ 已刪除：{row.category} ${row.amount:.0f}"

        # 用類別刪除（刪最後一筆）
        matched = [r for r in rows if r.category == target]
        if not matched:
            return f"今天沒有「{target}」的記錄"
        row = matched[-1]
        db.delete(row)
        db.commit()
        return f"✅ 已刪除：{row.category} ${row.amount:.0f}"

    finally:
        db.close()

def query_today(user_id):
    db = SessionLocal()
    try:
        today = datetime.now().date()
        rows = db.query(Transaction).filter(
            Transaction.user_id == user_id,
            text("DATE(created_at) = :today")
        ).params(today=today).all()
        if not rows:
            return "今天還沒有記錄 📭"
        total = sum(r.amount for r in rows)
        lines = [
            f"{i+1}. {r.category} ${r.amount:.0f}" + (f"（{r.note}）" if r.note else "")
            for i, r in enumerate(rows)
        ]
        return "📋 今日記錄：\n" + "\n".join(lines) + f"\n\n💰 合計：${total:.0f}\n\n🗑 刪除請輸入：刪除 編號\n例如：刪除 1"
    finally:
        db.close()

def query_month(user_id):
    db = SessionLocal()
    try:
        now = datetime.now()
        rows = db.query(Transaction).filter(
            Transaction.user_id == user_id,
            text("EXTRACT(YEAR FROM created_at) = :year AND EXTRACT(MONTH FROM created_at) = :month")
        ).params(year=now.year, month=now.month).all()
        if not rows:
            return "本月還沒有記錄 📭"
        total = sum(r.amount for r in rows)
        # 依類別統計
        summary = {}
        for r in rows:
            summary[r.category] = summary.get(r.category, 0) + r.amount
        lines = [f"{cat}：${amt:.0f}" for cat, amt in sorted(summary.items(), key=lambda x: -x[1])]
        return f"📊 本月統計（{now.month}月）：\n" + "\n".join(lines) + f"\n\n💰 總計：${total:.0f}"
    finally:
        db.close()