add fastapi example (#342)

Author: Nutchanon Ninyawee

examples/fastapi-echo/README.md

@@ -0,0 +1,19 @@
+# FastAPI Echo
+
+Sample echo-bot using [fastapi](https://fastapi.tiangolo.com/)
+
+## Getting started
+
+```
+$ export LINE_CHANNEL_SECRET=YOUR_LINE_CHANNEL_SECRET
+$ export LINE_CHANNEL_ACCESS_TOKEN=YOUR_LINE_CHANNEL_ACCESS_TOKEN
+
+$ pip install -r requirements.txt
+```
+
+Run FastAPI sample
+
+```
+$ uvicorn main:app --reload
+```
+

examples/fastapi-echo/main.py

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+# -*- coding: utf-8 -*-
+
+#  Licensed under the Apache License, Version 2.0 (the "License"); you may
+#  not use this file except in compliance with the License. You may obtain
+#  a copy of the License at
+#
+#       https://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#  License for the specific language governing permissions and limitations
+#  under the License.
+
+import os
+import sys
+
+import aiohttp
+
+from fastapi import Request, FastAPI, HTTPException
+
+
+from linebot import (
+    AsyncLineBotApi, WebhookParser
+)
+from linebot.aiohttp_async_http_client import AiohttpAsyncHttpClient
+from linebot.exceptions import (
+    InvalidSignatureError
+)
+from linebot.models import (
+    MessageEvent, TextMessage, TextSendMessage,
+)
+
+# get channel_secret and channel_access_token from your environment variable
+channel_secret = os.getenv('LINE_CHANNEL_SECRET', None)
+channel_access_token = os.getenv('LINE_CHANNEL_ACCESS_TOKEN', None)
+if channel_secret is None:
+    print('Specify LINE_CHANNEL_SECRET as environment variable.')
+    sys.exit(1)
+if channel_access_token is None:
+    print('Specify LINE_CHANNEL_ACCESS_TOKEN as environment variable.')
+    sys.exit(1)
+
+
+app = FastAPI()
+session = aiohttp.ClientSession()
+async_http_client = AiohttpAsyncHttpClient(session)
+line_bot_api = AsyncLineBotApi(channel_access_token, async_http_client)
+parser = WebhookParser(channel_secret)
+
+@app.post("/callback")
+async def handle_callback(request: Request):
+    signature = request.headers['X-Line-Signature']
+
+    # get request body as text
+    body = await request.body()
+    body = body.decode()
+
+    try:
+        events = parser.parse(body, signature)
+    except InvalidSignatureError:
+        raise HTTPException(status_code=400, detail="Invalid signature")
+
+    for event in events:
+        if not isinstance(event, MessageEvent):
+            continue
+        if not isinstance(event.message, TextMessage):
+            continue
+
+        await line_bot_api.reply_message(
+            event.reply_token,
+            TextSendMessage(text=event.message.text)
+        )
+        
+    return 'OK'

examples/fastapi-echo/requirements.txt

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+line-bot-sdk
+fastapi
+uvicorn[standard]
+