LINE-BOT

A production-oriented LINE AI assistant backend built with ASP.NET Core, integrating text conversation, image understanding, document analysis, and cloud deployment workflows.

A practical backend foundation with secure webhook handling, background processing, resilient AI routing, and observable operations.

繁體中文 | English

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Documentation Guide

• General user guide: USER_GUIDE.md
• Non-engineer decision and document-review guide (Traditional Chinese): USER_GUIDE_NON_ENGINEER.zh-TW.md

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Product Overview

LINE-BOT is an AI assistant backend service that uses the LINE Messaging API as its entry point, designed for these goals:

• Natural language interaction within LINE
• Analyzing images uploaded by users
• Organizing and summarizing uploaded files
• Reducing hallucination risk through a grounded document pipeline
• Running a cloud-ready deployment flow with health verification

It is more than a basic webhook receiver. It includes signature verification, queue-based background dispatch, provider failover support, downloadable outputs, and runtime safeguards for stability.

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Why This Project

Most LINE Bot examples only do "receive a message, send a reply."

This project goes several steps further:

• Handles text, image, file, and postback events through dedicated flows
• Adds throttling, short-window merge, response cache, and cooldown protection
• Uses queue + hosted worker to avoid request-thread fire-and-forget patterns
• Adds CI test gate and post-deploy verification before considering release complete

In other words, this repository is closer to an "extensible product foundation" rather than a minimal demo.

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Core Capabilities

Text Interaction Processes user text with mention-gate rules, AI replies, optional web search, and quick-reply suggestions.

Image Understanding Downloads image content and routes it to AI analysis with throttling and cooldown safeguards.

Document Summarization Extracts document text, selects grounded chunks, generates summary output, and provides a downloadable result link.

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Product Highlights

1. Modern Webhook Architecture

• Built on ASP.NET Core Web API
• Verifies LINE request signatures before any meaningful processing
• Enqueues events into a bounded background queue
• Processes queue items in a hosted worker and dispatches by message/event type

2. Production-Oriented Stability Design

• Per-user throttling
• AI 429 cooldown mechanism
• AI quota exhaustion protection
• Reply caching
• Deduplication of repeated requests within short time windows
• Readiness endpoint with queue-aware operational snapshot

3. A More Trustworthy Document Processing Pipeline

• Extracts document text content first
• Performs chunk organization and grounding
• Generates AI summary at the end
• Produces downloadable markdown output with temporary tokenized access

4. Deployable, Extensible, and Maintainable

• Dockerfile included
• CI workflow includes restore, test gate, image build, deploy trigger, and deployment verification
• Clear structure for extending handlers, providers, and document capabilities

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Use Cases

This project is particularly well-suited for the following scenarios:

Scenario	Description
Personal AI Assistant	Ask questions and get concise responses directly in LINE
Team Knowledge Organization	Upload files and quickly extract highlights, conclusions, and action items
Image Content Interpretation	Send an image and receive structured key-point analysis
Custom AI Bot Backend	Reuse as a secure, extensible backend foundation
Deployment Validation Demo	Demonstrate test-gated CI and post-deploy health verification

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Supported Content

Supported Message Types

Type	Description
Text message	Conversational AI reply
Image message	Image content analysis
File message	Document extraction, summarization, and downloadable output

Supported File Formats

Format	Support Status
.txt	Supported
.md	Supported
.csv	Supported
.json	Supported
.xml	Supported
.log	Supported
.pdf	Supported for text-extractable PDFs
.docx	Supported
.xlsx	Supported
.pptx	Supported

Current Limitations

• Scanned PDFs are not yet supported
• Image-only PDFs are not yet supported
• Binary file summarization is not yet supported
• Process-local runtime state is not shared across instances

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System Architecture

LINE Platform
    |
    v
POST /api/line/webhook
    |
    +-- Verify x-line-signature
    +-- Parse webhook events
    +-- Enqueue to bounded background queue
            |
            v
      WebhookBackgroundService (hosted worker)
            |
            v
      Dispatcher
        |       |       |        \
        |       |       |         +-- Postback handling
        |       |       +------------ FileMessageHandler
        |       +-------------------- ImageMessageHandler
        +---------------------------- TextMessageHandler (mention gate in group/room)
                                        |
                                        +-- AI Failover Service
                                        +-- Web Search Service (optional)
                                        +-- Cache / Throttle / Backoff / Merge

Other HTTP endpoints:
- GET /
- GET /health
- GET /ready
- GET /downloads/{token}