Add Copilot instructions for development

Includes build/test/lint commands, architecture overview, and key
conventions specific to this codebase.

Author: marcwrobel

.github/copilot-instructions.md

@@ -0,0 +1,139 @@
+# Copilot Instructions for lcc-slack-bot
+
+A Slack bot for automating show notes creation for _Les Cast Codeurs_ podcast. Built with Quarkus, the bot collects messages from Slack channels and publishes formatted show notes to GitHub.
+
+## Build, Test, and Lint
+
+### Prerequisites
+
+- Java 17 (Eclipse Temurin)
+- Gradle (see `.tool-versions` for exact version)
+- Quarkus CLI (optional but recommended)
+
+Use asdf to install dependencies: `asdf install`
+
+### Build Commands
+
+```bash
+# Development mode with live reload
+quarkus dev
+
+# Production build
+quarkus build
+
+# Or with Gradle
+gradle build
+
+# Run the built application
+java -jar build/quarkus-app/quarkus-run.jar
+```
+
+### Testing
+
+```bash
+# Run all tests
+gradle test
+
+# Run a single test class
+gradle test --tests com.lescastcodeurs.bot.ShowNotesTest
+
+# Run a single test method
+gradle test --tests com.lescastcodeurs.bot.ShowNotesTest.testMethodName
+```
+
+### Code Formatting
+
+Code is automatically formatted during build using google-java-format (Google Java Style).
+
+```bash
+# Manually format code
+gradle spotlessApply
+
+# Check formatting (without auto-fixing)
+gradle spotlessCheck
+```
+
+**Important**: Code is auto-formatted on local builds but only checked on CI. Install the google-java-format IDE plugin if available.
+
+## Architecture Overview
+
+### High-Level Flow
+
+1. **Slack Integration**: Bot listens for mentions using Socket Mode (no webhook required)
+2. **Command Processing**: Commands are parsed via `SlackBotAction` enum which uses keyword matching
+3. **Show Notes Generation**: Slack threads are converted to show notes using Qute templates
+4. **GitHub Publishing**: Formatted markdown is committed to a GitHub repository
+
+### Key Components
+
+- **`SlackBotAction` (enum)**: Defines all bot commands with keywords, responses, and handlers. Commands are matched by normalizing input and checking keywords in `guessOrder` priority.
+- **`ShowNotes`**: Main domain model that aggregates `ShowNote` objects by category. Episode number is extracted from channel name using regex.
+- **`ShowNoteCategory` (enum)**: Categories mapped to custom Slack emoji reactions (e.g., `lcc_lang`, `lcc_lib`). Uses `INCLUDE`/`EXCLUDE` for inclusion/exclusion logic.
+- **`SlackThread`**: Represents a Slack message thread with reactions and replies. First message is the show note, replies are comments.
+- **`GitHubClient`**: Publishes show notes to GitHub repository using GitHub API.
+- **Qute Templates** (`src/main/resources/templates/`): Generate markdown from show notes data.
+
+### Package Structure
+
+```
+com.lescastcodeurs.bot/
+├── github/          # GitHub API integration
+├── slack/           # Slack API integration and message handling
+├── conferences/     # Conference data retrieval
+└── internal/        # Utility classes (StringUtils, etc.)
+```
+
+### Show Note Processing Logic
+
+- Threads are considered show notes if:
+  - First message is from a user (not a bot)
+  - Has a categorization reaction OR contains a link with no mentions
+  - Not explicitly excluded with `:lcc_exclude:` reaction
+- Replies are included if:
+  - Written by a user (not a bot)
+  - No `:lcc_exclude:` reaction
+  - Has `:lcc_include:` reaction OR contains no mentions
+- Ordering: Custom reactions `:lcc_1:` through `:lcc_9:` control sort order, otherwise chronological
+
+## Key Conventions
+
+### Enum-Driven Command Pattern
+
+Commands are defined as enum values in `SlackBotAction`. Each action has:
+- `keywords`: List of normalized keywords to match
+- `response`: Default response message
+- `handlerAddress`: Optional Vert.x event bus address for async processing
+- `canReplyTo()`: Override for custom matching logic
+
+New commands: Add a new enum value with appropriate `guessOrder` (determines evaluation priority).
+
+### Reaction-Based Categorization
+
+Categories use custom Slack emojis (all prefixed `lcc_`):
+- Category reactions: `lcc_lang`, `lcc_lib`, `lcc_infra`, etc.
+- Special reactions: `lcc_include`, `lcc_exclude` (inclusion/exclusion)
+- Ordering reactions: `lcc_1` through `lcc_9`
+
+The last reaction added wins (except `:lcc_exclude:` which is always prioritized).
+
+### Configuration via Environment Variables
+
+Runtime configuration uses environment variables (not `application.properties`):
+- `SLACK_BOT_TOKEN`, `SLACK_APP_TOKEN`: Slack credentials
+- `GITHUB_TOKEN`, `GITHUB_REPOSITORY`: GitHub publishing
+- `CONFERENCES_JSON_URL`, `CONFERENCES_SELECTION_CRITERIA`: Conference list filtering
+- `LCC_RECORD_DATE_CRITERION`: String to identify record date messages
+
+Default values in `application.properties` are for local development only.
+
+### Quarkus Dependency Injection
+
+Uses Quarkus CDI (`@ApplicationScoped`, `@Inject`). Avoid manual instantiation of services; let the container manage lifecycle.
+
+### Vert.x Event Bus for Async Processing
+
+Commands requiring heavy processing (e.g., `GENERATE_SHOW_NOTES`) publish events to Vert.x event bus addresses. Handlers are registered with `@ConsumeEvent`.
+
+## Publishing
+
+Releases are triggered by creating a GitHub release with tag `x.y.z`. The `publish.yml` workflow publishes to GitHub Packages (Maven repository). Update `CHANGELOG.md` before creating the release.