✨ feat: Add new slash commands for problem lookup and historical daily challenges

[cxyfer]

Summary

• Add /problem command for querying LeetCode problems by ID
• Extend /daily and /daily_cn commands with optional date parameter for historical lookup
• Refactor common display logic into reusable functions
• Add automatic command synchronization on bot startup

New Features

/problem Command

• Query LeetCode problems by problem ID (1-4000+)
• Support both leetcode.com and leetcode.cn domains
• Input validation and error handling
• Auto-complete for domain selection
• Same display format as daily challenges

Enhanced Daily Commands

• Optional date parameter for /daily and /daily_cn
• Support YYYY-MM-DD format for historical lookup
• Date validation with user-friendly error messages
• Backward compatible - no date means current day

Code Improvements

• Extract create_problem_embed() for unified embed creation
• Extract create_problem_view() for consistent button layouts
• Reduce code duplication by ~200 lines
• Maintain consistent UI/UX across all commands

Auto Command Sync

• Automatic slash command synchronization on bot startup
• Ensures new commands appear without manual intervention

Test Plan

• Syntax validation passes
• Code compiles without errors
• Test /problem command with valid problem IDs
• Test /problem command with invalid inputs
• Test /daily with date parameter
• Test /daily_cn with date parameter
• Verify commands appear in Discord after bot restart
• Test backward compatibility of existing commands

🤖 Generated with Claude Code

[Copilot]

Pull Request Overview

Adds historical date support to daily challenge commands, introduces a new /problem lookup command, refactors embed/view creation, and enables automatic command synchronization on startup.

• Extend /daily and /daily_cn with an optional date parameter for historical lookup.
• Add /problem command to fetch LeetCode problem details by ID with input validation and autocomplete.
• Refactor embed/view logic into create_problem_embed and create_problem_view; auto-sync slash commands in on_ready.

Reviewed Changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 2 comments.

File	Description
cogs/slash_commands_cog.py	Add date validation, historical daily lookup logic, and new /problem.
cogs/schedule_manager_cog.py	Extract embed/view functions and update send_daily_challenge.
bot.py	Implement on_ready to initialize schedules and auto-sync commands.

Comments suppressed due to low confidence (4)

cogs/slash_commands_cog.py:124

• The upper bound of 4000 conflicts with the description mentioning "1-3500+"; clarify the supported ID range to avoid user confusion.

        if problem_id > 4000:  # Add upper bound validation

cogs/slash_commands_cog.py:105

• There are no tests covering the new /problem command. Consider adding unit or integration tests for valid, invalid, and edge-case inputs.

    @app_commands.command(name="problem", description="根據題號查詢 LeetCode 題目資訊")

cogs/schedule_manager_cog.py:163

• The docstring for create_problem_embed doesn't describe the is_daily and date_str parameters; update it to document all arguments.

    async def create_problem_embed(self, problem_info: dict, domain: str = "com", is_daily: bool = False, date_str: str = None):

bot.py:252

• [nitpick] The comment suggests syncing commands is optional, but the code always calls bot.tree.sync(). Update the comment or add a guard to reflect actual behavior.

    # Auto-sync commands on startup (optional, comment out if not needed)

[Copilot]

[nitpick] Consider extracting the date validation regex into a shared constant or helper function to avoid duplication and improve maintainability.

Suggested change

	if not re.match(r'^\d{4}-\d{2}-\d{2}$', date):
	if not re.match(DATE_REGEX, date):

[Copilot]

[nitpick] The same regex appears in both /daily and /daily_cn; extract it into a common validator to DRY up the code.

Suggested change

	if date:
	# Validate date format
	if not re.match(r'^\d{4}-\d{2}-\d{2}$', date):
	await interaction.followup.send("日期格式錯誤，請使用 YYYY-MM-DD 格式（例如：2024-01-15）", ephemeral=True)
	return
	if date:
	# Validate date format
	if not self.validate_date_format(date):
	await interaction.followup.send("日期格式錯誤，請使用 YYYY-MM-DD 格式（例如：2024-01-15）", ephemeral=True)
	return