specs/leaderboard_spec.md

# Wrdler Leaderboard System Specification

**Document Version:** 1.4.1
**Project Version:** 0.2.7
**Author:** GitHub Copilot
**Last Updated:** 2025-12-08
**Status:** ✅ Implemented and Documented

---

## Table of Contents

1. [Executive Summary](#1-executive-summary)
2. [Goals and Objectives](#2-goals-and-objectives)
3. [System Architecture](#3-system-architecture)
4. [Data Models](#4-data-models)
5. [New Python Modules](#5-new-python-modules)
6. [Implementation Steps](#6-implementation-steps)
7. [Version Changes](#7-version-changes)
8. [File Changes Summary](#8-file-changes-summary)
9. [API Reference](#9-api-reference)
10. [UI Components](#10-ui-components)
11. [Testing Requirements](#11-testing-requirements)
12. [Migration Notes](#12-migration-notes)
13. [Operational Considerations](#13-operational-considerations)

---

## 1. Executive Summary

This specification documents the implemented **Daily and Weekly Leaderboard System** for Wrdler. The system:

- ✅ Tracks top 25 scores for daily leaderboards (resets at UTC midnight)
- ✅ Tracks top 25 scores for weekly leaderboards (resets at UTC Monday 00:00)
- ✅ Creates separate leaderboards for each unique combination of game-affecting settings
- ✅ Automatically adds qualifying scores from any game completion (including challenge mode)
- ✅ Provides a dedicated leaderboard page with historical lookup capabilities
- ✅ Stores leaderboard data in HuggingFace repository using existing storage infrastructure
- ✅ Uses folder-based discovery (no index.json) with descriptive folder names
- ✅ Uses a unified JSON format consistent with existing challenge settings.json files

**Implementation Status:** All features complete and deployed as of version 0.2.0

---

## 2. Goals and Objectives

### Primary Goals

1. **Settings-Based Leaderboards**: Each unique combination of game-affecting settings creates a separate leaderboard. Players using different settings compete on different leaderboards.

2. **Daily Leaderboards**: Create and maintain daily leaderboards with top 25 entries displayed (can store more), organized by date folders (e.g., `games/leaderboards/daily/2025-01-27/`)

3. **Weekly Leaderboards**: Create and maintain weekly leaderboards with top 25 entries displayed (can store more), organized by ISO week folders (e.g., `games/leaderboards/weekly/2025-W04/`)

4. **Automatic Qualification**: Every game completion (challenge or solo) checks if score qualifies for the matching daily/weekly leaderboard based on current settings

5. **Leaderboard Page**: New Streamlit page displaying:
   - Last 7 days of daily leaderboards (filtered by current settings)
   - Last 5 weeks of weekly leaderboards with per-week expanders (current week open unless `week=YYYY-Www` query overrides)
   - Historical lookup via dropdown

6. **Folder-Based Discovery**: No index.json file. Leaderboards are discovered by scanning folder names. Folder names include settings info for fast filtering.

7. **Unified File Format**: Leaderboard files use the same structure as challenge settings.json with an `entry_type` field to distinguish between "daily", "weekly", and "challenge" entries

### Secondary Goals

- Maintain backward compatibility with existing challenge system
- Minimize HuggingFace API calls through caching
- Support sorting by score (descending), then time (ascending), then difficulty (descending)
- Use `challenge_id` as the primary identifier across all entry types

### Game-Affecting Settings

The following settings define a unique leaderboard:

| Setting | Type | Description |
|---------|------|-------------|
| `game_mode` | string | `"classic"`, `"easy"`, `"too easy"` |
| `wordlist_source` | string | Wordlist file (e.g., `"classic.txt"`, `"easy.txt"`) |
| `show_incorrect_guesses` | bool | Whether incorrect guesses are shown |
| `enable_free_letters` | bool | Whether free letters feature is enabled |
| `puzzle_options` | object | Puzzle configuration (`spacer`, `may_overlap`) |

**Example:** A player using `game_mode: "easy"` with `wordlist_source: "easy.txt"` competes on a different leaderboard than a player using `game_mode: "classic"` with `wordlist_source: "classic.txt"`.

---

## 3. System Architecture

### 3.1 Storage Structure

Each date/week has settings-based subfolders. The folder name (file_id) encodes the settings for fast discovery. All leaderboards use `settings.json` as the filename (consistent with challenges):

```
HF_REPO_ID/
├── games/                          # All game-related storage
│   ├── {challenge_id}/             # Existing challenge storage
│   │   └── settings.json           # entry_type: "challenge"
│   └── leaderboards/
│       ├── daily/
│       │   ├── 2025-01-27/
│       │   │   ├── classic-classic-0/
│       │   │   │   └── settings.json
│       │   │   └── easy-easy-0/
│       │   │       └── settings.json
│       │   └── 2025-01-26/
│       │       └── classic-classic-0/
│       │           └── settings.json
│       └── weekly/
│           ├── 2025-W04/
│           │   ├── classic-classic-0/
│           │   │   └── settings.json
│           │   └── easy-too_easy-0/
│           │       └── settings.json
│           └── 2025-W03/
│               └── classic-classic-0/
│                   └── settings.json
└── shortener.json                  # Existing URL shortener
```

### 3.2 File ID Format

The `file_id` (folder name) encodes settings for discovery without an index:

```
{wordlist_source}-{game_mode}-{sequence}
```

**Examples:**
- `classic-classic-0` - Classic wordlist, classic mode, first instance
- `easy-easy-0` - Easy wordlist, easy mode, first instance
- `classic-too_easy-1` - Classic wordlist, "too easy" mode, second instance

**Sanitization Rules:**
- `.txt` extension is removed from wordlist_source
- Spaces are replaced with underscores
- All lowercase

### 3.3 Folder-Based Discovery

Instead of maintaining an `index.json` file, leaderboards are discovered by:

1. **List period folders**: Scan `games/leaderboards/daily/` or `games/leaderboards/weekly/` for date/week folders
2. **List file_id folders**: For each period, scan for settings folders
3. **Filter by prefix**: Match file_ids that start with `{wordlist_source}-{game_mode}-`
4. **Load and verify**: Load `settings.json` to verify full settings match

**Benefits:**
- No index synchronization issues
- Self-documenting folder structure
- Can browse folders directly
- Reduced write operations (no index updates)

### 3.4 Data Flow

```
┌────────────────────┐
│  Game Completion   │
└────────────────────┘
          │
          ▼
┌────────────────────┐
│ Get current game   │
│ settings           │
└────────────────────┘
          │
          ▼
┌────────────────────┐
│ Build file_id      │
│ prefix from        │
│ settings           │
└────────────────────┘
          │
          ▼
┌────────────────────┐
│ Scan folders for   │
│ matching file_id   │
│ or create new      │
└────────────────────┘
          │
    ┌─────┴─────┐
    │           │
    ▼           ▼
┌───────┐ ┌───────────┐
│ Daily │ │ Weekly    │
│ LB    │ │ LB        |
└───────┘ └───────────┘
    │          │
    └────┬─────┘
         │
         ▼
┌─────────────────────┐
│ Check if score      │
│ qualifies (top      │
│ 25 displayed)       │
└─────────────────────┘
          │
          ▼
┌─────────────────────┐
│ Update & Upload     │
│ to HF repo          │
└─────────────────────┘
```

---

## 4. Data Models

### 4.1 Entry Type Definition

The `entry_type` field distinguishes between different types of game entries:

| entry_type | Description | Storage Location |
|------------|-------------|------------------|
| `"challenge"` | Player-created challenge for others to compete | `games/{challenge_id}/settings.json` |
| `"daily"` | Daily leaderboard entry | `games/leaderboards/daily/{date}/{file_id}/settings.json` |
| `"weekly"` | Weekly leaderboard entry | `games/leaderboards/weekly/{week}/{file_id}/settings.json` |

### 4.2 Unified File Schema (Consistent with Challenge settings.json)

Both leaderboard files and challenge files use the **same base structure**. The settings in the file define what makes this leaderboard unique:

```json
{
  "challenge_id": "2025-01-27/classic-classic-0",
  "entry_type": "daily",
  "game_mode": "classic",
  "grid_size": 8,
  "puzzle_options": {
    "spacer": 0,
    "may_overlap": false
  },
  "users": [
    {
      "uid": "20251130T190249Z-0XLG5O",
      "username": "Charles",
      "word_list": ["CHEER", "PLENTY", "REAL", "ARRIVE", "DEAF", "DAILY"],
      "word_list_difficulty": 117.48,
      "score": 39,
      "time": 132,
      "timestamp": "2025-11-30T19:02:49.544933+00:00",
      "source_challenge_id": null
    }
  ],
  "created_at": "2025-11-30T19:02:49.544933+00:00",
  "version": "0.2.0",
  "show_incorrect_guesses": true,
  "enable_free_letters": true,
  "wordlist_source": "classic.txt",
  "game_title": "Wrdler Gradio AI",
  "max_display_entries": 25
}
```

### 4.3 Field Descriptions

| Field | Type | Description |
|-------|------|-------------|
| `challenge_id` | string | Unique identifier. For daily: `"2025-01-27/classic-classic-0"`, weekly: `"2025-W04/easy-easy-0"`, challenge: `"20251130T190249Z-ABCDEF"` |
| `entry_type` | string | One of: `"daily"`, `"weekly"`, `"challenge"` |
| `game_mode` | string | Game difficulty: `"classic"`, `"easy"`, `"too easy"` |
| `grid_size` | int | Grid width (8 for Wrdler) |
| `puzzle_options` | object | Puzzle configuration (defines leaderboard uniqueness) |
| `users` | array | Array of user entries (sorted by score desc, time asc, difficulty desc) |
| `created_at` | string | ISO 8601 timestamp when entry was created |
| `version` | string | Schema version |
| `show_incorrect_guesses` | bool | Display setting (defines leaderboard uniqueness) |
| `enable_free_letters` | bool | Free letters feature toggle (defines leaderboard uniqueness) |
| `wordlist_source` | string | Source wordlist file (defines leaderboard uniqueness) |
| `game_title` | string | Game title for display |
| `max_display_entries` | int | Maximum entries to display (default 25, configurable via MAX_DISPLAY_ENTRIES env var) |

### 4.4 User Entry Schema

Each user entry in the `users` array:

```json
{
  "uid": "20251130T190249Z-0XLG5O",
  "username": "Charles",
  "word_list": ["CHEER", "PLENTY", "REAL", "ARRIVE", "DEAF", "DAILY"],
  "word_list_difficulty": 117.48,
  "score": 39,
  "time": 132,
  "timestamp": "2025-11-30T19:02:49.544933+00:00",
  "source_challenge_id": null
}
```

| Field | Type | Description |
|-------|------|-------------|
| `uid` | string | Unique user entry ID |
| `username` | string | Player display name |
| `word_list` | array | 6 words played |
| `word_list_difficulty` | float | Calculated difficulty score |
| `score` | int | Final score |
| `time` | int | Time in seconds |
| `timestamp` | string | ISO 8601 when entry was recorded |
| `source_challenge_id` | string\|null | If from a challenge, the original challenge_id |

### 4.5 Settings Matching

Two leaderboards are considered the same if ALL of the following match:
- `game_mode`
- `wordlist_source` (after sanitization - .txt removed, lowercase)
- `show_incorrect_guesses`
- `enable_free_letters`
- `puzzle_options.spacer`
- `puzzle_options.may_overlap`

### 4.6 Weekly Leaderboard Naming

Uses ISO 8601 week numbering:
- Format: `YYYY-Www` (e.g., `2025-W04`)
- Week starts on Monday
- Week 1 is the week containing the first Thursday of the year

---

## 5. New Python Modules

### 5.1 `wrdler/leaderboard.py` (NEW FILE)

**Purpose:** Core leaderboard logic for managing daily and weekly leaderboards with settings-based separation and folder-based discovery.

Key classes:
- `GameSettings` - Settings that define a unique leaderboard
- `UserEntry` - Single user entry in a leaderboard
- `LeaderboardSettings` - Unified leaderboard/challenge settings format

Key functions:
- `_sanitize_wordlist_source()` - Remove .txt extension and normalize
- `_build_file_id()` - Create file_id from settings
- `_parse_file_id()` - Parse file_id into components
- `find_matching_leaderboard()` - Find leaderboard by scanning folders
- `create_or_get_leaderboard()` - Get or create a leaderboard
- `submit_score_to_all_leaderboards()` - Main entry point for submissions

### 5.2 `wrdler/modules/storage.py` (UPDATED)

Added functions:
- `_list_repo_folders()` - List folder names under a path in HuggingFace repo
- `_list_repo_files_in_folder()` - List files in a folder

---

## 6. Implementation Steps

### Phase 1: Core Leaderboard Module (v0.2.0-alpha) ✅ COMPLETE

| Step | Task | Files | Status |
|------|------|-------|--------|
| 1.1 | Create `wrdler/leaderboard.py` with `GameSettings` and data models | NEW | ✅ Complete |
| 1.2 | Implement folder listing in storage.py | storage.py | ✅ Complete (_list_repo_folders) |
| 1.3 | Implement `find_matching_leaderboard()` with folder scanning | leaderboard.py | ✅ Complete |
| 1.4 | Implement `check_qualification()` and sorting | leaderboard.py | ✅ Complete (_sort_users) |
| 1.5 | Implement `submit_to_leaderboard()` and `submit_score_to_all_leaderboards()` | leaderboard.py | ✅ Complete |
| 1.6 | Write unit tests for leaderboard logic including settings matching | tests/test_leaderboard.py | ⏳ Recommended |

### Phase 2: UI Integration (v0.2.0-beta) ✅ COMPLETE

| Step | Task | Files | Status |
|------|------|-------|--------|
| 2.1 | Create `wrdler/leaderboard_page.py` with settings filtering | NEW | ✅ Complete |
| 2.2 | Add leaderboard navigation to `ui.py` sidebar | ui.py | ✅ Complete (footer menu) |
| 2.3 | Integrate score submission in `_game_over_content()` with current settings | ui.py | ✅ Complete |
| 2.4 | Add leaderboard results display in game over dialog | ui.py | ✅ Complete |
| 2.5 | Style leaderboard tables to match ocean theme | leaderboard_page.py | ✅ Complete (pandas dataframe styling) |

### Phase 3: Challenge Format Migration (v0.2.0-beta) ✅ COMPLETE

| Step | Task | Files | Status |
|------|------|-------|--------|
| 3.1 | Add `entry_type` field to existing challenge saves | game_storage.py | ✅ Complete |
| 3.2 | Update challenge loading to handle `entry_type` | game_storage.py | ✅ Complete (defaults to "challenge") |
| 3.3 | Test backward compatibility with old challenges | Manual | ✅ Verified |

### Phase 4: Testing & Polish (v0.2.0-rc) ✅ COMPLETE

| Step | Task | Files | Status |
|------|------|-------|--------|
| 4.1 | Integration testing with HuggingFace | Manual | ✅ Verified |
| 4.2 | Add caching for leaderboard data | leaderboard.py | ⏳ Future optimization |
| 4.3 | Add error handling and retry logic | leaderboard.py | ✅ Complete (logging) |
| 4.4 | Update documentation | README.md, specs/, CLAUDE.md | ✅ Complete |
| 4.5 | Version bump and release notes | pyproject.toml, __init__.py | ✅ Complete (v0.2.0)

---

## 7. Version Changes

### pyproject.toml

```toml
[project]
name = "wrdler"
version = "0.2.0"  # Updated from 0.1.0
description = "Wrdler vocabulary puzzle game with daily/weekly leaderboards"
```

### wrdler/__init__.py

```python
__version__ = "0.2.0"  # Updated from existing version
```

### wrdler/game_storage.py

```python
__version__ = "0.2.0"  # Updated from 0.1.5
```

### wrdler/leaderboard.py (NEW)

```python
__version__ = "0.2.0"
```

### wrdler/leaderboard_page.py (NEW)

```python
__version__ = "0.2.0"
```

### wrdler/modules/storage.py

```python
__version__ = "0.1.6"  # Updated to add folder listing functions
```

---

## 8. File Changes Summary

### New Files

| File | Purpose |
|------|---------|
| `wrdler/leaderboard.py` | Core leaderboard logic with folder-based discovery |
| `wrdler/leaderboard_page.py` | Streamlit leaderboard page |
| `tests/test_leaderboard.py` | Unit tests for leaderboard |
| `specs/leaderboard_spec.md` | This specification |

### Modified Files

| File | Changes |
|------|---------|
| `pyproject.toml` | Version bump to 0.2.0 |
| `wrdler/__init__.py` | Version bump, add leaderboard exports |
| `wrdler/modules/storage.py` | Add `_list_repo_folders()` and `_list_repo_files_in_folder()` |
| `wrdler/game_storage.py` | Version bump, add `entry_type` field, integrate leaderboard submission |
| `wrdler/ui.py` | Add leaderboard nav, integrate submission in game over |
| `wrdler/modules/__init__.py` | Export new functions if needed |

---

## 9. API Reference

### Public Functions in `wrdler/leaderboard.py`

```python
def submit_score_to_all_leaderboards(
    username: str,
    score: int,
    time_seconds: int,
    word_list: List[str],
    settings: GameSettings,
    word_list_difficulty: Optional[float] = None,
    source_challenge_id: Optional[str] = None,
    repo_id: Optional[str] = None
) -> Dict[str, Any]:
    """Main entry point for submitting scores after game completion."""

def load_leaderboard(
    entry_type: EntryType,
    period_id: str,
    file_id: str,
    repo_id: Optional[str] = None
) -> Optional[LeaderboardSettings]:
    """Load a specific leaderboard by file ID."""

def find_matching_leaderboard(
    entry_type: EntryType,
    period_id: str,
    settings: GameSettings,
    repo_id: Optional[str] = None
) -> Tuple[Optional[str], Optional[LeaderboardSettings]]:
    """Find a leaderboard matching given settings."""

def get_last_n_daily_leaderboards(
    n: int = 7,
    settings: Optional[GameSettings] = None,
    repo_id: Optional[str] = None
) -> List[Tuple[str, Optional[LeaderboardSettings]]]:
    """Get recent daily leaderboards for display."""

def list_available_periods(
    entry_type: EntryType,
    limit: int = 30,
    repo_id: Optional[str] = None
) -> List[str]:
    """List available period IDs from folder structure."""

def list_settings_for_period(
    entry_type: EntryType,
    period_id: str,
    repo_id: Optional[str] = None
) -> List[Dict[str, Any]]:
    """List all settings combinations for a period."""

def get_current_daily_id() -> str:
    """Get today's period ID."""

def get_current_weekly_id() -> str:
    """Get this week's period ID."""
```

---

## 10. UI Components

### 10.1 Sidebar Navigation

Add to `_render_sidebar()` in `ui.py`:

```python
st.header("Navigation")
if st.button("🏆 Leaderboards", width="stretch"):
    st.session_state["show_leaderboard_page"] = True
    st.rerun()
```

### 10.2 Game Over Integration

Modify `_game_over_content()` in `ui.py` to:

1. Call `submit_score_to_all_leaderboards()` after generating share link
2. Display qualification results:

```python
# After score submission
if results["daily"]["qualified"]:
    st.success(f"🏆 You ranked #{results['daily']['rank']} on today's leaderboard!")
if results["weekly"]["qualified"]:
    st.success(f"🏆 You ranked #{results['weekly']['rank']} on this week's leaderboard!")
```

### 10.3 Leaderboard Page Routing

In `run_app()`:

```python
# Check if leaderboard page should be shown
if st.session_state.get("show_leaderboard_page", False):
    from wrdler.leaderboard_page import render_leaderboard_page
    render_leaderboard_page()
    if st.button("← Back to Game"):
        st.session_state["show_leaderboard_page"] = False
        st.rerun()
    return  # Don't render game UI
```

---

## 11. Testing Requirements

### Unit Tests (`tests/test_leaderboard.py`)

```python
class TestUserEntry:
    def test_create_entry(self): ...
    def test_to_dict_roundtrip(self): ...
    def test_from_legacy_time_seconds_field(self): ...

class TestLeaderboardSettings:
    def test_create_leaderboard(self): ...
    def test_entry_type_values(self): ...
    def test_get_display_users_limit(self): ...
    def test_format_matches_challenge(self): ...

class TestGameSettings:
    def test_settings_matching_same(self): ...
    def test_settings_matching_different_mode(self): ...
    def test_settings_matching_txt_extension_ignored(self): ...
    def test_get_file_id_prefix(self): ...

class TestFileIdFunctions:
    def test_sanitize_wordlist_source_removes_txt(self): ...
    def test_build_file_id(self): ...
    def test_parse_file_id(self): ...

class TestQualification:
    def test_qualify_empty_leaderboard(self): ...
    def test_qualify_not_full(self): ...
    def test_qualify_by_score(self): ...
    def test_qualify_by_time_tiebreaker(self): ...
    def test_qualify_by_difficulty_tiebreaker(self): ...
    def test_not_qualify_lower_score(self): ...

class TestDateIds:
    def test_daily_id_format(self): ...
    def test_weekly_id_format(self): ...
    def test_daily_path(self): ...  # Tests new folder structure
    def test_weekly_path(self): ...  # Tests new folder structure
```


### Integration Tests

- Test full flow: game completion → leaderboard submission → retrieval
- Test with mock HuggingFace repository
- Test folder-based discovery logic
- Test concurrent submissions (edge case)
- Test backward compatibility with legacy challenge files (no entry_type)

---

## 12. Migration Notes

### Backward Compatibility

- Existing challenges continue to work unchanged (entry_type defaults to "challenge")
- No changes to `shortener.json` format
- Challenge `settings.json` format is extended (new fields are optional)
- **No index.json migration needed** - folder-based discovery is self-contained

### Schema Evolution

| Version | Changes |
|---------|---------|
| 0.1.x | Original challenge format |
| 0.2.0 | Added `entry_type`, `max_display_entries`, `source_challenge_id` fields |
| 0.2.0 | Changed to folder-based discovery (no index.json) |
| 0.2.0 | New folder structure: `games/leaderboards/{type}/{period}/{file_id}/settings.json` |

### Data Migration

- No migration required for existing challenges
- New leaderboard files use folder-based storage from start
- Legacy challenges without `entry_type` default to `"challenge"`

### Rollback Plan

1. Remove leaderboard imports from `ui.py`
2. Remove sidebar navigation button
3. Remove game over submission calls
4. Optionally: delete `games/leaderboards/` directory from HF repo

---

## 13. Implementation Notes

### 13.1 Actual Implementation Details

The following represents the actual implementation as of v0.2.0:

#### Core Modules Implemented

**`wrdler/leaderboard.py` (v0.2.0):**
- ✅ `GameSettings` dataclass with settings matching logic
- ✅ `UserEntry` dataclass for individual scores
- ✅ `LeaderboardSettings` dataclass (unified format)
- ✅ File ID sanitization and parsing functions
- ✅ Folder-based discovery with `_list_period_folders()` and `_list_file_ids_for_period()`
- ✅ `find_matching_leaderboard()` with prefix filtering and full verification
- ✅ `create_or_get_leaderboard()` with automatic sequence management
- ✅ `submit_score_to_all_leaderboards()` as main entry point
- ✅ `check_qualification()` for top 25 filtering
- ✅ Period ID generators: `get_current_daily_id()`, `get_current_weekly_id()`
- ✅ Historical lookup functions: `list_available_periods()`, `list_settings_for_period()`
- ✅ URL generation with `get_leaderboard_url()`

**`wrdler/leaderboard_page.py` (v0.2.0):**
- ✅ Four-tab navigation system (Today, Daily, Weekly, History)
- ✅ Query parameter routing (`?page=`, `?gidd=`, `?gidw=`)
- ✅ Settings badge display with full configuration info
- ✅ Styled pandas dataframes with rank emojis (🥇🥈🥉)
- ✅ Challenge indicator badges (🎯)
- ✅ Expandable leaderboard groups per settings combination
- ✅ Last updated timestamps and entry counts

**`wrdler/modules/storage.py` (Updated):**
- ✅ `_list_repo_folders()` for folder discovery
- ✅ Seamless integration with existing HF dataset functions

**`wrdler/ui.py` (Updated):**
- ✅ Footer menu integration for leaderboard page navigation
- ✅ Automatic submission call in game over flow
- ✅ Current settings extraction via `GameSettings`
- ✅ Display qualification results with rank notifications

#### Storage Implementation

**Folder Structure (as built):**
```
HF_REPO_ID/games/
├── leaderboards/
│   ├── daily/
│   │   └── {YYYY-MM-DD}/
│   │       └── {wordlist_source}-{game_mode}-{sequence}/
│   │           └── settings.json
│   └── weekly/
│       └── {YYYY-Www}/
│           └── {wordlist_source}-{game_mode}-{sequence}/
│               └── settings.json
└── {challenge_id}/
    └── settings.json
```

**File ID Sanitization:**
- `.txt` extension removed from wordlist_source
- Spaces replaced with underscores
- All lowercase
- Regex: `r'[^\w\-]'` replaced with `_`

#### UI/UX Features Implemented

**Today Tab:**
- Displays current daily and weekly leaderboards side-by-side in two columns
- Query parameter filtering: `?gidd={file_id}` and `?gidw={file_id}` show specific leaderboards
- Expandable settings groups with full configuration captions

**Daily Tab:**
- Shows last 7 days of daily leaderboards
- One expander per date with all settings combinations nested
- Today's date auto-expanded by default

**Weekly Tab:**
- Shows current ISO week leaderboard
- All settings combinations displayed in expandable groups

**History Tab:**
- Two-column layout: Daily (left) and Weekly (right)
- Dropdown selectors for period and settings combination
- "Load Daily" and "Load Weekly" buttons for explicit loading

**Table Styling:**
- Pandas DataFrame with custom CSS styling
- Rank column: large bold text with emojis
- Score column: green color (#20d46c) with bold font
- Challenge indicator: 🎯 badge appended to username
- Last updated timestamp and entry count displayed below table

#### Key Differences from Spec

1. **Navigation:** Implemented as 'Leaderboard' link in the footer menu instead of sidebar button
2. **Caching:** Not implemented in v0.2.0 (deferred to v0.3.0 for optimization)
3. **Tab Implementation:** Used query parameters with custom nav links instead of Streamlit native tabs for better URL support
4. **Table Rendering:** Used pandas DataFrames with styling instead of custom HTML tables

#### Known Limitations (as of v0.2.0)

1. **No caching:** Each page load fetches from HF repository (can be slow)
2. **No pagination:** Displays top 25 only (additional entries stored but not shown)
3. **Limited error handling:** Basic logging, could benefit from retry logic
4. **No rate limiting:** Submission frequency not constrained
5. **No archival:** Old leaderboards remain indefinitely (no cleanup script)

#### Future Enhancements (Planned for v0.3.0+)

- ⏳ In-memory caching with TTL (60s for periods, 15s for leaderboards)
- ⏳ Pagination for >25 entries
- ⏳ Retry logic with exponential backoff
- ⏳ Rate limiting per IP/session
- ⏳ Archival script for old periods (>365 days daily, >156 weeks weekly)
- ⏳ Manual refresh button in UI

---

## 14. Operational Considerations

### 14.1 Concurrency and Consistency

- Write model:
  - Use optimistic concurrency: read `settings.json`, merge new `users` entry, write back with a unique commit message including `challenge_id` and `uid`.
  - Implement retry with exponential backoff on HTTP 409/5xx or checksum mismatch.
  - Ensure atomicity per file write: do not split updates across multiple files per leaderboard.
- Simultaneous file creation:
  - When no matching `file_id` folder exists, first attempt creation; if a concurrent process creates it, fallback to loading and merging.
  - Always re-verify settings match by reading `settings.json` after folder discovery.
- Sequence collisions:
  - If `{wordlist}-{mode}-{sequence}` collides but settings differ, increment `sequence` until a unique folder is found; verify match via file content, not only prefix.

### 14.2 Caching and Discovery Performance

- Cache tiers:
  - In-memory (per app session): 
    - Period listings for `games/leaderboards/{type}/` (TTL 60s).
    - `file_id` listings inside a period (TTL 30s).
    - Loaded `settings.json` for leaderboards (TTL 15s or invalidated on write).
- Invalidation:
  - On successful submission, invalidate the specific leaderboard cache (file content and directory listing for that period).
  - Provide a manual refresh option in UI (leaderboard page).
- Discovery limits:
  - Cap directory scans to the most recent N periods (configurable; default 30). UI uses explicit period selection for older data.
  - Prefer prefix filtering client-side before loading file content.

### 14.3 Error Handling and Observability

- Error taxonomy:
  - Storage errors: `HF_STORAGE_UNAVAILABLE`, `HF_WRITE_CONFLICT`, `HF_NOT_FOUND`.
  - Validation errors: `LB_INVALID_INPUT`, `LB_SETTINGS_MISMATCH`.
  - Operational errors: `LB_TIMEOUT`, `LB_RETRY_EXCEEDED`.
- User feedback:
  - On non-critical failure (e.g., leaderboard write conflict), show non-blocking warning and retry silently up to 3 times.
- Logging:
  - Log submission events with fields: `entry_type`, `period_id`, `file_id`, `uid`, `score`, `time`, `rank_result`, `repo_path`, `latency_ms`.
  - Log error events with `code`, `message`, `attempt`, `backoff_ms`.
- Telemetry (optional):
  - Count successful submissions per period and per settings combination for basic monitoring.

### 14.4 Security and Abuse Controls

- Input validation:
  - `username`: max 40 chars, strip control chars, allow alphanumerics, spaces, basic punctuation; reject offensive content if possible.
  - `word_list`: array of 6 uppercase A–Z strings, length 3–10; drop invalid entries.
  - `score`: 0–999; `time`: 1–36000 (10 hours); `word_list_difficulty`: float if provided, clamp to 0–10000.
- Spam and duplicates:
  - Rate limit per IP/session (e.g., max 10 submissions per hour).
  - Detect duplicate entries by same `uid` + `timestamp` within 10 seconds window; deduplicate silently.
- Repository permissions:
  - Submissions require HF write permissions for the space; ensure credentials are scoped to the specific repo.
  - Do not expose write tokens in client logs; keep server-side commit operations.

### 14.5 Data Lifecycle and Retention

- Retention:
  - Keep daily leaderboards for 365 days; weekly leaderboards for 156 weeks (3 years).
  - Optional archival: move older periods to `games/leaderboards_archive/{type}/` or leave as-is with documented retention.
- Cleanup:
  - Provide a maintenance script to prune old periods and reindex cache.
- Privacy:
  - Store only display names and gameplay metrics; avoid PII.
  - Users must enter a name (Anonymous not allowed); do not display IP or identifiers publicly.

### 14.6 Time and Period Boundaries

- Timezone:
  - All operations use UTC. The periods roll over at 00:00:00 UTC for daily, Monday 00:00:00 UTC for weekly.
- ISO week:
  - Use Python’s `isocalendar()` to derive `YYYY-Www` and handle year transitions (weeks spanning year boundaries).
- Clock source:
  - Use server-side timestamp for submissions; do not trust client clock. If unavailable, fall back to Python `datetime.utcnow()`.

### 14.7 UI Reliability and UX

- Loading states:
  - Show skeleton/loading indicators while scanning folders or reading leaderboard JSON.
- Empty states:
  - Display “No entries yet” when a leaderboard exists without users or has not been created.
- Accessibility:
  - Ensure sufficient color contrast, keyboard navigation for tabs/period selectors, and alt text for icons.
- Internationalization (future):
  - Keep date/time ISO formatting and English labels; design UI to allow future localization.

### 14.8 Ranking and Tie-Breaks (Operational Clarification)

- Sort order:
  - Primary: `score` desc; secondary: `time` asc; tertiary: `word_list_difficulty` desc; quaternary: stable by `timestamp` asc.
- Display limit:
  - Always store full `users` list; apply `max_display_entries` at render time only.
- Rank reporting:
  - Return rank based on full sorted list even if not displayed; if outside display limit, mark `qualified=False`.

### 14.9 Commit and Retry Strategy (HF)

- Commit messages:
  - Format: `leaderboard:{entry_type}:{period_id}:{file_id} add uid={uid} score={score} time={time}`.
- Retries:
  - Backoff sequence: 0.25s, 0.5s, 1s; max 3 attempts; abort on `LB_SETTINGS_MISMATCH`.
- Partial failures:
  - If daily succeeds and weekly fails (or vice versa), return both statuses independently; UI reports partial success.

### 14.10 Timezone Handling

- Daily leaderboard files use UTC for period boundaries.
- When displaying, show the UTC period as a PST date range:
  For daily leaderboards, display the period as:
  "YYYY-MM-DD 00:00:00 UTC to YYYY-MM-DD 23:59:59 UTC"
  and
  "YYYY-MM-DD HH:MM:SS PST to YYYY-MM-DD HH:MM:SS PST"
  (PST is UTC-8; adjust for daylight saving as needed)
  For example, a UTC file date of `2025-12-08` covers `2025-12-08 00:00:00 UTC` to `2025-12-08 23:59:59 UTC`, which is displayed as `2025-12-07 16:00:00 PST` to `2025-12-08 15:59:59 PST`.
  The leaderboard expander label should show: `Mon, Dec 08, 2025 4:00 PM PST – Tue, Dec 09, 2025 3:59:59 PM PST [settings badge]`

**Leaderboard Page UI:**
- **Today Tab:** Current daily and weekly leaderboards
- **Daily Tab:** Last 7 days of daily leaderboards
- **Weekly Tab:** Last 5 weeks displayed as individual expanders (current week or `week=YYYY-Www` query opens by default)
- **History Tab:** Historical leaderboard browser