# Architecture: Hand History Logging & Tournament Improvements

**Document Version:** 1.0  
**Date:** 2026-05-19  
**Scope:** Two major features for the rusty-marvin poker simulation engine

---

## Table of Contents

1. [Overview](#overview)
2. [Feature 1: Hand History Logging in iPoker Format](#feature-1-hand-history-logging)
3. [Feature 2: Tournament Improvements](#feature-2-tournament-improvements)
4. [Implementation Plan](#implementation-plan)
5. [Data Structures](#data-structures)
6. [Integration Points](#integration-points)

---

## Overview

This document describes the architecture for two major features:

1. **Hand History Logging** — Log every hand played in PokerTracker 3 / iPoker format for later review, analysis, and a future hand tester function.
2. **Tournament Improvements** — Explicit blind arrays, SNG configuration with all 6 bot types, prize structure configuration, multi-tournament execution with balance tracking.

---

## Feature 1: Hand History Logging

### 1.1 Module Structure

A new module `holdem_core/src/game/hand_history.rs` will be the sole location for all hand history formatting and file I/O. It will be registered in [`holdem_core/src/game/mod.rs`](holdem_core/src/game/mod.rs:21).

```
holdem_core/src/game/
├── hand_history.rs    ← NEW: iPoker formatter + file writer
├── hand_runner.rs     ← MODIFY: expose action history in HandResult
├── table.rs           ← MODIFY: pass HandHistoryContext to logger
├── simulation.rs      ← MODIFY: integrate logging into cash game loop
├── tournament.rs      ← MODIFY: integrate logging into tournament loop
└── config.rs          ← MODIFY: extend OutputConfig with log directory
```

### 1.2 Data Flow

The hand history logger needs data from multiple points in the hand lifecycle. The key challenge is that [`HandResult`](holdem_core/src/game/hand_runner.rs:87) currently does NOT include action history or player names — only pot winners, hand values, board, chip movements, and rake.

```mermaid
flowchart TD
    A[Table::run_hand] --> B[HandRunner executes hand]
    B --> C[HandRunner collects actions_this_hand]
    B --> D[HandRunner produces HandResult]
    D --> E[Table::complete_hand restores seats]
    E --> F{log_hands enabled?}
    F -->|Yes| G[Build HandHistoryRecord]
    F -->|No| H[Skip logging]
    G --> I[HandHistoryLogger::log_hand]
    I --> J[Format iPoker text]
    J --> K[Write to logs/hand_N_YYYY-MM-DD_HH-MM-SS.txt]
    
    subgraph Data Sources
        L[HandResult: pot_winners, hand_values, board, chip_movements, rake]
        M[HandHistoryRecord: actions, player_names, hole_cards, blind_positions, timestamp]
    end
    
    L --> G
    M --> G
```

### 1.3 Design Decision: Extend HandResult with Action History

**Decision:** Add action history and supplementary data to [`HandResult`](holdem_core/src/game/hand_runner.rs:87) rather than exposing it separately from `HandRunner`.

**Rationale:**
- [`HandRunner::actions_this_hand`](holdem_core/src/game/hand_runner.rs:146) is a private field that already collects `Vec<Vec<(PlayerId, Action)>>` (4 elements: preflop, flop, turn, river).
- [`HandRunner::into_seats()`](holdem_core/src/game/hand_runner.rs:838) consumes the runner, so actions must be extracted before or during that call.
- Adding actions to `HandResult` keeps the API clean — callers get everything from one struct.
- The `HandRunner::run_to_completion()` method already builds `HandResult` internally; we extend it to include actions.

### 1.4 New Data Structures

#### `HandHistoryRecord`

A self-contained record with everything needed to produce an iPoker hand history file. This is NOT stored in `HandResult` — it is assembled by the caller (Table or simulation loop) from `HandResult` plus external context.

```rust
/// Complete record of a hand for history logging.
pub struct HandHistoryRecord {
    /// Hand number within the session.
    pub hand_number: u64,
    /// Timestamp when the hand started.
    pub timestamp: chrono::DateTime<chrono::Utc>,
    /// Table name (e.g., "Tournament 12345, Table 1" or "Cash Game Table 1").
    pub table_name: String,
    /// Maximum seats at the table.
    pub max_seats: u8,
    /// Dealer button seat index (1-based for iPoker format).
    pub button_seat: u8,
    /// Player entries: seat number, name, starting stack.
    pub players: Vec<HandHistoryPlayer>,
    /// Blind postings: player name, amount, type (SB/BB/Ante).
    pub blind_postings: Vec<BlindPosting>,
    /// Actions per street: preflop, flop, turn, river.
    /// Each street is a list of (player_name, action_description).
    pub street_actions: Vec<Vec<StreetAction>>,
    /// Board cards per street.
    pub board_cards: Vec<Vec<Card>>,
    /// Showdown entries: player name, hole cards, hand description.
    pub showdown_entries: Vec<ShowdownEntry>,
    /// Pot collection entries: player name, amount.
    pub collections: Vec<PotCollection>,
    /// Total pot and rake.
    pub total_pot: ChipCount,
    pub total_rake: ChipCount,
    /// Summary information.
    pub summary: HandSummary,
}
```

#### Supporting types:

```rust
pub struct HandHistoryPlayer {
    pub seat: u8,           // 1-based
    pub name: String,
    pub stack: ChipCount,
}

pub struct BlindPosting {
    pub player_name: String,
    pub amount: ChipCount,
    pub blind_type: BlindType,  // SmallBlind, BigBlind, Ante
}

pub struct StreetAction {
    pub player_name: String,
    pub action_type: ActionDescription,
    pub amount: ChipCount,      // 0 for fold/check
}

pub enum ActionDescription {
    Fold,
    Check,
    Call,
    Raise { total: ChipCount },
    Bet { total: ChipCount },
    AllIn { total: ChipCount },
}

pub struct ShowdownEntry {
    pub player_name: String,
    pub seat: u8,
    pub hole_cards: Option<HoleCards>,
    pub hand_description: String,  // e.g., "a pair of Aces"
    pub result: ShowdownResult,    // Won, Lost
}

pub struct PotCollection {
    pub player_name: String,
    pub amount: ChipCount,
}

pub struct HandSummary {
    pub total_pot: ChipCount,
    pub rake: ChipCount,
    pub board: Vec<Card>,
    pub player_summaries: Vec<PlayerSummary>,
}

pub struct PlayerSummary {
    pub seat: u8,
    pub name: String,
    pub action: String,  // e.g., "collected 800", "showed [As Kh] and lost"
}
```

### 1.5 Changes to HandResult

Extend [`HandResult`](holdem_core/src/game/hand_runner.rs:87) to include action history:

```rust
pub struct HandResult {
    // ... existing fields ...
    pub pot_winners: Vec<Vec<PotWinner>>,
    pub hand_values: HashMap<PlayerId, HandValue>,
    pub board: Board,
    pub chip_movements: HashMap<PlayerId, i64>,
    pub total_rake: ChipCount,
    pub rake_per_pot: Vec<ChipCount>,
    
    // NEW FIELDS:
    /// Actions taken during the hand, grouped by street.
    /// Index 0 = preflop, 1 = flop, 2 = turn, 3 = river.
    pub actions: Vec<Vec<(PlayerId, Action)>>,
    
    /// Hole cards for each player who was dealt cards.
    /// Keyed by PlayerId. Available for all players, not just showdown.
    pub hole_cards: HashMap<PlayerId, HoleCards>,
    
    /// Seat assignments: PlayerId -> seat index (0-based).
    pub seat_assignments: HashMap<PlayerId, SeatIndex>,
    
    /// Blind positions: SB and BB seat indices.
    pub sb_seat: SeatIndex,
    pub bb_seat: SeatIndex,
    
    /// Dealer seat index.
    pub dealer_seat: SeatIndex,
    
    /// Small blind and big blind amounts used.
    pub small_blind: ChipCount,
    pub big_blind: ChipCount,
    pub ante: ChipCount,
}
```

**Where to populate:** In [`HandRunner::run_to_completion()`](holdem_core/src/game/hand_runner.rs), after the hand finishes and before returning the result. The data is already available in `HandRunner`'s private fields:
- `actions_this_hand` → `result.actions`
- `seats[].hole_cards` → `result.hole_cards`
- `seats[].index` → `result.seat_assignments`
- `sb_seat_idx`, `bb_seat_idx` → `result.sb_seat`, `result.bb_seat`
- `dealer_seat` → `result.dealer_seat`
- `small_blind`, `big_blind`, `ante` → already available

### 1.6 HandHistoryLogger

The logger is a struct that manages file output:

```rust
/// Logs hand histories in iPoker format.
pub struct HandHistoryLogger {
    /// Directory for log files.
    log_dir: PathBuf,
    /// Whether logging is enabled.
    enabled: bool,
}

impl HandHistoryLogger {
    pub fn new(log_dir: PathBuf, enabled: bool) -> Self;
    
    /// Ensures the log directory exists (creates if needed).
    pub fn ensure_dir(&self) -> std::io::Result<()>;
    
    /// Logs a hand to a file.
    pub fn log_hand(&self, record: &HandHistoryRecord) -> std::io::Result<()>;
    
    /// Generates the filename for a hand.
    fn filename(&self, record: &HandHistoryRecord) -> String {
        format!(
            "hand_{}_{}.txt",
            record.hand_number,
            record.timestamp.format("%Y-%m-%d_%H-%M-%S")
        )
    }
}
```

### 1.7 iPoker Format Specification

The formatter produces text matching the PokerTracker 3 / iPoker format. The format sections are:

```
Game #<hand_number> starts on <YYYY/MM/DD HH:MM:SS>
Table "<table_name>" (<max_seats>-max) Seat #<button_seat_1based> is the button
Seat <N>: <name> (<stack> in chips)
<name>: posts small blind <amount>
<name>: posts big blind <amount>
<name>: posts ante <amount>
*** HOLE CARDS ***
Dealt to <name> [<card1> <card2>]
<name>: folds
<name>: calls <amount>
<name>: raises <raise_amount> to <total>
<name>: checks
*** FLOP *** [<c1> <c2> <c3>]
... actions ...
*** TURN *** [<c1> <c2> <c3>] [<c4>]
... actions ...
*** RIVER *** [<c1> <c2> <c3> <c4>] [<c5>]
... actions ...
*** SHOW DOWN ***
<name>: shows [<c1> <c2>] (<hand_description>)
<name> collects <amount> from pot
*** SUMMARY ***
Total pot <amount> | Rake <amount>
Board: [<c1> <c2> <c3> <c4> <c5>]
Seat <N>: <name> collected <amount> (showed [<c1> <c2>] and won with <hand_desc>)
Seat <N>: <name> showed [<c1> <c2>] and lost with <hand_desc>
Seat <N>: <name> folded before flop (did not show)
```

**Card formatting:** Cards use the notation from [`Card::Display`](holdem_core/src/card.rs) — rank char + suit char, e.g., `As`, `Kh`, `Td`, `2c`. Rank mapping: `2-9, T, J, Q, K, A`. Suit mapping: `h, d, c, s`.

**Hand description mapping** from [`HandRank`](holdem_core/src/evaluator/evaluator.rs:14):

| HandRank | iPoker Description |
|----------|-------------------|
| HighCard | "high card Ace" / "high card King" etc. |
| Pair | "a pair of Aces" |
| TwoPair | "two pairs, Kings over Queens" |
| ThreeOfAKind | "three of a kind, Aces" |
| Straight | "a straight, Ace to Five" |
| Flush | "a flush, Ace high" |
| FullHouse | "a full house, Aces over Kings" |
| FourOfAKind | "four of a kind, Aces" |
| StraightFlush | "a straight flush, Ace to Five" |
| RoyalFlush | "a royal flush" |

### 1.8 Integration Points

#### Cash Game Integration

In [`run_cash_game()`](holdem_core/src/game/simulation.rs:33), after each `table.run_hand()`:

```rust
// Create logger from config
let logger = HandHistoryLogger::new(
    PathBuf::from("logs"),
    config_output.log_hands,
);
logger.ensure_dir()?;

// In the hand loop:
match table.run_hand() {
    Ok(result) => {
        stats.record_hand_result(&result, &player_names);
        
        if logger.is_enabled() {
            let record = build_hand_history_record(
                &result, &player_names, &table, "Cash Game Table 1"
            );
            logger.log_hand(&record)?;
        }
    }
    // ...
}
```

#### Tournament Integration

In [`Tournament::run_next_hands()`](holdem_core/src/game/tournament.rs:362), after each hand result:

```rust
// Tournament accepts an optional HandHistoryLogger
if let Some(ref logger) = self.hand_logger {
    let record = build_hand_history_record(
        &hand_result, &self.player_names, &table, &table_name
    );
    logger.log_hand(&record)?;
}
```

### 1.9 Building HandHistoryRecord

A helper function constructs `HandHistoryRecord` from the components:

```rust
/// Builds a HandHistoryRecord from a completed hand result.
///
/// Requires:
/// - HandResult (with extended action/seat data)
/// - Player name mapping (PlayerId -> name)
/// - Table reference (for table name, max seats)
pub fn build_hand_history_record(
    result: &HandResult,
    player_names: &HashMap<PlayerId, String>,
    table: &Table,
    table_name: &str,
) -> HandHistoryRecord {
    // 1. Map seat_assignments to HandHistoryPlayer list
    // 2. Extract blind postings from actions[0] (preflop) where action is Raise for SB/BB
    // 3. Map actions per street to StreetAction with player names
    // 4. Map board cards from result.board
    // 5. Build showdown entries from result.pot_winners + result.hand_values + result.hole_cards
    // 6. Build collections from result.pot_winners
    // 7. Build summary
}
```

### 1.10 Config Changes

Extend [`OutputConfig`](holdem_core/src/game/config.rs:442):

```rust
pub struct OutputConfig {
    pub directory: Option<String>,
    pub log_hands: bool,
    pub log_actions: bool,
    // NEW:
    /// Directory for hand history log files. Defaults to "logs".
    #[serde(default = "default_log_dir")]
    pub log_dir: Option<String>,
}

fn default_log_dir() -> String {
    "logs".to_string()
}
```

### 1.11 Dependency Addition

Add `chrono` to [`holdem_core/Cargo.toml`](holdem_core/Cargo.toml) for timestamp support:

```toml
[dependencies]
chrono = { version = "0.4", features = ["serde"] }
```

---

## Feature 2: Tournament Improvements

### 2.1 Explicit Blind Levels in TOML

#### Config Changes

Add optional `blind_levels` field to [`GameConfig`](holdem_core/src/game/config.rs:235):

```rust
pub struct GameConfig {
    // ... existing fields ...
    
    /// Explicit blind levels. If present, overrides num_blind_levels and hands_per_level.
    #[serde(default)]
    pub blind_levels: Vec<BlindLevelConfig>,
}

/// Serde-compatible blind level for TOML configuration.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct BlindLevelConfig {
    pub small_blind: ChipCount,
    pub big_blind: ChipCount,
    #[serde(default)]
    pub ante: ChipCount,
    #[serde(default = "default_hands_per_level")]
    pub hands: u32,
}
```

TOML format:

```toml
[[game.blind_levels]]
small_blind = 10
big_blind = 20
ante = 0
hands = 10

[[game.blind_levels]]
small_blind = 15
big_blind = 30
ante = 0
hands = 10
```

#### Updated `to_blind_schedule()`

Modify [`GameConfig::to_blind_schedule()`](holdem_core/src/game/config.rs:391) to check for explicit levels first:

```rust
pub fn to_blind_schedule(&self) -> BlindSchedule {
    if !self.blind_levels.is_empty() {
        // Use explicit levels from config
        let levels: Vec<BlindLevel> = self.blind_levels
            .iter()
            .enumerate()
            .map(|(i, lc)| BlindLevel {
                level: (i + 1) as u32,
                small_blind: lc.small_blind,
                big_blind: lc.big_blind,
                ante: lc.ante,
                duration_hands: lc.hands,
            })
            .collect();
        BlindSchedule::custom(levels)
    } else {
        // Existing standard doubling schedule
        // ... (current code)
    }
}
```

### 2.2 Custom Prize Structure

#### Config Changes

Add optional `prizes` field to [`GameConfig`](holdem_core/src/game/config.rs:235):

```rust
pub struct GameConfig {
    // ... existing fields ...
    
    /// Custom prize structure as absolute amounts. If present, overrides
    /// standard_sng / standard_mtt calculations.
    /// Example: [5, 3, 2] means 1st=5, 2nd=3, 3rd=2.
    #[serde(default)]
    pub prizes: Vec<ChipCount>,
}
```

TOML format:

```toml
[game]
prizes = [5, 3, 2]
```

#### Updated `to_prize_structure()`

Modify [`GameConfig::to_prize_structure()`](holdem_core/src/game/config.rs:423):

```rust
pub fn to_prize_structure(&self) -> PrizeStructure {
    if !self.prizes.is_empty() {
        PrizeStructure { prizes: self.prizes.clone() }
    } else {
        match self.game_type {
            GameType::Cash => PrizeStructure::standard_sng(self.buy_in, num_players),
            GameType::SitAndGo => PrizeStructure::standard_sng(self.buy_in, num_players),
            GameType::MultiTableTournament => {
                PrizeStructure::standard_mtt(self.buy_in, total_entries)
            }
        }
    }
}
```

### 2.3 Seat Switching Between Tournaments

#### Current Behavior

- [`TableConfig.randomize_seats`](holdem_core/src/game/table.rs:51) shuffles seats before each hand in cash games.
- [`Table::shuffle_seats()`](holdem_core/src/game/table.rs) already exists and works.
- In tournaments, [`Table::start_hand()`](holdem_core/src/game/table.rs:327) calls `shuffle_seats()` if `randomize_seats` is true, but this is per-hand, not per-tournament.

#### Design

For multi-tournament SNG, we need seat randomization **between tournaments**, not between hands within a tournament. The approach:

1. **Keep `randomize_seats` on `GameConfig`** with its current meaning for cash games.
2. **In the multi-tournament runner** (new function), call `table.shuffle_seats()` once before each tournament starts, but set `randomize_seats = false` on the `TableConfig` so it does not shuffle per-hand.

```rust
/// Runs multiple SNG tournaments and aggregates results.
pub fn run_sng_series(
    config: &GameConfig,
    num_tournaments: u32,
) -> Result<SngSeriesResult, GameError> {
    let mut aggregate_stats = SimulationStats::new("SitAndGo Series");
    
    for tournament_num in 0..num_tournaments {
        let mut table_config = config.to_table_config();
        table_config.randomize_seats = false; // don't shuffle per-hand
        
        let blind_schedule = config.to_blind_schedule();
        let prize_structure = config.to_prize_structure();
        
        let mut tournament = Tournament::new_sng(
            table_config,
            blind_schedule,
            prize_structure,
            config.starting_chips,
            config.buy_in,
        );
        
        // Register bots (fresh instances each tournament)
        for (i, bot_config) in config.bots.iter().enumerate() {
            let player_id = PlayerId(i as u64);
            let bot = create_bot(bot_config, player_id)?;
            tournament.register_player(bot)?;
        }
        
        // Shuffle seats between tournaments
        if config.randomize_seats {
            tournament.shuffle_seats()?;  // NEW method on Tournament
        }
        
        // Run tournament
        tournament.run_to_completion()?;
        
        // Record results
        aggregate_stats.record_tournament_result(
            &tournament, &player_names, config.buy_in
        );
    }
    
    // ... compute aggregate stats
}
```

#### New `Tournament::shuffle_seats()`

Add a method to [`Tournament`](holdem_core/src/game/tournament.rs:228) that shuffles seats on all tables:

```rust
/// Shuffles seat assignments on all tables.
/// Used between tournaments in a series to randomize positions.
pub fn shuffle_seats(&mut self) {
    for table in &mut self.tables {
        table.shuffle_seats();
    }
}
```

### 2.4 Multi-Tournament Execution

#### Config Changes

Add `num_tournaments` to [`OutputConfig`](holdem_core/src/game/config.rs:442) (or `GameConfig`):

```rust
pub struct OutputConfig {
    // ... existing fields ...
    
    /// Number of tournaments to run in a series. Default: 1.
    #[serde(default = "default_one")]
    pub num_tournaments: u32,
}
```

TOML:

```toml
[output]
log_hands = true
num_tournaments = 100
```

#### New: SngSeriesResult

Aggregate results across multiple tournaments:

```rust
/// Results from a series of SNG tournaments.
pub struct SngSeriesResult {
    /// Number of tournaments played.
    pub tournaments_played: u32,
    /// Per-player aggregate statistics.
    pub player_results: HashMap<PlayerId, SngPlayerSeriesResult>,
    /// Total hands played across all tournaments.
    pub total_hands: u64,
}

/// Aggregate results for one player across a tournament series.
pub struct SngPlayerSeriesResult {
    pub player_id: PlayerId,
    pub name: String,
    /// Number of tournaments this player won (1st place).
    pub wins: u32,
    /// Number of times this player finished in each paid position.
    pub finishes: HashMap<u32, u32>,  // position -> count
    /// Total entry fees paid (num_tournaments * buy_in).
    pub total_entry_fees: ChipCount,
    /// Total prize money won.
    pub total_prize_money: ChipCount,
    /// Net profit = total_prize_money - total_entry_fees.
    pub net_profit: i64,
    /// ROI as percentage = (net_profit / total_entry_fees) * 100.
    pub roi_percent: f64,
    /// Average finishing position.
    pub avg_finish: f64,
}
```

### 2.5 Balance Tracking (Money, Not Chips)

The balance tracking is about tracking **real money** (entry fees vs. prize money) across multiple tournaments, not chip balances within a single tournament.

**Key insight:** Within a single tournament, chips are play money. The financial outcome is:
- **Cost:** `buy_in` per tournament
- **Revenue:** `prize` based on finishing position
- **Profit:** `prize - buy_in`

This is already partially implemented in [`SimulationStats::record_tournament_result()`](holdem_core/src/game/stats.rs:224) which computes `profit = prize - buy_in`. The multi-tournament aggregation adds:

1. Accumulating profits across N tournaments
2. Computing ROI across the series
3. Tracking position distribution (how often each player finishes 1st, 2nd, 3rd, etc.)

### 2.6 Data Flow for Multi-Tournament

```mermaid
flowchart TD
    A[Load SimulationConfig] --> B[Parse blind_levels, prizes, num_tournaments]
    B --> C{For each tournament 1..N}
    C --> D[Create fresh Tournament instance]
    D --> E[Create fresh bot instances]
    E --> F{randomize_seats?}
    F -->|Yes| G[Tournament.shuffle_seats]
    F -->|No| H[Skip]
    G --> I[Register bots]
    H --> I
    I --> J[Tournament.run_to_completion]
    J --> K[Record tournament result]
    K --> L[Accumulate SngPlayerSeriesResult]
    L --> C
    C -->|Done| M[Compute aggregate stats]
    M --> N[Print summary table]
    M --> O[Optionally log individual tournament results]
```

### 2.7 Main.rs Changes

Update [`holdem_sim/src/main.rs`](holdem_sim/src/main.rs) to handle multi-tournament:

```rust
fn run_tournament_simulation(config: &GameConfig, output_config: &OutputConfig) {
    let num_tournaments = output_config.num_tournaments.max(1);
    
    if num_tournaments > 1 {
        // Run SNG series
        run_sng_series(config, num_tournaments);
    } else {
        // Single tournament (existing behavior)
        // ... current code ...
    }
}
```

The `SimulationConfig` needs to be threaded through to the tournament runner so `output.num_tournaments` is accessible.

---

## Implementation Plan

### Phase 1: Hand History Logging

| Step | File | Action |
|------|------|--------|
| 1.1 | `holdem_core/Cargo.toml` | Add `chrono` dependency |
| 1.2 | `holdem_core/src/game/hand_runner.rs` | Extend `HandResult` with `actions`, `hole_cards`, `seat_assignments`, `sb_seat`, `bb_seat`, `dealer_seat`, `small_blind`, `big_blind`, `ante` fields. Populate them in `run_to_completion()` before returning. |
| 1.3 | `holdem_core/src/game/hand_history.rs` | Create new module with `HandHistoryRecord`, supporting types, `HandHistoryLogger`, `build_hand_history_record()`, and iPoker formatter |
| 1.4 | `holdem_core/src/game/mod.rs` | Add `pub mod hand_history;` and re-export key types |
| 1.5 | `holdem_core/src/game/config.rs` | Add `log_dir` field to `OutputConfig` |
| 1.6 | `holdem_core/src/game/simulation.rs` | Integrate `HandHistoryLogger` into `run_cash_game()` |
| 1.7 | `holdem_core/src/game/table.rs` | Expose `hand_number()` and `config()` publicly if not already |
| 1.8 | Tests | Unit tests for iPoker formatter, integration test for full hand logging |

### Phase 2: Tournament Config Improvements

| Step | File | Action |
|------|------|--------|
| 2.1 | `holdem_core/src/game/config.rs` | Add `BlindLevelConfig` struct, `blind_levels` field to `GameConfig`, `prizes` field to `GameConfig` |
| 2.2 | `holdem_core/src/game/config.rs` | Update `to_blind_schedule()` to use explicit levels when present |
| 2.3 | `holdem_core/src/game/config.rs` | Update `to_prize_structure()` to use custom prizes when present |
| 2.4 | `holdem_core/examples/configs/sng_tournament.toml` | Update example config with explicit blind levels and prize structure |
| 2.5 | Tests | Unit tests for TOML parsing of explicit blind levels and custom prizes |

### Phase 3: Multi-Tournament Execution

| Step | File | Action |
|------|------|--------|
| 3.1 | `holdem_core/src/game/config.rs` | Add `num_tournaments` to `OutputConfig` |
| 3.2 | `holdem_core/src/game/tournament.rs` | Add `Tournament::shuffle_seats()` method |
| 3.3 | `holdem_core/src/game/simulation.rs` | Create `run_sng_series()` function with `SngSeriesResult` |
| 3.4 | `holdem_core/src/game/stats.rs` | Add `SngPlayerSeriesResult` and aggregation logic |
| 3.5 | `holdem_sim/src/main.rs` | Update to pass `OutputConfig` to tournament runner, handle `num_tournaments > 1` |
| 3.6 | Tests | Integration test for multi-tournament series |

### Phase 4: Tournament Hand Logging Integration

| Step | File | Action |
|------|------|--------|
| 4.1 | `holdem_core/src/game/tournament.rs` | Add optional `HandHistoryLogger` to `Tournament`, integrate into `run_next_hands()` |
| 4.2 | `holdem_core/src/game/tournament.rs` | Track player names mapping inside Tournament for logging |
| 4.3 | Tests | Integration test verifying hand logs from tournament play |

---

## Data Structures

### Summary of All New Types

| Type | Location | Purpose |
|------|----------|---------|
| `HandHistoryRecord` | `hand_history.rs` | Complete hand record for logging |
| `HandHistoryPlayer` | `hand_history.rs` | Player info in hand history |
| `BlindPosting` | `hand_history.rs` | Blind/ante posting record |
| `StreetAction` | `hand_history.rs` | Player action on a street |
| `ActionDescription` | `hand_history.rs` | Action type for logging |
| `ShowdownEntry` | `hand_history.rs` | Showdown participant |
| `PotCollection` | `hand_history.rs` | Pot collection record |
| `HandSummary` | `hand_history.rs` | Hand summary section |
| `PlayerSummary` | `hand_history.rs` | Per-player summary |
| `HandHistoryLogger` | `hand_history.rs` | File writer for hand histories |
| `BlindLevelConfig` | `config.rs` | TOML-deserializable blind level |
| `SngSeriesResult` | `simulation.rs` | Multi-tournament aggregate |
| `SngPlayerSeriesResult` | `simulation.rs` | Per-player series statistics |

### Summary of Modified Types

| Type | Location | Changes |
|------|----------|---------|
| `HandResult` | `hand_runner.rs` | Add `actions`, `hole_cards`, `seat_assignments`, blind position fields |
| `GameConfig` | `config.rs` | Add `blind_levels: Vec<BlindLevelConfig>`, `prizes: Vec<ChipCount>` |
| `OutputConfig` | `config.rs` | Add `log_dir: Option<String>`, `num_tournaments: u32` |
| `Tournament` | `tournament.rs` | Add `shuffle_seats()` method, optional `HandHistoryLogger` |

---

## Integration Points

### How New Code Connects to Existing Code

```mermaid
flowchart LR
    subgraph Config Layer
        GC[GameConfig]
        OC[OutputConfig]
    end
    
    subgraph Engine Layer
        HR[HandRunner]
        T[Table]
        TN[Tournament]
    end
    
    subgraph New Modules
        HH[hand_history.rs]
        SS[run_sng_series]
    end
    
    subgraph Output
        LOG[logs/ directory]
        STATS[SimulationStats]
        SNG[SngSeriesResult]
    end
    
    GC -->|blind_levels| TN
    GC -->|prizes| TN
    OC -->|log_hands, log_dir| HH
    OC -->|num_tournaments| SS
    
    HR -->|Extended HandResult| HH
    HR -->|Extended HandResult| STATS
    T -->|run_hand result| HH
    TN -->|per-hand results| HH
    TN -->|standings| STATS
    SS -->|aggregate| SNG
    
    HH -->|writes| LOG
```

### Key API Surfaces

1. **`HandResult` extensions** — The extended struct is backward-compatible. New fields are populated automatically by `HandRunner::run_to_completion()`. Existing callers that destructure `HandResult` will get compiler warnings for unused fields but no breakage.

2. **`HandHistoryLogger`** — Standalone struct with no trait dependencies. Created by the simulation runner and optionally passed to `Table`/`Tournament`.

3. **`BlindLevelConfig`** — Pure config struct. Only affects `GameConfig::to_blind_schedule()`.

4. **`run_sng_series()`** — New function in `simulation.rs`. Does not modify existing `run_cash_game()` or single-tournament flow.

5. **`Tournament::shuffle_seats()`** — Delegates to existing `Table::shuffle_seats()`. No new behavior, just an access method.

### Backward Compatibility

- All new `GameConfig` fields use `#[serde(default)]`, so existing TOML configs continue to work.
- `HandResult` extensions are additive — existing code that ignores new fields is unaffected.
- `OutputConfig` extensions are additive with sensible defaults.
- The single-tournament path in `main.rs` is preserved; multi-tournament is triggered only when `num_tournaments > 1`.