diff --git a/docs/card-game-integration.md b/docs/card-game-integration.md new file mode 100644 index 0000000..39288fb --- /dev/null +++ b/docs/card-game-integration.md @@ -0,0 +1,156 @@ +# Integrating `card_game` / `klondike` as the Solitaire Core + +**Context:** A collaborator ([Quaternions](https://git.aleshym.co/Quaternions/card_game)) is building a pure-logic Klondike library in Rust. This document maps what that library currently provides against what Ferrous Solitaire's `solitaire_core` crate requires. + +**Approach:** Most gaps are closed in Ferrous Solitaire's own `solitaire_core` crate via a wrapper/adapter layer. Gaps 1 and 4 were addressed upstream and are now merged as `card_game v0.3.0` / `klondike v0.2.0`. Integration is ready to begin. + +--- + +## What `card_game` + `klondike` Already Has + +### `card_game` crate (generic primitives) — v0.3.0 +| Feature | Notes | +|---|---| +| `Card` (Deck + Suit + Rank packed in 1 byte) | `NonZeroU8` layout — no heap allocation | +| `Suit`, `Rank`, `Deck` enums | Full A→K, 4 suits, up to 4 deck IDs | +| `Stack` | Const-generic `ArrayVec` wrapper | +| `Pile` | Face-down + face-up stacks; `flip_up`, `pop_flip_up` | +| `Game` trait | `possible_instructions`, `is_instruction_valid`, `process_instruction`, `is_win` | +| `Session` | Wraps a `Game`; tracks history, replays for undo | +| `SessionInstruction::Undo` | Undo via full-state replay from seed | +| `no_std`-compatible design | Const generics on stack sizes | + +### `klondike` crate (Klondike rules) — v0.2.0 +| Feature | Notes | +|---|---| +| 7 tableau + 4 foundation + 1 stock | Fully dealt from a seeded RNG | +| Draw-1 / Draw-3 config | `KlondikeConfig::draw_stock` (`DrawStockConfig`) | +| `MoveFromFoundationConfig` | `Allowed` (upstream default) / `Disallowed`; controls foundation → tableau rule | +| `ScoringConfig` | Configurable deltas: `move_to_foundation` (+10), `flip_up_bonus` (+5), `move_to_tableau` (+5), `move_from_foundation` (−15), `recycle` (0 by default) | +| `KlondikeStats::score(&config)` | Computes score from per-event counters × `ScoringConfig` deltas | +| `KlondikeStats` counters | `move_to_foundation_count`, `flip_up_bonus_count`, `move_to_tableau_count`, `move_from_foundation_count`, `recycle_count`, `moves` | +| Foundation placement (Ace start, suit-matched A→K) | ✅ | +| Tableau placement (alternating colour, K on empty) | ✅ | +| Multi-card stack moves (via `SkipCards`) | ✅ | +| `RotateStock` (recycle waste → stock) | ✅ | +| `is_win_trivial` (all face-down cards cleared) | Auto-complete trigger | +| `get_auto_move` / `get_sorted_moves` | Priority-ranked move suggestion (take `&KlondikeConfig`) | +| Benchmark suite (`klondike-bench`) | 1 000-game throughput test | +| CLI display (`klondike-cli`) | Terminal renderer | + +--- + +## What Ferrous Solitaire's `solitaire_core` Needs (Gaps) + +### 1. Scoring — remaining adapter responsibilities +Ferrous uses **Windows XP Standard** scoring. The exact table already implemented in `solitaire_core/src/scoring.rs`: + +| Event | Delta | Handled by | +|---|---|---| +| Any card → foundation | +10 | `KlondikeStats` / `ScoringConfig::move_to_foundation` ✅ | +| Waste → tableau | +5 | `KlondikeStats` / `ScoringConfig::move_to_tableau` ✅ | +| Flip face-down tableau card | +5 | `KlondikeStats` / `ScoringConfig::flip_up_bonus` ✅ | +| Foundation → tableau | −15 | `KlondikeStats` / `ScoringConfig::move_from_foundation` ✅ | +| Undo | −15 | **Our adapter** (klondike has no undo event) | +| Recycle (Draw-1, after 1st free) | −100 | **Our adapter** — see below | +| Recycle (Draw-3, after 3rd free) | −20 | **Our adapter** — see below | +| Score floor | `score.max(0)` always | **Our adapter** | +| Time bonus on win | `700_000 / elapsed_seconds` | **Our adapter** (not wasm-portable) | + +Reference: + +**Recycle penalty note:** `ScoringConfig::recycle` is a flat delta (default 0 = free every time). WXP scoring allows a fixed number of free recycles (1 for Draw-1, 3 for Draw-3) and only charges the penalty afterwards. Our adapter must track `recycle_count` from `KlondikeStats` and apply the penalty only beyond the free allowance — it cannot delegate this to `ScoringConfig` directly. + +**In our wrapper:** Configure `ScoringConfig` with the WXP deltas for the events upstream tracks. Additionally implement undo penalty (−15), recycle-with-free-allowance logic, score floor (`score.max(0)`), and time bonus in the adapter. + +### 2. Game Modes +Ferrous has three modes that alter scoring and undo behaviour: + +| Mode | Scoring | Undo | +|---|---|---| +| **Classic** | Full WXP scoring (table above) | Allowed (−15 penalty) | +| **Zen** | All deltas suppressed — score stays 0 | Allowed (no penalty) | +| **Challenge** | Full WXP scoring | **Disabled** — returns an error | + +Zen is intended for relaxed play where the score does not matter. Challenge is a timed daily puzzle where the no-undo constraint is the difficulty mechanic. + +**In our wrapper:** Add `GameMode` to `solitaire_core::GameState`; intercept undo calls and scoring deltas in the adapter before delegating to `KlondikeState`. + +### 3. Solvability Solver +The engine has a Settings toggle — "Winnable deals only" — backed by a DFS solver with canonical-state memoisation (`solitaire_core::solver`). The solver classifies each deal as `Winnable`, `Unwinnable`, or `Inconclusive` (budget exceeded). `klondike` has no equivalent. + +**In our wrapper:** Port the existing DFS solver to run against `KlondikeState`. The memoisation key must be a deterministic canonical hash of the full game state. + +### 4. `take_from_foundation` House Rule *(upstream merged — v0.2.0)* +`MoveFromFoundationConfig` is now part of `KlondikeConfig`. When set to `Disallowed`, `is_instruction_valid` blocks foundation → tableau instructions. + +**Important:** The upstream default is `MoveFromFoundationConfig::Allowed`. Ferrous Solitaire uses the standard rule (foundation cards cannot be moved back) as the default, with the house rule as an opt-in. Our adapter must explicitly set `Disallowed` in the default `KlondikeConfig` and switch to `Allowed` only when the user toggles the house-rule option. + +**In our wrapper:** Construct `KlondikeConfig { move_from_foundation: MoveFromFoundationConfig::Disallowed, .. }` by default; mirror the user's settings toggle to `Allowed`. No custom intercept needed — `klondike` enforces the rule automatically. + +### 5. JSON Serialisation / Persistence +`solitaire_core::GameState` serialises the full mid-game state to JSON via `serde` so the engine can save on exit and restore on launch. `KlondikeState` derives `Clone` + `Eq` + `Hash` but not `Serialize` / `Deserialize`. No upstream changes are needed — this is handled externally. + +**In our wrapper:** Serialise the `solitaire_core` wrapper struct (which owns `KlondikeState` by value) using newtypes. Reconstruct `KlondikeState` from the seed + move history on load, or snapshot it as an opaque field. Schema version field lives on our wrapper. + +### 6. Typed Move Errors +`solitaire_core::error::MoveError` returns structured errors the engine uses to trigger UI feedback (wrong-destination toast, stock-empty chime, etc.): + +``` +GameAlreadyWon +UndoStackEmpty +StockEmpty +InvalidSource +InvalidDestination +RuleViolation(String) +``` + +`KlondikeInstruction` is always constructed by game code from valid entity layout, so invalid moves are only detectable at `solitaire_core`'s construction boundary — the error lives there, not inside `klondike`. + +**In our wrapper:** `MoveError` variants are generated when `solitaire_core` fails to construct a `KlondikeInstruction` from the player's requested move. No translation of `is_instruction_valid`'s bool return is required; by the time an instruction reaches `klondike`, it is already known to be structurally valid. + +### 7. Waste Pile as Separate Concept +Ferrous tracks `PileType::Waste` as a distinct pile. `klondike` folds waste into `Stock` (the face-up half of the stock `Pile`). The engine's UI and scoring logic reference the waste pile directly; the mapping needs to be explicit. + +**In our wrapper:** Project the face-up half of `klondike`'s stock `Pile` as `PileType::Waste` when building pile snapshots for the engine. + +### 8. Undo Stack Approach *(resolved — not an issue)* +`Session` undoes by replaying all moves from the seed — O(n). Benchmark shows 1 000 000 moves/second throughput; a maximum game length of ~192 moves gives a worst-case undo time of 0.02 ms — imperceptible on any hardware. + +**Resolution:** Use `Session::undo` as-is. The snapshot ring-buffer plan is dropped. + +--- + +## Integration Path (All work in `solitaire_core`) + +Steps in dependency order. Upstream issues #10 and #11 are closed and merged; no further upstream work is pending. + +1. **Add `klondike = "0.2.0"` as a dependency** of `solitaire_core`; stub out a `KlondikeAdapter` struct that wraps `KlondikeState` and passes all existing tests. +2. **Map pile types** — project `klondike`'s stock face-up half as `PileType::Waste`; expose the same `HashMap` the engine already reads (gap 7). +3. **Configure `KlondikeConfig`** — set `move_from_foundation: MoveFromFoundationConfig::Disallowed` by default; wire the user's house-rule toggle to `Allowed` (gap 4, now upstream). +4. **Port scoring** — pass WXP deltas into `ScoringConfig` for the four events upstream handles; implement undo penalty, recycle-with-free-allowance, score floor, and time bonus in the adapter (gap 1). +5. **Port `GameMode`** — intercept undo + scoring in the adapter based on mode (gap 2). +6. **Port the DFS solver** to run against `KlondikeAdapter` (gap 3). +7. **Implement `serde`** on the adapter wrapper using newtypes; migrate save-file schema (gap 5). + +--- + +## What Does NOT Need to Change + +- The `solitaire_engine` Bevy layer — it works against `solitaire_core` types; changes are isolated to `solitaire_core`. +- The `solitaire_sync` merge logic — operates on a `SyncPayload` DTO, independent of core card types. +- The `solitaire_server` — speaks only `SyncPayload` JSON, unaffected. + +--- + +## References + +- Quaternions' repo: +- `card_game v0.3.0` release commit: `31e7cdbc` +- `klondike v0.2.0` release commit: `50cf2f37` +- Upstream scoring PR: (closes issue #10) +- Upstream foundation config PR: (closes issue #11) +- `solitaire_core` source: `solitaire_core/src/` +- Scoring spec: `solitaire_core/src/scoring.rs` +- Solver spec: `solitaire_core/src/solver.rs` +- Architecture overview: `ARCHITECTURE.md`