P3.3: turn accounting + special-match flagging (pure sx)

Extend the pure-sx board model with the model-level pieces P5 (input) and
P7 (turn/goal loop) will call:

- Turn accounting on Board: `moves_made` + configurable `move_limit`
  (DEFAULT_MOVE_LIMIT), with `moves_remaining()` derived from the two so
  the counters can't drift. `init` resets them.
- Special-match flagging: `count_specials` tallies a detection round's
  maximal runs of length exactly 4 and length 5+, surfaced over a whole
  settle as Cascade.len4 / len5_plus (+ had_len4 / had_len5_plus). A hook
  for future special gems — detection only, no gem behavior.
- `commit_swap`: the single player-move entry point. Legal swap → apply,
  resolve (scoring accrues), spend one move; illegal → revert, no move
  spent. Returns a PlayerMove with the settle's payout + special flags.

Adds tests/turn.sx (+ golden) asserting: legal swap decrements the move
counter by exactly 1 and accrues score; illegal swap leaves counter,
score and board untouched; len4/len5+/len3 rounds set the documented
flags. Existing goldens unchanged; ios-sim build compiles.

board.sx

@@ -77,6 +77,13 @@ BOARD_COLS :: 8;
 BOARD_ROWS :: 8;
 BOARD_CELLS :: BOARD_COLS * BOARD_ROWS;
 
+// Default per-game move budget (P3.3). `init` seeds `Board.move_limit` with
+// this; `moves_remaining` counts down from it as committed swaps spend moves.
+// The turn/goal loop (P7) owns enforcing the budget — the model only TRACKS it,
+// so `moves_remaining` may legitimately reach 0 (or below, if a caller keeps
+// committing) without `commit_swap` refusing.
+DEFAULT_MOVE_LIMIT :: 30;
+
 Board :: struct {
     // Row-major: cell (col, row) lives at row*BOARD_COLS + col.
     cells: [BOARD_CELLS]Gem;
@@ -94,10 +101,28 @@ Board :: struct {
     // field. A hand-built board must zero this before accumulating.
     score: s64;
 
+    // Turn accounting (P3.3). `moves_made` counts the swaps actually COMMITTED —
+    // only a legal swap (one that resolved into >=1 match) via `commit_swap`
+    // increments it; an illegal, reverted swap does not. `move_limit` is the
+    // game's move budget (`init` sets it to DEFAULT_MOVE_LIMIT); `moves_remaining`
+    // is derived from the two, so there is a single source of truth and the
+    // counters can never drift apart. A hand-built board must set both before
+    // committing swaps.
+    moves_made: s64;
+    move_limit: s64;
+
     idx :: (col: s64, row: s64) -> s64 {
         row * BOARD_COLS + col
     }
 
+    // Moves still available against the budget: `move_limit - moves_made`. Goes
+    // to 0 when the budget is spent (and below it only if a caller keeps
+    // committing past the budget — see DEFAULT_MOVE_LIMIT). The turn/goal loop
+    // (P7) reads this to decide when the game ends.
+    moves_remaining :: (self: *Board) -> s64 {
+        self.move_limit - self.moves_made
+    }
+
     at :: (self: *Board, col: s64, row: s64) -> Gem {
         self.cells[Board.idx(col, row)]
     }
@@ -115,6 +140,8 @@ Board :: struct {
     init :: (self: *Board, seed: s64) {
         self.rng = rng_seeded(seed);
         self.score = 0;
+        self.moves_made = 0;
+        self.move_limit = DEFAULT_MOVE_LIMIT;
         for 0..BOARD_ROWS: (row) {
             for 0..BOARD_COLS: (col) {
                 self.set(col, row, pick_gem(self, @self.rng, col, row));
@@ -478,10 +505,27 @@ refill :: (board: *Board) -> s64 {
 // `Board.score`: the sum over rounds of `score_round * combo_multiplier(round)`
 // (P3.2), so the HUD (P4.4) and turn accounting (P3.3) can read a swap's payout
 // without re-deriving it. A depth-0 (already-stable) board awards 0.
+//
+// `len4` / `len5_plus` tally the special-match runs cleared across the WHOLE
+// settle (summed over rounds): the number of maximal runs of length exactly 4,
+// and of length 5 or more (P3.3 special-match flagging). They are a HOOK for
+// future special gems — nothing here creates or alters a gem; the tallies only
+// make "did this settle clear a 4 / 5+ run" observable. `had_len4` /
+// `had_len5_plus` are the boolean view of the same counts.
 Cascade :: struct {
     depth: s64;
     cleared: List(s64);
     awarded: s64;
+    len4: s64;
+    len5_plus: s64;
+
+    had_len4 :: (self: *Cascade) -> bool {
+        self.len4 > 0
+    }
+
+    had_len5_plus :: (self: *Cascade) -> bool {
+        self.len5_plus > 0
+    }
 }
 
 // One resolution round: detect matches and, if any, clear them, collapse under
@@ -503,11 +547,13 @@ resolve_step :: (board: *Board) -> s64 {
 // Each round adds `score_round * combo_multiplier(round)` (round 1-based) to
 // `Board.score`; an already-stable board returns depth 0, awards 0, untouched.
 resolve :: (board: *Board) -> Cascade {
-    result := Cascade.{ depth = 0, cleared = List(s64).{}, awarded = 0 };
+    result := Cascade.{ depth = 0, cleared = List(s64).{}, awarded = 0, len4 = 0, len5_plus = 0 };
     while true {
-        // Read the round's base points while its runs are still on the board:
+        // Read the round's base points AND its special-match tally while the runs
-        // `resolve_step` clears them, so the score has to be taken first.
+        // are still on the board: `resolve_step` clears them, so both have to be
+        // taken first. A no-match round scores 0 and tallies nothing, then breaks.
         base := score_round(board);
+        sp := count_specials(board);
         n := resolve_step(board);
         if n == 0 { break; }
         result.depth += 1;
@@ -515,6 +561,8 @@ resolve :: (board: *Board) -> Cascade {
         board.score += points;
         result.awarded += points;
         result.cleared.append(n);
+        result.len4 += sp.len4;
+        result.len5_plus += sp.len5_plus;
     }
     result
 }
@@ -637,6 +685,43 @@ combo_multiplier :: (round: s64) -> s64 {
     round
 }
 
+// ── Special-match flagging (P3.3) ──────────────────────────────────────────
+// A HOOK for future special gems: surface, per detection round, how many of the
+// board's maximal runs are long enough to (later) spawn one — a run of length
+// exactly 4, and a run of length 5 or more. This is detection ONLY: nothing here
+// creates, marks, or alters a gem; later work reads these counts to decide what
+// special gem (if any) a clear produces. Length 3 runs are ordinary and counted
+// by neither tier.
+
+// Per-round tally of special-length runs: `len4` is the number of maximal runs
+// of length exactly 4, `len5_plus` the number of length 5 or more. Boolean
+// "did any occur" lives on `Cascade` (`had_len4` / `had_len5_plus`) for the
+// whole settle; a single round reads these counts directly.
+SpecialCounts :: struct {
+    len4: s64;
+    len5_plus: s64;
+}
+
+// Count the board's currently-matched runs that hit a special length, by the
+// same `find_runs` enumeration scoring uses (so an L/T's horizontal and vertical
+// runs are counted independently by their own lengths). Pure and read-only — it
+// inspects the board but changes nothing, so it must be called BEFORE the round's
+// clear, while the runs are still present. A board with no run (or only length-3
+// runs) tallies zero in both tiers.
+count_specials :: (board: *Board) -> SpecialCounts {
+    runs := find_runs(board);
+    counts := SpecialCounts.{ len4 = 0, len5_plus = 0 };
+    for 0..runs.len: (i) {
+        len := runs.items[i].len;
+        if len == 4 {
+            counts.len4 += 1;
+        } else if len >= 5 {
+            counts.len5_plus += 1;
+        }
+    }
+    counts
+}
+
 // Deterministic textual dump of an enumerated run list, in `find_runs` order: a
 // count header, then one run per line as `<axis> len <n> at fixed <f> start <s>`
 // where axis is H (horizontal) or V (vertical). An empty list dumps as just
@@ -650,3 +735,42 @@ dump_runs :: (runs: *List(Run)) -> string {
     }
     result
 }
+
+// ── Player move (P3.3) ─────────────────────────────────────────────────────
+// The single model-level entry point a player's swap goes through — what the
+// swipe input (P5) and turn/goal loop (P7) will call. It ties legality, the
+// swap, the cascade settle, and turn accounting together so callers don't
+// re-implement the sequence.
+
+// Outcome of attempting one player swap via `commit_swap`. `legal` says whether
+// the swap resolved into at least one match and was therefore COMMITTED: when
+// false the board is untouched, no move was spent, and `cascade` is the empty
+// (depth-0) settle; when true the swap was applied, the board resolved (scoring
+// accrued into `Board.score`) and exactly one move was spent. `cascade` carries
+// the settle's full outcome — depth, per-round cleared counts, awarded points,
+// and the special-match (len4 / len5+) tallies. `moves_remaining` snapshots the
+// board's remaining budget AFTER the move, so a caller has it without re-reading.
+PlayerMove :: struct {
+    legal: bool;
+    cascade: Cascade;
+    moves_remaining: s64;
+}
+
+// Attempt the player's intended swap of two adjacent cells. If the swap is legal
+// (`swap_legal`: adjacent AND it forms a match), apply it, `resolve` the cascade
+// — which accrues score into `Board.score` and reports the awarded points and
+// special-match flags — then spend one move (`moves_made += 1`). If it is illegal
+// (non-adjacent, or forms no match) the board is left exactly as it was — no swap,
+// no resolve, no move spent — and an empty depth-0 cascade is returned. Move
+// accounting only TRACKS the budget; it does not refuse a swap when the budget is
+// spent (that is the P7 turn-loop's call) — see DEFAULT_MOVE_LIMIT.
+commit_swap :: (board: *Board, a: Cell, b: Cell) -> PlayerMove {
+    if !swap_legal(board, a, b) {
+        empty := Cascade.{ depth = 0, cleared = List(s64).{}, awarded = 0, len4 = 0, len5_plus = 0 };
+        return PlayerMove.{ legal = false, cascade = empty, moves_remaining = board.moves_remaining() };
+    }
+    swap(board, a, b);
+    cascade := resolve(board);
+    board.moves_made += 1;
+    PlayerMove.{ legal = true, cascade = cascade, moves_remaining = board.moves_remaining() }
+}

tests/expected/turn.exit

@@ -0,0 +1 @@
+0

tests/expected/turn.stdout

@@ -0,0 +1,98 @@
+== turn (accounting + special-match flagging) ==
+== flag-len3-none ==
+OGOGOGOG
+GOGOGOGO
+OGOGOGOG
+GORRROGO
+OGOGOGOG
+GOGOGOGO
+OGOGOGOG
+GOGOGOGO
+len4 0 len5_plus 0
+had_len4 false had_len5_plus false
+== flag-len4 ==
+OGOGOGOG
+GOGOGOGO
+OGOGOGOG
+GORRRRGO
+OGOGOGOG
+GOGOGOGO
+OGOGOGOG
+GOGOGOGO
+len4 1 len5_plus 0
+had_len4 true had_len5_plus false
+== flag-len5 ==
+OGOGOGOG
+GRRRRRGO
+OGOGOGOG
+GOGOGOGO
+OGOGOGOG
+GOGOGOGO
+OGOGOGOG
+GOGOGOGO
+len4 0 len5_plus 1
+had_len4 false had_len5_plus true
+== flag-len4-and-len5 ==
+RRRGOGOG
+GOGOGOGO
+GOBBBBOG
+OGOGOGOG
+GPPPPPGO
+OGOGOGOG
+GOGOGOGO
+OGOGOGOG
+len4 1 len5_plus 1
+had_len4 true had_len5_plus true
+== commit-legal-len3 ==
+RROGOGOG
+GGROGOGO
+OGOGOGOG
+GOGOGOGO
+OGOGOGOG
+GOGOGOGO
+OGOGOGOG
+GOGOGOGO
+before: score 0 moves_made 0 moves_remaining 5
+after: legal true depth 1 awarded 30 len4 0 len5_plus 0
+after: score 30 moves_made 1 moves_remaining 4
+RBRGOGOG
+GGOOGOGO
+OGOGOGOG
+GOGOGOGO
+OGOGOGOG
+GOGOGOGO
+OGOGOGOG
+GOGOGOGO
+== commit-illegal ==
+OGOGOGOG
+GOGOGOGO
+OGOGOGOG
+GOGOGOGO
+OGOGOGOG
+GOGOGOGO
+OGOGOGOG
+GOGOGOGO
+before: score 0 moves_made 0 moves_remaining 5
+after: legal false depth 0 awarded 0 len4 0 len5_plus 0
+after: score 0 moves_made 0 moves_remaining 5
+== commit-legal-len4 ==
+RROROGOG
+GGROGOGO
+OGOGOGOG
+GOGOGOGO
+OGOGOGOG
+GOGOGOGO
+OGOGOGOG
+GOGOGOGO
+after: legal true depth 1 awarded 60 len4 1 len5_plus 0
+after: had_len4 true had_len5_plus false
+after: score 60 moves_made 1 moves_remaining 4
+RBRROGOG
+GGOOGOGO
+OGOGOGOG
+GOGOGOGO
+OGOGOGOG
+GOGOGOGO
+OGOGOGOG
+GOGOGOGO
+ok: turn accounting + special-match flagging

tests/turn.sx

@@ -0,0 +1,216 @@
+// Turn accounting + special-match flagging golden (P3.3).
+//
+// Two things are proven over crafted, deterministic boards:
+//
+//   1. Special-match FLAGGING (pure, no RNG): `count_specials` tallies a single
+//      detection round's maximal runs by special length — runs of length exactly
+//      4 (`len4`) and of length 5 or more (`len5_plus`). A round with only
+//      length-3 runs tallies neither; the tiers are independent and length-3 runs
+//      never count. This is a HOOK for future special gems — detection only.
+//
+//   2. Turn ACCOUNTING via `commit_swap`, the single player-move entry point P5
+//      (input) and P7 (turn loop) will call. A legal swap (one that forms a
+//      match) is committed — applied, resolved (scoring accrues), and it spends
+//      exactly one move; the returned `PlayerMove` reports the settle's payout
+//      and special flags. An illegal swap is rejected — board reverted, no move
+//      spent, no score change.
+//
+// Every counter/flag is asserted independently of the dump AND printed so the
+// golden is self-explanatory and deterministic.
+#import "modules/std.sx";
+#import "board.sx";
+t :: #import "test.sx";
+
+SEED  :: 7;
+LIMIT :: 5;
+
+// Inverse of `gem_char`: map a board character back to its Gem so each board can
+// be written as a human-readable grid. The hole glyph maps to `.empty`.
+char_to_gem :: (c: u8) -> Gem {
+    if c == EMPTY_CHAR { return .empty; }
+    for 0..GEM_COUNT: (i) {
+        if GEM_CHARS[i] == c { return cast(Gem) i; }
+    }
+    .red
+}
+
+// Load an 8x8 board from `rows` (top row first, each exactly BOARD_COLS chars),
+// seeded RNG, running score zeroed, and the turn counters reset to a fresh game
+// (no moves made, the given move budget).
+load_board :: (rows: []string, seed: s64, move_limit: s64) -> Board {
+    b : Board = ---;
+    for 0..BOARD_ROWS: (row) {
+        line := rows[row];
+        for 0..BOARD_COLS: (col) {
+            b.set(col, row, char_to_gem(line[col]));
+        }
+    }
+    b.rng = rng_seeded(seed);
+    b.score = 0;
+    b.moves_made = 0;
+    b.move_limit = move_limit;
+    b
+}
+
+boards_equal :: (a: *Board, b: *Board) -> bool {
+    for 0..BOARD_CELLS: (i) { if a.cells[i] != b.cells[i] { return false; } }
+    true
+}
+
+// One flag scene: snapshot the board, then count its single round's special
+// runs and assert the tallies (and the boolean flags derived from them) are
+// exactly the documented values. No RNG, no clear — pure detection.
+flag_scene :: (name: string, rows: []string, want_len4: s64, want_len5_plus: s64) {
+    print("== {} ==\n", name);
+    b := load_board(rows, 0, LIMIT);
+    out(board_dump(@b));
+    sp := count_specials(@b);
+    print("len4 {} len5_plus {}\n", sp.len4, sp.len5_plus);
+    print("had_len4 {} had_len5_plus {}\n", sp.len4 > 0, sp.len5_plus > 0);
+    t.expect(sp.len4 == want_len4, concat(name, ": len4 count exact"));
+    t.expect(sp.len5_plus == want_len5_plus, concat(name, ": len5_plus count exact"));
+}
+
+main :: () -> s32 {
+    print("== turn (accounting + special-match flagging) ==\n");
+
+    // ── Special-match flagging (single round, no RNG) ──────────────────────
+    // Only length-3 runs: a lone horizontal RRR -> neither tier flags.
+    flag_scene("flag-len3-none", .[
+        "OGOGOGOG",
+        "GOGOGOGO",
+        "OGOGOGOG",
+        "GORRROGO",
+        "OGOGOGOG",
+        "GOGOGOGO",
+        "OGOGOGOG",
+        "GOGOGOGO",
+    ], 0, 0);
+
+    // A length-4 run -> len4 flags, len5_plus does not.
+    flag_scene("flag-len4", .[
+        "OGOGOGOG",
+        "GOGOGOGO",
+        "OGOGOGOG",
+        "GORRRRGO",
+        "OGOGOGOG",
+        "GOGOGOGO",
+        "OGOGOGOG",
+        "GOGOGOGO",
+    ], 1, 0);
+
+    // A length-5 run -> len5_plus flags, len4 does not.
+    flag_scene("flag-len5", .[
+        "OGOGOGOG",
+        "GRRRRRGO",
+        "OGOGOGOG",
+        "GOGOGOGO",
+        "OGOGOGOG",
+        "GOGOGOGO",
+        "OGOGOGOG",
+        "GOGOGOGO",
+    ], 0, 1);
+
+    // A length-3, a length-4 and a length-5 run together: the length-3 is ignored
+    // and the two special tiers each count their own run -> len4 1, len5_plus 1.
+    flag_scene("flag-len4-and-len5", .[
+        "RRRGOGOG",
+        "GOGOGOGO",
+        "GOBBBBOG",
+        "OGOGOGOG",
+        "GPPPPPGO",
+        "OGOGOGOG",
+        "GOGOGOGO",
+        "OGOGOGOG",
+    ], 1, 1);
+
+    // ── Turn accounting via commit_swap ────────────────────────────────────
+    // A legal swap that forms a length-3 run. Swapping (2,0)<->(2,1) drops a red
+    // into row 0 to complete RRR at cols 0-2 (the donor row 1 is shaped so the
+    // displaced gem makes no second run). The swap is committed: applied,
+    // resolved (score accrues), and it spends exactly one move.
+    print("== commit-legal-len3 ==\n");
+    bl := load_board(.[
+        "RROGOGOG",
+        "GGROGOGO",
+        "OGOGOGOG",
+        "GOGOGOGO",
+        "OGOGOGOG",
+        "GOGOGOGO",
+        "OGOGOGOG",
+        "GOGOGOGO",
+    ], SEED, LIMIT);
+    out(board_dump(@bl));
+    score_before := bl.score;
+    made_before  := bl.moves_made;
+    rem_before   := bl.moves_remaining();
+    print("before: score {} moves_made {} moves_remaining {}\n", score_before, made_before, rem_before);
+    mv := commit_swap(@bl, Cell.{ col = 2, row = 0 }, Cell.{ col = 2, row = 1 });
+    print("after: legal {} depth {} awarded {} len4 {} len5_plus {}\n",
+          mv.legal, mv.cascade.depth, mv.cascade.awarded, mv.cascade.len4, mv.cascade.len5_plus);
+    print("after: score {} moves_made {} moves_remaining {}\n", bl.score, bl.moves_made, mv.moves_remaining);
+    out(board_dump(@bl));
+    t.expect(mv.legal, "legal-len3: swap committed");
+    t.expect(bl.moves_made == made_before + 1, "legal-len3: moves_made +1");
+    t.expect(mv.moves_remaining == rem_before - 1, "legal-len3: reported moves_remaining -1");
+    t.expect(bl.moves_remaining() == rem_before - 1, "legal-len3: board moves_remaining -1");
+    t.expect(bl.score > score_before, "legal-len3: score accrued");
+    t.expect(mv.cascade.awarded == bl.score - score_before, "legal-len3: awarded equals score delta");
+    t.expect(mv.cascade.depth >= 1, "legal-len3: settled at least one round");
+
+    // An illegal swap on a run-free checkerboard: adjacent but forms no match.
+    // It must be rejected outright — board reverted, no move spent, no score.
+    print("== commit-illegal ==\n");
+    bi := load_board(.[
+        "OGOGOGOG",
+        "GOGOGOGO",
+        "OGOGOGOG",
+        "GOGOGOGO",
+        "OGOGOGOG",
+        "GOGOGOGO",
+        "OGOGOGOG",
+        "GOGOGOGO",
+    ], SEED, LIMIT);
+    before := bi;
+    out(board_dump(@bi));
+    print("before: score {} moves_made {} moves_remaining {}\n", bi.score, bi.moves_made, bi.moves_remaining());
+    miv := commit_swap(@bi, Cell.{ col = 0, row = 0 }, Cell.{ col = 1, row = 0 });
+    print("after: legal {} depth {} awarded {} len4 {} len5_plus {}\n",
+          miv.legal, miv.cascade.depth, miv.cascade.awarded, miv.cascade.len4, miv.cascade.len5_plus);
+    print("after: score {} moves_made {} moves_remaining {}\n", bi.score, bi.moves_made, miv.moves_remaining);
+    t.expect(!miv.legal, "illegal: swap rejected");
+    t.expect(miv.cascade.depth == 0, "illegal: no cascade");
+    t.expect(miv.cascade.awarded == 0, "illegal: no points");
+    t.expect(bi.moves_made == 0, "illegal: no move spent");
+    t.expect(miv.moves_remaining == LIMIT, "illegal: full budget remains");
+    t.expect(bi.score == 0, "illegal: score unchanged");
+    t.expect(boards_equal(@before, @bi), "illegal: board reverted");
+
+    // A legal swap that forms a length-4 run (RRRR at cols 0-3): proves the
+    // special-match flag rides through the whole settle onto the PlayerMove.
+    print("== commit-legal-len4 ==\n");
+    b4 := load_board(.[
+        "RROROGOG",
+        "GGROGOGO",
+        "OGOGOGOG",
+        "GOGOGOGO",
+        "OGOGOGOG",
+        "GOGOGOGO",
+        "OGOGOGOG",
+        "GOGOGOGO",
+    ], SEED, LIMIT);
+    out(board_dump(@b4));
+    m4 := commit_swap(@b4, Cell.{ col = 2, row = 0 }, Cell.{ col = 2, row = 1 });
+    print("after: legal {} depth {} awarded {} len4 {} len5_plus {}\n",
+          m4.legal, m4.cascade.depth, m4.cascade.awarded, m4.cascade.len4, m4.cascade.len5_plus);
+    print("after: had_len4 {} had_len5_plus {}\n", m4.cascade.had_len4(), m4.cascade.had_len5_plus());
+    print("after: score {} moves_made {} moves_remaining {}\n", b4.score, b4.moves_made, m4.moves_remaining);
+    out(board_dump(@b4));
+    t.expect(m4.legal, "legal-len4: swap committed");
+    t.expect(m4.cascade.had_len4(), "legal-len4: settle flags a length-4 run");
+    t.expect(b4.moves_made == 1, "legal-len4: one move spent");
+    t.expect(b4.score > 0, "legal-len4: score accrued");
+
+    print("ok: turn accounting + special-match flagging\n");
+    return 0;
+}