Fix bridges visible crossing cycle

frontend/src/components/PuzzleEditor.tsx

@@ -106,6 +106,11 @@ function bridgeLevelFromChar(opportunity: BridgesOpportunity, char: string): 0 |
   return char === '"' ? 2 : char === "|" ? 1 : 0;
 }
 
+function bridgeOpportunitiesShareCell(a: BridgesOpportunity, b: BridgesOpportunity): boolean {
+  const bCells = new Set(b.cells.map(([r, c]) => `${r}:${c}`));
+  return a.cells.some(([r, c]) => bCells.has(`${r}:${c}`));
+}
+
 function parseBridges(problemAscii: string) {
   const lines = splitLines(problemAscii);
   const opportunities: BridgesOpportunity[] = [];
@@ -201,8 +206,10 @@ function bridgeClickCountForOpportunity(
 }
 
 function cycleBridgesOpportunities(
+  parsed: ReturnType<typeof parseBridges>,
   states: Record<string, 0 | 1 | 2>,
   opportunities: BridgesOpportunity[],
+  clickedChar = ".",
 ): Record<string, 0 | 1 | 2> {
   if (opportunities.length === 0) {
     return states;
@@ -215,6 +222,13 @@ function cycleBridgesOpportunities(
     const opportunity = candidates[0];
     const level = (((nextStates[opportunity.id] ?? 0) + 1) % 3) as 0 | 1 | 2;
     nextStates[opportunity.id] = level;
+    if (level > 0) {
+      for (const other of parsed.opportunities) {
+        if (other.id !== opportunity.id && bridgeOpportunitiesShareCell(other, opportunity)) {
+          nextStates[other.id] = 0;
+        }
+      }
+    }
     return nextStates;
   }
 
@@ -225,28 +239,13 @@ function cycleBridgesOpportunities(
     ]),
     null,
   ];
-  const isSequenceMatch = (entry: (typeof sequence)[number]) =>
-    candidates.every((opportunity) => {
-      const expected = entry?.opportunity.id === opportunity.id ? entry.level : 0;
-      return (nextStates[opportunity.id] ?? 0) === expected;
-    });
-  let currentIndex = sequence.findIndex(isSequenceMatch);
-
-  if (currentIndex === -1) {
-    const active = candidates.find((opportunity) => (nextStates[opportunity.id] ?? 0) > 0);
-    currentIndex = active
-      ? sequence.findIndex(
-          (entry) =>
-            entry?.opportunity.id === active.id &&
-            entry.level === (nextStates[active.id] ?? 0),
-        )
-      : sequence.length - 1;
-    if (currentIndex === -1) {
-      currentIndex = sequence.length - 1;
-    }
-  }
+  const currentIndex =
+    sequence.findIndex(
+      (entry) => entry !== null && bridgeSymbol(entry.opportunity, entry.level) === clickedChar,
+    ) ?? -1;
+  const normalizedCurrentIndex = currentIndex === -1 ? sequence.length - 1 : currentIndex;
 
-  const nextEntry = sequence[(currentIndex + 1) % sequence.length];
+  const nextEntry = sequence[(normalizedCurrentIndex + 1) % sequence.length];
   for (const opportunity of candidates) {
     nextStates[opportunity.id] = 0;
   }
@@ -555,9 +554,15 @@ function legendColor(letter: string) {
 function BridgesEditor({ problemAscii, boardAscii, onChange }: Omit<Props, "puzzleType">) {
   const parsed = parseBridges(problemAscii);
   const states = bridgesStatesFromBoard(problemAscii, boardAscii);
+  const boardLines = splitLines(boardAscii);
 
-  function cycle(opportunities: BridgesOpportunity[]) {
-    const nextStates = cycleBridgesOpportunities(states, opportunities);
+  function cycle(opportunities: BridgesOpportunity[], r: number, c: number) {
+    const nextStates = cycleBridgesOpportunities(
+      parsed,
+      states,
+      opportunities,
+      boardLines[r]?.[c] ?? ".",
+    );
     onChange(bridgesBoardFromStates(problemAscii, nextStates));
   }
 
@@ -571,7 +576,7 @@ function BridgesEditor({ problemAscii, boardAscii, onChange }: Omit<Props, "puzz
         {parsed.lines.flatMap((line, r) =>
           [...line].map((char, c) => {
             const opportunities = parsed.cellToOpportunities.get(`${r}:${c}`) ?? [];
-            const boardChar = splitLines(boardAscii)[r]?.[c] ?? char;
+            const boardChar = boardLines[r]?.[c] ?? char;
             const className = isClueChar(char)
               ? "board-cell fixed island-cell"
               : opportunities.length > 0
@@ -584,7 +589,7 @@ function BridgesEditor({ problemAscii, boardAscii, onChange }: Omit<Props, "puzz
                 key={`${r}-${c}`}
                 type="button"
                 className={className}
-                onClick={() => cycle(opportunities)}
+                onClick={() => cycle(opportunities, r, c)}
                 disabled={opportunities.length === 0}
               >
                 {isClueChar(char) ? char : display}

frontend/test/pipeline/roundtrip.test.ts

@@ -124,13 +124,18 @@ describe("bridges generated click plans", () => {
         throw new Error(`click index out of bounds: ${idx}`);
       };
 
+      let board = f.problem;
       let states: Record<string, 0 | 1 | 2> = {};
       for (const idx of bridgesClickPlan[f.filename] ?? []) {
         const [r, c] = indexToCoord(idx);
+        const clickedChar = T.splitLines(board)[r]?.[c] ?? ".";
         states = T.cycleBridgesOpportunities(
+          parsed,
           states,
           parsed.cellToOpportunities.get(`${r}:${c}`) ?? [],
+          clickedChar,
         );
+        board = T.bridgesBoardFromStates(f.problem, states);
       }
 
       for (const opportunity of parsed.opportunities) {
@@ -166,27 +171,48 @@ describe("bridges ambiguous route cells", () => {
     expect(vertical).toBeTruthy();
 
     let states: Record<string, 0 | 1 | 2> = {};
-    states = T.cycleBridgesOpportunities(states, centerCandidates);
+    states = T.cycleBridgesOpportunities(parsed, states, centerCandidates, ".");
     expect(states[horizontal!.id]).toBe(1);
     expect(states[vertical!.id] ?? 0).toBe(0);
 
-    states = T.cycleBridgesOpportunities(states, centerCandidates);
+    states = T.cycleBridgesOpportunities(parsed, states, centerCandidates, "-");
     expect(states[horizontal!.id]).toBe(2);
     expect(states[vertical!.id] ?? 0).toBe(0);
 
-    states = T.cycleBridgesOpportunities(states, centerCandidates);
+    states = T.cycleBridgesOpportunities(parsed, states, centerCandidates, "=");
     expect(states[horizontal!.id] ?? 0).toBe(0);
     expect(states[vertical!.id]).toBe(1);
 
-    states = T.cycleBridgesOpportunities(states, centerCandidates);
+    states = T.cycleBridgesOpportunities(parsed, states, centerCandidates, "|");
     expect(states[horizontal!.id] ?? 0).toBe(0);
     expect(states[vertical!.id]).toBe(2);
 
-    states = T.cycleBridgesOpportunities(states, centerCandidates);
+    states = T.cycleBridgesOpportunities(parsed, states, centerCandidates, "\"");
     expect(states[horizontal!.id] ?? 0).toBe(0);
     expect(states[vertical!.id] ?? 0).toBe(0);
   });
 
+  it("cycles a shared cell through all visible states after each board render", () => {
+    const parsed = T.parseBridges(crossingProblem);
+    const centerCandidates = parsed.cellToOpportunities.get("2:2") ?? [];
+    let board = crossingProblem;
+    const visible: string[] = [];
+
+    for (let i = 0; i < 5; i += 1) {
+      const states = T.bridgesStatesFromBoard(crossingProblem, board);
+      const nextStates = T.cycleBridgesOpportunities(
+        parsed,
+        states,
+        centerCandidates,
+        T.splitLines(board)[2]?.[2] ?? ".",
+      );
+      board = T.bridgesBoardFromStates(crossingProblem, nextStates);
+      visible.push(T.splitLines(board)[2]?.[2] ?? ".");
+    }
+
+    expect(visible).toEqual(["-", "=", "|", "\"", "."]);
+  });
+
   it("cycles a unique cell route independently", () => {
     const parsed = T.parseBridges(crossingProblem);
     const centerCandidates = parsed.cellToOpportunities.get("2:2") ?? [];
@@ -201,10 +227,10 @@ describe("bridges ambiguous route cells", () => {
     expect(vertical).toBeTruthy();
 
     let states: Record<string, 0 | 1 | 2> = {};
-    states = T.cycleBridgesOpportunities(states, centerCandidates);
-    states = T.cycleBridgesOpportunities(states, verticalCandidates);
+    states = T.cycleBridgesOpportunities(parsed, states, centerCandidates, ".");
+    states = T.cycleBridgesOpportunities(parsed, states, verticalCandidates, ".");
 
-    expect(states[horizontal!.id]).toBe(1);
+    expect(states[horizontal!.id] ?? 0).toBe(0);
     expect(states[vertical!.id]).toBe(1);
   });