refactor: extract shared helpers, fix naming, split god file

src/lib/algorithms/bubble-sort.js

@@ -0,0 +1,50 @@
+// bubble-sort.js — Bubble sort algorithm with visualization step tracking
+// Extracted from sortingAlgorithms.js for single-responsibility.
+
+/**
+ * Bubble sort — compares adjacent elements and swaps if out of order.
+ * Returns an array of step objects for animation.
+ * @param {Array} arr - Array of {width, ...} objects to sort
+ * @returns {Array} Array of {xx, yy, changed} step objects
+ */
+export function bubbleSort(arr){
+    const pairs= [];
+    let n = arr.length;
+    const prevRect = arr.slice();
+    for (let i = 0; i < n-1; i++){
+        for (let j = 0; j < n-i-1; j++){
+            if (prevRect[j].width > prevRect[j+1].width) {
+                // swap arr[j+1] and arr[j]
+                const recti = {...prevRect[j]};
+                const rectj = {...prevRect[j+1]};
+                prevRect[j+1] = recti;
+                prevRect[j] = rectj;
+                pairs.push( {
+                    xx:j,
+                    yy:j+1,
+                    changed:true
+                } );
+            } else{
+                pairs.push( {
+                    xx:j,
+                    yy:j+1,
+                    changed:false
+                } );
+            }
+            if( j === n-i-2 ){
+                pairs.push( {
+                    xx:n-i-1,
+                    yy:n-i-1,
+                    changed:false
+                } );
+            }
+        }
+    }
+    pairs.push({
+            xx:0,
+            yy:0,
+            changed:false
+        }
+    )
+    return pairs;
+}

src/lib/algorithms/grahamScan.js

@@ -1,4 +1,11 @@
-export function convex_hull(points){
+/**
+ * Graham scan convex hull algorithm.
+ * Returns [hull_points, edge_animation_steps].
+ * Note: Previously named `convex_hull` (snake_case). Alias kept for backward compatibility.
+ * @param {Array} points - Array of {xx, yy} point objects (sorted by xx)
+ * @returns {Array} [hullPoints, animationLines]
+ */
+export function convexHull(points){
     if( points.size === 1 ){
         return;
     }
@@ -56,7 +63,11 @@ export function convex_hull(points){
     return [pairs,lines];
 }
 
-function cw(a, b, c) {
+/**
+ * Check if three points make a clockwise turn.
+ * Uses cross product: (b-a) × (c-a) < 0 means clockwise.
+ */
+function isClockwiseTurn(a, b, c) {
     if( a.xx*(b.yy-c.yy)+b.xx*(c.yy-a.yy)+c.xx*(a.yy-b.yy) < 0 ){
         return true;
     } else{
@@ -65,11 +76,21 @@ function cw(a, b, c) {
 
 }
 
-function ccw(a, b, c){
+/**
+ * Check if three points make a counter-clockwise turn.
+ * Uses cross product: (b-a) × (c-a) > 0 means counter-clockwise.
+ */
+function isCounterClockwiseTurn(a, b, c){
     if( a.xx * (b.yy - c.yy) + b.xx * (c.yy - a.yy) + c.xx * (a.yy - b.yy) > 0 ){
         return true;
     } else {
         return false;
     }
 
-}
+}
+
+// Backward-compatible aliases
+const cw = isClockwiseTurn;
+const ccw = isCounterClockwiseTurn;
+// Backward-compatible alias (original snake_case name)
+export { convexHull as convex_hull };

src/lib/algorithms/graph.js

@@ -8,6 +8,8 @@
 //   { type: 'markEdge', id, state }  -> 'tree' | 'path' | 'normal'
 //   { type: 'clear' }                -> reset traversal marks (start/finish rings kept)
 
+import { buildPathActions } from './helpers/graph-helpers.js';
+
 let userCounter = 0;
 export const newNodeId = () => `u${++userCounter}`;
 export const edgeId = (source, target) => `e_${source}_${target}`;
@@ -117,23 +119,8 @@ export function edgeList(edges, directed) {
 }
 
 // Reconstruct start->finish path actions from parent maps.
-function pathActions(parent, parentEdge, startId, endId) {
-    const nodes = [];
-    const edgeSteps = [];
-    let cur = endId;
-    while (cur !== undefined && cur !== null) {
-        nodes.push(cur);
-        if (parentEdge[cur] != null) edgeSteps.push({ id: parentEdge[cur], from: parent[cur], to: cur });
-        if (cur === startId) break;
-        cur = parent[cur];
-    }
-    nodes.reverse();
-    edgeSteps.reverse();
-    return [
-        ...nodes.map((id) => ({ type: 'markNode', id, state: 'path' })),
-        ...edgeSteps.map((e) => ({ type: 'markEdge', id: e.id, state: 'path', from: e.from, to: e.to })),
-    ];
-}
+// buildPathActions is now imported from helpers/graph-helpers.js
+export { buildPathActions as pathActions };
 
 export function bfsActions(adj, startId, finishId) {
     const actions = [];
@@ -155,7 +142,7 @@ export function bfsActions(adj, startId, finishId) {
         }
         actions.push({ type: 'markNode', id: u, state: 'current' });
         if (u === finishId) {
-            actions.push(...pathActions(parent, parentEdge, startId, u));
+            actions.push(...buildPathActions(parent, parentEdge, startId, u));
             return actions;
         }
         visited.add(u);
@@ -195,7 +182,7 @@ export function dfsActions(adj, startId, finishId) {
         }
         actions.push({ type: 'markNode', id: u, state: 'current' });
         if (u === finishId) {
-            actions.push(...pathActions(parent, parentEdge, startId, u));
+            actions.push(...buildPathActions(parent, parentEdge, startId, u));
             return actions;
         }
         visited.add(u);

src/lib/algorithms/helpers/graph-helpers.js

@@ -0,0 +1,34 @@
+// graph-helpers.js — Shared utilities for graph-based algorithm visualizations
+//
+// Extracted from duplicated code across graph.js and shortestPath.js.
+// Both files had identical pathActions() implementations.
+// Dijkstra.js and Astar.js shared getAllNodes, sortNodesByDistance,
+// updateUnvisitedNeighbors, getUnvisitedNeighbors.
+
+/**
+ * Reconstruct a start→end path from parent maps and emit markNode/markEdge actions.
+ * Shared by BFS, DFS, Dijkstra, and Bellman-Ford action planners.
+ *
+ * @param {Object} parent - Map of nodeId → parent nodeId
+ * @param {Object} parentEdge - Map of nodeId → edge id used to reach this node
+ * @param {string} startId - Source node ID
+ * @param {string} endId - Destination node ID
+ * @returns {Array} Array of markNode/markEdge action objects
+ */
+export function buildPathActions(parent, parentEdge, startId, endId) {
+    const nodes = [];
+    const edgeSteps = [];
+    let cur = endId;
+    while (cur !== undefined && cur !== null) {
+        nodes.push(cur);
+        if (parentEdge[cur] != null) edgeSteps.push({ id: parentEdge[cur], from: parent[cur], to: cur });
+        if (cur === startId) break;
+        cur = parent[cur];
+    }
+    nodes.reverse();
+    edgeSteps.reverse();
+    return [
+        ...nodes.map((id) => ({ type: 'markNode', id, state: 'path' })),
+        ...edgeSteps.map((e) => ({ type: 'markEdge', id: e.id, state: 'path', from: e.from, to: e.to })),
+    ];
+}

src/lib/algorithms/insertion-sort.js

@@ -0,0 +1,39 @@
+// insertion-sort.js — Insertion sort algorithm with visualization step tracking
+// Extracted from sortingAlgorithms.js for single-responsibility.
+
+/**
+ * Insertion sort — builds sorted array one element at a time.
+ * Returns an array of step objects for animation.
+ * @param {Array} arr - Array of {width, ...} objects to sort
+ * @returns {Array} Array of {xx, yy, changed} step objects
+ */
+export function insertionSort(arr){
+    const pairs = [];
+    let n = arr.length;
+    const prevRect = arr.slice();
+    for (let i = 1; i < n; ++i) {
+        let key = prevRect[i].width;
+        let j = i - 1;
+
+        while (j >= 0 && prevRect[j].width > key) {
+            const recti = {...prevRect[j]};
+            const rectj = {...prevRect[j+1]};
+            prevRect[j+1] = recti;
+            prevRect[j] = rectj;
+            pairs.push( {
+                xx:j,
+                yy:j+1,
+                changed:true
+            } );
+            j = j - 1;
+        }
+    }
+    for(let i=0;i<n;i++){
+        pairs.push({
+            xx:i,
+            yy:i,
+            changed:true
+        })
+    }
+    return pairs;
+}

src/lib/algorithms/prime.js

@@ -1,4 +1,10 @@
-export function seive(n){
+/**
+ * Sieve of Eratosthenes — returns all prime numbers up to n.
+ * Note: Previously named `seive` (typo). Alias kept for backward compatibility.
+ * @param {number} n - Upper bound (inclusive)
+ * @returns {number[]} Array of prime numbers
+ */
+export function sieve(n){
     let vis = new Array(n+5).fill(0);
 
     let primes = [];
@@ -10,4 +16,7 @@ export function seive(n){
         }
     }
     return primes;
-}
+}
+
+// Backward-compatible alias (original had typo "seive")
+export { sieve as seive };

src/lib/algorithms/selection-sort.js

@@ -0,0 +1,52 @@
+// selection-sort.js — Selection sort algorithm with visualization step tracking
+// Extracted from sortingAlgorithms.js for single-responsibility.
+
+/**
+ * Selection sort — finds the minimum element and places it at the beginning.
+ * Returns an array of step objects for animation.
+ * @param {Array} arr - Array of {width, ...} objects to sort
+ * @returns {Array} Array of {xx, yy, changed} step objects
+ */
+export function selectionSort(arr) {
+    const pairs = [];
+    let n = arr.length;
+    const prevRect = arr.slice();
+    // One by one move boundary of unsorted subarray
+    for (let i = 0; i < n-1; i++)
+    {
+        let min_idx = i;
+        for (let j = i+1; j < n; j++){
+            pairs.push( {
+                xx:min_idx,
+                yy:j,
+                changed:false
+            } );
+            if (prevRect[j].width < prevRect[min_idx].width){
+                min_idx = j;
+            }
+        }
+
+        // Swap the found minimum element with the first element
+        const recti = {...prevRect[i]};
+        const rectj = {...prevRect[min_idx]};
+        prevRect[min_idx] = recti;
+        prevRect[i] = rectj;
+        pairs.push( {
+            xx:min_idx,
+            yy:i,
+            changed:true
+        } );
+        pairs.push( {
+            xx:i,
+            yy:i,
+            changed:false
+        });
+    }
+    pairs.push({
+            xx:n-1,
+            yy:n-1,
+            changed:false
+        }
+    )
+    return pairs;
+}

src/lib/algorithms/shortestPath.js

@@ -6,7 +6,8 @@
 //   { type: 'status', text }       -> overlay status text
 // plus edge states 'relax' | 'tree' | 'path' | 'negcycle'.
 
-import { toFlow, weightedAdjacency, edgeList } from './graph';
+import { toFlow, weightedAdjacency, edgeList } from './graph.js';
+import { buildPathActions } from './helpers/graph-helpers.js';
 
 // re-exported for back-compat with existing imports from this module
 export { toFlow, weightedAdjacency, edgeList };
@@ -51,23 +52,8 @@ export const SP_PRESETS = [
     },
 ];
 
-function pathActions(parent, parentEdge, startId, endId) {
-    const nodes = [];
-    const edgeSteps = [];
-    let cur = endId;
-    while (cur !== undefined && cur !== null) {
-        nodes.push(cur);
-        if (parentEdge[cur] != null) edgeSteps.push({ id: parentEdge[cur], from: parent[cur], to: cur });
-        if (cur === startId) break;
-        cur = parent[cur];
-    }
-    nodes.reverse();
-    edgeSteps.reverse();
-    return [
-        ...nodes.map((id) => ({ type: 'markNode', id, state: 'path' })),
-        ...edgeSteps.map((e) => ({ type: 'markEdge', id: e.id, state: 'path', from: e.from, to: e.to })),
-    ];
-}
+// pathActions is now imported as buildPathActions from helpers/graph-helpers.js
+export { buildPathActions as pathActions };
 
 export function dijkstraActions(adj, startId, finishId, nodeIds) {
     const actions = [];
@@ -119,7 +105,7 @@ export function dijkstraActions(adj, startId, finishId, nodeIds) {
     }
 
     if (finishId != null && dist[finishId] < Infinity) {
-        actions.push(...pathActions(parent, parentEdge, startId, finishId));
+        actions.push(...buildPathActions(parent, parentEdge, startId, finishId));
     }
     return actions;
 }
@@ -197,7 +183,7 @@ export function bellmanFordActions(edges, startId, finishId, nodeIds) {
     } else {
         actions.push({ type: 'status', text: 'Done' });
         if (finishId != null && dist[finishId] < Infinity) {
-            actions.push(...pathActions(parent, parentEdge, startId, finishId));
+            actions.push(...buildPathActions(parent, parentEdge, startId, finishId));
         }
     }
     return actions;