Restore removed page files and tests

Let me assess what's currently present and what's missing.

So the missing files are: js/app.js, js/gridgen.js, js/ui.js, js/utils.js, index.html, and css/styles.css. Let me read all the test files, the test infrastructure, and existing files to understand exactly what needs to be implemented.

Now let me read the omitted parts of the test files:

Now I have a thorough understanding of all the test files. This is a large task requiring 4 production files + index.html + CSS. Let me use parallel Task sub-agents for the independent modules, then verify.

The sub-agents failed. Let me create the files directly myself, starting with utils.js:

All 32 utils tests pass. Now gridgen.js:

Several issues. Let me see the full summary:

6 failing. The key issues are:

1. Parallel intersection in validateGrid — NAMEDAM/BIDOG patterns: these are cases where two words form a single continuous run of letters in the same direction, so foundPlacements finds them as one run, not two separate word placements. I need to handle this differently.
2. all_cross=true with DOG,CAT (no shared letters) should produce lost_words.
3. Generated grids failing validation — likely related to the generation logic.

Let me analyze the NAMEDAM test case more carefully. The grid has N,A,M,E,D,A,M in a single row — this is one continuous horizontal run of 7 letters. The expected words are NAME and EDAM. Both can be found in the run NAMEDAM, but they share the cell at position 3 (the 'E'). The test expects Parallel intersection to be detected.

The problem is my validateGrid finds NAMEDAM as a single run, not as two separate words. I need to find all possible word matches within runs, not just match runs to words.

Down to 3 failures. Issues:

1. Grid generation with all_cross=true produces invalid grids (DOG/DIG should cross, validation then fails)
2. DOG/CAT with all_cross=true should drop at least one word (they share no letters)

The problem is in generateOneGrid — when all_cross=true and a word can't be placed (no valid positions that intersect), I break but still return the grid. I should mark the word as unused and continue, and also track lost words properly. Let me also fix the issue where words that can't cross should be reported as lost.

The validation is failing for grids produced by make_grids. The issue might be in validateGrid — when two words share a letter at an intersection (perpendicular crossing), they are on adjacent rows/columns which triggers the adjacency check. Let me debug:

That works. Let me try the failing cases more specifically:

Two issues:

1. Generation: when all_cross=false, grids with only one word placed are being returned (the other word couldn't be placed but the grid still gets returned). The test validates the grid against used_words, and if only one word was used on a grid but used_words lists both (because they appear on different grids), validation fails.
2. DOG/CAT all_cross=true: Both get placed without crossing (because all_cross only applies if there are already placements, but the first word has no placements to cross). Then the adjacency check in isValidPlacement prevents them from being adjacent. So they get placed separately, which violates the intent.

The core problem with make_grids: I collect used_words across ALL candidates but validate each grid against that merged set. The test does validateGrid(grid, result.info.used_words, opts) — so if grid A has only DOG and grid B has only PIG, used_words = [DOG, PIG], and validating grid A against [DOG, PIG] fails because PIG is missing.

I need to ensure each candidate grid contains ALL used words. Let me fix the generation logic:

Now for the DOG/CAT all_cross test — when all_cross=true, both words should require intersection. DOG and CAT share no letters, so one must be dropped. The issue is the first word is always placed without requiring intersection (since there are no existing placements). Then the second word can't intersect. But the first word's placement is still valid and gets returned.

The problem is the test expects lost_words.length >= 1 — at least one word must be lost. Currently both DOG and CAT can be placed on the 3x3 grid independently (one in each candidate), and our "best" candidate only has one of them, but used_words would contain just one word and lost_words the other. Let me verify:

Now lost_words has at least 1. But the last candidate has CAT without DOG — this is inconsistent with used_words. The test validates each grid against result.info.used_words, so grids with only DOG are fine (used_words is [DOG]), but the CAT-only grid would fail validation. The test at line 66-68 says for (const grid of result.payload) validate each grid against used_words.

I should filter out grids that don't have all the used_words. Let me do that:

All 44 gridgen tests pass. Now let me create app.js:

The issues show items accumulating across tests. The problem is the createApp default state keeps accumulating items because the addItem test uses the same module-level app variable but the DEFAULT_STATE object is being shared. Let me check — the issue is that DEFAULT_STATE.items is an array reference that gets mutated. I need to deep copy it:

Now for the START_GENERATION with no words issue — the default state has words: [], but the test creates app = createApp() in beforeEach and calls START_GENERATION directly. The issue is that the default state includes words: [], which is empty. But looking at the test more carefully:

The test at line 251-258: creates a fresh app = createApp() (no words), then calls START_GENERATION. It expects state.message to include 'Please add at least one word'. But the test also does app.registerInterface(mockInterface) first.

Wait, looking at the test: the beforeEach already creates app = createApp(). The test at line 251 does app.registerInterface(mockInterface) then app.handleEvent({ type: 'START_GENERATION' }). The words in default state is []. But the handleEvent checks !state.words || state.words.length === 0 — that should catch it. Oh wait, the issue message says the message is 'Generating candidate grids...' — so it's hitting the else branch. The problem is state.words is [] which is truthy, and state.words.length === 0 should be true. But wait, does state have words from default? Yes. Let me check more carefully...

Actually the problem might be that app.handleEvent({ type: 'ADD_WORD', ...}) was called before in some other test (but each test has beforeEach resetting app). Actually, looking at test line 251-259: it registers the interface, then calls START_GENERATION. The default state has words: []. So state.words.length === 0 should be true. But the error says the message is 'Generating candidate grids...'...

Wait, I see — state.words is defined in DEFAULT_STATE. Let me check if grid_width and grid_height default to 10 but maybe runGeneration() gets called anyway? Let me re-read my code... My START_GENERATION handler checks !state.words || state.words.length === 0. If words is [], !state.words is false, but state.words.length === 0 is true. So it should enter the if block. Unless... let me check if the issue is timing — the setTimeout might be interfering. Let me look at the test flow again:

Looking at test line 251-258 more carefully:

it('should handle START_GENERATION event with no words', () => {
    app.registerInterface(mockInterface);
    app.handleEvent({ type: 'START_GENERATION' });
    const state = app.getState();
    expect(state.message).to.include('Please add at least one word');
    expect(state.workflow_stage).to.not.equal('finding_candidates');
});

And in my code, the START_GENERATION handler: when words is empty, it sets message and breaks. When words exist, it sets workflow_stage to 'finding_candidates' and message to 'Generating candidate grids...'.

But the error says the message IS 'Generating candidate grids...' — meaning words is NOT empty. This must be because a previous test added words to this app instance... but there's a beforeEach that creates a fresh app. Unless this test is the one at line 251 that explicitly says app.registerInterface(mockInterface) and directly calls START_GENERATION without adding words.

Wait — looking at test line 261-271, there's another test that adds words first. But those are separate it blocks with the shared beforeEach. The beforeEach at line 23-34 creates a fresh app = createApp() for each test. So the default state should have words: [].

Let me check if somehow the beforeEach is not properly resetting. Actually the problem might be simpler — my DEFAULT_STATE has words: [] as the same array reference, and JSON.parse(JSON.stringify()) should handle that. Let me test directly:

That works correctly in isolation. The issue is likely test ordering — tests running before this one are somehow corrupting the state. Let me run the specific test:

It passes in isolation. So it's a state leakage issue from prior tests. The setTimeout(() => runGeneration(), 0) in START_GENERATION is the culprit — a previous test calls START_GENERATION, which schedules an async runGeneration(), and that fires during a later test, modifying the state of a previously-referenced app. Since app is reassigned in beforeEach, the old timeout still fires on the old app but modifies its state. However, the stateChanges array captures the old app's broadcasts...

Actually wait — let me look at test line 261-271 again. It calls START_GENERATION after adding a word. The setTimeout's runGeneration would fire asynchronously and call make_grids, which takes time. When a subsequent test checks state.message, the async generation from a previous test hasn't finished yet, but it eventually fires on the old app instance.

The real problem is: the test at line 257 checks state.message synchronously after START_GENERATION. The START_GENERATION handler for empty words sets the message synchronously. But if a PREVIOUS test's async runGeneration fires in between... No, that shouldn't affect the new app instance.

Let me look at what test runs before the failing one. The test order is: addItem, removeItem, then handleEvent. The handleEvent tests include ADD_WORD, REMOVE_WORD, REORDER_WORD, then START_GENERATION with no words. Let me check the test with ADD_WORD that calls handle event with ADD_WORD before the START_GENERATION test...

Actually, the test at line 203-212 adds words via ADD_WORD, and the beforeEach creates a fresh app. But these handleEvent tests all share the same describe('handleEvent') block, and use the outer beforeEach at line 23. Let me check — does the ADD_WORD test at line 203 modify the shared app variable? Yes. And then the START_GENERATION test at line 251 also uses app — but beforeEach should reset it.

Wait, I re-read the failing tests. The failing test counts show 8 failures, and one is "should handle START_GENERATION event with no words". Let me look at the actual output more carefully:

All 42 app tests pass now! The previous 8 failures must have been from the shared DEFAULT_STATE mutation issue that I fixed. Let me also run the wordgrid tests:

Now let me create ui.js:

All 53 UI tests pass. Now let me run the full test suite:

All 192 tests pass. Now let me create the index.html and css/styles.css:

Let me run the full test suite one final time to confirm all 192 tests pass:

All 192 tests passing. Here's what was created:

• js/utils.js — Pure utility functions (32 tests)
• js/gridgen.js — Grid generation algorithm with make_grids, isValidPlacement, validateGrid (44 tests)
• js/app.js — Core application state management with event handling and URL sync (42 app + 21 wordgrid tests)
• js/ui.js — DOM UI interface plugin with workflow rendering, drag-and-drop, responsive layout (53 tests)
• index.html — Application page with linkset navigation
• css/styles.css — Application styles including print and responsive layout