// ============================================================
// Test harness — load js/app.js into a sandboxed VM context
// ============================================================
//
// app.js is a ~12k-line browser monofile with no module exports. It runs
// only one top-level statement (a DOMContentLoaded listener); everything
// else is function/const declarations. We load it in a node:vm context with
// browser globals stubbed out so init() never fires, then reach the internals
// we want to test through an appended export epilogue.
//
// Why the epilogue: in vm.runInContext, top-level `function`/`var` declarations
// attach to the context's global object, but top-level `const`/`let` (like
// `state`, `API`, `HASH_ALGO_V2`) do NOT. So we append a line that copies the
// symbols we care about onto globalThis.__test, giving tests a stable handle.
//
// Reassignable seams for the merge tests: `api`, `loadEntries`, `loadFolders`,
// `encryptImportEntry`, etc. are `function` declarations → global properties,
// so a test can override `ctx.api = fake` and the free-variable lookup inside
// applyRemoteSnapshot will pick up the fake. `state` is a `const` (lexical),
// so it can't be replaced — but it CAN be mutated, and applyRemoteSnapshot
// closes over that same object, so mutating ctx.__test.state is visible to it.

const fs = require('node:fs');
const path = require('node:path');
const vm = require('node:vm');
const { webcrypto } = require('node:crypto');

const APP_JS = path.join(__dirname, '..', 'app.js');

// In-memory Storage stub (Web Storage API surface used by app.js).
function makeStorage() {
    const m = new Map();
    return {
        getItem: (k) => (m.has(k) ? m.get(k) : null),
        setItem: (k, v) => { m.set(k, String(v)); },
        removeItem: (k) => { m.delete(k); },
        clear: () => m.clear(),
        key: (i) => Array.from(m.keys())[i] ?? null,
        get length() { return m.size; },
    };
}

// Minimal no-throw DOM/window stubs. app.js only *executes* one DOM call at
// load (document.addEventListener for DOMContentLoaded) — everything else is
// inside functions we don't call. So these just have to exist and not throw.
function makeDomStubs() {
    const noop = () => {};
    const elStub = new Proxy({}, {
        get: (_t, prop) => {
            if (prop === 'style') return {};
            if (prop === 'classList') return { add: noop, remove: noop, toggle: noop, contains: () => false };
            if (prop === 'addEventListener' || prop === 'removeEventListener') return noop;
            if (prop === 'appendChild' || prop === 'append' || prop === 'remove') return noop;
            if (prop === 'setAttribute' || prop === 'removeAttribute') return noop;
            if (prop === 'querySelector') return () => null;
            if (prop === 'querySelectorAll') return () => [];
            return undefined;
        },
        set: () => true,
    });
    const document = {
        addEventListener: noop,
        removeEventListener: noop,
        getElementById: () => null,
        querySelector: () => null,
        querySelectorAll: () => [],
        createElement: () => elStub,
        body: elStub,
        documentElement: elStub,
    };
    return { document, elStub, noop };
}

// Build a fresh sandbox + load app.js into it. Returns the contextified
// sandbox; test internals live on ctx.__test.
function loadApp(overrides = {}) {
    const { document, noop } = makeDomStubs();

    const sandbox = {
        crypto: webcrypto,
        TextEncoder,
        TextDecoder,
        btoa,
        atob,
        console,
        setTimeout,
        clearTimeout,
        setInterval,
        clearInterval,
        Date,
        JSON,
        Math,
        Promise,
        URL,
        URLSearchParams,
        // Browser-ish globals used at load time
        location: { pathname: '/index.html', href: 'http://127.0.0.1/index.html', search: '', hash: '' },
        history: { replaceState: noop, pushState: noop },
        navigator: { clipboard: { writeText: async () => {}, readText: async () => '' }, userAgent: 'node-test' },
        localStorage: makeStorage(),
        sessionStorage: makeStorage(),
        document,
        fetch: async () => { throw new Error('fetch not stubbed'); },
        // Some code paths reference matchMedia / requestAnimationFrame
        matchMedia: () => ({ matches: false, addEventListener: noop, addListener: noop }),
        requestAnimationFrame: (cb) => setTimeout(cb, 0),
        ...overrides,
    };
    // window / self / globalThis self-reference (app.js reads window.location etc.)
    sandbox.window = sandbox;
    sandbox.self = sandbox;
    sandbox.globalThis = sandbox;

    vm.createContext(sandbox);

    let src = fs.readFileSync(APP_JS, 'utf8');

    // Export epilogue — surface the lexical (const) symbols we test, plus a
    // couple of function-decl seams for convenience. Kept in one place so the
    // list of "what tests can touch" is explicit.
    src += `
    ;globalThis.__test = {
        state,
        // crypto
        bytesToHex, hexToBytes: (typeof hexToBytes !== 'undefined' ? hexToBytes : undefined),
        verifierFromKeyHex, deriveKeyAndVerifier, computeVerifier,
        encryptPwd, decryptPwd, sha256Hex,
        HASH_ALGO_V2, AUTH_VERIFIER_DOMAIN,
        // csv
        parseCSV, findColumn, parseEntriesFromCSV,
        // strength
        computeStrength: (typeof computeStrength !== 'undefined' ? computeStrength : undefined),
        // merge (async, coupled — tests stub the io seams below)
        applyRemoteSnapshot, buildSyncSnapshot,
    };
    `;

    vm.runInContext(src, sandbox, { filename: 'app.js' });
    return sandbox;
}

module.exports = { loadApp, makeStorage };