// ==FINGERPRINT (drop-in utility) ==
// Purpose: Generate a strong, stable fingerprint string for an assistant message element.
//
// This utility is designed to uniquely identify assistant messages across dynamic UIs
// (ChatGPT, Claude, Gemini). It uses multiple content- and position-aware components:
//  - ch: content hash of the most "command-like" text in the element (prefers fenced code)
//  - ph: hash of the immediately preceding assistant messages' trailing text (context)
//  - ih: hash of the text right before the first @bridge@...@end@ block (intra-message prefix)
//  - hint: small DOM hint (tag#id.class) hashed to keep size small
//  - n: ordinal among elements with same ch+ph+ih on the page at this moment
//
// The combination helps disambiguate near-duplicate messages, re-ordered DOM, and small edits.
// Fingerprints are stable enough to persist in localStorage for de-duplication.
//
// Notes:
// - All hashes are short base36 strings derived from a djb2-xor style hash; fast and sufficient.
// - Inputs are normalized (trim, strip zero-width spaces, normalize whitespace before newlines).
// - The algorithm intentionally looks at at most ~2000 chars per slice for performance.
// - The module is side-effect free except for optional caching of a stable fingerprint in dataset.
(function(){
    /**
     * CSS selectors that identify assistant messages across supported sites.
     * These are joined with "," and used for querySelectorAll when scanning neighbors.
     */
    const MSG_SELECTORS = [
        '[data-message-author-role="assistant"]',
        '.chat-message:not([data-message-author-role="user"])',
        '.message-content'
    ];

    /**
     * Normalize text by removing carriage returns and zero-width spaces, squashing trailing
     * whitespace before newlines, and trimming ends. Keeps a consistent basis for hashing.
     * @param {string} s
     * @returns {string}
     */
    function norm(s){ return (s||'').replace(/\r/g,'').replace(/\u200b/g,'').replace(/[ \t]+\n/g,'\n').trim(); }

    /**
     * Fast, low-collision string hash. djb2 variant using XOR; returns unsigned base36 string.
     * @param {string} s
     * @returns {string}
     */
    function hash(s){ let h=5381; for(let i=0;i<s.length;i++) h=((h<<5)+h)^s.charCodeAt(i); return (h>>>0).toString(36); }

    /**
     * Extract the most relevant, command-like text from a message element.
     * Preference order:
     *  - Any code/pre blocks that appear to contain a valid @bridge@ ... @end@ command with `action:`
     *  - Otherwise, fall back to the element's textContent (first 2000 chars), normalized.
     * @param {Element} el
     * @returns {string}
     */
    function commandLikeText(el){
        const blocks = el.querySelectorAll('pre code, pre, code');
        for (const b of blocks) {
            const t = norm(b.textContent || '');
            // Must look like a complete runnable command block
            if (/@end@\s*$/m.test(t) && /(^|\n)\s*@bridge@\b/m.test(t) && /(^|\n)\s*action\s*:/m.test(t)) return t;
        }
        return norm((el.textContent || '').slice(0, 2000));
    }

    /**
     * Build a hash of the immediate previous assistant messages' trailing text (up to 2000 chars).
     * This captures conversational context that helps distinguish repeated content.
     * @param {Element} el - The current message element
     * @returns {string} base36 hash of the context window
     */
    function prevContextHash(el) {
        const list = Array.from(document.querySelectorAll(MSG_SELECTORS.join(',')));
        const idx = list.indexOf(el); if (idx <= 0) return '0';
        let rem = 2000, buf = '';
        for (let i=idx-1; i>=0 && rem>0; i--){
            const t = norm(list[i].textContent || ''); if (!t) continue;
            const take = t.slice(-rem); buf = take + buf; rem -= take.length;
        }
        return hash(buf.slice(-2000));
    }

    /**
     * Compute a hash of the text immediately preceding the first command block within this element.
     * If there is no @bridge@ block, hashes the trailing slice of the whole element text.
     * @param {Element} el
     * @returns {string}
     */
    function intraPrefixHash(el){
        const t = el.textContent || '';
        const m = t.match(/@bridge@[\s\S]*?@end@/m);
        const endIdx = m ? t.indexOf(m[0]) : t.length;
        return hash(norm(t.slice(Math.max(0, endIdx - 2000), endIdx)));
    }

    /**
     * Produce a tiny DOM hint string (tag#id.class) to help separate identical content in different
     * containers. Limited to 40 chars and later hashed before inclusion in the final fingerprint.
     * @param {Element} node
     * @returns {string}
     */
    function domHint(node) {
        if (!node) return '';
        const id = node.id || '';
        const cls = (node.className && typeof node.className === 'string') ? node.className.split(' ')[0] : '';
        return `${node.tagName || ''}#${id}.${cls}`.slice(0, 40);
    }

    /**
     * Determine the ordinal index (0-based) of this element among all message elements that share
     * the same content/context key on the page. This disambiguates duplicates that have identical
     * ch+ph+ih values by adding their order of appearance.
     * @param {Element} el
     * @param {string} key - The key built from ch|ph|ih for this element
     * @returns {number}
     */
    function ordinalForKey(el, key) {
        const list = Array.from(document.querySelectorAll(MSG_SELECTORS.join(',')));
        let n = 0;
        for (const node of list) {
            const nodeKey = node === el ? key : (() => {
                const ch = hash(commandLikeText(node).slice(0, 2000));
                const ph = prevContextHash(node);
                const ih = intraPrefixHash(node);
                return `ch:${ch}|ph:${ph}|ih:${ih}`;
            })();
            if (nodeKey === key) {
                if (node === el) return n;
                n++;
            }
        }
        return n;
    }

    /**
     * Generate a composite fingerprint for the given message element.
     * Format: "ch:<..>|ph:<..>|ih:<..>|hint:<..>|n:<ordinal>"
     * @param {Element} el
     * @returns {string}
     */
    function fingerprintElement(el){
        const ch = hash(commandLikeText(el).slice(0, 2000));
        const ph = prevContextHash(el);
        const ih = intraPrefixHash(el);
        const dh = hash(domHint(el));
        const key = `ch:${ch}|ph:${ph}|ih:${ih}`;
        const n = ordinalForKey(el, key);
        return `${key}|hint:${dh}|n:${n}`;
    }

    /**
     * Retrieve (and cache) a stable fingerprint for the element. The first time it's computed,
     * the value is stored in el.dataset.aiRcStableFp so subsequent calls don't recompute.
     * @param {Element} el
     * @returns {string}
     */
    function getStableFingerprint(el) {
        if (el?.dataset?.aiRcStableFp) return el.dataset.aiRcStableFp;
        const fp = fingerprintElement(el);
        try { if (el && el.dataset) el.dataset.aiRcStableFp = fp; } catch {}
        return fp;
    }

    // Expose both for backward compatibility with older modules that expect these globals
    window.AI_REPO_FINGERPRINT = fingerprintElement;
    window.AI_REPO_STABLE_FINGERPRINT = getStableFingerprint;
})();