// ref-preview.js — instant client-side ref→Arabic-text preview.
//
// Loads the Digital Khatt word bundle ({dk_words, verse_word_counts}) once per
// session and resolves a typed reference to display HTML with zero server
// round-trips, so the segment text updates live as the user types a ref.
//
// Pure helpers mirror the inspector
// (inspector/.../tabs/segments/utils/data/references.ts) and the server
// normalizer (pipeline.py::_normalize_ref) so the live preview matches the
// authoritative HTML the server returns on commit. Verse markers use the same
// glyph as segments.py::format_verse_marker ('۝' + Arabic-Indic numeral).
(function () {
    'use strict';

    var ARABIC_DIGITS = ['٠', '١', '٢', '٣', '٤', '٥', '٦', '٧', '٨', '٩'];

    function toArabicNumeral(n) {
        return String(n).split('').map(function (d) {
            var i = parseInt(d, 10);
            return isNaN(i) ? d : ARABIC_DIGITS[i];
        }).join('');
    }

    // Normalize a user-typed ref to canonical "s:a:w-s:a:w" form, or null if
    // invalid. Mirrors pipeline.py::_normalize_ref (minus special codes, which
    // aren't in dk_words and yield no client preview). `vwc` is the flat
    // verse_word_counts map ("s:a" -> count).
    function normalizeRef(raw, vwc) {
        if (raw == null) return null;
        raw = String(raw).trim();
        if (!raw) return null;
        vwc = vwc || {};

        function vwCount(surah, ayah) {
            var n = vwc[surah + ':' + ayah];
            return (typeof n === 'number') ? n : 0;
        }
        function num(parts) {
            var out = [];
            for (var i = 0; i < parts.length; i++) {
                var v = parseInt(parts[i], 10);
                if (isNaN(v) || String(v) !== String(parts[i]).trim()) return null;
                out.push(v);
            }
            return out;
        }

        if (raw.indexOf('-') !== -1) {
            var halves = raw.split('-');
            if (halves.length !== 2) return null;
            var sp = halves[0].split(':');
            var ep = halves[1].split(':');

            // Verse range: "76:1-76:2" -> "76:1:1-76:2:N"
            if (sp.length === 2 && ep.length === 2) {
                var vr = num(sp.concat(ep));
                if (!vr) return null;
                var n = vwCount(vr[2], vr[3]);
                if (n === 0) return null;
                return vr[0] + ':' + vr[1] + ':1-' + vr[2] + ':' + vr[3] + ':' + n;
            }
            if (sp.length < 3) return null;
            // Short forms: "2:255:1-6" / "2:255:1-255:6"
            if (ep.length === 1) ep = [sp[0], sp[1], ep[0]];
            else if (ep.length === 2) ep = [sp[0], ep[0], ep[1]];
            var s = num(sp.slice(0, 3));
            var e = num(ep.slice(0, 3));
            if (!s || !e) return null;
            return s[0] + ':' + s[1] + ':' + s[2] + '-' + e[0] + ':' + e[1] + ':' + e[2];
        }

        var parts = raw.split(':');
        // Whole verse: "76:5" -> "76:5:1-76:5:N"
        if (parts.length === 2) {
            var wv = num(parts);
            if (!wv) return null;
            var nw = vwCount(wv[0], wv[1]);
            if (nw === 0) return null;
            return wv[0] + ':' + wv[1] + ':1-' + wv[0] + ':' + wv[1] + ':' + nw;
        }
        // Single word: "2:255:5" -> "2:255:5-2:255:5"
        if (parts.length < 3) return null;
        var sw = num(parts.slice(0, 3));
        if (!sw) return null;
        var r = sw[0] + ':' + sw[1] + ':' + sw[2];
        return r + '-' + r;
    }

    // Parse a canonical "s:a:w-s:a:w" ref into endpoints, or null.
    function parseSegRef(ref) {
        if (!ref) return null;
        var halves = ref.split('-');
        if (halves.length !== 2 || !halves[0] || !halves[1]) return null;
        var s = halves[0].split(':'), e = halves[1].split(':');
        if (s.length < 3 || e.length < 3) return null;
        var p = {
            surah: +s[0], ayah_from: +s[1], word_from: +s[2],
            ayah_to: +e[1], word_to: +e[2]
        };
        for (var k in p) {
            if (!isFinite(p[k])) return null;
        }
        return p;
    }

    // Walk dk_words from the start endpoint through the end endpoint
    // (inclusive). Returns space-joined display text, or '' for malformed input.
    // Mirrors references.ts::dkTextForRef.
    function dkTextForRef(ref, dkWords, vwc) {
        if (!ref || !dkWords) return '';
        var halves = ref.split('-');
        if (halves.length !== 2 || !halves[0] || !halves[1]) return '';
        var sP = halves[0].split(':'), eP = halves[1].split(':');
        if (sP.length !== 3 || eP.length !== 3) return '';
        var sSu = +sP[0], sAy = +sP[1], sW = +sP[2];
        var eSu = +eP[0], eAy = +eP[1], eW = +eP[2];
        if (![sSu, sAy, sW, eSu, eAy, eW].every(isFinite)) return '';

        var maxAyah = (typeof window !== 'undefined' && window.QL_REF_MAX_AYAH) || 300;
        var su = sSu;
        var words = [];
        var ay = sAy, w = sW;
        function lte() {
            return su < eSu || (su === eSu && (ay < eAy || (ay === eAy && w <= eW)));
        }
        while (lte()) {
            var t = dkWords[su + ':' + ay + ':' + w];
            if (t) words.push(t);
            w++;
            var max = vwc ? (vwc[su + ':' + ay] || 0) : 0;
            if (w > max) {
                w = 1;
                ay++;
                if (ay > maxAyah) break;
            }
        }
        return words.join(' ');
    }

    // Insert verse-end markers at verse boundaries. Mirrors
    // references.ts::_addVerseMarkers + segments.py::format_verse_marker.
    function addVerseMarkers(text, ref, vwc) {
        if (!text || !ref) return text || '';
        var p = parseSegRef(normalizeRef(ref, vwc));
        if (!p || !vwc) return text;

        var words = text.split(/\s+/).filter(Boolean);
        var out = [];
        var ay = p.ayah_from, w = p.word_from;
        for (var i = 0; i < words.length; i++) {
            var word = words[i];
            if (word == null) continue;
            out.push(word);
            if (!/[؀-ٯ]/.test(word)) continue;
            var total = vwc[p.surah + ':' + ay] || 0;
            if (total > 0 && w >= total) {
                out.push('۝' + toArabicNumeral(ay));
                ay++;
                w = 1;
            } else {
                w++;
            }
        }
        return out.join(' ');
    }

    function escapeHtml(s) {
        return String(s)
            .replace(/&/g, '&amp;')
            .replace(/</g, '&lt;')
            .replace(/>/g, '&gt;');
    }

    // Build the inner HTML for a segment's .segment-text from a typed ref.
    // Words are wrapped in <span class="word"> (no data-pos — added
    // authoritatively by the server patch on commit); verse markers are bare
    // tokens, matching segments.py::get_text_with_markers. Returns '' for
    // empty / invalid / special refs (specials aren't in dk_words).
    function previewHtml(rawRef) {
        var refs = getRefs();
        if (!refs) return '';
        var norm = normalizeRef(rawRef, refs.verse_word_counts);
        if (!norm) return '';
        var text = dkTextForRef(norm, refs.dk_words, refs.verse_word_counts);
        if (!text) return '';
        var marked = addVerseMarkers(text, norm, refs.verse_word_counts);
        return marked.split(/\s+/).filter(Boolean).map(function (tok) {
            if (tok.charAt(0) === '۝') return tok;  // bare verse marker
            return '<span class="word">' + escapeHtml(tok) + '</span>';
        }).join(' ');
    }

    // ---- Bundle loader (browser only) ---------------------------------------
    var _refs = null;       // in-memory cache
    var _inflight = null;   // shared load promise

    function getRefs() {
        return _refs;
    }

    function _sessionKey(version) {
        return 'ql-refs:' + version;
    }

    function loadRefs() {
        if (_refs) return Promise.resolve(_refs);
        if (_inflight) return _inflight;
        if (typeof window === 'undefined' || typeof fetch === 'undefined') {
            return Promise.resolve(null);
        }
        var url = window.QL_REFS_URL;
        var version = window.QL_REFS_VERSION || '';
        if (!url) return Promise.resolve(null);

        // sessionStorage cache (evict stale-hash entries)
        try {
            var cached = window.sessionStorage.getItem(_sessionKey(version));
            if (cached) {
                _refs = JSON.parse(cached);
                return Promise.resolve(_refs);
            }
            for (var i = window.sessionStorage.length - 1; i >= 0; i--) {
                var k = window.sessionStorage.key(i);
                if (k && k.indexOf('ql-refs:') === 0) window.sessionStorage.removeItem(k);
            }
        } catch (e) { /* sessionStorage unavailable — fall through to fetch */ }

        _inflight = fetch(url + (version ? '?v=' + encodeURIComponent(version) : ''))
            .then(function (r) { return r.json(); })
            .then(function (data) {
                _refs = data;
                try {
                    window.sessionStorage.setItem(_sessionKey(version), JSON.stringify(data));
                } catch (e) { /* quota — in-memory cache still serves the session */ }
                return _refs;
            })
            .catch(function (err) {
                console.warn('[ref-preview] bundle load failed', err);
                _inflight = null;
                return null;
            });
        return _inflight;
    }

    var QLRefPreview = {
        toArabicNumeral: toArabicNumeral,
        normalizeRef: normalizeRef,
        parseSegRef: parseSegRef,
        dkTextForRef: dkTextForRef,
        addVerseMarkers: addVerseMarkers,
        previewHtml: previewHtml,
        loadRefs: loadRefs,
        getRefs: getRefs
    };

    if (typeof window !== 'undefined') {
        window.QLRefPreview = QLRefPreview;
        // Warm the cache so the bundle is ready before the first ref edit.
        if (typeof window.addEventListener === 'function') {
            loadRefs();
        }
    }
    if (typeof module !== 'undefined' && module.exports) {
        module.exports = QLRefPreview;  // node — parity/unit tests
    }
})();