// wikicomplete.js — the `[[` wikilink autocomplete source for CodeMirror.
//
// Triggers when the cursor sits in a `[[…` token (freshly typed or re-edited
// inside an existing `[[…]]`), queries the existing /_search JSON endpoint
// (debounced), and offers matching page paths. Selecting a result inserts the
// absolute path and auto-closes `]]`, leaving the cursor before the close so a
// `::display` alias can be typed (decision 7). Exposes window.WikiComplete.source
// for main.js to register via CM's autocompletion().
window.WikiComplete = (function () {
    var DEBOUNCE_MS = 100;
    var MIN_QUERY_LEN = 2;

    // Mirrors the Go validator (wikilinks.go isValidWikiTarget) and the old
    // client check: absolute path, no empty/'.'/'..' segments. Server results
    // are wiki paths so this is mostly a guard against odd index entries.
    function isValidWikiTarget(p) {
        if (!p || p[0] !== '/') return false;
        var trimmed = p.replace(/^\/+|\/+$/g, '');
        if (trimmed === '') return true;
        var segs = trimmed.split('/');
        for (var i = 0; i < segs.length; i++) {
            if (segs[i] === '' || segs[i] === '.' || segs[i] === '..') return false;
        }
        return true;
    }

    // Build the apply() for a chosen result. Inserts the path over the typed
    // query and ensures a single trailing `]]`, cursor parked before it. If the
    // user (or closeBrackets) already produced `]]`, we don't double it up.
    function makeApply(path) {
        return function (view, completion, from, to) {
            var closed = view.state.sliceDoc(to, to + 2) === ']]';
            var insert = closed ? path : path + ']]';
            view.dispatch({
                changes: { from: from, to: to, insert: insert },
                selection: { anchor: from + path.length },
                scrollIntoView: true,
            });
        };
    }

    function fetchSuggest(query) {
        return fetch('/_search?q=' + encodeURIComponent(query), {
            credentials: 'same-origin',
            headers: { 'Accept': 'application/json' },
        }).then(function (r) {
            if (!r.ok) throw new Error('HTTP ' + r.status);
            return r.json();
        });
    }

    // CM completion source. `[[` plus any run of non-`]`, non-newline chars
    // before the cursor is the trigger; the query is the text after `[[`. The
    // replaced range extends past the cursor to the end of the inner token (up
    // to `]]`/EOL) so re-editing inside an existing `[[…]]` replaces the whole
    // target instead of duplicating the trailing text.
    function source(context) {
        var match = context.matchBefore(/\[\[[^\]\n]*/);
        if (!match) return null;
        var query = context.state.sliceDoc(match.from + 2, context.pos);
        if (query.length < MIN_QUERY_LEN && !context.explicit) return null;

        var line = context.state.doc.lineAt(context.pos);
        var to = context.pos;
        while (to < line.to && context.state.sliceDoc(to, to + 1) !== ']') to++;

        return new Promise(function (resolve) {
            var timer = setTimeout(function () {
                if (context.aborted) { resolve(null); return; }
                fetchSuggest(query).then(function (resp) {
                    if (context.aborted) { resolve(null); return; }
                    var options = (resp.results || []).reduce(function (acc, r) {
                        var path = '/' + r.path;
                        if (isValidWikiTarget(path)) {
                            acc.push({ label: path, detail: r.name, apply: makeApply(path) });
                        }
                        return acc;
                    }, []);
                    resolve({ from: match.from + 2, to: to, options: options });
                }).catch(function () {
                    resolve(null);
                });
            }, DEBOUNCE_MS);
            // CM doesn't cancel pending promises, but it sets context.aborted;
            // clear the timer too if the doc moved on before it fired.
            if (context.addEventListener) {
                context.addEventListener('abort', function () { clearTimeout(timer); });
            }
        });
    }

    return { source: source, isValidWikiTarget: isValidWikiTarget };
})();