// wikicomplete.js — the `[[` autocomplete source for CodeMirror.
//
// Wiki links are search queries, so the popup is the same typeahead the header
// search box uses: the text typed after `[[` goes to `/_search` and each match
// is offered by name. Picking one replaces the query segment with that page's
// name — never a path — so what lands in the document is still a query. The
// trailing `]]` and any `::display` tail are left untouched.
//
// Exposes window.WikiComplete.source for main.js to register via CM's
// autocompletion().
window.WikiComplete = (function () {
    // Matches search-suggest.js so both surfaces fire at the same point.
    var MIN_QUERY_LEN = 2;

    function fetchSuggestions(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();
        });
    }

    // queryEnd returns where the current query segment ends: the first `]`, the
    // `::` that starts the display text, or end of line. Replacing only up to
    // there keeps a re-edit from eating an existing alias or the closing `]]`.
    function queryEnd(context, pos) {
        var line = context.state.doc.lineAt(pos);
        var to = pos;
        while (to < line.to) {
            var ch = context.state.sliceDoc(to, to + 1);
            if (ch === ']') break;
            if (ch === ':' && context.state.sliceDoc(to, to + 2) === '::') break;
            to++;
        }
        return to;
    }

    // CM completion source. Activates on `[[` followed by at least
    // MIN_QUERY_LEN characters; a cursor past a `::` is in the display tail and
    // gets nothing.
    function source(context) {
        var match = context.matchBefore(/\[\[[^\]\n]*/);
        if (!match) return null;
        var content = context.state.sliceDoc(match.from + 2, context.pos);
        if (content.indexOf('::') !== -1) return null;
        var query = content.trim();
        if (query.length < MIN_QUERY_LEN) return null;

        var from = match.from + 2;
        var to = queryEnd(context, context.pos);

        return new Promise(function (resolve) {
            if (context.aborted) { resolve(null); return; }
            fetchSuggestions(query).then(function (resp) {
                if (context.aborted) { resolve(null); return; }
                var options = (resp.results || []).map(function (r) {
                    return { label: r.name, detail: '/' + r.path, apply: r.name };
                });
                // filter:false — the server already ranked these fuzzily, and
                // CM's own prefix filter would drop the near-misses (typos,
                // token reorderings) that make the fuzzy search worth having.
                // No validFor either: every keystroke re-queries from scratch.
                resolve({ from: from, to: to, options: options, filter: false });
            }).catch(function () {
                resolve(null);
            });
        });
    }

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