// linerangelog.js - JavaScript utilities for followlines UI

//

// Copyright 2017 Logilab SA <contact@logilab.fr>

//

// This software may be used and distributed according to the terms of the

// GNU General Public License version 2 or any later version.

//** Install event listeners for line block selection and followlines action */

function installLineSelect() {

    var sourcelines = document.getElementsByClassName('sourcelines')[0];

    if (typeof sourcelines === 'undefined') {

        return;

    }

    // URL to complement with "linerange" query parameter

    var targetUri = sourcelines.dataset.logurl;

    if (typeof targetUri === 'undefined') {

        return;

    }

    // retrieve all direct <span> children of <pre class="sourcelines">

    var spans = Array.prototype.filter.call(

        sourcelines.children,

        function(x) { return x.tagName === 'SPAN' });

    var lineSelectedCSSClass = 'followlines-selected';

    //** add CSS class on <span> element in `from`-`to` line range */

    function addSelectedCSSClass(from, to) {

        for (var i = from; i <= to; i++) {

            spans[i].classList.add(lineSelectedCSSClass);

        }

    }

    //** remove CSS class from previously selected lines */

    function removeSelectedCSSClass() {

        var elements = sourcelines.getElementsByClassName(

            lineSelectedCSSClass);

        while (elements.length) {

            elements[0].classList.remove(lineSelectedCSSClass);

        }

    }

    // ** return the <span> element parent of `element` */

    function findParentSpan(element) {

        var parent = element.parentElement;

        if (parent === null) {

            return null;

        }

        if (element.tagName == 'SPAN' && parent.isSameNode(sourcelines)) {

            return element;

        }

        return findParentSpan(parent);

    }

    //** event handler for "click" on the first line of a block */

    function lineSelectStart(e) {

        var startElement = findParentSpan(e.target);

        if (startElement === null) {

            // not a <span> (maybe <a>): abort, keeping event listener

            // registered for other click with <span> target

            return;

        }

        var startId = parseInt(startElement.id.slice(1));

        startElement.classList.add(lineSelectedCSSClass); // CSS

        // remove this event listener

        sourcelines.removeEventListener('click', lineSelectStart);

        //** event handler for "click" on the last line of the block */

        function lineSelectEnd(e) {

            var endElement = findParentSpan(e.target);

            if (endElement === null) {

                // not a <span> (maybe <a>): abort, keeping event listener

                // registered for other click with <span> target

                return;

            }

            // remove this event listener

            sourcelines.removeEventListener('click', lineSelectEnd);

            // compute line range (startId, endId)

            var endId = parseInt(endElement.id.slice(1));

            if (endId == startId) {

                // clicked twice the same line, cancel and reset initial state

                // (CSS and event listener for selection start)

                removeSelectedCSSClass();

                sourcelines.addEventListener('click', lineSelectStart);

                return;

            }

            var inviteElement = endElement;

            if (endId < startId) {

                var tmp = endId;

                endId = startId;

                startId = tmp;

                inviteElement = startElement;

            }

            addSelectedCSSClass(startId - 1, endId -1);  // CSS

            // append the <div id="followlines"> element to last line of the

            // selection block

            var divAndButton = followlinesBox(targetUri, startId, endId);

            var div = divAndButton[0],

                button = divAndButton[1];

            inviteElement.appendChild(div);

            //** event handler for cancelling selection */

            function cancel() {

                // remove invite box

                div.parentNode.removeChild(div);

                // restore initial event listeners

                sourcelines.addEventListener('click', lineSelectStart);

                sourcelines.removeEventListener('click', cancel);

                // remove styles on selected lines

                removeSelectedCSSClass();

            }

            // bind cancel event to click on <button>

            button.addEventListener('click', cancel);

            // as well as on an click on any source line

            sourcelines.addEventListener('click', cancel);

        }

        sourcelines.addEventListener('click', lineSelectEnd);

    }

    sourcelines.addEventListener('click', lineSelectStart);

}

//** return a <div id="followlines"> and inner cancel <button> elements */

function followlinesBox(targetUri, fromline, toline) {

    // <div id="followlines">

    var div = document.createElement('div');

    div.id = 'followlines';

    //   <div class="followlines-cancel">

    var buttonDiv = document.createElement('div');

    buttonDiv.classList.add('followlines-cancel');

    //     <button>x</button>

    var button = document.createElement('button');

    button.textContent = 'x';

    buttonDiv.appendChild(button);

    div.appendChild(buttonDiv);

    //   <div class="followlines-link">

    var aDiv = document.createElement('div');

    aDiv.classList.add('followlines-link');

    //     <a href="/log/<rev>/<file>?patch=&linerange=...">

    var a = document.createElement('a');

    var url = targetUri + '?patch=&linerange=' + fromline + ':' + toline;

    a.setAttribute('href', url);

    a.textContent = 'follow lines ' + fromline + ':' + toline;

    aDiv.appendChild(a);

    div.appendChild(aDiv);

    return [div, button];

}

document.addEventListener('DOMContentLoaded', installLineSelect, false);