// nodes.js — node elements and their content.
//
// Content HTML is cached by *content*, not by node id. That is what makes undo
// free: undoing a text edit restores the previous string, whose rendered HTML
// is already in the cache, so no request is made. Keying by node id would turn
// every Ctrl+Z into a render round trip.
//
// The server pre-renders every text and file node and ships the result with the
// page, so a canvas opens with the cache already warm and issues no content
// requests at all until something is edited.
window.Canvas = window.Canvas || {};

Canvas.Nodes = (function () {
    var Doc = Canvas.Doc;
    var Select = Canvas.Select;

    var nodeLayer = null;
    var groupLayer = null;
    var els = {};        // node id -> element
    var cache = {};      // content key -> rendered HTML
    var inflight = {};   // content key -> Promise

    var SIDES = ['top', 'right', 'bottom', 'left'];
    var CORNERS = ['nw', 'ne', 'se', 'sw'];

    // SEP separates the fields of a content key. A NUL can never appear in a
    // path or in markdown, so no two different nodes can collide on one key.
    var SEP = ' ';

    // contentKey identifies what a node displays. Null for nodes the browser
    // builds itself (link cards, groups), which never need the server.
    function contentKey(n) {
        if (n.type === 'text') return 't' + SEP + (n.text || '');
        if (n.type === 'file') return 'f' + SEP + (n.file || '') + SEP + (n.subpath || '');
        return null;
    }

    // decorate applies the same link treatment page content gets: a favicon in
    // front of external links, and a new tab so following one does not throw
    // away unsaved canvas state.
    function decorate(root) {
        root.querySelectorAll('a[href^="http"]').forEach(function (a) {
            a.target = '_blank';
            a.rel = 'noopener';
            if (a.querySelector('img.link-favicon')) return;
            var img = document.createElement('img');
            img.className = 'link-favicon';
            img.src = 'https://icons.duckduckgo.com/ip3/' + new URL(a.href).hostname + '.ico';
            img.width = 16;
            img.height = 16;
            img.alt = '';
            a.prepend(img);
        });
    }

    function fetchContent(n, key) {
        if (inflight[key]) return inflight[key];
        var body = new URLSearchParams();
        body.set('type', n.type);
        if (n.type === 'file') {
            body.set('file', n.file || '');
            body.set('subpath', n.subpath || '');
        } else {
            body.set('text', n.text || '');
        }
        var p = fetch('/_canvas/render', {
            method: 'POST',
            credentials: 'same-origin',
            headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
            body: body.toString()
        }).then(function (r) {
            if (!r.ok) throw new Error('HTTP ' + r.status);
            return r.text();
        }).then(function (html) {
            cache[key] = html;
            delete inflight[key];
            return html;
        }).catch(function (err) {
            delete inflight[key];
            throw err;
        });
        inflight[key] = p;
        return p;
    }

    function applyContent(el, n) {
        var body = el.querySelector('.canvas-node-body');
        if (!body) return;
        var key = contentKey(n);

        if (key === null) {
            buildStatic(body, n);
            return;
        }
        if (body.dataset.key === key) return;
        body.dataset.key = key;

        if (Object.prototype.hasOwnProperty.call(cache, key)) {
            body.innerHTML = cache[key];
            body.classList.remove('canvas-broken');
            decorate(body);
            return;
        }
        body.textContent = '...';
        fetchContent(n, key).then(function (html) {
            // The node may have been edited again (or deleted) while the render
            // was in flight; only the response matching the current content wins.
            if (body.dataset.key !== key) return;
            body.innerHTML = html;
            body.classList.remove('canvas-broken');
            decorate(body);
        }).catch(function () {
            if (body.dataset.key !== key) return;
            body.textContent = 'could not render this node';
            body.classList.add('canvas-broken');
        });
    }

    // buildStatic renders the node types that need no server round trip: for
    // now just the link card (favicon, host, url).
    function buildStatic(body, n) {
        if (n.type !== 'link') { body.textContent = ''; return; }
        if (body.dataset.url === n.url) return;
        body.dataset.url = n.url;
        body.textContent = '';

        var host = '';
        try { host = new URL(n.url).hostname; } catch (e) { host = n.url; }

        var a = document.createElement('a');
        a.href = n.url;
        a.target = '_blank';
        a.rel = 'noopener';
        a.className = 'canvas-link-card';

        var img = document.createElement('img');
        img.className = 'link-favicon';
        img.src = 'https://icons.duckduckgo.com/ip3/' + host + '.ico';
        img.width = 32;
        img.height = 32;
        img.alt = '';

        var hostEl = document.createElement('span');
        hostEl.className = 'canvas-link-host';
        hostEl.textContent = host;

        var urlEl = document.createElement('span');
        urlEl.className = 'canvas-link-url truncate';
        urlEl.textContent = n.url;

        a.appendChild(img);
        a.appendChild(hostEl);
        a.appendChild(urlEl);
        body.appendChild(a);
    }

    function createEl(n) {
        var el = document.createElement('div');
        el.className = 'canvas-node canvas-node-' + n.type;
        el.dataset.id = n.id;

        if (n.type === 'file') {
            var title = document.createElement('div');
            title.className = 'canvas-node-title truncate';
            el.appendChild(title);
        }
        if (n.type === 'group') {
            var label = document.createElement('div');
            label.className = 'canvas-group-label truncate';
            el.appendChild(label);
        }

        var body = document.createElement('div');
        body.className = 'canvas-node-body content';
        el.appendChild(body);

        SIDES.forEach(function (side) {
            var port = document.createElement('span');
            port.className = 'canvas-port canvas-port-' + side;
            port.dataset.side = side;
            el.appendChild(port);
        });
        CORNERS.forEach(function (corner) {
            var handle = document.createElement('span');
            handle.className = 'canvas-handle canvas-handle-' + corner;
            handle.dataset.corner = corner;
            el.appendChild(handle);
        });
        return el;
    }

    function applyGeom(el, n) {
        el.style.left = n.x + 'px';
        el.style.top = n.y + 'px';
        el.style.width = n.width + 'px';
        el.style.height = n.height + 'px';
    }

    function applyColor(el, n) {
        var c = n.color || '';
        if (c && c.charAt(0) === '#') {
            el.dataset.color = 'custom';
            el.style.setProperty('--node-accent', c);
        } else if (c) {
            el.dataset.color = c;
            el.style.removeProperty('--node-accent');
        } else {
            delete el.dataset.color;
            el.style.removeProperty('--node-accent');
        }
    }

    function applyMeta(el, n) {
        if (n.type === 'file') {
            var title = el.querySelector('.canvas-node-title');
            if (title) {
                var name = (n.file || '').split('/').filter(Boolean).pop() || n.file || '';
                title.textContent = name + (n.subpath || '');
                title.title = (n.file || '') + (n.subpath || '');
            }
        }
        if (n.type === 'group') {
            var label = el.querySelector('.canvas-group-label');
            if (label) label.textContent = n.label || '';
            if (n.background) {
                // Reuse the thumbnail endpoint rather than the original: a group
                // background is decoration and never needs full resolution.
                el.style.backgroundImage = 'url("/_thumb' + encodeURI(n.background) + '?w=1200")';
                el.dataset.bgStyle = n.backgroundStyle || 'cover';
            } else {
                el.style.removeProperty('background-image');
                delete el.dataset.bgStyle;
            }
        }
    }

    return {
        init: function (nodeLayerEl, groupLayerEl) {
            nodeLayer = nodeLayerEl;
            groupLayer = groupLayerEl;
        },

        // seed primes the cache from the server's pre-rendered payload so the
        // first paint needs no requests.
        seed: function (rendered, doc) {
            if (!rendered) return;
            doc.nodes.forEach(function (n) {
                var key = contentKey(n);
                if (key !== null && Object.prototype.hasOwnProperty.call(rendered, n.id)) {
                    cache[key] = rendered[n.id];
                }
            });
        },

        el: function (id) { return els[id] || null; },
        contentKey: contentKey,

        // render reconciles the DOM against the document: create what is new,
        // update what changed, drop what is gone. Groups live in their own
        // layer so they always paint behind the edges and the other nodes.
        render: function () {
            var seen = {};
            Doc.nodes().forEach(function (n) {
                seen[n.id] = true;
                var el = els[n.id];
                // A type change means a different element shape; rebuild rather
                // than try to morph one into the other.
                if (el && el.className.indexOf('canvas-node-' + n.type) === -1) {
                    el.remove();
                    el = null;
                }
                if (!el) {
                    el = createEl(n);
                    els[n.id] = el;
                    (n.type === 'group' ? groupLayer : nodeLayer).appendChild(el);
                }
                applyGeom(el, n);
                applyColor(el, n);
                applyMeta(el, n);
                applyContent(el, n);
                el.classList.toggle('is-selected', Select.hasNode(n.id));
            });
            Object.keys(els).forEach(function (id) {
                if (seen[id]) return;
                els[id].remove();
                delete els[id];
            });
        },

        // syncGeom writes one node's geometry straight to its element. Used on
        // every frame of a drag or resize, where a full render would be wasted
        // work (nothing else has changed).
        syncGeom: function (id) {
            var n = Doc.node(id);
            var el = els[id];
            if (n && el) applyGeom(el, n);
        },

        syncSelection: function () {
            Object.keys(els).forEach(function (id) {
                els[id].classList.toggle('is-selected', Select.hasNode(id));
            });
        }
    };
})();