// ==========================================
// Mermaid Diagram Renderer — Browser Extension
// ==========================================
// Renders ```mermaid code blocks as interactive SVG diagrams.
// Features: zoom/pan viewport, SVG/PNG export, source copy.
// Loads mermaid.js dynamically on first use.
// ==========================================

Extensions.register({
    id: 'mermaid-renderer',

    _mermaidReady: false,
    _mermaidLoading: null,

    async init(ctx) {
        const self = this;

        // ── Inject styles ──
        this._injectStyles();

        // ── Block renderer: match ```mermaid, output placeholder ──
        ctx.renderers.register('mermaid', {
            type: 'block',
            pattern: 'mermaid',
            priority: 10,
            render(lang, code, container) {
                const id = 'mmd-' + Math.random().toString(36).slice(2, 9);
                container.innerHTML = `
                    <div class="mermaid-block" data-mermaid-id="${id}">
                        <div class="mermaid-toolbar">
                            <span class="mermaid-title">📊 Diagram</span>
                            <span class="mermaid-zoom-label" data-zoom-label="${id}">100%</span>
                            <div class="mermaid-toolbar-btns">
                                <button class="mmd-btn" data-action="zoom-in" data-target="${id}" title="Zoom in">+</button>
                                <button class="mmd-btn" data-action="zoom-out" data-target="${id}" title="Zoom out">−</button>
                                <button class="mmd-btn" data-action="zoom-fit" data-target="${id}" title="Fit to view">⊡</button>
                                <button class="mmd-btn" data-action="zoom-reset" data-target="${id}" title="Reset zoom">1:1</button>
                                <span class="mmd-sep"></span>
                                <button class="mmd-btn" data-action="export-svg" data-target="${id}" title="Download SVG">SVG</button>
                                <button class="mmd-btn" data-action="export-png" data-target="${id}" title="Download PNG">PNG</button>
                            </div>
                        </div>
                        <div class="mermaid-viewport" data-viewport="${id}">
                            <div class="mermaid-diagram" data-mermaid-src="${encodeURIComponent(code.trim())}" data-diagram="${id}">
                                <div class="mermaid-loading">
                                    <span class="mermaid-spinner"></span> Rendering diagram…
                                </div>
                            </div>
                        </div>
                        <details class="mermaid-source">
                            <summary>
                                <span>📋 View source</span>
                                <button class="mmd-btn mmd-copy-src" data-action="copy-src" data-target="${id}" title="Copy source" onclick="event.stopPropagation()">Copy</button>
                            </summary>
                            <pre><code class="language-mermaid" data-source="${id}">${self._escapeHtml(code.trim())}</code></pre>
                        </details>
                    </div>
                `;
            }
        });

        // ── Post renderer: render diagrams + wire interactivity ──
        ctx.renderers.register('mermaid-post', {
            type: 'post',
            priority: 10,
            render(container) {
                const diagrams = container.querySelectorAll('.mermaid-diagram[data-mermaid-src]');
                if (diagrams.length === 0) return;

                diagrams.forEach(el => {
                    if (el.dataset.rendered) return;
                    el.dataset.rendered = 'pending';
                    self._renderDiagram(el);
                });

                // Wire toolbar buttons (event delegation on the container)
                self._wireToolbar(container);
            }
        });

        // Pre-load mermaid library
        this._loadMermaid();
    },

    // ── Zoom/Pan State ──────────────────────

    _getState(id) {
        const vp = document.querySelector(`[data-viewport="${id}"]`);
        if (!vp) return null;
        if (!vp._mmdState) {
            vp._mmdState = { scale: 1, panX: 0, panY: 0, dragging: false, startX: 0, startY: 0 };
        }
        return vp._mmdState;
    },

    _applyTransform(id) {
        const state = this._getState(id);
        if (!state) return;
        const diagram = document.querySelector(`[data-diagram="${id}"]`);
        if (!diagram) return;
        diagram.style.transform = `translate(${state.panX}px, ${state.panY}px) scale(${state.scale})`;
        const label = document.querySelector(`[data-zoom-label="${id}"]`);
        if (label) label.textContent = Math.round(state.scale * 100) + '%';
    },

    _zoom(id, delta) {
        const state = this._getState(id);
        if (!state) return;
        state.scale = Math.max(0.1, Math.min(5, state.scale * (1 + delta)));
        this._applyTransform(id);
    },

    _zoomReset(id) {
        const state = this._getState(id);
        if (!state) return;
        state.scale = 1; state.panX = 0; state.panY = 0;
        this._applyTransform(id);
    },

    _zoomFit(id) {
        const state = this._getState(id);
        if (!state) return;
        const vp = document.querySelector(`[data-viewport="${id}"]`);
        const diagram = document.querySelector(`[data-diagram="${id}"]`);
        const svg = diagram?.querySelector('svg');
        if (!vp || !svg) return;

        // Reset to measure natural size
        state.scale = 1; state.panX = 0; state.panY = 0;
        diagram.style.transform = '';

        requestAnimationFrame(() => {
            const vpRect = vp.getBoundingClientRect();
            const svgRect = svg.getBoundingClientRect();
            if (svgRect.width === 0 || svgRect.height === 0) return;

            const scaleX = (vpRect.width - 32) / svgRect.width;
            const scaleY = (vpRect.height - 32) / svgRect.height;
            state.scale = Math.min(scaleX, scaleY, 2); // Cap at 2x
            this._applyTransform(id);
        });
    },

    // ── Toolbar Wiring ──────────────────────

    _wireToolbar(container) {
        const self = this;

        // Skip if already wired
        if (container._mmdWired) return;
        container._mmdWired = true;

        // Button clicks (delegation)
        container.addEventListener('click', (e) => {
            const btn = e.target.closest('[data-action]');
            if (!btn) return;
            const action = btn.dataset.action;
            const id = btn.dataset.target;
            if (!id) return;

            switch (action) {
                case 'zoom-in':    self._zoom(id, 0.25); break;
                case 'zoom-out':   self._zoom(id, -0.2); break;
                case 'zoom-reset': self._zoomReset(id); break;
                case 'zoom-fit':   self._zoomFit(id); break;
                case 'export-svg': self._exportSVG(id); break;
                case 'export-png': self._exportPNG(id); break;
                case 'copy-src':   self._copySource(id, btn); break;
            }
        });

        // Wire each viewport for mouse/touch interaction
        container.querySelectorAll('.mermaid-viewport').forEach(vp => {
            if (vp._mmdWired) return;
            vp._mmdWired = true;
            const id = vp.dataset.viewport;

            // Mouse wheel zoom
            vp.addEventListener('wheel', (e) => {
                e.preventDefault();
                const delta = e.deltaY > 0 ? -0.1 : 0.1;
                self._zoom(id, delta);
            }, { passive: false });

            // Pan: mousedown → mousemove → mouseup
            vp.addEventListener('mousedown', (e) => {
                if (e.button !== 0) return;
                const state = self._getState(id);
                if (!state) return;
                state.dragging = true;
                state.startX = e.clientX - state.panX;
                state.startY = e.clientY - state.panY;
                vp.classList.add('mmd-grabbing');
                e.preventDefault();
            });

            vp.addEventListener('mousemove', (e) => {
                const state = self._getState(id);
                if (!state?.dragging) return;
                state.panX = e.clientX - state.startX;
                state.panY = e.clientY - state.startY;
                self._applyTransform(id);
            });

            const endDrag = () => {
                const state = self._getState(id);
                if (!state) return;
                state.dragging = false;
                vp.classList.remove('mmd-grabbing');
            };
            vp.addEventListener('mouseup', endDrag);
            vp.addEventListener('mouseleave', endDrag);

            // Touch: single-finger pan, two-finger pinch zoom
            let lastTouchDist = 0;
            vp.addEventListener('touchstart', (e) => {
                const state = self._getState(id);
                if (!state) return;
                if (e.touches.length === 1) {
                    state.dragging = true;
                    state.startX = e.touches[0].clientX - state.panX;
                    state.startY = e.touches[0].clientY - state.panY;
                } else if (e.touches.length === 2) {
                    lastTouchDist = Math.hypot(
                        e.touches[0].clientX - e.touches[1].clientX,
                        e.touches[0].clientY - e.touches[1].clientY
                    );
                }
            }, { passive: true });

            vp.addEventListener('touchmove', (e) => {
                const state = self._getState(id);
                if (!state) return;
                if (e.touches.length === 1 && state.dragging) {
                    state.panX = e.touches[0].clientX - state.startX;
                    state.panY = e.touches[0].clientY - state.startY;
                    self._applyTransform(id);
                    e.preventDefault();
                } else if (e.touches.length === 2) {
                    const dist = Math.hypot(
                        e.touches[0].clientX - e.touches[1].clientX,
                        e.touches[0].clientY - e.touches[1].clientY
                    );
                    if (lastTouchDist > 0) {
                        self._zoom(id, (dist - lastTouchDist) / lastTouchDist);
                    }
                    lastTouchDist = dist;
                    e.preventDefault();
                }
            }, { passive: false });

            vp.addEventListener('touchend', () => {
                const state = self._getState(id);
                if (state) state.dragging = false;
                lastTouchDist = 0;
            }, { passive: true });
        });
    },

    // ── Export ───────────────────────────────

    _exportSVG(id) {
        const diagram = document.querySelector(`[data-diagram="${id}"]`);
        const svg = diagram?.querySelector('svg');
        if (!svg) return;

        const clone = svg.cloneNode(true);
        clone.setAttribute('xmlns', 'http://www.w3.org/2000/svg');
        const blob = new Blob([clone.outerHTML], { type: 'image/svg+xml' });
        this._download(blob, `diagram-${id}.svg`);
    },

    _exportPNG(id) {
        const diagram = document.querySelector(`[data-diagram="${id}"]`);
        const svg = diagram?.querySelector('svg');
        if (!svg) return;

        const clone = svg.cloneNode(true);
        clone.setAttribute('xmlns', 'http://www.w3.org/2000/svg');

        const svgData = new XMLSerializer().serializeToString(clone);
        const svgBlob = new Blob([svgData], { type: 'image/svg+xml;charset=utf-8' });
        const url = URL.createObjectURL(svgBlob);
        const self = this;

        const img = new Image();
        img.onload = () => {
            const scale = 2; // 2x for retina
            const canvas = document.createElement('canvas');
            canvas.width = img.naturalWidth * scale;
            canvas.height = img.naturalHeight * scale;
            const ctx = canvas.getContext('2d');
            ctx.scale(scale, scale);
            ctx.drawImage(img, 0, 0);
            URL.revokeObjectURL(url);

            canvas.toBlob((blob) => {
                if (blob) self._download(blob, `diagram-${id}.png`);
            }, 'image/png');
        };
        img.onerror = () => {
            URL.revokeObjectURL(url);
            console.error('[Mermaid] PNG export failed');
        };
        img.src = url;
    },

    _download(blob, filename) {
        const a = document.createElement('a');
        a.href = URL.createObjectURL(blob);
        a.download = filename;
        document.body.appendChild(a);
        a.click();
        document.body.removeChild(a);
        setTimeout(() => URL.revokeObjectURL(a.href), 1000);
    },

    _copySource(id, btn) {
        const code = document.querySelector(`[data-source="${id}"]`);
        if (!code) return;
        navigator.clipboard.writeText(code.textContent).then(() => {
            const orig = btn.textContent;
            btn.textContent = '✓';
            setTimeout(() => { btn.textContent = orig; }, 1500);
        });
    },

    // ── Diagram Rendering ───────────────────

    async _renderDiagram(el) {
        const code = decodeURIComponent(el.dataset.mermaidSrc);

        try {
            await this._loadMermaid();

            const svgId = 'mmd-svg-' + Math.random().toString(36).slice(2, 9);
            const { svg } = await mermaid.render(svgId, code);
            el.innerHTML = svg;
            el.dataset.rendered = 'true';

            const svgEl = el.querySelector('svg');
            if (svgEl) {
                svgEl.removeAttribute('height');
                svgEl.style.maxWidth = 'none'; // Viewport handles sizing
            }
        } catch (e) {
            el.innerHTML = `
                <div class="mermaid-error">
                    <strong>Diagram error:</strong> ${this._escapeHtml(e.message || String(e))}
                </div>
            `;
            el.dataset.rendered = 'error';
        }
    },

    // ── Mermaid Library Loading ──────────────

    _loadMermaid() {
        if (this._mermaidReady) return Promise.resolve();
        if (this._mermaidLoading) return this._mermaidLoading;

        this._mermaidLoading = new Promise((resolve, reject) => {
            if (typeof mermaid !== 'undefined') {
                this._initMermaid();
                this._mermaidReady = true;
                resolve();
                return;
            }

            const base = (window.__BASE__ || '');
            const localSrc = `${base}/vendor/mermaid/mermaid.min.js`;
            const cdnSrc = 'https://cdn.jsdelivr.net/npm/mermaid@11/dist/mermaid.min.js';

            const script = document.createElement('script');
            script.src = localSrc;
            script.onload = () => {
                this._initMermaid();
                this._mermaidReady = true;
                resolve();
            };
            script.onerror = () => {
                console.warn('[Mermaid] Local vendor not found, trying CDN');
                const cdn = document.createElement('script');
                cdn.src = cdnSrc;
                cdn.onload = () => {
                    this._initMermaid();
                    this._mermaidReady = true;
                    resolve();
                };
                cdn.onerror = () => {
                    console.error('[Mermaid] Failed to load from both local and CDN');
                    reject(new Error('Failed to load mermaid.js'));
                };
                document.head.appendChild(cdn);
            };
            document.head.appendChild(script);
        });

        return this._mermaidLoading;
    },

    _initMermaid() {
        if (typeof mermaid === 'undefined') return;

        const isDark = document.body.classList.contains('dark-theme') ||
                       window.matchMedia('(prefers-color-scheme: dark)').matches;

        mermaid.initialize({
            startOnLoad: false,
            theme: isDark ? 'dark' : 'default',
            securityLevel: 'strict',
            fontFamily: 'inherit',
            logLevel: 'error',
        });
    },

    // ── Styles ──────────────────────────────

    _injectStyles() {
        if (document.getElementById('ext-style-mermaid-renderer')) return;
        const style = document.createElement('style');
        style.id = 'ext-style-mermaid-renderer';
        style.textContent = `
.mermaid-block {
    background: var(--bg-2); border: 1px solid var(--border);
    border-radius: 8px; overflow: hidden; margin: 12px 0;
}

/* Toolbar */
.mermaid-toolbar {
    display: flex; align-items: center; gap: 6px;
    padding: 4px 10px; border-bottom: 1px solid var(--border);
    font-size: 12px; color: var(--text-3); flex-wrap: wrap;
}
.mermaid-title { font-weight: 600; color: var(--text-2); margin-right: auto; }
.mermaid-zoom-label {
    font-family: var(--mono); font-size: 11px; min-width: 36px;
    text-align: center; color: var(--text-3);
}
.mermaid-toolbar-btns { display: flex; gap: 2px; align-items: center; }
.mmd-btn {
    background: none; border: 1px solid var(--border); border-radius: 4px;
    padding: 1px 7px; font-size: 11px; cursor: pointer;
    color: var(--text-3); font-family: var(--mono); line-height: 1.6;
}
.mmd-btn:hover { color: var(--text-1); border-color: var(--text-3); background: var(--bg-3); }
.mmd-sep { width: 1px; height: 16px; background: var(--border); margin: 0 4px; }

/* Viewport: zoom/pan container */
.mermaid-viewport {
    overflow: hidden; position: relative;
    min-height: 80px; max-height: 600px;
    cursor: grab; user-select: none;
}
.mermaid-viewport.mmd-grabbing { cursor: grabbing; }

/* Diagram: the transform target */
.mermaid-diagram {
    padding: 16px; text-align: center; min-height: 60px;
    transform-origin: center center;
    will-change: transform;
}
.mermaid-diagram svg { height: auto; }

/* Loading / Error */
.mermaid-loading {
    color: var(--text-3); font-size: 13px; padding: 20px;
    display: flex; align-items: center; justify-content: center; gap: 8px;
}
.mermaid-spinner {
    display: inline-block; width: 14px; height: 14px;
    border: 2px solid var(--border); border-top-color: var(--accent);
    border-radius: 50%; animation: mmd-spin 0.8s linear infinite;
}
@keyframes mmd-spin { to { transform: rotate(360deg); } }
.mermaid-error {
    color: var(--error, #e74c3c); background: var(--bg-3, rgba(231,76,60,0.1));
    padding: 12px 16px; border-radius: 4px; font-size: 13px;
    font-family: var(--mono); white-space: pre-wrap;
}

/* Source panel */
.mermaid-source { border-top: 1px solid var(--border); font-size: 12px; }
.mermaid-source summary {
    padding: 6px 12px; cursor: pointer; color: var(--text-3);
    user-select: none; display: flex; align-items: center; gap: 8px;
}
.mermaid-source summary:hover { color: var(--text-2); }
.mermaid-source summary span { flex: 1; }
.mmd-copy-src { font-size: 11px; }
.mermaid-source pre {
    margin: 0; border-radius: 0; border: none;
    max-height: 200px; overflow: auto;
}`;
        document.head.appendChild(style);
    },

    _escapeHtml(str) {
        const div = document.createElement('div');
        div.textContent = str;
        return div.innerHTML;
    },

    destroy() {
        document.getElementById('ext-style-mermaid-renderer')?.remove();
    }
});