// ==========================================
// Mermaid Diagram Renderer — Browser Extension
// ==========================================
// Renders ```mermaid code blocks as SVG diagrams.
// Loads mermaid.js dynamically on first use.
//
// Install: Admin → Extensions → paste manifest + this script.
// ==========================================

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

    _mermaidReady: false,
    _mermaidLoading: null,
    _renderQueue: [],

    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="${id}">
                        <div class="mermaid-diagram" data-mermaid-src="${encodeURIComponent(code.trim())}">
                            <div class="mermaid-loading">
                                <span class="mermaid-spinner"></span> Rendering diagram…
                            </div>
                        </div>
                        <details class="mermaid-source">
                            <summary>📊 View source</summary>
                            <pre><code class="language-mermaid">${self._escapeHtml(code.trim())}</code></pre>
                        </details>
                    </div>
                `;
            }
        });

        // ── Post renderer: find placeholders, render with mermaid.js ──
        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 => {
                    // Skip already-rendered diagrams
                    if (el.dataset.rendered) return;
                    el.dataset.rendered = 'pending';
                    self._renderDiagram(el);
                });
            }
        });

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

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

        try {
            await this._loadMermaid();

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

            // Styling handled by .mermaid-diagram svg in CSS
            const svgEl = el.querySelector('svg');
            if (svgEl) {
                svgEl.removeAttribute('height');
            }
        } catch (e) {
            el.innerHTML = `
                <div class="mermaid-error">
                    <strong>Diagram error:</strong> ${this._escapeHtml(e.message || String(e))}
                </div>
            `;
            el.dataset.rendered = 'error';
        }
    },

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

        this._mermaidLoading = new Promise((resolve, reject) => {
            // Check if already loaded (e.g. by another script)
            if (typeof mermaid !== 'undefined') {
                this._initMermaid();
                this._mermaidReady = true;
                resolve();
                return;
            }

            // Try local vendor first, fall back to CDN
            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 = () => {
                // Local failed — try CDN
                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;

        // Detect dark mode
        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',
        });
    },

    _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;
}
.mermaid-diagram {
    padding: 16px; text-align: center; min-height: 60px;
    max-height: 600px; overflow: auto;
}
.mermaid-diagram svg {
    max-width: 100%; max-height: 560px;
    height: auto; width: auto;
}
.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;
}
.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;
}
.mermaid-source summary:hover { color: var(--text-2); }
.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();
    }
});