app/src/content/embeds/d3-matrix.html

<div class="d3-matrix"></div>
<style>
  .d3-matrix {
    position: relative;
  }

  .d3-matrix .panels {
    display: flex;
    flex-wrap: wrap;
    gap: 16px;
    margin-bottom: 4px;
  }

  .d3-matrix .panel {
    flex: 1 1 320px;
    min-width: 280px;
  }

  .d3-matrix .panel__title {
    color: var(--text-color);
    font-size: 12px;
    line-height: 1.35;
    margin: 0 0 6px 0;
    font-weight: 600;
  }

  .d3-matrix .axis-label {
    fill: var(--text-color);
    font-size: 11px;
    font-weight: 700;
  }

  .d3-matrix .cell-border {
    stroke: var(--border-color);
    stroke-width: 1px;
    fill: none;
  }

  .d3-matrix .cell-text {
    fill: var(--muted-color);
    font-size: 11px;
    pointer-events: none;
  }

  .d3-matrix .chart-card {
    background: var(--surface-bg);
    border: 1px solid var(--border-color);
    border-radius: 10px;
    padding: 8px;
  }
</style>
<script>
  (() => {
    // Load D3 from CDN once
    const ensureD3 = (cb) => {
      if (window.d3 && typeof window.d3.select === 'function') return cb();
      let s = document.getElementById('d3-cdn-script');
      if (!s) {
        s = document.createElement('script');
        s.id = 'd3-cdn-script';
        s.src = 'https://cdn.jsdelivr.net/npm/d3@7/dist/d3.min.js';
        document.head.appendChild(s);
      }
      const onReady = () => { if (window.d3 && typeof window.d3.select === 'function') cb(); };
      s.addEventListener('load', onReady, { once: true });
      if (window.d3) onReady();
    };

    const bootstrap = () => {
      const scriptEl = document.currentScript;
      let container = scriptEl ? scriptEl.previousElementSibling : null;
      if (!(container && container.classList && container.classList.contains('d3-matrix'))) {
        const cs = Array.from(document.querySelectorAll('.d3-matrix')).filter(el => !(el.dataset && el.dataset.mounted === 'true'));
        container = cs[cs.length - 1] || null;
      }
      if (!container) return;
      if (container.dataset) {
        if (container.dataset.mounted === 'true') return;
        container.dataset.mounted = 'true';
      }

      // Tooltip (HTML, single instance inside container)
      container.style.position = container.style.position || 'relative';
      let tip = container.querySelector('.d3-tooltip');
      let tipInner;
      if (!tip) {
        tip = document.createElement('div');
        tip.className = 'd3-tooltip';
        Object.assign(tip.style, {
          position: 'absolute',
          top: '0px',
          left: '0px',
          transform: 'translate(-9999px, -9999px)',
          pointerEvents: 'none',
          padding: '8px 10px',
          borderRadius: '8px',
          fontSize: '12px',
          lineHeight: '1.35',
          border: '1px solid var(--border-color)',
          background: 'var(--surface-bg)',
          color: 'var(--text-color)',
          boxShadow: '0 4px 24px rgba(0,0,0,.18)',
          opacity: '0',
          transition: 'opacity .12s ease'
        });
        tipInner = document.createElement('div');
        tipInner.className = 'd3-tooltip__inner';
        tipInner.style.textAlign = 'left';
        tip.appendChild(tipInner);
        container.appendChild(tip);
      } else {
        tipInner = tip.querySelector('.d3-tooltip__inner') || tip;
      }

      // Panels container (two side-by-side matrices)
      const panels = document.createElement('div');
      panels.className = 'panels';
      const panelA = document.createElement('div');
      panelA.className = 'panel';
      const titleA = document.createElement('div'); titleA.className = 'panel__title'; titleA.textContent = 'Baseline (row-normalized %)';
      panelA.appendChild(titleA);
      const mountA = document.createElement('div'); panelA.appendChild(mountA);
      const panelB = document.createElement('div');
      panelB.className = 'panel';
      const titleB = document.createElement('div'); titleB.className = 'panel__title'; titleB.textContent = 'Delta (Improved − Baseline, pp)';
      panelB.appendChild(titleB);
      const mountB = document.createElement('div'); panelB.appendChild(mountB);
      panels.appendChild(panelA);
      panels.appendChild(panelB);
      container.appendChild(panels);

      // SVG scaffolding
      const cardA = document.createElement('div'); cardA.className = 'chart-card'; mountA.appendChild(cardA);
      const svgA = d3.select(cardA).append('svg').attr('width', '100%').style('display', 'block');
      const gRootA = svgA.append('g');
      const gCellsA = gRootA.append('g');
      const gAxesA = gRootA.append('g');
      const cardB = document.createElement('div'); cardB.className = 'chart-card'; mountB.appendChild(cardB);
      const svgB = d3.select(cardB).append('svg').attr('width', '100%').style('display', 'block');
      const gRootB = svgB.append('g');
      const gCellsB = gRootB.append('g');
      const gAxesB = gRootB.append('g');

      // Demo data (two distinct 10x10 matrices: Baseline vs Improved)
      // Rows / Columns are generic class labels
      const classes = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9'];
      const matrixA = [
        [90, 2, 1, 0, 0, 0, 1, 0, 5, 1],
        [3, 85, 5, 1, 0, 1, 2, 1, 1, 1],
        [1, 6, 70, 10, 4, 4, 1, 1, 1, 2],
        [0, 1, 8, 65, 10, 10, 2, 1, 1, 2],
        [0, 0, 2, 6, 83, 3, 1, 1, 3, 1],
        [0, 1, 2, 12, 4, 70, 5, 2, 2, 2],
        [1, 2, 1, 0, 1, 2, 88, 1, 3, 1],
        [0, 1, 1, 1, 1, 1, 2, 90, 1, 2],
        [6, 2, 2, 4, 6, 3, 3, 2, 70, 2],
        [1, 1, 1, 1, 2, 1, 1, 2, 1, 89]
      ];
      const matrixB = [
        [94, 1, 0, 0, 0, 0, 1, 0, 3, 1],
        [2, 90, 3, 1, 0, 0, 1, 1, 1, 1],
        [1, 4, 78, 7, 3, 3, 1, 1, 1, 1],
        [0, 1, 5, 74, 7, 8, 1, 1, 1, 2],
        [0, 0, 1, 4, 88, 2, 1, 1, 2, 1],
        [0, 1, 1, 9, 3, 78, 3, 1, 2, 2],
        [1, 1, 1, 0, 1, 1, 91, 1, 2, 1],
        [0, 1, 1, 1, 1, 1, 1, 92, 1, 1],
        [4, 1, 1, 3, 4, 2, 2, 2, 79, 2],
        [1, 1, 1, 1, 2, 1, 1, 1, 1, 90]
      ];

      // Colors: sequential palette via window.ColorPalettes with graceful fallback
      const getSequentialColors = (count) => {
        try {
          if (window.ColorPalettes && typeof window.ColorPalettes.getColors === 'function') {
            return window.ColorPalettes.getColors('sequential', count);
          }
        } catch (_) { }
        // Fallback: generate a monochrome scale using the primary color with varying opacity
        const arr = [];
        for (let i = 0; i < count; i++) arr.push('var(--primary-color)');
        return arr;
      };

      const palette = getSequentialColors(13);
      const getDivergingColors = (count) => {
        try {
          if (window.ColorPalettes && typeof window.ColorPalettes.getColors === 'function') {
            return window.ColorPalettes.getColors('diverging', count);
          }
        } catch (_) { }
        const steps = Math.max(3, count | 0);
        const arr = [];
        for (let i = 0; i < steps; i++) {
          const t = i / (steps - 1);
          const pct = Math.round(t * 100);
          arr.push(`color-mix(in srgb, #D64545 ${100 - pct}%, #3A7BD5 ${pct}%)`);
        }
        return arr;
      };

      let width = 800;
      let height = 480;
      const margin = { top: 36, right: 24, bottom: 26, left: 56 };

      function updateSize() {
        const isDark = document.documentElement.getAttribute('data-theme') === 'dark';
        width = container.clientWidth || 800;
        const gap = 16; // matches CSS .panels gap
        const minPanel = 320;
        const nCols = (width >= (minPanel * 2 + gap)) ? 2 : 1;
        const panelWidth = nCols === 2 ? Math.max(minPanel, Math.floor((width - gap) / 2)) : Math.max(minPanel, width);
        const base = Math.max(minPanel, Math.round(panelWidth * 0.92));
        height = base;
        // Responsive SVG: width 100%, height auto, preserve aspect via viewBox
        svgA
          .attr('viewBox', `0 0 ${panelWidth} ${height}`)
          .attr('preserveAspectRatio', 'xMidYMid meet')
          .style('width', '100%')
          .style('height', 'auto');
        svgB
          .attr('viewBox', `0 0 ${panelWidth} ${height}`)
          .attr('preserveAspectRatio', 'xMidYMid meet')
          .style('width', '100%')
          .style('height', 'auto');
        gRootA.attr('transform', `translate(${margin.left},${margin.top})`);
        gRootB.attr('transform', `translate(${margin.left},${margin.top})`);
        const innerWidth = panelWidth - margin.left - margin.right;
        const innerHeight = height - margin.top - margin.bottom;
        return { innerWidth, innerHeight, isDark };
      }

      function computeValues(normalization, matrix) {
        const n = classes.length;
        const totalsByRow = matrix.map(row => row.reduce((a, b) => a + b, 0));
        const flat = [];
        let minV = Infinity, maxV = -Infinity;
        for (let r = 0; r < n; r++) {
          for (let c = 0; c < n; c++) {
            const count = matrix[r][c];
            const value = normalization === 'row' ? (totalsByRow[r] ? count / totalsByRow[r] : 0) : count;
            if (value < minV) minV = value;
            if (value > maxV) maxV = value;
            flat.push({ r, c, count, value });
          }
        }
        return { data: flat, minV, maxV };
      }

      function getColorScale(values, minV, maxV) {
        // If ColorPalettes is available, use quantiles to enhance visual variation across the distribution
        const hasPalette = !(palette.length === 0);
        if (hasPalette && (window.ColorPalettes && typeof window.ColorPalettes.getColors === 'function')) {
          const scale = d3.scaleQuantile().domain(values).range(palette);
          return (v) => scale(v);
        }
        // Fallback: primary color with opacity mapped to normalized value
        const norm = d3.scaleLinear().domain([minV, maxV]).range([0.08, 0.9]).clamp(true);
        return (v) => `color-mix(in oklab, var(--primary-color) ${Math.round(norm(v) * 100)}%, var(--surface-bg))`;
      }

      // Compute a fixed readable text color from a CSS rgb()/rgba() string
      function chooseFixedReadableTextOnBg(bgCss) {
        try {
          const m = String(bgCss || '').match(/rgba?\(([^)]+)\)/);
          if (!m) return '#0e1116';
          const parts = m[1].split(',').map(s => parseFloat(s.trim()));
          const [r, g, b] = parts;
          // sRGB → relative luminance
          const srgb = [r, g, b].map(v => Math.max(0, Math.min(255, v)) / 255);
          const linear = srgb.map(c => (c <= 0.03928 ? c / 12.92 : Math.pow((c + 0.055) / 1.055, 2.4)));
          const L = 0.2126 * linear[0] + 0.7152 * linear[1] + 0.0722 * linear[2];
          // Threshold ~ 0.5 for readability; darker BG → white text, else near-black
          return L < 0.5 ? '#ffffff' : '#0e1116';
        } catch (_) { return '#0e1116'; }
      }

      function render() {
        const { innerWidth, innerHeight } = updateSize();
        const n = classes.length;
        const gridSize = Math.min(innerWidth, innerHeight);
        const cellSize = gridSize / n;

        const x = d3.scaleBand().domain(d3.range(n)).range([0, gridSize]).paddingInner(0.06);
        const y = d3.scaleBand().domain(d3.range(n)).range([0, gridSize]).paddingInner(0.06);

        // Panel A: Baseline (row-normalized)
        const dataA = computeValues('row', matrixA);
        const colorA = getColorScale(dataA.data.map(d => d.value), dataA.minV, dataA.maxV);

        gCellsA.selectAll('rect.cell-bg')
          .data([0])
          .join('rect')
          .attr('class', 'cell-bg')
          .attr('x', 0)
          .attr('y', 0)
          .attr('width', gridSize)
          .attr('height', gridSize)
          .attr('fill', 'none')
          .attr('stroke', 'var(--border-color)')
          .attr('stroke-width', 1);

        const cellsA = gCellsA.selectAll('g.cell')
          .data(dataA.data, d => `${d.r}-${d.c}-A`);

        const cellsEnterA = cellsA.enter()
          .append('g')
          .attr('class', 'cell');

        cellsEnterA.append('rect')
          .attr('rx', 2)
          .attr('ry', 2)
          .on('mousemove', (event, d) => {
            const [px, py] = d3.pointer(event, container);
            tipInner.innerHTML = `<strong>${classes[d.r]}</strong> → <strong>${classes[d.c]}</strong><br/>${(d.value * 100).toFixed(1)}% (${d.count})`;
            tip.style.transform = `translate(${px + 10}px, ${py + 10}px)`;
            tip.style.opacity = '1';
          })
          .on('mouseleave', () => {
            tip.style.opacity = '0';
          });

        cellsEnterA.append('text')
          .attr('class', 'cell-text')
          .attr('text-anchor', 'middle')
          .attr('dominant-baseline', 'middle');

        const cellsMergedA = cellsEnterA.merge(cellsA);

        cellsMergedA.select('text')
          .attr('x', d => x(d.c) + x.bandwidth() / 2)
          .attr('y', d => y(d.r) + y.bandwidth() / 2)
          .text(d => `${Math.round(d.value * 100)}`)
          .style('fill', function (d) {
            try {
              const rect = this && this.parentNode ? this.parentNode.querySelector('rect') : null;
              const bg = rect ? getComputedStyle(rect).fill : colorA(d.value);
              return chooseFixedReadableTextOnBg(bg);
            } catch (_) {
              return '#0e1116';
            }
          });

        cellsMergedA.select('rect')
          .attr('x', d => x(d.c))
          .attr('y', d => y(d.r))
          .attr('width', Math.max(1, x.bandwidth()))
          .attr('height', Math.max(1, y.bandwidth()))
          .attr('fill', d => colorA(d.value));

        cellsA.exit().remove();

        gAxesA.selectAll('*').remove();

        gAxesA.append('g')
          .selectAll('text')
          .data(classes)
          .join('text')
          .attr('class', 'axis-label')
          .attr('text-anchor', 'middle')
          .attr('x', (_, i) => x(i) + x.bandwidth() / 2)
          .attr('y', -8)
          .text(d => d);

        gAxesA.append('g')
          .selectAll('text')
          .data(classes)
          .join('text')
          .attr('class', 'axis-label')
          .attr('text-anchor', 'end')
          .attr('x', -8)
          .attr('y', (_, i) => y(i) + y.bandwidth() / 2)
          .attr('dominant-baseline', 'middle')
          .text(d => d);

        gAxesA.append('text')
          .attr('class', 'axis-label')
          .attr('text-anchor', 'middle')
          .attr('x', gridSize / 2)
          .attr('y', innerHeight + 20)
          .text('Columns');

        gAxesA.append('text')
          .attr('class', 'axis-label')
          .attr('text-anchor', 'middle')
          .attr('transform', `translate(${-40}, ${gridSize / 2}) rotate(-90)`)
          .text('Rows');

        // Panel B: Delta (Improved − Baseline), row-normalized differences in percentage points
        const dataB = computeValues('row', matrixB);
        const diverging = getDivergingColors(13);
        // Build delta values aligned to A's ordering
        const mapA = new Map(dataA.data.map(d => [d.r + '-' + d.c, d.value]));
        const delta = dataB.data.map(d => ({ r: d.r, c: d.c, count: d.count, value: (d.value - (mapA.get(d.r + '-' + d.c) || 0)) }));
        // Symmetric domain around 0 (in proportions), express later as pp in labels
        const maxAbsDelta = Math.max(0.01, d3.max(delta, d => Math.abs(d.value)) || 0.01);
        const colorB = d3.scaleQuantize().domain([-maxAbsDelta / 2, maxAbsDelta]).range(diverging);

        gCellsB.selectAll('rect.cell-bg')
          .data([0])
          .join('rect')
          .attr('class', 'cell-bg')
          .attr('x', 0)
          .attr('y', 0)
          .attr('width', gridSize)
          .attr('height', gridSize)
          .attr('fill', 'none')
          .attr('stroke', 'var(--border-color)')
          .attr('stroke-width', 1);

        const cellsB = gCellsB.selectAll('g.cell')
          .data(dataB.data, d => `${d.r}-${d.c}-B`);

        const cellsEnterB = cellsB.enter()
          .append('g')
          .attr('class', 'cell');

        cellsEnterB.append('rect')
          .attr('rx', 2)
          .attr('ry', 2)
          .on('mousemove', (event, d) => {
            const [px, py] = d3.pointer(event, container);
            const a = dataA.data.find(x => x.r === d.r && x.c === d.c);
            const b = dataB.data.find(x => x.r === d.r && x.c === d.c);
            const dv = ((b ? b.value : 0) - (a ? a.value : 0)) * 100;
            tipInner.innerHTML = `<strong>${classes[d.r]}</strong> → <strong>${classes[d.c]}</strong>` +
              `<br/>baseline ${(a ? a.value * 100 : 0).toFixed(1)}%` +
              `<br/>improved ${(b ? b.value * 100 : 0).toFixed(1)}%` +
              `<br/>delta ${dv.toFixed(1)} pp`;
            tip.style.transform = `translate(${px + 10}px, ${py + 10}px)`;
            tip.style.opacity = '1';
          })
          .on('mouseleave', () => {
            tip.style.opacity = '0';
          });

        cellsEnterB.append('text')
          .attr('class', 'cell-text')
          .attr('text-anchor', 'middle')
          .attr('dominant-baseline', 'middle');

        const cellsMergedB = cellsEnterB.merge(cellsB);

        cellsMergedB.select('rect')
          .attr('x', d => x(d.c))
          .attr('y', d => y(d.r))
          .attr('width', Math.max(1, x.bandwidth()))
          .attr('height', Math.max(1, y.bandwidth()))
          .attr('fill', d => colorB(delta.find(x => x.r === d.r && x.c === d.c).value));

        cellsMergedB.select('text')
          .attr('x', d => x(d.c) + x.bandwidth() / 2)
          .attr('y', d => y(d.r) + y.bandwidth() / 2)
          .text(d => {
            const dv = delta.find(x => x.r === d.r && x.c === d.c).value; return `${Math.round(dv * 100)}`;
          })
          .style('fill', function (d) {
            try {
              const rect = this && this.parentNode ? this.parentNode.querySelector('rect') : null;
              const dv = delta.find(x => x.r === d.r && x.c === d.c).value;
              const bg = rect ? getComputedStyle(rect).fill : colorB(dv);
              return chooseFixedReadableTextOnBg(bg);
            } catch (_) {
              return '#0e1116';
            }
          });

        cellsB.exit().remove();

        gAxesB.selectAll('*').remove();

        gAxesB.append('g')
          .selectAll('text')
          .data(classes)
          .join('text')
          .attr('class', 'axis-label')
          .attr('text-anchor', 'middle')
          .attr('x', (_, i) => x(i) + x.bandwidth() / 2)
          .attr('y', -8)
          .text(d => d);

        gAxesB.append('g')
          .selectAll('text')
          .data(classes)
          .join('text')
          .attr('class', 'axis-label')
          .attr('text-anchor', 'end')
          .attr('x', -8)
          .attr('y', (_, i) => y(i) + y.bandwidth() / 2)
          .attr('dominant-baseline', 'middle')
          .text(d => d);

        gAxesB.append('text')
          .attr('class', 'axis-label')
          .attr('text-anchor', 'middle')
          .attr('x', gridSize / 2)
          .attr('y', innerHeight + 20)
          .text('Columns');

        gAxesB.append('text')
          .attr('class', 'axis-label')
          .attr('text-anchor', 'middle')
          .attr('transform', `translate(${-40}, ${gridSize / 2}) rotate(-90)`)
          .text('Rows');
      }

      // Initial render + resize handling
      render();
      const rerender = () => render();
      if (window.ResizeObserver) {
        const ro = new ResizeObserver(() => rerender());
        ro.observe(container);
      } else {
        window.addEventListener('resize', rerender);
      }
    };

    if (document.readyState === 'loading') {
      document.addEventListener('DOMContentLoaded', () => ensureD3(bootstrap), { once: true });
    } else {
      ensureD3(bootstrap);
    }
  })();
</script>