import { bar, probColor } from './scoring.js';

// Locale-independent thousands grouping, matching the Python app's f"{n:,}".
export const formatNumber = (n) => n.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ',');

const escapeHtml = (s) =>
  s.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;');

export function highlightHtml(text, spans, scores) {
  const parts = ['<div class="aid-highlight">'];
  let cursor = 0;
  spans.forEach((span, i) => {
    parts.push(escapeHtml(text.slice(cursor, span.start)).replace(/\n/g, '<br>'));
    const score = scores[i];
    parts.push(
      `<span title="P(AI) = ${score.toFixed(3)}" data-p="${score.toFixed(3)}" ` +
        `style="background:${probColor(score)}; border-radius:3px; padding:1px 2px;">` +
        `${escapeHtml(span.sentence)}</span>`,
    );
    cursor = span.end;
  });
  parts.push(escapeHtml(text.slice(cursor)).replace(/\n/g, '<br>'));
  parts.push('</div>');
  return parts.join('');
}

export function reportMarkdown(
  result,
  { threshold, aggregation, modelRepo, device, dtype, chars },
) {
  const label = aggregation === 'max' ? 'Max' : 'Mean';
  const note =
    result.windows === 1
      ? 'one window, so mean and max are identical'
      : aggregation === 'max'
        ? 'highest-scoring window'
        : `average across ${result.windows} windows`;
  const scores = result.sentences.map((s) => s.score);
  const atOrAbove = scores.filter((s) => s >= threshold).length;
  return [
    '# AI Text Detection Report',
    '',
    `**Model:** \`${modelRepo}\``,
    `**Backend:** ${dtype} ONNX on ${device}`,
    `**Characters:** ${formatNumber(chars)}  |  **Sentences:** ${scores.length}  |  **Windows scored:** ${result.windows}`,
    `**Aggregation:** ${label} (${note})  |  **Threshold:** ${threshold.toFixed(2)}`,
    '',
    '## Verdict',
    '',
    `### ${result.verdict}`,
    '',
    `\`${bar(result.score)}\` **score = ${result.score.toFixed(3)}** (${result.aboveThreshold ? 'above' : 'below'} ${threshold.toFixed(2)})`,
    '',
    '| Metric | Value |',
    '| --- | --- |',
    `| Score (${label} of windows) | ${result.score.toFixed(3)} |`,
    `| Mean of windows | ${result.scoreMean.toFixed(3)} |`,
    `| Max of windows | ${result.scoreMax.toFixed(3)} |`,
    `| Sentences at or above threshold | ${atOrAbove}/${scores.length} |`,
    `| Max sentence score | ${Math.max(...scores).toFixed(3)} |`,
    `| Min sentence score | ${Math.min(...scores).toFixed(3)} |`,
    `| Decision threshold | ${threshold.toFixed(2)} |`,
    '',
    '## Sentence-level breakdown',
    '',
    ...result.sentences.map((s) => {
      const snippet = s.sentence.length <= 160 ? s.sentence : `${s.sentence.slice(0, 157)}...`;
      return `- \`${s.score.toFixed(3)}\` \`${bar(s.score, 12)}\` ${snippet}`;
    }),
    '',
    '## Most AI-like passages',
    '',
    ...[...result.sentences]
      .sort((a, b) => b.score - a.score)
      .slice(0, 5)
      .map((s) => `> **${s.score.toFixed(3)}** - ${s.sentence}`),
    '',
    '---',
    '',
    '_Scores come from an ONNX model running in your browser, and nothing is uploaded. They are probabilities, not proof: the model card warns against using this detector as the sole basis for high-stakes decisions. The threshold is a display choice, only 0.50 comes from the model card, and no false-positive rate is claimed for any other value._',
  ].join('\n');
}