Create a colour based on note name

autoCover.js

module.exports = async (params) => {
  const { app } = params;
  const file = app.workspace.getActiveFile();
  if (!file) return;

  // Only run for Markdown files
  if (!file.name.endsWith(".md")) return;

  // Read full note text
  let content = await app.vault.read(file);

  // Hash → deterministic muted hex color for backgrounds
  function stringToColor(str) {
    let hash = 0;
    for (let i = 0; i < str.length; i++) {
      hash = str.charCodeAt(i) + ((hash << 5) - hash);
    }

    // Generate muted colors by constraining RGB values to a narrower, lighter range
    let color = "#";
    for (let i = 0; i < 3; i++) {
      // Get base value from hash
      const rawValue = (hash >> (i * 8)) & 0xff;
      // Map to muted range: 160-220 (instead of 0-255) for softer colors
      const mutedValue = 160 + (rawValue % 61);
      color += ("00" + mutedValue.toString(16)).slice(-2);
    }
    return '"' + color + '"';
  }

  // Check if a cover value is an image link/URL
  function isImageLink(coverValue) {
    if (!coverValue) return false;

    // Remove quotes and whitespace
    const cleanValue = coverValue.replace(/['"]/g, "").trim();

    // Check for common image extensions
    const imageExtensions = /\.(jpg|jpeg|png|gif|bmp|svg|webp)$/i;
    if (imageExtensions.test(cleanValue)) return true;

    // Check for URLs (http/https)
    if (/^https?:\/\//.test(cleanValue)) return true;

    // Check for Obsidian internal links [[filename]]
    if (/^\[\[.*\]\]$/.test(cleanValue)) return true;

    // Check for markdown image syntax ![alt](url)
    if (/^!\[.*\]\(.*\)$/.test(cleanValue)) return true;

    return false;
  }

  const title = file.basename.trim();
  const newColor = stringToColor(title);

  // Ensure frontmatter exists
  if (!/^---/.test(content)) {
    content = `---\ncover: ${newColor}\n---\n\n${content}`;
  } else if (/^cover: .*/m.test(content)) {
    // Check if existing cover is an image link before replacing
    const existingCoverMatch = content.match(/^cover: (.*)$/m);
    if (existingCoverMatch && !isImageLink(existingCoverMatch[1])) {
      // Only replace if it's not an image link
      content = content.replace(/^cover: .*/m, `cover: ${newColor}`);
    }
    // If it is an image link, don't replace it
  } else {
    // Insert cover into frontmatter block
    content = content.replace(
      /^---([\s\S]*?)---/,
      (match, inner) => `---${inner}\ncover: ${newColor}\n---`
    );
  }

  await app.vault.modify(file, content);
};