fix: preserve code blocks in embedded markdown files (fixes #106)

Previously, embedded content was extracted from rendered HTML which
converted code blocks (like mermaid) to their rendered form. This
made it impossible to preserve the original code block syntax.

Now reads raw markdown directly from source files, preserving all
code blocks in their original format.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: bingryan

src/utils.ts

@@ -449,38 +449,159 @@ export async function tryCopyMarkdown(
     }
 }
 
+/**
+ * Extract heading content from a file (from heading to next heading of same or higher level)
+ */
+async function getHeadingContent(
+    plugin: MarkdownExportPlugin,
+    filePath: string,
+    heading: string
+): Promise<string | null> {
+    try {
+        const file = plugin.app.vault.getAbstractFileByPath(filePath);
+        if (!(file instanceof TFile)) {
+            return null;
+        }
+
+        const content = await plugin.app.vault.cachedRead(file);
+        const lines = content.split("\n");
+
+        // Normalize heading for comparison (remove # and spaces, lowercase)
+        const normalizedTarget = heading.toLowerCase().trim();
+
+        // Find the heading line
+        let startIndex = -1;
+        let headingLevel = 0;
+
+        for (let i = 0; i < lines.length; i++) {
+            const headingMatch = lines[i].match(/^(#{1,6})\s+(.+)$/);
+            if (headingMatch) {
+                const level = headingMatch[1].length;
+                const text = headingMatch[2].toLowerCase().trim();
+
+                if (text === normalizedTarget) {
+                    startIndex = i;
+                    headingLevel = level;
+                    break;
+                }
+            }
+        }
+
+        if (startIndex === -1) {
+            return null;
+        }
+
+        // Find the end (next heading of same or higher level, or end of file)
+        let endIndex = lines.length;
+        for (let i = startIndex + 1; i < lines.length; i++) {
+            const nextHeadingMatch = lines[i].match(/^(#{1,6})\s/);
+            if (nextHeadingMatch) {
+                const nextLevel = nextHeadingMatch[1].length;
+                if (nextLevel <= headingLevel) {
+                    endIndex = i;
+                    break;
+                }
+            }
+        }
+
+        const headingLines = lines.slice(startIndex, endIndex);
+        return headingLines.join("\n");
+    } catch (error) {
+        console.error("Error getting heading content:", error);
+        return null;
+    }
+}
+
+/**
+ * Get embed content by reading raw markdown from the source file
+ * This preserves code blocks (like mermaid) in their original format
+ */
+async function getEmbedContentFromSource(
+    plugin: MarkdownExportPlugin,
+    embedLink: string,
+    currentPath: string
+): Promise<string | null> {
+    const parsed = parseEmbedLink(embedLink, currentPath);
+
+    if (!parsed.filePath) {
+        return null;
+    }
+
+    try {
+        const file = plugin.app.vault.getAbstractFileByPath(parsed.filePath);
+        if (!(file instanceof TFile)) {
+            return null;
+        }
+
+        let content = await plugin.app.vault.cachedRead(file);
+
+        // Extract specific section if needed
+        if (parsed.blockId) {
+            const blockContent = await getBlockContent(
+                plugin,
+                parsed.filePath,
+                parsed.blockId
+            );
+            // Remove YAML header if configured (in case block is at start of file)
+            if (plugin.settings.removeYamlHeader && blockContent) {
+                return blockContent.replace(EMBED_METADATA_REGEXP, "");
+            }
+            return blockContent;
+        }
+
+        if (parsed.heading) {
+            const headingContent = await getHeadingContent(
+                plugin,
+                parsed.filePath,
+                parsed.heading
+            );
+            // Remove YAML header if configured (in case heading is at start of file)
+            if (plugin.settings.removeYamlHeader && headingContent) {
+                return headingContent.replace(EMBED_METADATA_REGEXP, "");
+            }
+            return headingContent;
+        }
+
+        // Remove YAML header if configured for full file content
+        if (plugin.settings.removeYamlHeader) {
+            content = content.replace(EMBED_METADATA_REGEXP, "");
+        }
+
+        return content;
+    } catch (error) {
+        console.error("Error getting embed content from source:", error);
+        return null;
+    }
+}
+
 export async function getEmbedMap(
     plugin: MarkdownExportPlugin,
     content: string,
     path: string
 ) {
-    // key：link url
-    // value： embed content parse from html document
     const embedMap = new Map();
-    const embedList = Array.from(
-        document.documentElement.getElementsByClassName("internal-embed")
-    );
+    const embeds = await getEmbeds(content);
 
-    Array.from(embedList).forEach((el) => {
-        // markdown-embed-content markdown-embed-page
-        const embedContentHtml = el.getElementsByClassName(
-            "markdown-embed-content"
-        )[0];
+    for (const embedMatch of embeds) {
+        const embedLink = embedMatch[1];
 
-        if (embedContentHtml) {
-            let embedValue = htmlToMarkdown(embedContentHtml.innerHTML);
-            if (plugin.settings.removeYamlHeader) {
-                embedValue = embedValue.replace(EMBED_METADATA_REGEXP, "");
-            }
-            embedValue =
+        // Try to get content from raw markdown source
+        const rawContent = await getEmbedContentFromSource(
+            plugin,
+            embedLink,
+            path
+        );
+
+        if (rawContent !== null) {
+            // Format as quote block
+            let embedValue =
                 "> " +
-                (embedValue as string)
+                rawContent
                     .replaceAll("# \n\n", "# ")
                     .replaceAll("\n", "\n> ");
-            const embedKey = el.getAttribute("src");
-            embedMap.set(embedKey, embedValue);
+            embedMap.set(embedLink, embedValue);
         }
-    });
+    }
 
     return embedMap;
 }