Add a blog post about markdowndb computed fields

README.md

@@ -1,6 +1,10 @@
 # Blog
 ---
 
+**2024-05-08**
+
+[[markdowndb-computed-fields|Learn how to extract any data from markdown files]]
+
 **2024-05-03**
 
 [[style-your-datahub-cloud-site-with-css|Learn how to style your DataHub Cloud sites with custom CSS]]

markdowndb-computed-fields.md

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+# Building a website with markdown: extract data from markdown Files with markdownDB
+
+Let's face it, keeping your website content organized can be a challenge. When you rely on Markdown files, extracting titles or description efficiently for an index page can feel like a chore. But fear not! Here's where MarkdownDB comes in to save the day.
+
+**A Smoother Workflow for Your Content:**
+
+1. **Prepare Your Content Files:** Your Markdown files are the building blocks. Feel free to include a YAML frontmatter section at the beginning to store metadata like title, date, tags, and more. Here's an example:
+
+    ```md
+    ---
+    title: My Awesome Blog Post
+    date: 2024-05-08
+    tags: [markdown, tutorial]
+    ---
+
+    # This is my fantastic blog post!
+    ```
+
+2. **Install and Run MarkdownDB:** The magic tool is the `mddb` package. Install it using npm or yarn:
+
+    ```Bash
+    npm install mddb
+    ```
+
+3. **Extracting data from markdown**
+you can extract any data from a markdown file by adding a function in the configuration file. we will add an example on how to extract titles from markdown file by adding some functions in the computed fields property in the `markdown.config.js` file
+
+    ```javascript
+    export default {
+      computedFields: [
+        (fileInfo, ast) => {
+          const stack = [ast];
+          while (stack.length > 0) {
+            const current = stack.pop();
+
+            // Only get the first header h1
+            if (current.type === 'heading' && current.depth === 1) {
+              fileInfo.title = getNodeValue(current)
+            }
+
+            if (current.children) {
+              // Since we want to process children in reverse order, we push them onto the stack in reverse
+              for (let i = current.children.length - 1; i >= 0; i--) {
+                stack.push(current.children[i]);
+              }
+            }
+          }
+        }
+      ]
+    };
+
+    // get the text for a given node
+    function getNodeValue(node) {
+      if (node.type === 'text') {
+        return node.value;
+      }
+      if (node.children && node.children.length > 0) {
+        let value = '';
+        node.children.forEach(child => {
+          value += getNodeValue(child);
+        });
+        return value;
+      }
+      return '';
+    }
+    ```
+
+4. Now, let MarkdownDB index your Markdown files into an SQLite database! Simply point it to the folder containing your Markdown content:
+
+    ```Bash
+    npx mddb ./blog-posts
+    ```
+
+    This creates a `markdown.db` file in your current directory, housing all the indexed data.
+
+5. **Querying Your Content:**
+    MarkdownDB gives you two ways to retrieve information: SQL and a handy Node.js API.
+**5.1 Querying with SQL (Optional):** If you're comfortable with SQL, you can directly query the database. Here's an example to find all files with the "markdown" tag:
+
+```sql
+SELECT files.*
+FROM files
+INNER JOIN file_tags ON files._id = file_tags.file
+WHERE file_tags.tag = 'markdown'
+```
+
+**5.2 Database Connection Library:**
+
+```JavaScript
+// @/lib/mddb.mjs
+import { MarkdownDB } from 'mddb';
+
+const dbPath = 'markdown.db';
+
+const client = new MarkdownDB({
+  client: 'sqlite3',
+  connection: {
+ filename: dbPath,
+  },
+});
+
+const clientPromise = client.init();
+
+
+
+export default clientPromise;
+/* To run quries
+const client = await clientPromise
+const results = client.query({
+  Your query parameters here, e.g., select title from files
+});
+*/
+```
+
+**Explanation:**
+
+- The `Blog` component renders a list of titles and links from the `blogs` props.
+- `getStaticProps` fetches files using the MarkdownDB API.
+- The retrieved files are mapped to an array of blog objects containing extracted titles and URL paths.
+- The `mddb.mjs` file establishes the connection to the MarkdownDB database.
+
+**Additional Considerations:**
+
+- You can customize title extraction logic (e.g., using a specific header level) by modifying the `computedFields` configuration in your MarkdownDB setup.
+- Consider alternative database options for specific use cases. ( e.g. extracting description )
+
+**Embrace Flexibility and Efficiency:** MarkdownDB empowers you to do a lot of things. Visit the following page for more information about the other cool features of MarkdownDB: [https://markdowndb.com/docs](https://markdowndb.com/docs).