fix: resolve static front page .md URL generation (#5)

[jdevalk]

Closes #5

Summary

Fixes invalid markdown URL generation when a static page is configured as the front page.

Problem

When a static page is set as the front page (Settings → Reading), get_permalink() returns the site root (e.g., https://example.com/). The plugin was appending .md directly, resulting in https://example.com.md, which looks like an invalid TLD.

Solution

• Detect when a permalink is the site root (front page)
• Convert to /index.md instead of .md
• Added special routing logic to handle /index.md requests
• Added rewrite rule for index.md

Changes

• AlternateLinkHandler: Added convert_to_markdown_url() method to generate proper markdown URLs
• RewriteHandler: Added matching convert_to_markdown_url() method for Accept header negotiation
• RewriteHandler: Added special case handling in parse_markdown_url() for /index.md
• RewriteHandler: Added dedicated rewrite rule for ^index\.md$

Test Plan

• Set a static page as front page (Settings → Reading)
• Verify <link rel="alternate"> in HTML shows https://example.com/index.md
• Verify Accept: text/markdown on front page redirects to /index.md
• Verify /index.md serves front page content as markdown
• Verify /.md returns 404 (does not resolve to front page)
• Verify regular posts/pages still work correctly with .md URLs

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR fixes a bug where setting a static page as the WordPress front page resulted in an invalid markdown URL (e.g., https://example.com.md instead of https://example.com/index.md). The fix introduces special handling for the front page by detecting when a permalink matches the site root and converting it to /index.md.

Changes:

• Added convert_to_markdown_url() methods in both AlternateLinkHandler and RewriteHandler to handle front page URL generation
• Added special routing logic in parse_markdown_url() to resolve /index.md requests to the configured front page
• Added a dedicated rewrite rule for index.md pattern

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
src/Router/RewriteHandler.php	Added rewrite rule for index.md, special handling in parse_markdown_url() for front page resolution, new convert_to_markdown_url() method, and updated Accept header negotiation to use the new method
src/Discovery/AlternateLinkHandler.php	Added convert_to_markdown_url() method for generating proper markdown URLs in alternate link tags

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[Copilot]

The convert_to_markdown_url() method is duplicated between RewriteHandler and AlternateLinkHandler classes. This is a maintainability concern - any future changes to the URL conversion logic would need to be made in two places, increasing the risk of inconsistencies.

Consider extracting this method to a shared utility class or trait that both classes can use. For example, create a MarkdownUrlConverter utility class or a trait that both handlers can use.

[Copilot]

There's a potential collision if a user creates an actual page with the slug "index". When visiting /index.md, the current logic will always treat it as the front page (lines 103-110) rather than checking if there's an actual page with slug "index".

The logic should first attempt to resolve "index" as a regular page slug, and only fall back to treating it as the front page if no such page exists. Suggested fix:

// Handle /index.md - could be front page or a page with slug "index"
if ($matches[1] === 'index') {
    // First try to resolve as a regular page
    $clean_url = home_url('/index');
    $post_id = url_to_postid($clean_url);
    
    // If no page with slug "index" exists, treat as front page
    if (!$post_id) {
        $page_on_front = get_option('page_on_front');
        if ($page_on_front) {
            $post_id = (int) $page_on_front;
        } else {
            return;
        }
    }
}

Suggested change

	// Handle /index.md as the front page
	if ($matches[1] === 'index') {
	$page_on_front = get_option('page_on_front');
	if ($page_on_front) {
	$post_id = (int) $page_on_front;
	} else {
	// No static front page set - let WordPress show its normal behavior
	return;
	// Handle /index.md - could be front page or a page with slug "index"
	if ($matches[1] === 'index') {
	// First try to resolve as a regular page with slug "index"
	$clean_url = home_url('/index');
	$post_id = url_to_postid($clean_url);
	// If no page with slug "index" exists, treat as front page
	if (!$post_id) {
	$page_on_front = get_option('page_on_front');
	if ($page_on_front) {
	$post_id = (int) $page_on_front;
	} else {
	// No static front page set - let WordPress show its normal behavior
	return;
	}

[jdevalk]

Consolidation note: treating this as the primary PR for static front-page markdown URL behavior (supersedes #6). Recommended to merge early before rewrite refactors.