[Feature Request / Todo]: Intra-board link resolution with --single-file

[Hate9]

Presently, single-file board downloads do not alter in-text links to other threads, and treat them as absolute web links.
However, it should be possible during parsing to detect whether a given link is to a thread within the board being downloaded, and replace such links with relative links to the relevant posts within the single-file epub.

This will likely also require adding id attributes to content-blocks.

[Hate9]

Additional todo: find an actual example of intra-board links. I'm pretty sure I've seen some in the Scholomance megacontinuity, and I might have in Planecrash, but they'll be hard to find.

[QuartzLibrary]

This doesn't feel desirable to me because I expect an epub to be a 'reading unit', so to speak, not a catch all for anything related. So I would want to download that post or board separately.

Maybe an option to list all linked boards to a certain level of depth so the user can download everything relevant ahead of time?

[Hate9]

Oh, no, "intra-", not "inter-". This refers to links to other posts within the downloaded board. Downloading all linked boards/posts seems excessive to me, too.

[QuartzLibrary]

Ops, that makes sense!

[Hate9]

Ok, so I've just now decided to take a look at doing this. It seems pretty easy to create a few functions for handling links similarly to how we already handle interning images, and then just compare all the links in the board to the list of posts and replies in it, and add those to the replacement list we're already using for image links.

However, there's a bit of a problem. In order to link to something within the Epub, we need it's internal filename - and we currently chunk replies in pages of 30 each.

So... why are we doing that? If there's a good reason for it, we can probably work around it, but it'd make this much easier if we don't have to.

[QuartzLibrary]

So... why are we doing that?

Some epub readers struggle with very large chapters.

---

Something along these lines should work and be fairly straightforward:

// Pass `url_map` in like the current one, type parameter should be `impl FnMut(String) -> String`.
// The remapping should be applied to all elements rather than just images.
let url_map = move |url: String| -> String {
  if let Some(url) = continuity.internal_url_map(url).cloned() {
    return url;
  }
  image_map.get(&url).cloned().unwrap_or(url)
};

impl Continuity {
  fn internal_url_map(&self, url: &str) -> Option<String> {
    // Made up match statement
    match &url {
      section_id => format!("section_{section_id}_title.xhtml"),
      (section_id, post_id) => format!("section_{section_id}_post_{post_id}_title.xhtml"),
      (section_id, post_id, reply_id) => {
        let i = self.reply_position(..) / PART_LEN;
        format!("section_{section_id}_post_{post_id}_part_{i}.xhtml")
    }
  }
}

[Hate9]

That makes sense!

…But you should probably unclose the issue until it's actually implemented lol

[QuartzLibrary]

🤦 Ops