Lemmy federation protocol: How is the "posts from all communities" view sourced?

use serde::{Deserialize, Serialize};
use std::collections::HashMap;

fn main() {
    let rt = tokio::runtime::Builder::new_current_thread()
        .enable_all()
        .build()
        .unwrap();

    let to_page = Some(5);
    let posts = rt.block_on(get_posts_to(to_page)).unwrap();

    println!("-----------");
    println!(
        "All posts to page {} as JSON:",
        to_page.map(|v| v.to_string()).unwrap_or("infinity".into())
    );
    println!("-----------");
    println!("{}", serde_json::to_string(&posts).unwrap());
}

#[derive(Serialize, Deserialize, Debug, Clone)]
struct PostData {
    id: usize,
    name: String,
}

#[derive(Serialize, Deserialize, Debug)]
struct PageItem {
    post: PostData,
}

#[derive(Serialize, Deserialize, Debug)]
struct PostPageResult {
    posts: Vec<PageItem>,
}

async fn get_page(index: usize) -> Result<HashMap<usize, PostData>, ()> {
    let result = reqwest::get(format!(
        "https://programming.dev/api/v3/post/list?dataType=Post&listingType=All&sort=New&page={}",
        index
    ))
    .await;

    if let Ok(r) = result {
        if let Ok(text) = r.text().await {
            if let Ok(data) = serde_json::from_str(&text) {
                let data: PostPageResult = data;

                let map =
                    data.posts
                        .iter()
                        .fold(HashMap::new(), |mut map, post| {
                            map.insert(post.post.id, post.post.clone());

                            map
                        });

                if map.len() > 0 {
                    return Ok(map);
                }
            } else {
                println!("{:?}", serde_json::from_str::<PostPageResult>(&text));
            }
        }
    }

    Err(())
}

/// If page is not `None` then it stops after the page count. Otherwise it continues forever
async fn get_posts_to(page: Option<usize>) -> Result<HashMap<usize, PostData>, ()> {
    let mut idx = 1;
    let mut map = HashMap::new();

    while let Ok(more_posts) = get_page(idx).await {
        println!("page: {}, {:#?}", idx, more_posts);
        map.extend(more_posts.into_iter());
        idx += 1;

        if let Some(page) = page {
            if idx > page {
                break;
            }
        }
    }

    Ok(map)
}

[package]
name = "lemmyposts"
version = "0.1.0"
edition = "2021"

[dependencies]
reqwest = "0.12.7"
serde = { version = "1.0", features = ["derive"] }
serde_json = "1.0.128"
tokio = { version = "1.4", features = ["rt"] }