From d4956e943c0e4a6ce77f926f256d7b8cf69bada7 Mon Sep 17 00:00:00 2001
From: Josh McKinney <joshka@users.noreply.github.com>
Date: Wed, 26 Apr 2023 18:53:23 -0700
Subject: [PATCH] fix: next/prev page handling in Page struct

Improve the handling of next and previous pages in the `Page` struct
by fixing a bug that caused the URLs to be set to None when a page with
no data was loaded. This change allows for the next and previous page
URLs to be preserved for future retrieval even when there are no
results in the current page.
---
 src/page.rs | 42 +++++++++++++++++++++++++++++-------------
 1 file changed, 29 insertions(+), 13 deletions(-)

diff --git a/src/page.rs b/src/page.rs
index 9dcc418..23e8640 100644
--- a/src/page.rs
+++ b/src/page.rs
@@ -5,18 +5,24 @@ use log::{as_debug, as_serde, debug, error, trace};
 use reqwest::{header::LINK, Response, Url};
 use serde::{Deserialize, Serialize};
 use uuid::Uuid;
-// use url::Url;
 
 macro_rules! pages {
     ($($direction:ident: $fun:ident),*) => {
 
         $(
             doc_comment!(concat!(
-                    "Method to retrieve the ", stringify!($direction), " page of results"),
+                    "Method to retrieve the ", stringify!($direction), " page of results",
+                    "Returns Ok(None) if there is no data in the ", stringify!($direction), " page.\n",
+                "Returns Ok(Some(Vec<T>)) if there are results.\n",
+                "Returns Err(Error) if there is an error.\n",
+                "If there are results, the next and previous page urls are stored.\n",
+                "If there are no results, the next and previous page urls are not stored.\n",
+                "This allows for the next page to be retrieved in the future even when\n",
+                "there are no results.",
+                ),
             pub async fn $fun(&mut self) -> Result<Option<Vec<T>>> {
-                let url = match self.$direction.take() {
-                    Some(s) => s,
-                    None => return Ok(None),
+                let Some(ref url) = self.$direction else {
+                    return Ok(None);
                 };
 
                 debug!(
@@ -25,22 +31,30 @@ macro_rules! pages {
                     direction = stringify!($direction);
                     "making API request"
                 );
-                let url: String = url.into(); // <- for logging
+                let url: String = url.to_string();
                 let response = self.mastodon.authenticated(self.mastodon.client.get(&url)).send().await?;
                 match response.error_for_status() {
                     Ok(response) => {
                         let (prev, next) = get_links(&response, self.call_id)?;
-                        let response = read_response(response).await?;
+                        let response: Vec<T> = read_response(response).await?;
+                        if response.is_empty() && prev.is_none() && next.is_none() {
+                            debug!(
+                                url = url, method = "get", call_id = as_debug!(self.call_id),
+                                direction = stringify!($direction);
+                                "received an empty page with no links"
+                            );
+                            return Ok(None);
+                        }
                         debug!(
-                            url = url, method = "get", next = as_debug!(next),
-                            prev = as_debug!(prev), call_id = as_debug!(self.call_id),
+                            url = url, method = "get",call_id = as_debug!(self.call_id),
+                            direction = stringify!($direction),
+                            prev = as_debug!(prev),
+                            next = as_debug!(next),
                             response = as_serde!(response);
                             "received next pages from API"
                         );
                         self.next = next;
                         self.prev = prev;
-
-
                         Ok(Some(response))
                     }
                     Err(err) => {
@@ -91,8 +105,10 @@ macro_rules! pages {
 #[derive(Debug, Clone)]
 pub struct Page<T: for<'de> Deserialize<'de> + Serialize> {
     mastodon: Mastodon,
-    next: Option<Url>,
-    prev: Option<Url>,
+    /// next url
+    pub next: Option<Url>,
+    /// prev url
+    pub prev: Option<Url>,
     /// Initial set of items
     pub initial_items: Vec<T>,
     pub(crate) call_id: Uuid,