From b5468bced2698d3efd84e977d94ce68322ac376f Mon Sep 17 00:00:00 2001
From: Bill Thiede <git@xinu.tv>
Date: Mon, 22 Jul 2024 09:28:12 -0700
Subject: [PATCH] Implement pagination for newsreader

---
 server/sql/threads.sql   |   4 +-
 server/src/newsreader.rs | 106 ++++++++++++++++++++++++++++-----------
 2 files changed, 79 insertions(+), 31 deletions(-)

diff --git a/server/sql/threads.sql b/server/sql/threads.sql
index 69f9cc7..a476710 100644
--- a/server/sql/threads.sql
+++ b/server/sql/threads.sql
@@ -15,4 +15,6 @@ WHERE
     )
 ORDER BY
     date DESC,
-    title
+    title OFFSET $3
+LIMIT
+    $4
diff --git a/server/src/newsreader.rs b/server/src/newsreader.rs
index 3cf9cb0..7e96ae1 100644
--- a/server/src/newsreader.rs
+++ b/server/src/newsreader.rs
@@ -49,41 +49,86 @@ pub async fn search(
         before,
         first,
         last,
-        |after, before, first, last| async move {
+        |after: Option<usize>, before: Option<usize>, first, last| async move {
             info!("search page info {after:#?}, {before:#?}, {first:#?}, {last:#?}");
-            let rows = sqlx::query_file!("sql/threads.sql", site, query.unread_only,)
-                .fetch_all(pool)
-                .await?;
-
-            let slice = rows.into_iter().map(|r| {
-                let tags = if r.is_read.unwrap_or(false) {
-                    vec![site.clone()]
-                } else {
-                    vec!["unread".to_string(), site.clone()]
-                };
-                ThreadSummary {
-                    thread: format!("{THREAD_PREFIX}{}", r.uid),
-                    timestamp: r
-                        .date
-                        .expect("post missing date")
-                        .assume_utc()
-                        .unix_timestamp() as isize,
-                    date_relative: "TODO date_relative".to_string(),
-                    matched: 0,
-                    total: 1,
-                    authors: r.name.unwrap_or_else(|| site.clone()),
-                    subject: r.title.unwrap_or("NO TITLE".to_string()),
-                    tags,
+            let default_page_size = 100;
+            let (offset, limit) = match (after, before, first, last) {
+                // Reasonable defaults
+                (None, None, None, None) => (0, default_page_size),
+                (None, None, Some(first), None) => (0, first),
+                (Some(after), None, None, None) => (after, default_page_size),
+                (Some(after), None, Some(first), None) => (after, first),
+                (None, Some(before), None, None) => {
+                    (before.saturating_sub(default_page_size), default_page_size)
                 }
-            });
-            let mut connection = Connection::new(false, false);
-            // TODO
-            let start = 0;
+                (None, Some(before), None, Some(last)) => (before.saturating_sub(last), last),
+                (None, None, None, Some(_)) => {
+                    panic!("specifying last and no before doesn't make sense")
+                }
+                (None, None, Some(_), Some(_)) => {
+                    panic!("specifying first and last doesn't make sense")
+                }
+                (None, Some(_), Some(_), _) => {
+                    panic!("specifying before and first doesn't make sense")
+                }
+                (Some(_), Some(_), _, _) => {
+                    panic!("specifying after and before doesn't make sense")
+                }
+                (Some(_), None, None, Some(_)) => {
+                    panic!("specifying after and last doesn't make sense")
+                }
+                (Some(_), None, Some(_), Some(_)) => {
+                    panic!("specifying after, first and last doesn't make sense")
+                }
+            };
+            // The +1 is to see if there are more pages of data available.
+            let limit = limit + 1;
+
+            info!("search page offset {offset} limit {limit}");
+            let rows = sqlx::query_file!(
+                "sql/threads.sql",
+                site,
+                query.unread_only,
+                offset as i64,
+                limit as i64
+            )
+            .fetch_all(pool)
+            .await?;
+
+            let mut slice = rows
+                .into_iter()
+                .map(|r| {
+                    let tags = if r.is_read.unwrap_or(false) {
+                        vec![site.clone()]
+                    } else {
+                        vec!["unread".to_string(), site.clone()]
+                    };
+                    ThreadSummary {
+                        thread: format!("{THREAD_PREFIX}{}", r.uid),
+                        timestamp: r
+                            .date
+                            .expect("post missing date")
+                            .assume_utc()
+                            .unix_timestamp() as isize,
+                        date_relative: "TODO date_relative".to_string(),
+                        matched: 0,
+                        total: 1,
+                        authors: r.name.unwrap_or_else(|| site.clone()),
+                        subject: r.title.unwrap_or("NO TITLE".to_string()),
+                        tags,
+                    }
+                })
+                .collect::<Vec<_>>();
+            let has_more = slice.len() == limit;
+            let mut connection = Connection::new(offset > 0, has_more);
+            if has_more {
+                slice.pop();
+            };
             connection.edges.extend(
                 slice
                     .into_iter()
                     .enumerate()
-                    .map(|(idx, item)| Edge::new(start + idx, item)),
+                    .map(|(idx, item)| Edge::new(offset + idx, item)),
             );
             Ok::<_, async_graphql::Error>(connection)
         },
@@ -91,7 +136,8 @@ pub async fn search(
     .await
 }
 
-pub async fn tags(pool: &PgPool, needs_unread: bool) -> Result<Vec<Tag>, ServerError> {
+pub async fn tags(pool: &PgPool, _needs_unread: bool) -> Result<Vec<Tag>, ServerError> {
+    // TODO: optimize query by using needs_unread
     let tags = sqlx::query_file!("sql/tags.sql").fetch_all(pool).await?;
     let tags = tags
         .into_iter()