From dbe84bc9f4304d4c0325aa9ac7882b06318308cc Mon Sep 17 00:00:00 2001
From: Lumither Tao <lumither@outlook.com>
Date: Thu, 25 Jul 2024 00:37:10 +0800
Subject: [PATCH] feat(blog) add `adj` (adjacent posts) to get_post

---
 backend/src/api/get/get_post.rs | 46 +++++++++++++++++++++++++++++++--
 backend/src/model/blog/meta.sql | 40 ++++++++++++++++++++++++----
 2 files changed, 79 insertions(+), 7 deletions(-)

diff --git a/backend/src/api/get/get_post.rs b/backend/src/api/get/get_post.rs
index a9c9fec..a38eb89 100644
--- a/backend/src/api/get/get_post.rs
+++ b/backend/src/api/get/get_post.rs
@@ -102,11 +102,53 @@ WHERE post_id = $1;
         }
     };
 
-    // todo: next, prev post
+    let adjacent = match query(r"
+WITH target_post AS (SELECT t.date FROM meta t WHERE post_id = $1),
+     prev AS (SELECT post_id, t.title, t.sub_title, t.header_img
+              FROM meta t
+              WHERE t.date < (SELECT date FROM target_post)
+              ORDER BY t.date DESC
+              LIMIT 1),
+     next AS (SELECT post_id, t.title, t.sub_title, t.header_img
+              FROM meta t
+              WHERE t.date > (SELECT date FROM target_post)
+              ORDER BY t.date
+              LIMIT 1)
+SELECT json_strip_nulls(json_build_object(
+        'prev',
+        (SELECT json_build_object('id', post_id, 'title', title, 'sub_title', sub_title, 'header_img', header_img)
+         FROM prev),
+        'next',
+        (SELECT json_build_object('id', post_id, 'title', title, 'sub_title', sub_title, 'header_img', header_img)
+         FROM next)
+                        )) AS result;
+"
+    )
+        .bind(post_id)
+        .fetch_one(&db_connection)
+        .await
+    {
+        Ok(res) => {res.get::<Value, _>("result")}
+        Err(e) => {
+            error!(
+                "Database error on Reading `{}` from table `{}`: <{}>: {}",
+                "adjoint posts data",
+                "meta",
+                post_id.to_string(),
+                e.to_string()
+            );
+            return Err((
+                StatusCode::INTERNAL_SERVER_ERROR,
+                Json::from(json!({"error": e.to_string()})),
+            ));
+        }
+
+    };
 
     let mut res = post.as_object().unwrap().to_owned();
     res.insert("tags".to_string(), tags.into());
-    res.insert("meta".to_string(), meta.into());
+    res.insert("meta".to_string(), meta);
+    res.insert("adj".to_string(), adjacent);
 
     Ok(Json::from(json!(res)))
 }
diff --git a/backend/src/model/blog/meta.sql b/backend/src/model/blog/meta.sql
index ce8a376..6cf903a 100644
--- a/backend/src/model/blog/meta.sql
+++ b/backend/src/model/blog/meta.sql
@@ -8,20 +8,25 @@ DROP table meta;
 DO
 $$
     DECLARE
-        _post_id        UUID  := 'd5a209d4-93b1-474e-8e4e-9c78d6e6e763'; -- test data
-        _meta_cols      JSONB := '{"title": " title", "tags": "example tags", "new_col1": "new_value1", "new_col3": "new_value2"}'; -- test data
+        _post_id        UUID   := '{}';
+        _meta_cols      JSONB  := '{}';
         _exists         BOOLEAN;
         _col_name       TEXT;
         _col_value      TEXT;
         _sql            TEXT;
-        _insert_columns TEXT  := 'post_id';
-        _insert_values  TEXT  := quote_literal(_post_id);
-        _update_set     TEXT  := '';
+        _insert_columns TEXT   := 'post_id';
+        _insert_values  TEXT   := quote_literal(_post_id);
+        _update_set     TEXT   := '';
+        _blacklist      TEXT[] := ARRAY ['id', 'tags'];
     BEGIN
         SELECT EXISTS(SELECT 1 FROM meta WHERE post_id = _post_id) INTO _exists;
 
         FOR _col_name, _col_value IN SELECT key, value FROM jsonb_each_text(_meta_cols)
             LOOP
+                IF _col_name = ANY (_blacklist) THEN
+                    CONTINUE;
+                END IF;
+
                 IF NOT EXISTS (SELECT 1
                                FROM information_schema.columns
                                WHERE table_name = 'meta'
@@ -47,3 +52,28 @@ $$
         END IF;
     END;
 $$ LANGUAGE plpgsql;
+
+SELECT jsonb_strip_nulls(to_jsonb(t)) AS meta
+FROM meta t
+WHERE post_id = '8ca3fa2b-f040-448c-8885-81aab56db9bb';
+
+WITH target_post AS (SELECT t.date FROM meta t WHERE post_id = '8ca3fa2b-f040-448c-8885-81aab56db9bb'),
+     prev AS (SELECT post_id, t.title, t.sub_title, t.header_img
+              FROM meta t
+              WHERE t.date < (SELECT date FROM target_post)
+              ORDER BY t.date DESC
+              LIMIT 1),
+     next AS (SELECT post_id, t.title, t.sub_title, t.header_img
+              FROM meta t
+              WHERE t.date > (SELECT date FROM target_post)
+              ORDER BY t.date
+              LIMIT 1)
+SELECT json_strip_nulls(json_build_object(
+        'prev',
+        (SELECT json_build_object('id', post_id, 'title', title, 'sub_title', sub_title, 'header_img', header_img)
+         FROM prev),
+        'next',
+        (SELECT json_build_object('id', post_id, 'title', title, 'sub_title', sub_title, 'header_img', header_img)
+         FROM next)
+                        )) AS result;
+