From 3059909deb5e21746d3d95e4989a78db51ccec33 Mon Sep 17 00:00:00 2001
From: Brian Picciano <mediocregopher@gmail.com>
Date: Sat, 21 May 2022 11:15:37 -0600
Subject: Publish new posts to mailing list

---
 srv/src/post/post.go      | 24 ++++++++++++++++++------
 srv/src/post/post_test.go | 20 ++++++++++++++------
 2 files changed, 32 insertions(+), 12 deletions(-)

(limited to 'srv/src/post')

diff --git a/srv/src/post/post.go b/srv/src/post/post.go
index 29a984f..a39af61 100644
--- a/srv/src/post/post.go
+++ b/srv/src/post/post.go
@@ -48,9 +48,10 @@ type StoredPost struct {
 // Store is used for storing posts to a persistent storage.
 type Store interface {
 
-	// Set sets the Post data into the storage, keyed by the Post's ID. It
-	// overwrites a previous Post with the same ID, if there was one.
-	Set(post Post, now time.Time) error
+	// Set sets the Post data into the storage, keyed by the Post's ID. If there
+	// was not a previously existing Post with the same ID then Set returns
+	// true. It overwrites the previous Post with the same ID otherwise.
+	Set(post Post, now time.Time) (bool, error)
 
 	// Get returns count StoredPosts, sorted time descending, offset by the
 	// given page number. The returned boolean indicates if there are more pages
@@ -114,13 +115,15 @@ func (s *store) withTx(cb func(*sql.Tx) error) error {
 	return nil
 }
 
-func (s *store) Set(post Post, now time.Time) error {
+func (s *store) Set(post Post, now time.Time) (bool, error) {
 
 	if post.ID == "" {
-		return errors.New("post ID can't be empty")
+		return false, errors.New("post ID can't be empty")
 	}
 
-	return s.withTx(func(tx *sql.Tx) error {
+	var first bool
+
+	err := s.withTx(func(tx *sql.Tx) error {
 
 		nowTS := now.Unix()
 
@@ -173,8 +176,17 @@ func (s *store) Set(post Post, now time.Time) error {
 			}
 		}
 
+		err = tx.QueryRow(
+			`SELECT 1 FROM posts WHERE id=? AND last_updated_at IS NULL`,
+			post.ID,
+		).Scan(new(int))
+
+		first = !errors.Is(err, sql.ErrNoRows)
+
 		return nil
 	})
+
+	return first, err
 }
 
 func (s *store) get(
diff --git a/srv/src/post/post_test.go b/srv/src/post/post_test.go
index b6d8a2e..c7f9cdc 100644
--- a/srv/src/post/post_test.go
+++ b/srv/src/post/post_test.go
@@ -108,7 +108,9 @@ func TestStore(t *testing.T) {
 		post := testPost(0)
 		post.Tags = []string{"foo", "bar"}
 
-		assert.NoError(t, h.store.Set(post, now))
+		first, err := h.store.Set(post, now)
+		assert.NoError(t, err)
+		assert.True(t, first)
 
 		gotPost, err := h.store.GetByID(post.ID)
 		assert.NoError(t, err)
@@ -129,7 +131,9 @@ func TestStore(t *testing.T) {
 		post.Body = "anything"
 		post.Tags = []string{"bar", "baz"}
 
-		assert.NoError(t, h.store.Set(post, newNow))
+		first, err = h.store.Set(post, newNow)
+		assert.NoError(t, err)
+		assert.False(t, first)
 
 		gotPost, err = h.store.GetByID(post.ID)
 		assert.NoError(t, err)
@@ -160,7 +164,8 @@ func TestStore(t *testing.T) {
 		}
 
 		for _, post := range posts {
-			assert.NoError(t, h.store.Set(post.Post, now))
+			_, err := h.store.Set(post.Post, now)
+			assert.NoError(t, err)
 		}
 
 		gotPosts, hasMore, err := h.store.Get(0, 2)
@@ -174,7 +179,8 @@ func TestStore(t *testing.T) {
 		assertPostsEqual(t, posts[2:4], gotPosts)
 
 		posts = append([]StoredPost{h.testStoredPost(4)}, posts...)
-		assert.NoError(t, h.store.Set(posts[0].Post, now))
+		_, err = h.store.Set(posts[0].Post, now)
+		assert.NoError(t, err)
 
 		gotPosts, hasMore, err = h.store.Get(1, 2)
 		assert.NoError(t, err)
@@ -204,7 +210,8 @@ func TestStore(t *testing.T) {
 		posts[2].Series = "bar"
 
 		for _, post := range posts {
-			assert.NoError(t, h.store.Set(post.Post, now))
+			_, err := h.store.Set(post.Post, now)
+			assert.NoError(t, err)
 		}
 
 		fooPosts, err := h.store.GetBySeries("foo")
@@ -238,7 +245,8 @@ func TestStore(t *testing.T) {
 		posts[2].Tags = []string{"bar"}
 
 		for _, post := range posts {
-			assert.NoError(t, h.store.Set(post.Post, now))
+			_, err := h.store.Set(post.Post, now)
+			assert.NoError(t, err)
 		}
 
 		fooPosts, err := h.store.GetByTag("foo")
-- 
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