From 205f94cc891ad153e4e70b347c5cc529df59d6a2 Mon Sep 17 00:00:00 2001
From: David Stotijn <dstotijn@gmail.com>
Date: Sat, 15 May 2021 20:16:04 +0200
Subject: [PATCH] Add "append block children" endpoint support

---
 README.md |  2 +-
 block.go  |  2 +-
 client.go | 38 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index 8bf678f..fb85a23 100644
--- a/README.md
+++ b/README.md
@@ -22,7 +22,7 @@ Go client for the [Notion API](https://developers.notion.com/reference).
 ### Blocks
 
 - [x] [Retrieve block children](client.go)
-- [ ] Append block children
+- [x] [Append block children](client.go)
 
 ### Users
 
diff --git a/block.go b/block.go
index 2f9469e..c8e3a99 100644
--- a/block.go
+++ b/block.go
@@ -10,7 +10,7 @@ type Block struct {
 	Type           BlockType  `json:"type"`
 	CreatedTime    *time.Time `json:"created_time,omitempty"`
 	LastEditedTime *time.Time `json:"last_edited_time,omitempty"`
-	HasChildren    bool       `json:"has_children"`
+	HasChildren    bool       `json:"has_children,omitempty"`
 
 	Paragraph        *RichTextBlock `json:"paragraph,omitempty"`
 	Heading1         *Heading       `json:"heading_1,omitempty"`
diff --git a/client.go b/client.go
index f82b659..8fc47f3 100644
--- a/client.go
+++ b/client.go
@@ -261,3 +261,41 @@ func (c *Client) FindBlockChildrenByID(ctx context.Context, blockID string, quer
 
 	return result, nil
 }
+
+// AppendBlockChildren appends child content (blocks) to an existing block.
+// See: https://developers.notion.com/reference/patch-block-children
+func (c *Client) AppendBlockChildren(ctx context.Context, blockID string, children []Block) (block Block, err error) {
+	type PostBody struct {
+		Children []Block `json:"children"`
+	}
+
+	dto := PostBody{children}
+	body := &bytes.Buffer{}
+
+	err = json.NewEncoder(body).Encode(dto)
+	if err != nil {
+		return Block{}, fmt.Errorf("notion: failed to encode body params to JSON: %w", err)
+	}
+
+	req, err := c.newRequest(ctx, http.MethodPatch, fmt.Sprintf("/blocks/%v/children", blockID), body)
+	if err != nil {
+		return Block{}, fmt.Errorf("notion: invalid request: %w", err)
+	}
+
+	res, err := c.httpClient.Do(req)
+	if err != nil {
+		return Block{}, fmt.Errorf("notion: failed to make HTTP request: %w", err)
+	}
+	defer res.Body.Close()
+
+	if res.StatusCode != http.StatusOK {
+		return Block{}, fmt.Errorf("notion: failed to append block children: %w", parseErrorResponse(res))
+	}
+
+	err = json.NewDecoder(res.Body).Decode(&block)
+	if err != nil {
+		return Block{}, fmt.Errorf("notion: failed to parse HTTP response: %w", err)
+	}
+
+	return block, nil
+}