From cd696c16241284b10f9c65cea5bb2446b0cbcaf3 Mon Sep 17 00:00:00 2001
From: David Stotijn <dstotijn@gmail.com>
Date: Sat, 15 May 2021 19:04:57 +0200
Subject: [PATCH] Add "retrieve block children" endpoint support

---
 README.md |  2 +-
 block.go  | 14 +++++++++++++-
 client.go | 41 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 55 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index 7719f64..8bf678f 100644
--- a/README.md
+++ b/README.md
@@ -21,7 +21,7 @@ Go client for the [Notion API](https://developers.notion.com/reference).
 
 ### Blocks
 
-- [ ] Retrieve block children
+- [x] [Retrieve block children](client.go)
 - [ ] Append block children
 
 ### Users
diff --git a/block.go b/block.go
index 398f764..2f9469e 100644
--- a/block.go
+++ b/block.go
@@ -17,7 +17,7 @@ type Block struct {
 	Heading2         *Heading       `json:"heading_2,omitempty"`
 	Heading3         *Heading       `json:"heading_3,omitempty"`
 	BulletedListItem *RichTextBlock `json:"bulleted_list_item,omitempty"`
-	NumberedListItem *RichText      `json:"numbered_list_item,omitempty"`
+	NumberedListItem *RichTextBlock `json:"numbered_list_item,omitempty"`
 	ToDo             *ToDo          `json:"to_do,omitempty"`
 	Toggle           *RichTextBlock `json:"toggle,omitempty"`
 	ChildPage        *ChildPage     `json:"rich_text,omitempty"`
@@ -55,3 +55,15 @@ const (
 	BlockTypeChildPage        BlockType = "child_page"
 	BlockTypeUnsupported      BlockType = "unsupported"
 )
+
+type FindBlockChildrenQuery struct {
+	StartCursor string
+	PageSize    int
+}
+
+// BlockChildrenResponse contains results (block children) and pagination data returned from a find request.
+type BlockChildrenResponse struct {
+	Results    []Block `json:"results"`
+	HasMore    bool    `json:"has_more"`
+	NextCursor *string `json:"next_cursor"`
+}
diff --git a/client.go b/client.go
index 380680e..f82b659 100644
--- a/client.go
+++ b/client.go
@@ -7,6 +7,8 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"net/url"
+	"strconv"
 )
 
 const (
@@ -220,3 +222,42 @@ func (c *Client) UpdatePageProps(ctx context.Context, pageID string, params Upda
 
 	return page, nil
 }
+
+// FindBlockChildrenByID returns a list of block children for a given block ID.
+// See: https://developers.notion.com/reference/post-database-query
+func (c *Client) FindBlockChildrenByID(ctx context.Context, blockID string, query *FindBlockChildrenQuery) (result BlockChildrenResponse, err error) {
+	body := &bytes.Buffer{}
+
+	req, err := c.newRequest(ctx, http.MethodGet, fmt.Sprintf("/blocks/%v/children", blockID), body)
+	if err != nil {
+		return BlockChildrenResponse{}, fmt.Errorf("notion: invalid request: %w", err)
+	}
+
+	if query != nil {
+		q := url.Values{}
+		if query.StartCursor != "" {
+			q.Set("start_cursor", query.StartCursor)
+		}
+		if query.PageSize != 0 {
+			q.Set("page_size", strconv.Itoa(query.PageSize))
+		}
+		req.URL.RawQuery = q.Encode()
+	}
+
+	res, err := c.httpClient.Do(req)
+	if err != nil {
+		return BlockChildrenResponse{}, fmt.Errorf("notion: failed to make HTTP request: %w", err)
+	}
+	defer res.Body.Close()
+
+	if res.StatusCode != http.StatusOK {
+		return BlockChildrenResponse{}, fmt.Errorf("notion: failed to find block children: %w", parseErrorResponse(res))
+	}
+
+	err = json.NewDecoder(res.Body).Decode(&result)
+	if err != nil {
+		return BlockChildrenResponse{}, fmt.Errorf("notion: failed to parse HTTP response: %w", err)
+	}
+
+	return result, nil
+}