From c678dde4be5dfa6db97de193fa877dabd1e3f3ae Mon Sep 17 00:00:00 2001
From: Blaine Bublitz <blaine.bublitz@gmail.com>
Date: Wed, 6 May 2020 17:04:26 -0700
Subject: [PATCH 1/2] Allow datasource to use context

---
 src/types/connection/mod.rs   | 7 ++++---
 src/types/connection/slice.rs | 3 ++-
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/types/connection/mod.rs b/src/types/connection/mod.rs
index fef4b283..75613240 100644
--- a/src/types/connection/mod.rs
+++ b/src/types/connection/mod.rs
@@ -130,7 +130,7 @@ struct Pagination {
 ///     type Element = i32;
 ///     type EdgeFieldsObj = DiffFields;
 ///
-///     async fn query_operation(&self, operation: &QueryOperation) -> FieldResult<Connection<Self::Element, Self::EdgeFieldsObj>> {
+///     async fn query_operation(&self, ctx: &Context<'_>, operation: &QueryOperation) -> FieldResult<Connection<Self::Element, Self::EdgeFieldsObj>> {
 ///         let (start, end) = match operation {
 ///             QueryOperation::First {limit} => {
 ///                 let start = 0;
@@ -216,7 +216,7 @@ pub trait DataSource: Sync + Send {
     /// Execute the query.
     async fn query(
         &self,
-        _ctx: &Context<'_>,
+        ctx: &Context<'_>,
         after: Option<Cursor>,
         before: Option<Cursor>,
         first: Option<i32>,
@@ -335,12 +335,13 @@ pub trait DataSource: Sync + Send {
             },
         };
 
-        self.query_operation(&operation).await
+        self.query_operation(ctx, &operation).await
     }
 
     /// Parses the parameters and executes the query，Usually you just need to implement this method.
     async fn query_operation(
         &self,
+        ctx: &Context<'_>,
         operation: &QueryOperation,
     ) -> FieldResult<Connection<Self::Element, Self::EdgeFieldsObj>>;
 }
diff --git a/src/types/connection/slice.rs b/src/types/connection/slice.rs
index 974bc706..92999de6 100644
--- a/src/types/connection/slice.rs
+++ b/src/types/connection/slice.rs
@@ -1,5 +1,5 @@
 use crate::types::connection::{EmptyEdgeFields, QueryOperation};
-use crate::{Connection, DataSource, FieldResult};
+use crate::{Connection, Context, DataSource, FieldResult};
 use byteorder::{ReadBytesExt, BE};
 
 #[async_trait::async_trait]
@@ -9,6 +9,7 @@ impl<'a, T: Sync> DataSource for &'a [T] {
 
     async fn query_operation(
         &self,
+        _ctx: &Context<'_>,
         operation: &QueryOperation,
     ) -> FieldResult<Connection<Self::Element, Self::EdgeFieldsObj>> {
         let (start, end) = match operation {

From aed8f33ee594fcc8e035e95776d48b554fa5e38b Mon Sep 17 00:00:00 2001
From: Blaine Bublitz <blaine.bublitz@gmail.com>
Date: Wed, 6 May 2020 17:04:59 -0700
Subject: [PATCH 2/2] Update book

---
 docs/zh-CN/src/cursor_connections.md | 26 +++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

diff --git a/docs/zh-CN/src/cursor_connections.md b/docs/zh-CN/src/cursor_connections.md
index 7b62a699..29664682 100644
--- a/docs/zh-CN/src/cursor_connections.md
+++ b/docs/zh-CN/src/cursor_connections.md
@@ -22,25 +22,37 @@ impl DataSource for Integers {
     // 我们不需要扩展边的字段，所以传EmptyEdgeFields
     type EdgeFieldsObj = EmptyEdgeFields;
 
-    async fn query_operation(&self, operation: &QueryOperation<'_>) -> FieldResult<Connection<Self::Element, Self::EdgeFieldsObj>> {
+    async fn query_operation(&self, _ctx: &Context<'_>, operation: &QueryOperation<'_>) -> FieldResult<Connection<Self::Element, Self::EdgeFieldsObj>> {
         let (start, end) = match operation {
             // 向前查找
-            QueryOperation::Forward {after, limit} => {
+            QueryOperation::First {limit} => {
+                let start = 0;
+                let end = start + *limit as i32;
+                (start, end)
+            }
+            QueryOperation::FirstAfter {after, limit} => {
                 // 起始数字，从after+1开始，如果没有after参数，则从0开始
-                let start = after
-                    .and_then(|after| after.parse::<i32>().ok())
+                let start = after.parse::<i32>()
+                    .ok()
                     .map(|after| after + 1)
                     .unwrap_or(0);
                 (start, end + start + *limit)
             }
             // 向后查找
-            QueryOperation::Backward {before, limit} => {
+            QueryOperation::Last {limit} => {
+                let end = 0;
+                let start = end - *limit as i32;
+                (start, end)
+            }
+            QueryOperation::LastBefore {before, limit} => {
                 // 结束数字，如果没有before参数，则为0
-                let end = before
-                    .and_then(|before| before.parse::<i32>().ok())
+                let end = before.parse::<i32>()
+                    .ok()
                     .unwrap_or(0);
                 (end - *limit, end)
             }
+            // TODO: Advise to handle all cases
+            _ => (0, 10)
         };
 
         // 创建节点，每个节点都是一个包含三个值的元组，依次是游标，扩展边对象，节点值