From b1f8914cba7a413baa3f62878607d28f8fc8fb14 Mon Sep 17 00:00:00 2001
From: Stephan Dilly <dilly.stephan@gmail.com>
Date: Fri, 27 Mar 2020 09:49:57 +0100
Subject: [PATCH] clamp scroll position to valid range

---
 asyncgit/src/sync/diff.rs | 11 ++++++++---
 src/components/diff.rs    | 10 ++++++----
 2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/asyncgit/src/sync/diff.rs b/asyncgit/src/sync/diff.rs
index 61ac9d4b..3f2e9c89 100644
--- a/asyncgit/src/sync/diff.rs
+++ b/asyncgit/src/sync/diff.rs
@@ -61,7 +61,7 @@ pub struct Hunk(pub Vec<DiffLine>);
 
 ///
 #[derive(Default, Clone, Hash)]
-pub struct Diff(pub Vec<Hunk>);
+pub struct Diff(pub Vec<Hunk>, pub u16);
 
 ///
 pub fn get_diff(p: String, stage: bool) -> Diff {
@@ -94,6 +94,11 @@ pub fn get_diff(p: String, stage: bool) -> Diff {
     let mut current_lines = Vec::new();
     let mut current_hunk: Option<HunkHeader> = None;
 
+    let mut adder = |lines: &Vec<DiffLine>| {
+        res.0.push(Hunk(lines.clone()));
+        res.1 += lines.len() as u16;
+    };
+
     let mut put = |hunk: Option<DiffHunk>, line: git2::DiffLine| {
         if let Some(hunk) = hunk {
             let hunk_header = HunkHeader::from(hunk);
@@ -101,7 +106,7 @@ pub fn get_diff(p: String, stage: bool) -> Diff {
             match current_hunk {
                 None => current_hunk = Some(hunk_header),
                 Some(h) if h != hunk_header => {
-                    res.0.push(Hunk(current_lines.clone()));
+                    adder(&current_lines);
                     current_lines.clear();
                     current_hunk = Some(hunk_header)
                 }
@@ -170,7 +175,7 @@ pub fn get_diff(p: String, stage: bool) -> Diff {
     }
 
     if !current_lines.is_empty() {
-        res.0.push(Hunk(current_lines))
+        adder(&current_lines);
     }
 
     res
diff --git a/src/components/diff.rs b/src/components/diff.rs
index 9119c743..1bb18a09 100644
--- a/src/components/diff.rs
+++ b/src/components/diff.rs
@@ -4,7 +4,7 @@ use crate::{
 };
 use asyncgit::{hash, Diff, DiffLine, DiffLineType};
 use crossterm::event::{Event, KeyCode};
-use std::borrow::Cow;
+use std::{borrow::Cow, cmp};
 use tui::{
     backend::Backend,
     layout::{Alignment, Rect},
@@ -27,7 +27,7 @@ pub struct DiffComponent {
 impl DiffComponent {
     ///
     fn can_scroll(&self) -> bool {
-        self.diff.0.len() > 1
+        self.diff.1 > 1
     }
     ///
     pub fn current(&self) -> (String, bool) {
@@ -57,8 +57,10 @@ impl DiffComponent {
 
     fn scroll(&mut self, inc: bool) {
         if inc {
-            self.scroll =
-                self.scroll.checked_add(1).unwrap_or(self.scroll);
+            self.scroll = cmp::min(
+                self.diff.1.saturating_sub(1),
+                self.scroll.saturating_add(1),
+            );
         } else {
             self.scroll = self.scroll.saturating_sub(1);
         }