add ability to check whether a preview is outdated

src/config/preview.rs

@@ -10,13 +10,13 @@ pub struct JoshutoPreviewEntry {
 }
 
 #[derive(Debug, Default, Deserialize)]
-struct JoshutoPreviewCrude {
+struct JoshutoPreviewRaw {
     pub extension: Option<HashMap<String, JoshutoPreviewEntry>>,
     pub mimetype: Option<HashMap<String, JoshutoPreviewEntry>>,
 }
 
-impl From<JoshutoPreviewCrude> for JoshutoPreview {
-    fn from(crude: JoshutoPreviewCrude) -> Self {
+impl From<JoshutoPreviewRaw> for JoshutoPreview {
+    fn from(crude: JoshutoPreviewRaw) -> Self {
         let extension = crude.extension.unwrap_or_default();
         let mimetype = crude.mimetype.unwrap_or_default();
 
@@ -35,6 +35,6 @@ pub struct JoshutoPreview {
 
 impl TomlConfigFile for JoshutoPreview {
     fn get_config(file_name: &str) -> Self {
-        parse_to_config_file::<JoshutoPreviewCrude, JoshutoPreview>(file_name).unwrap_or_default()
+        parse_to_config_file::<JoshutoPreviewRaw, JoshutoPreview>(file_name).unwrap_or_default()
     }
 }

src/preview/preview_default.rs

@@ -23,7 +23,12 @@ pub fn load_preview_path(context: &mut AppContext, p: path::PathBuf, metadata: J
         let need_to_load = context
             .preview_context_ref()
             .get_preview_ref(p.as_path())
-            .is_none();
+            .map(|p| {
+                p.as_ref()
+                    .map(|p| p.modified < metadata.modified())
+                    .unwrap_or(true)
+            })
+            .unwrap_or(true);
 
         if need_to_load {
             preview_file::Background::preview_path_with_script(context, p);

src/preview/preview_file.rs

@@ -1,6 +1,7 @@
 use std::path;
 use std::process::{Command, Output};
 use std::thread;
+use std::time;
 
 use crate::context::AppContext;
 use crate::event::AppEvent;
@@ -10,16 +11,19 @@ pub struct FilePreview {
     pub status: std::process::ExitStatus,
     pub output: String,
     pub index: usize,
+    pub modified: time::SystemTime,
 }
 
 impl std::convert::From<Output> for FilePreview {
     fn from(output: Output) -> Self {
         let s = String::from_utf8_lossy(&output.stdout).to_string();
         let s2 = s.replace('\t', "        ");
         let status = output.status;
+        let modified = time::SystemTime::now();
         Self {
             status,
             output: s2,
+            modified,
             index: 0,
         }
     }