From 75bee04b5a25350127ed1711ece720ed9aed0038 Mon Sep 17 00:00:00 2001
From: David Bliss <vivid.map6767@davidbliss.me>
Date: Thu, 4 Apr 2024 06:57:16 +0100
Subject: [PATCH] Parallel processing for preview generation

---
 Cargo.lock                              |  1 +
 Cargo.toml                              |  1 +
 core/src/preview.rs                     |  2 +-
 src/app/background/generate_previews.rs | 32 ++++++++++++-------------
 4 files changed, 18 insertions(+), 18 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 2f86c62f..2e7a8f07 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1345,6 +1345,7 @@ dependencies = [
  "humansize",
  "itertools",
  "photos_core",
+ "rayon",
  "relm4",
  "tracing",
  "tracing-subscriber",
diff --git a/Cargo.toml b/Cargo.toml
index 54a30c3d..318129ea 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -22,6 +22,7 @@ tracing-subscriber = "0.3"
 relm4 = { version = "0.8.1", features = ["libadwaita", "gnome_45"] }
 itertools = "0.12.1"
 humansize = "2.1.3"
+rayon = "1.10.0"
 
 
 [dependencies.photos_core]
diff --git a/core/src/preview.rs b/core/src/preview.rs
index dc624c47..2abe7fa1 100644
--- a/core/src/preview.rs
+++ b/core/src/preview.rs
@@ -10,7 +10,7 @@ use image::io::Reader as ImageReader;
 use image::DynamicImage;
 use std::path;
 
-const EDGE: u32 = 400;
+const EDGE: u32 = 200;
 
 #[derive(Debug, Clone)]
 pub struct Previewer {
diff --git a/src/app/background/generate_previews.rs b/src/app/background/generate_previews.rs
index 96b73fc3..182120fc 100644
--- a/src/app/background/generate_previews.rs
+++ b/src/app/background/generate_previews.rs
@@ -8,6 +8,7 @@ use std::sync::{Arc, Mutex};
 use photos_core::Result;
 use photos_core::repo::PictureId;
 use std::path::PathBuf;
+use rayon::prelude::*;
 
 #[derive(Debug)]
 pub enum GeneratePreviewsInput {
@@ -38,23 +39,20 @@ impl GeneratePreviews {
         // Process newer photos first.
         pics.reverse();
 
-        for mut pic in pics {
-            let result = self.previewer.set_preview(&mut pic);
-            if let Err(e) = result {
-                println!("Failed set_preview: {:?}", e);
-                continue;
-            }
-
-            let result = self.repo.lock().unwrap().add_preview(&pic);
-            if let Err(e) = result {
-                println!("Failed add_preview: {:?}", e);
-                continue;
-            }
-
-            if let Err(e) = sender.output(GeneratePreviewsOutput::PreviewUpdated(pic.picture_id, pic.square_preview_path)) {
-                println!("Failed sending PreviewUpdated: {:?}", e);
-            }
-        }
+        pics.clone().par_iter_mut()
+            .filter(|pic| !pic.square_preview_path.as_ref().is_some_and(|p| p.exists()))
+            .map(|mut pic| {
+                self.previewer.set_preview(&mut pic);
+                pic
+            })
+            .for_each(|pic| {
+                let result = self.repo.lock().unwrap().add_preview(&pic);
+                if let Err(e) = result {
+                    println!("Failed add_preview: {:?}", e);
+                } else if let Err(e) = sender.output(GeneratePreviewsOutput::PreviewUpdated(pic.picture_id, pic.square_preview_path.clone())) {
+                    println!("Failed sending PreviewUpdated: {:?}", e);
+                }
+            });
 
         println!("Generated {} previews in {} seconds.", pics_count, start.elapsed().as_secs());