From b4c3bd7356b68e74e23748db0dad7ceb3997fb68 Mon Sep 17 00:00:00 2001
From: Gwilym Kuiper <gw@ilym.me>
Date: Tue, 20 Apr 2021 21:07:57 +0100
Subject: [PATCH] Don't generate if source hasn't been modified

---
 agb-image-converter/src/lib.rs | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/agb-image-converter/src/lib.rs b/agb-image-converter/src/lib.rs
index 3209ac37..681b1be4 100644
--- a/agb-image-converter/src/lib.rs
+++ b/agb-image-converter/src/lib.rs
@@ -1,6 +1,9 @@
+use std::fs;
 use std::fs::File;
+use std::io;
 use std::io::BufWriter;
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
+use std::time::SystemTime;
 
 mod colour;
 mod image_loader;
@@ -35,6 +38,15 @@ pub struct ImageConverterConfig {
 }
 
 pub fn convert_image(settings: &ImageConverterConfig) {
+    let source_modified_time =
+        get_modified_time(&settings.input_image).unwrap_or(SystemTime::now());
+    let target_modified_time =
+        get_modified_time(&settings.output_file).unwrap_or(SystemTime::UNIX_EPOCH);
+
+    if source_modified_time < target_modified_time {
+        return;
+    }
+
     let image = Image::load_from_file(&settings.input_image);
 
     let tile_size = settings.tile_size.to_size();
@@ -82,3 +94,8 @@ fn optimiser_for_image(image: &Image, tile_size: usize) -> palette16::Palette16O
 
     palette_optimiser
 }
+
+fn get_modified_time(path: impl AsRef<Path>) -> io::Result<SystemTime> {
+    let metadata = fs::metadata(path)?;
+    metadata.modified()
+}