Store source modified timestamp with processed, lightmap and map tiles

Allows to check whether the source is newer than the last update of the
output files.

src/bin/minedmap/region_processor.rs

@@ -1,4 +1,4 @@
-use std::path::Path;
+use std::{path::Path, time::SystemTime};
 
 use anyhow::{Context, Result};
 
@@ -65,14 +65,25 @@ impl<'a> RegionProcessor<'a> {
 		})
 	}
 
-	fn save_region(&self, coords: TileCoords, processed_region: &ProcessedRegion) -> Result<()> {
+	fn save_region(
+		&self,
+		coords: TileCoords,
+		processed_region: &ProcessedRegion,
+		timestamp: SystemTime,
+	) -> Result<()> {
 		let output_path = self.config.processed_path(coords);
-		storage::write(&output_path, processed_region)
+		storage::write(&output_path, processed_region, timestamp)
 	}
 
-	fn save_lightmap(&self, coords: TileCoords, lightmap: &image::GrayAlphaImage) -> Result<()> {
-		fs::create_with_tmpfile(
+	fn save_lightmap(
+		&self,
+		coords: TileCoords,
+		lightmap: &image::GrayAlphaImage,
+		timestamp: SystemTime,
+	) -> Result<()> {
+		fs::create_with_timestamp(
 			&self.config.tile_path(TileKind::Lightmap, 0, coords),
+			timestamp,
 			|file| {
 				lightmap
 					.write_to(file, image::ImageFormat::Png)
@@ -90,6 +101,8 @@ impl<'a> RegionProcessor<'a> {
 		let mut processed_region = ProcessedRegion::default();
 		let mut lightmap = image::GrayAlphaImage::new(N, N);
 
+		let timestamp = fs::modified_timestamp(path)?;
+
 		minedmap::io::region::from_file(path)?.foreach_chunk(
 			|chunk_coords, data: world::de::Chunk| {
 				let Some(layer::LayerData{ blocks, biomes, block_light, depths }) = self
@@ -111,8 +124,8 @@ impl<'a> RegionProcessor<'a> {
 			},
 		)?;
 
-		self.save_region(coords, &processed_region)?;
-		self.save_lightmap(coords, &lightmap)?;
+		self.save_region(coords, &processed_region, timestamp)?;
+		self.save_lightmap(coords, &lightmap, timestamp)?;
 
 		Ok(())
 	}

src/bin/minedmap/tile_renderer.rs

@@ -1,3 +1,5 @@
+use std::time::SystemTime;
+
 use anyhow::{Context, Result};
 
 use minedmap::{
@@ -17,9 +19,12 @@ impl<'a> TileRenderer<'a> {
 		TileRenderer { config }
 	}
 
-	fn load_region(&self, coords: TileCoords) -> Result<ProcessedRegion> {
+	fn load_region(&self, coords: TileCoords) -> Result<(ProcessedRegion, SystemTime)> {
 		let processed_path = self.config.processed_path(coords);
-		storage::read(&processed_path).context("Failed to load processed region data")
+		let timestamp = fs::modified_timestamp(&processed_path)?;
+		let region =
+			storage::read(&processed_path).context("Failed to load processed region data")?;
+		Ok((region, timestamp))
 	}
 
 	fn render_chunk(image: &mut image::RgbaImage, coords: ChunkCoords, chunk: &ProcessedChunk) {
@@ -69,11 +74,11 @@ impl<'a> TileRenderer<'a> {
 				.display(),
 		);
 
-		let region = self.load_region(coords)?;
+		let (region, timestamp) = self.load_region(coords)?;
 		let mut image = image::RgbaImage::new(N, N);
 		Self::render_region(&mut image, &region);
 
-		fs::create_with_tmpfile(&output_path, |file| {
+		fs::create_with_timestamp(&output_path, timestamp, |file| {
 			image
 				.write_to(file, image::ImageFormat::Png)
 				.context("Failed to save image")

src/io/fs.rs

@@ -2,19 +2,34 @@ use std::{
 	fs::{self, File},
 	io::{BufReader, BufWriter, Read, Write},
 	path::{Path, PathBuf},
+	time::SystemTime,
 };
 
 use anyhow::{Context, Ok, Result};
+use serde::Serialize;
 
-fn tmpfile_name(path: &Path) -> PathBuf {
+#[derive(Debug, Serialize)]
+struct FileMeta {
+	timestamp: SystemTime,
+}
+
+fn suffix_name(path: &Path, suffix: &str) -> PathBuf {
 	let mut file_name = path.file_name().unwrap_or_default().to_os_string();
-	file_name.push(".tmp");
+	file_name.push(suffix);
 
 	let mut ret = path.to_path_buf();
 	ret.set_file_name(file_name);
 	ret
 }
 
+fn tmpfile_name(path: &Path) -> PathBuf {
+	suffix_name(path, ".tmp")
+}
+
+fn metafile_name(path: &Path) -> PathBuf {
+	suffix_name(path, ".meta")
+}
+
 pub fn create_dir_all(path: &Path) -> Result<()> {
 	fs::create_dir_all(path)
 		.with_context(|| format!("Failed to create directory {}", path.display(),))
@@ -84,3 +99,29 @@ where
 
 	ret
 }
+
+pub fn modified_timestamp(path: &Path) -> Result<SystemTime> {
+	fs::metadata(path)
+		.and_then(|meta| meta.modified())
+		.with_context(|| {
+			format!(
+				"Failed to get modified timestamp of file {}",
+				path.display()
+			)
+		})
+}
+
+pub fn create_with_timestamp<T, F>(path: &Path, timestamp: SystemTime, f: F) -> Result<T>
+where
+	F: FnOnce(&mut BufWriter<File>) -> Result<T>,
+{
+	let ret = create_with_tmpfile(path, f)?;
+
+	let meta_path = metafile_name(path);
+	create(&meta_path, |file| {
+		serde_json::to_writer(file, &FileMeta { timestamp })?;
+		Ok(())
+	})?;
+
+	Ok(ret)
+}

src/io/storage.rs

@@ -2,6 +2,7 @@ use std::{
 	fs::File,
 	io::{Read, Write},
 	path::Path,
+	time::SystemTime,
 };
 
 use anyhow::{Context, Result};
@@ -9,8 +10,8 @@ use serde::{de::DeserializeOwned, Serialize};
 
 use super::fs;
 
-pub fn write<T: Serialize>(path: &Path, value: &T) -> Result<()> {
-	fs::create_with_tmpfile(path, |file| {
+pub fn write<T: Serialize>(path: &Path, value: &T, timestamp: SystemTime) -> Result<()> {
+	fs::create_with_timestamp(path, timestamp, |file| {
 		let data = bincode::serialize(value)?;
 		let len = u32::try_from(data.len())?;
 		let compressed = zstd::bulk::compress(&data, 1)?;