extremely fancy code to transparently handle gzip

src/main.rs

@@ -97,7 +97,24 @@ fn get_texture_refs(dom:&rbx_dom_weak::WeakDom) -> Vec<rbx_dom_weak::types::Ref>
     objects
 }
 
-fn get_dom<R:Read+Seek>(input:&mut R)->AResult<rbx_dom_weak::WeakDom>{
+enum ReaderType<'a, R:Read+Seek>{
+    GZip(flate2::read::GzDecoder<&'a mut R>),
+    Raw(&'a mut R),
+}
+
+fn maybe_gzip_decode<R:Read+Seek>(input:&mut R)->AResult<ReaderType<R>>{
+    let mut first_2=[0u8;2];
+    if let (Ok(()),Ok(()))=(std::io::Read::read_exact(input, &mut first_2),std::io::Seek::rewind(input)){
+        match &first_2{
+            b"\x1f\x8b"=>Ok(ReaderType::GZip(flate2::read::GzDecoder::new(input))),
+            _=>Ok(ReaderType::Raw(input)),
+        }
+    }else{
+        Err(anyhow::Error::msg("failed to peek"))
+    }
+}
+
+fn load_dom<R:Read+Seek>(input:&mut R)->AResult<rbx_dom_weak::WeakDom>{
     let mut first_8=[0u8;8];
     if let (Ok(()),Ok(()))=(std::io::Read::read_exact(input, &mut first_8),std::io::Seek::rewind(input)){
         match &first_8[0..4]{
@@ -115,6 +132,19 @@ fn get_dom<R:Read+Seek>(input:&mut R)->AResult<rbx_dom_weak::WeakDom>{
     }
 }
 
+fn get_dom<R:Read+Seek>(input:&mut R)->AResult<rbx_dom_weak::WeakDom>{
+    match maybe_gzip_decode(input){
+        Ok(ReaderType::GZip(mut readable)) => {
+            //gzip
+            let mut extracted:Vec<u8>=Vec::new();
+            readable.read_to_end(&mut extracted)?;
+            Ok(load_dom(&mut std::io::Cursor::new(extracted))?)
+        },
+        Ok(ReaderType::Raw(readable)) => Ok(load_dom(readable)?),
+        Err(e) => Err(e)?,
+    }
+}
+
 fn get_id() -> AResult<u32>{
     match std::fs::read_to_string("id"){
         Ok(id_file)=>Ok(id_file.parse::<u32>()?),
@@ -306,24 +336,32 @@ fn download_textures(paths: Vec<std::path::PathBuf>) -> AResult<()>{
     Ok(())
 }
 
-fn convert(file_thing:std::fs::DirEntry) -> AResult<()>{
-    let mut input = std::io::BufReader::new(std::fs::File::open(file_thing.path())?);
+fn load_image<R:Read+Seek+std::io::BufRead>(input:&mut R)->AResult<image::DynamicImage>{
     let mut fourcc=[0u8;4];
     input.read_exact(&mut fourcc)?;
     input.rewind()?;
+    match &fourcc{
+        b"\x89PNG"=>Ok(image::load(input,image::ImageFormat::Png)?),
+        _=>Err(anyhow::Error::msg("Unknown texture format")),
+    }
+}
+
+fn convert(file_thing:std::fs::DirEntry) -> AResult<()>{
+    let mut input = std::io::BufReader::new(std::fs::File::open(file_thing.path())?);
 
     let mut extracted_input=None;
-    let image=if&fourcc==b"\x89PNG"{
-        image::load(input,image::ImageFormat::Png)?.to_rgba8()//this is setting a=0?
-    }else if &fourcc[0..2]==b"\x1f\x8b"{
-        //gzip
-        let mut extracted:Vec<u8>=Vec::new();
-        flate2::read::GzDecoder::new(input).read_to_end(&mut extracted)?;
-        extracted_input=Some(extracted.clone());
-        image::load(std::io::Cursor::new(extracted),image::ImageFormat::Png)?.to_rgba8()
-    }else{
-        return Err(anyhow::Error::msg("Unknown texture format"));
-    };
+    let image=match maybe_gzip_decode(&mut input){
+        Ok(ReaderType::GZip(mut readable)) => {
+            //gzip
+            let mut extracted:Vec<u8>=Vec::new();
+            //read the entire thing to the end so that I can clone the data and write a png to processed images
+            readable.read_to_end(&mut extracted)?;
+            extracted_input=Some(extracted.clone());
+            load_image(&mut std::io::Cursor::new(extracted))
+        },
+        Ok(ReaderType::Raw(readable)) => load_image(readable),
+        Err(e) => Err(e)?,
+    }?.to_rgba8();//this is setting a=0?
 
     let format=if image.width()%4!=0||image.height()%4!=0{
         image_dds::ImageFormat::R8G8B8A8Srgb