Iterators are melting my brain

Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "qoicodec"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

src/main.rs

@@ -1,5 +1,53 @@
+
+use std::{fs::File, io::Read};
+
 fn main() {
-    println!("Hello, world!");
+    let file = File::open("qoi_test_images/dice.qoi").unwrap();
+    let mut bytes = file.bytes()
+        .map(|maybe_bytes|
+        {
+            match maybe_bytes {
+                Ok(byte) => byte,
+                Err(oops) => panic!("Oops, the file failed to load: {}", oops)
+            }
+        });
+    if let Err(e) = try_read_magic(&mut bytes) {
+        match e {
+            DecodeError::Magic => panic!("QOI Magic bytes are bad!"),
+            DecodeError::EarlyIteratorExhaustion => panic!("File iterator exhausted earlier than expected."),
+            _ => panic!("Unhandled error reading magic: {:?}", e),
+        }
+    }
+
+    todo!("The rest of the main function");
+}
+
+fn try_read_magic<I: Iterator<Item=u8>>(bytes: &mut I) -> Result<(), DecodeError> {
+    let magic: [u8; 4] = [b'q', b'o', b'i', b'f'];
+    for i in 0..4 {
+        if let Some(letter) = bytes.next() {
+            if letter != magic[i] {
+                return Err(DecodeError::Magic)
+            }
+        } else {
+            return Err(DecodeError::EarlyIteratorExhaustion)
+        }
+    }
+    return Ok(())
+}
+
+fn try_read_u32<I: Iterator<Item=u8>>(bytes: &mut I) -> Result<u32, DecodeError> {
+    let mut res: u32 = 0;
+    
+    Ok(res) 
+}
+
+#[derive(Debug)]
+enum DecodeError {
+    Magic,
+    Channels,
+    ColorSpace,
+    EarlyIteratorExhaustion,
 }
 
 #[derive(Clone, Copy, Default, Debug, PartialEq)]