refactor nfc reader code a bit

src/drivers/nfc_pn532.rs

@@ -1,4 +1,5 @@
 use alloc::vec::Vec;
+use core::error::Error;
 use embedded_hal::i2c::I2c;
 use log::{error, info};
 use pn532::i2c::I2CInterface;
@@ -8,6 +9,7 @@ use pn532::{Pn532, Request};
 pub type Pn532Device<I2C> = Pn532<I2CInterface<I2C>, (), 34>;
 
 pub const PAGES_PER_READ: usize = 4;
+pub const BYTES_PER_READ: usize = PAGES_PER_READ * 4;
 
 /// PN532 NFC reader driver.
 pub struct NfcPn532Driver<I2C>
@@ -17,6 +19,35 @@ where
     pn532: Pn532Device<I2C>,
 }
 
+#[derive(Debug, Clone)]
+struct PageParseError<const N: usize> {
+    iteration: u8,
+    bytes: [u8; N],
+    status_code: Option<u8>,
+}
+
+impl<const N: usize> Error for PageParseError<N> {}
+
+impl<const N: usize> core::fmt::Display for PageParseError<N> {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        let PageParseError {
+            iteration,
+            bytes,
+            status_code,
+        } = self;
+        match status_code {
+            Some(code) => write!(
+                f,
+                "NFC pages parse error in iteration {iteration} with error code 0x{code:02x}: {bytes:02x?}"
+            ),
+            None => write!(
+                f,
+                "No data available for NFC page in iteration {iteration}: {bytes:02x?}"
+            ),
+        }
+    }
+}
+
 impl<I2C> NfcPn532Driver<I2C>
 where
     I2C: I2c,
@@ -57,16 +88,21 @@ where
         }
     }
 
-    pub fn parse_nfc_page(iteration: u8, bytes: &[u8]) -> Result<[u8; PAGES_PER_READ * 4], ()> {
-        let success = bytes.first().is_some_and(|x| *x == 0);
-        if success {
-            let slice_len = bytes.len().min(PAGES_PER_READ * 4 + 1);
-            let mut arr = [0; PAGES_PER_READ * 4];
+    fn parse_nfc_page(
+        iteration: u8,
+        bytes: &[u8],
+    ) -> Result<[u8; BYTES_PER_READ], PageParseError<BYTES_PER_READ>> {
+        let slice_len = bytes.len().min(BYTES_PER_READ + 1);
+        let mut arr = [0; BYTES_PER_READ];
         arr[..slice_len - 1].copy_from_slice(&bytes[1..slice_len]);
-            Ok(arr)
-        } else {
-            info!("err  {iteration}: {:02x?}", bytes);
-            Err(())
+
+        match bytes.first() {
+            Some(0x00) => Ok(arr),
+            error => Err(PageParseError {
+                iteration,
+                bytes: arr,
+                status_code: error.copied(),
+            }),
         }
     }
 
@@ -79,18 +115,25 @@ where
         let mut data: Vec<u8> = Vec::with_capacity(858);
 
         for i in (0x0B..=230).step_by(PAGES_PER_READ) {
-            let mut parse_result = Err(());
-            while parse_result.is_err() {
-                let Ok(result) = self
+            let bytes = loop {
+                let read = self
                     .pn532
-                    .process_async(&Request::ntag_read(i), PAGES_PER_READ * 4 + 1)
-                    .await
-                else {
+                    .process_async(&Request::ntag_read(i), BYTES_PER_READ + 1)
+                    .await;
+
+                let bytes = match read {
+                    Ok(bytes) => bytes,
+                    Err(e) => {
+                        error!("Reading page {i} failed: {e:?}");
                         continue;
-                };
-                parse_result = Self::parse_nfc_page(i, result);
                     }
-            let bytes = parse_result.unwrap();
+                };
+
+                match Self::parse_nfc_page(i, bytes) {
+                    Ok(data) => break data,
+                    Err(e) => error!("Parsing page failed: {e}"),
+                }
+            };
             let bytes = if i == 0x0B { &bytes[1..] } else { &bytes };
             data.extend(bytes);
         }