From 7b9bff64d6c13cc8ea592c2ef6fec96d7062f0c5 Mon Sep 17 00:00:00 2001
From: Stefan Kreutz <mail@skreutz.com>
Date: Sat, 28 May 2022 13:43:53 +0200
Subject: Return typed validation errors

---
 src/lib.rs | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 54 insertions(+), 11 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index f50dea0..e99418c 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -25,7 +25,7 @@
 //! assert_eq!(bytes_to_hex(&psk), "cb5de4e4d23b2ab0bf5b9ba0fe8132c1e2af3bb52298ec801af8ad520cea3437");
 //! ```
 
-use std::fmt::Display;
+use std::{error::Error, fmt::Display};
 
 use hmac::Hmac;
 use pbkdf2::pbkdf2;
@@ -36,13 +36,13 @@ use sha1::Sha1;
 pub struct Ssid<'a>(&'a [u8]);
 
 impl<'a> TryFrom<&'a [u8]> for Ssid<'a> {
-    type Error = &'static str;
+    type Error = ValidateSsidError;
 
     fn try_from(value: &'a [u8]) -> Result<Self, Self::Error> {
         if value.is_empty() {
-            Err("SSID must have at least one byte")
+            Err(ValidateSsidError::TooShort)
         } else if value.len() > 32 {
-            Err("SSID must have at most 32 bytes")
+            Err(ValidateSsidError::TooLong)
         } else {
             Ok(Ssid(value))
         }
@@ -50,27 +50,45 @@ impl<'a> TryFrom<&'a [u8]> for Ssid<'a> {
 }
 
 impl<'a> TryFrom<&'a str> for Ssid<'a> {
-    type Error = &'static str;
+    type Error = ValidateSsidError;
 
     fn try_from(value: &'a str) -> Result<Self, Self::Error> {
         Self::try_from(value.as_bytes())
     }
 }
 
+#[derive(Debug, PartialEq)]
+pub enum ValidateSsidError {
+    TooShort,
+    TooLong,
+}
+
+impl Error for ValidateSsidError {}
+
+impl Display for ValidateSsidError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let msg = match self {
+            ValidateSsidError::TooShort => "SSID must have at least one byte",
+            ValidateSsidError::TooLong => "SSID must have at most 32 bytes",
+        };
+        write!(f, "{msg}")
+    }
+}
+
 /// A passphrase consisting of 8 up to 63 printable ASCII characters.
 #[derive(Debug)]
 pub struct Passphrase<'a>(&'a [u8]);
 
 impl<'a> TryFrom<&'a [u8]> for Passphrase<'a> {
-    type Error = &'static str;
+    type Error = ValidatePassphraseError;
 
     fn try_from(value: &'a [u8]) -> Result<Self, Self::Error> {
         if value.len() < 8 {
-            Err("passphrase must have at least 8 bytes")
+            Err(ValidatePassphraseError::TooShort)
         } else if value.len() > 63 {
-            Err("passphrase must have at most 63 bytes")
+            Err(ValidatePassphraseError::TooLong)
         } else if value.iter().any(|i| !matches!(i, 32u8..=126)) {
-            Err("passphrase must consist of printable ASCII characters")
+            Err(ValidatePassphraseError::InvalidByte)
         } else {
             Ok(Passphrase(value))
         }
@@ -78,7 +96,7 @@ impl<'a> TryFrom<&'a [u8]> for Passphrase<'a> {
 }
 
 impl<'a> TryFrom<&'a str> for Passphrase<'a> {
-    type Error = &'static str;
+    type Error = ValidatePassphraseError;
 
     fn try_from(value: &'a str) -> Result<Self, Self::Error> {
         Self::try_from(value.as_bytes())
@@ -91,6 +109,28 @@ impl Display for Passphrase<'_> {
     }
 }
 
+#[derive(Debug, PartialEq)]
+pub enum ValidatePassphraseError {
+    TooShort,
+    TooLong,
+    InvalidByte,
+}
+
+impl Error for ValidatePassphraseError {}
+
+impl Display for ValidatePassphraseError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let msg = match self {
+            ValidatePassphraseError::TooShort => "passphrase must have at least 8 bytes",
+            ValidatePassphraseError::TooLong => "passphrase must have at most 63 bytes",
+            ValidatePassphraseError::InvalidByte => {
+                "passphrase must consist of printable ASCII characters"
+            }
+        };
+        write!(f, "{msg}")
+    }
+}
+
 /// Returns the WPA-PSK of the given SSID and passphrase.
 pub fn wpa_psk(ssid: &Ssid, passphrase: &Passphrase) -> [u8; 32] {
     wpa_psk_unchecked(ssid.0, passphrase.0)
@@ -125,7 +165,10 @@ mod tests {
 
     #[test]
     fn passphrase_too_short() {
-        Passphrase::try_from("foobar").unwrap_err();
+        assert_eq!(
+            Passphrase::try_from("foobar").unwrap_err(),
+            ValidatePassphraseError::TooShort
+        );
     }
 
     #[test]
-- 
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