Use a result for the parser

4 files changed, 57 insertions, 19 deletions

diff --git a/src/field/id.rs b/src/field/id.rs
index 07e02b2..fa854de 100644
--- a/src/field/id.rs
+++ b/src/field/id.rs
@@ -76,8 +76,22 @@ pub enum ID {
 }
 
 impl ID {
+    #[must_use]
     pub fn from_u16(id: u16) -> Self {
-        use ID::*;
+        use ID::{
+            AutomaticResponse, ChatID, ChatOptions, ChatSubject, CommunityBannerID, Data,
+            ErrorText, FileComment, FileCreateDate, FileCreatorString, FileModifyDate, FileName,
+            FileNameWithInfo, FileNewName, FileNewPath, FilePath, FileResumeData, FileSize,
+            FileType, FileTypeString, FileXferOptions, FolderItemCount, LegacyNewsCategoryListData,
+            NewsArticle1stChildArticle, NewsArticleData, NewsArticleDataFlavor, NewsArticleDate,
+            NewsArticleFlags, NewsArticleID, NewsArticleListData, NewsArticleNextArticle,
+            NewsArticleParentArticle, NewsArticlePoster, NewsArticlePrevArticle,
+            NewsArticleRecurseDel, NewsArticleTitle, NewsCategoryGUID, NewsCategoryListData,
+            NewsCategoryName, NewsPath, NoServerAgreement, Options, QuotingMessage,
+            ReferenceNumber, ServerAgreement, ServerBanner, ServerBannerType, ServerBannerUrl,
+            ServerName, TransferSize, Unknown, UserAccess, UserAlias, UserFlags, UserID,
+            UserIconID, UserLogin, UserName, UserNameWithInfo, UserPassword, Version, WaitingCount,
+        };
         match id {
             100 => ErrorText,
             101 => Data,
diff --git a/src/field/mod.rs b/src/field/mod.rs
index 277e7c4..a746ece 100644
--- a/src/field/mod.rs
+++ b/src/field/mod.rs
@@ -4,6 +4,13 @@ pub mod utils;
 pub use id::ID;
 
 use std::convert::TryInto;
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum Error {
+    #[error("Data could not be parsed as an integer.")]
+    InvalidInteger,
+}
 
 /// Hotline defines 3 data types in the wire format:
 /// 1) "integer" (16-bit or 32-bit, determined by magnitude)
@@ -33,9 +40,23 @@ pub struct Field {
 /// - Some field IDs are definitely “integer” (e.g. user ID).
 /// - Some are definitely “string” (e.g. user name).
 /// - Others are “binary” (which might contain sub-structures).
-pub fn parse_field_value(id: ID, data: &[u8]) -> Value {
-    use Value::*;
-    use ID::*;
+#[must_use]
+pub fn parse_field_value(id: ID, data: &[u8]) -> Result<Value, Error> {
+    use Value::{Binary, Integer, Text};
+    use ID::{
+        AutomaticResponse, ChatID, ChatOptions, ChatSubject, CommunityBannerID, Data, ErrorText,
+        FileComment, FileCreateDate, FileCreatorString, FileModifyDate, FileName, FileNameWithInfo,
+        FileNewName, FileNewPath, FilePath, FileResumeData, FileSize, FileType, FileTypeString,
+        FileXferOptions, FolderItemCount, LegacyNewsCategoryListData, NewsArticle1stChildArticle,
+        NewsArticleData, NewsArticleDataFlavor, NewsArticleDate, NewsArticleFlags, NewsArticleID,
+        NewsArticleListData, NewsArticleNextArticle, NewsArticleParentArticle, NewsArticlePoster,
+        NewsArticlePrevArticle, NewsArticleRecurseDel, NewsArticleTitle, NewsCategoryGUID,
+        NewsCategoryListData, NewsCategoryName, NewsPath, NoServerAgreement, Options,
+        QuotingMessage, ReferenceNumber, ServerAgreement, ServerBanner, ServerBannerType,
+        ServerBannerUrl, ServerName, TransferSize, Unknown, UserAccess, UserAlias, UserFlags,
+        UserID, UserIconID, UserLogin, UserName, UserNameWithInfo, UserPassword, Version,
+        WaitingCount,
+    };
 
     // By default, assume "binary"
     // Then override to integer or string if the spec clearly says so.
@@ -71,20 +92,18 @@ pub fn parse_field_value(id: ID, data: &[u8]) -> Value {
 
             let len = data.len();
             if len == 2 {
-                Integer(u16::from_be_bytes(data.try_into().unwrap()) as u32)
+                data.try_into()
+                    .map(u16::from_be_bytes)
+                    .map(u32::from)
+                    .map(Integer)
+                    .map_err(|_| Error::InvalidInteger)
             } else if len == 4 {
-                Integer(u32::from_be_bytes(data.try_into().unwrap()))
-            } else if len == 0 {
-                // no data => 0
-                Integer(0)
+                data.try_into()
+                    .map(u32::from_be_bytes)
+                    .map(Integer)
+                    .map_err(|_| Error::InvalidInteger)
             } else {
-                // fallback
-                // interpret first 4 bytes, or everything as 32-bit
-                let mut buf = [0u8; 4];
-                for (i, b) in data.iter().enumerate().take(4) {
-                    buf[i] = *b;
-                }
-                Integer(u32::from_be_bytes(buf))
+                Err(Error::InvalidInteger)
             }
         }
 
@@ -106,7 +125,7 @@ pub fn parse_field_value(id: ID, data: &[u8]) -> Value {
         | NewsArticleTitle
         | NewsArticlePoster => {
             let s = String::from_utf8_lossy(data).to_string();
-            Text(s)
+            Ok(Text(s))
         }
 
         // Some are definitely “binary,” but might happen to contain text:
@@ -133,6 +152,6 @@ pub fn parse_field_value(id: ID, data: &[u8]) -> Value {
         | NewsPath
         | NewsArticleDate
         | NewsArticleData
-        | Unknown(_) => Binary(data.to_vec()),
+        | Unknown(_) => Ok(Binary(data.to_vec())),
     }
 }
diff --git a/src/field/utils/access_privileges.rs b/src/field/utils/access_privileges.rs
index eea9557..fabaef4 100644
--- a/src/field/utils/access_privileges.rs
+++ b/src/field/utils/access_privileges.rs
@@ -42,6 +42,7 @@ pub const CAN_UPLOAD_FOLDERS: u64 = 2_u64.pow(38);
 pub const CAN_DOWNLOAD_FOLDERS: u64 = 2_u64.pow(39);
 pub const CAN_SEND_MESSAGES: u64 = 2_u64.pow(40);
 
+#[must_use]
 pub fn can(permission: u64, bits: u64) -> bool {
     bits & permission != 0
 }
diff --git a/src/field/utils/user_flags.rs b/src/field/utils/user_flags.rs
index 6c79e8b..06ac5db 100644
--- a/src/field/utils/user_flags.rs
+++ b/src/field/utils/user_flags.rs
@@ -1,22 +1,26 @@
-//! This module contains utilities to read the data in a UserFlags bitmap.
+//! This module contains utilities to read the data in a `UserFlags` bitmap.
 
 const AWAY: u32 = 0b0001;
 const ADMIN_OR_DISCONNECTED: u32 = 0b0010;
 const REFUSES_PRIVATE_MESSAGES: u32 = 0b0100;
 const REFUSES_PRIVATE_CHAT: u32 = 0b1000;
 
+#[must_use]
 pub fn is_away(bits: u32) -> bool {
     bits & AWAY != 0
 }
 
+#[must_use]
 pub fn is_admin_or_disconnected(bits: u32) -> bool {
     bits & ADMIN_OR_DISCONNECTED != 0
 }
 
+#[must_use]
 pub fn refuses_private_messages(bits: u32) -> bool {
     bits & REFUSES_PRIVATE_MESSAGES != 0
 }
 
+#[must_use]
 pub fn refuses_private_chat(bits: u32) -> bool {
     bits & REFUSES_PRIVATE_CHAT != 0
 }