Improve error handling and add Info::from_file()

Cargo.toml

@@ -12,3 +12,4 @@ categories = ["data-structures", "games"]
 [dependencies]
 serde = { version = "1.0.204", features = ["derive"] }
 serde_json = "1.0.121"
+thiserror = "1.0.63"

src/info.rs

@@ -1,9 +1,14 @@
 //! Module related to `Info.dat` map file.
 
-use std::path::PathBuf;
+use std::{
+    fs,
+    path::{Path, PathBuf},
+};
 
 use serde::{Deserialize, Serialize};
 
+use crate::Error;
+
 /// Describes basic metadata about the song and points to map's other files.
 ///
 /// Refer to the [BSMG Wiki](https://bsmg.wiki/mapping/map-format/info.html) for language-agnostic documentation.
@@ -52,6 +57,13 @@ impl Default for Info {
     }
 }
 
+impl Info {
+    /// Instatiates an [`Info`] from an info file, typically named `Info.dat`.
+    pub fn from_file(path: impl AsRef<Path>) -> Result<Self, Error> {
+        Ok(serde_json::from_str(&fs::read_to_string(path)?)?)
+    }
+}
+
 /// Describes basic metadata about the song.
 ///
 /// Refer to the [BSMG Wiki](https://bsmg.wiki/mapping/map-format/info.html#song-metadata) for language-agnostic documentation.

src/lib.rs

@@ -15,12 +15,23 @@
 mod hex;
 pub mod info;
 
-use std::{fs, path::PathBuf};
+use std::{io, path::Path};
 
-use serde::de::Error;
+use thiserror::Error;
 
 pub use self::info::Info;
 
+/// Any error that may occur from a function originating in this library.
+#[derive(Error, Debug)]
+pub enum Error {
+    /// Error from [`serde_json`].
+    #[error(transparent)]
+    SerdeJson(#[from] serde_json::Error),
+    /// Error from [`std::io`].
+    #[error(transparent)]
+    Io(#[from] io::Error),
+}
+
 /// Structural representation of a Beat Saber map folder.
 ///
 /// Refer to the [BSMG Wiki](https://bsmg.wiki/mapping/map-format.html) for language-agnostic documentation.
@@ -34,20 +45,9 @@ pub struct BeatSaberMap {
 
 impl BeatSaberMap {
     /// Deserializes the files in a map folder.
-    pub fn from_dir(dir: impl Into<PathBuf>) -> serde_json::Result<Self> {
+    pub fn from_dir(dir: impl AsRef<Path>) -> Result<Self, Error> {
         Ok(BeatSaberMap {
-            info: serde_json::from_str(&fs::read_to_string(dir.into().join("Info.dat")).map_err(
-                |err| {
-                    let err_string = err.to_string();
-
-                    serde_json::Error::custom(match err_string.chars().nth(0) {
-                        Some(first_char) => {
-                            first_char.to_lowercase().to_string() + &err_string[1..]
-                        }
-                        None => err_string,
-                    })
-                },
-            )?)?,
+            info: Info::from_file(dir.as_ref().join("Info.dat"))?,
         })
     }
 }