Rename a few files for clarity

src/errors.rs

@@ -0,0 +1,54 @@
+use nom::error::{ErrorKind, ParseError as NomParseError};
+use thiserror::Error;
+
+#[derive(Debug, Error)]
+pub enum DecodeError {
+    #[error("invalid ZZT file magic")]
+    InvalidMagic,
+
+    #[error("invalid tile count: {0}")]
+    InvalidTileCount(usize),
+
+    #[error("negative stat count")]
+    NegativeStatCount,
+
+    #[error("unexpected end of file")]
+    UnexpectedEof,
+
+    #[error("unknown decode error")]
+    Unknown,
+}
+
+impl<I> NomParseError<I> for DecodeError {
+    fn from_error_kind(_input: I, kind: ErrorKind) -> Self {
+        match kind {
+            ErrorKind::Eof => Self::UnexpectedEof,
+            _ => Self::Unknown,
+        }
+    }
+
+    fn append(_input: I, _kind: ErrorKind, other: Self) -> Self {
+        other
+    }
+}
+
+impl From<nom::Err<DecodeError>> for DecodeError {
+    fn from(value: nom::Err<DecodeError>) -> Self {
+        match value {
+            nom::Err::Error(e) | nom::Err::Failure(e) => e,
+            nom::Err::Incomplete(_) => Self::UnexpectedEof,
+        }
+    }
+}
+
+#[derive(Debug, Error)]
+pub enum EncodeError {
+    #[error("string too long")]
+    StringTooLong { max: u8 },
+
+    #[error("cannot encode character: {0}")]
+    EncodingError(char),
+
+    #[error("board data too large")]
+    BoardTooLarge,
+}