utils/input.rs
1//! Items relating to puzzle input.
2
3use std::error::Error;
4use std::fmt::{Display, Formatter};
5
6/// Enum for distinguishing between example and real inputs.
7///
8/// Some puzzles require this as different constants may be used for example inputs to simplify the
9/// problem. For example [2022 day 15](https://adventofcode.com/2022/day/15) part 1, which uses
10/// `y=10` in the example, but `y=2000000` for real inputs.
11///
12/// Most puzzle solutions should ignore this value.
13#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Debug)]
14pub enum InputType {
15 Example,
16 Real,
17}
18
19/// Error type that shows the error's location in the input, returned by puzzle `new` functions.
20///
21/// # Examples
22///
23/// ```
24/// # use utils::input::InputError;
25/// let input = "12 34\n56 78\n90 abc";
26/// let error = InputError::new(input, 15, "expected number");
27/// assert_eq!(error.to_string(), "
28/// invalid input: expected number
29/// --> line 3 column 4
30/// |
31/// 3 | 90 abc
32/// | ^
33/// ".trim_start());
34/// ```
35#[derive(Debug)]
36pub struct InputError {
37 line_number: usize,
38 column_number: usize,
39 line: String,
40 source: Box<dyn Error>,
41}
42
43impl InputError {
44 /// Create a new [`InputError`].
45 ///
46 /// See [`ToIndex`] implementations for details on supported indexes.
47 #[cold]
48 pub fn new(input: &str, index: impl ToIndex, source: impl Into<Box<dyn Error>>) -> Self {
49 let index = index.input_index(input);
50 let (line_number, column_number, line) = Self::line_position(input, index);
51 let line = line.replace('\t', " ");
52
53 InputError {
54 line_number,
55 column_number,
56 line,
57 source: source.into(),
58 }
59 }
60
61 #[cold]
62 fn line_position(input: &str, index: usize) -> (usize, usize, String) {
63 let start = input[..index].rfind('\n').map_or(0, |p| p + 1);
64 let end = input[start..].find('\n').map_or(input.len(), |p| p + start);
65 let line = input[start..end].trim_end_matches('\r');
66
67 let line_number = input[..start].matches('\n').count() + 1;
68 let column_number = index - start + 1;
69
70 (line_number, column_number, line.to_string())
71 }
72
73 /// Returns the source error.
74 #[must_use]
75 pub fn into_source(self) -> Box<dyn Error> {
76 self.source
77 }
78}
79
80impl Display for InputError {
81 fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), std::fmt::Error> {
82 let pad = " ".repeat(self.line_number.to_string().len());
83
84 write!(
85 f,
86 "invalid input: {}\n --> line {} column {}\n{pad} |\n{} | {}\n{pad} |{}^\n",
87 self.source,
88 self.line_number,
89 self.column_number,
90 self.line_number,
91 self.line,
92 " ".repeat(self.column_number),
93 )
94 }
95}
96
97impl Error for InputError {
98 fn source(&self) -> Option<&(dyn Error + 'static)> {
99 Some(&*self.source)
100 }
101}
102
103/// Helper trait to simplify error location tracking.
104///
105/// Used in [`InputError::new`].
106pub trait ToIndex {
107 fn input_index(self, input: &str) -> usize;
108}
109
110impl ToIndex for &str {
111 /// Find index of this substring in the provided input.
112 ///
113 /// Uses the pointer offset, meaning it works if this substring is not the first occurrence in
114 /// the string. This allows recovering the error position without tracking an offset into the
115 /// string, which is useful when using [`Iterator`]s such as [`str::lines`] on an input.
116 ///
117 /// # Panics
118 ///
119 /// This function panics if this string is not a substring inside the provided string.
120 ///
121 /// # Examples
122 ///
123 /// ```
124 /// # use utils::input::ToIndex;
125 /// let string = "abcabc";
126 /// assert_eq!(string[4..].input_index(string), 4);
127 /// ```
128 ///
129 /// ```should_panic
130 /// # use utils::input::ToIndex;
131 /// let string = "abcabc";
132 /// let mut other = String::new();
133 /// other.push('b');
134 /// other.push('c');
135 /// other.input_index(string);
136 /// ```
137 fn input_index(self, input: &str) -> usize {
138 self.as_bytes().input_index(input)
139 }
140}
141
142impl ToIndex for &[u8] {
143 /// Find index of this subslice in the provided input.
144 ///
145 /// For use with functions that iterate over a string's bytes.
146 /// See the [`&str`](#impl-ToIndex-for-%26str) implementation.
147 fn input_index(self, input: &str) -> usize {
148 let self_ptr = self.as_ptr() as usize;
149 let input_ptr = input.as_ptr() as usize;
150 match self_ptr.checked_sub(input_ptr) {
151 Some(offset) if offset + self.len() <= input.len() => offset,
152 _ => panic!("invalid string index: {self_ptr:#x} is not a substring of {input_ptr:#x}"),
153 }
154 }
155}
156
157impl ToIndex for char {
158 /// Find the first instance of this character in the string.
159 ///
160 /// Intended for puzzles where the entire input should be a certain set of characters, so
161 /// if an invalid character is found, the instance in the error doesn't matter.
162 ///
163 /// # Panics
164 ///
165 /// This function panics if this character is not present in the string
166 ///
167 /// # Examples
168 ///
169 /// ```
170 /// # use utils::input::ToIndex;
171 /// let string = "abca bc";
172 /// assert_eq!(' '.input_index(string), 4);
173 /// ```
174 ///
175 /// ```should_panic
176 /// # use utils::input::ToIndex;
177 /// let string = "abcdef";
178 /// ' '.input_index(string);
179 /// ```
180 fn input_index(self, input: &str) -> usize {
181 input
182 .find(self)
183 .unwrap_or_else(|| panic!("invalid string index: char {self:?} not found in {input:?}"))
184 }
185}
186
187impl ToIndex for usize {
188 /// Index into the input string.
189 ///
190 /// # Panics
191 ///
192 /// This function panics if the index is out of range for the provided string.
193 ///
194 /// # Examples
195 ///
196 /// ```
197 /// # use utils::input::ToIndex;
198 /// let string = "abcdef";
199 /// assert_eq!(4.input_index(string), 4);
200 /// ```
201 ///
202 /// ```should_panic
203 /// # use utils::input::ToIndex;
204 /// let string = "abcdef";
205 /// 10.input_index(string);
206 /// ```
207 fn input_index(self, input: &str) -> usize {
208 assert!(
209 self <= input.len(),
210 "invalid string index: index {self} out of range"
211 );
212 self
213 }
214}
215
216/// Extension trait to simplify converting errors and locations into [`InputError`]s.
217///
218/// Note that constructing [`InputError`] is expensive, and therefore conversion should be done as
219/// late as possible, to avoid unnecessary work if the error is discarded (for example,
220/// by [`Parser::or`](crate::parser::Parser::or)).
221pub trait MapWithInputExt {
222 type Output;
223 fn map_with_input(self, input: &str) -> Self::Output;
224}
225
226impl<E: Into<Box<dyn Error>>, I: ToIndex> MapWithInputExt for (E, I) {
227 type Output = InputError;
228
229 #[cold]
230 fn map_with_input(self, input: &str) -> Self::Output {
231 InputError::new(input, self.1, self.0)
232 }
233}
234
235impl<T, E: Into<Box<dyn Error>>, I: ToIndex> MapWithInputExt for Result<T, (E, I)> {
236 type Output = Result<T, InputError>;
237
238 #[inline]
239 fn map_with_input(self, input: &str) -> Self::Output {
240 self.map_err(|err| err.map_with_input(input))
241 }
242}