inform 0.3.4

Another Rust indentation formatter
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123

// Copyright (C) 2024 Ethan Uppal. All rights reserved.
//
// This file is part of inform. inform is free software: you can redistribute it
// and/or modify it under the terms of the GNU Lesser General Public License as
// published by the Free Software Foundation, either version 3 of the License,
// or (at your option) any later version. inform is distributed in the hope that
// it will be useful, but WITHOUT ANY WARRANTY; without even the implied
// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details. You should have received a
// copy of the GNU Lesser General Public License along with inform. If not, see
// <https://www.gnu.org/licenses/>.

//! Base implementation of an indent writer.

use std::marker::PhantomData;

use crate::marker::IndentWriteMarker;

/// A writer abstracting over [`std::io::Write`] (when `M` is
/// [`crate::marker::IO`]) and [`std::fmt::Write`] (when `M` is
/// [`crate::marker::Format`]).
pub(crate) trait IndentWrite<M: IndentWriteMarker> {
    /// Error type for I/O or formatting operations.
    type Error;

    fn write_char(&mut self, c: char) -> Result<(), Self::Error>;
    fn write_str(&mut self, str: &str) -> Result<(), Self::Error>;
    fn flush(&mut self) -> Result<(), Self::Error>;
}

/// Modular implementation of indent formatting generic over [`IndentWrite`].
pub(crate) struct IndentWriterImpl<'w, M: IndentWriteMarker, W: IndentWrite<M>>
{
    /// The amount to indent by.
    indent_delta: usize,

    /// The current indent as a string of spaces.
    current_indent: String,

    /// Whether the last character written was a newline.
    last_was_newline: bool,

    pub(crate) wrapped: &'w mut W,

    _marker: PhantomData<M>,
}

impl<'w, M: IndentWriteMarker, W: IndentWrite<M>> IndentWriterImpl<'w, M, W> {
    pub(crate) fn new(wrapped: &'w mut W, indent_delta: usize) -> Self {
        Self {
            indent_delta,
            current_indent: String::new(),
            last_was_newline: false,
            wrapped,
            _marker: PhantomData,
        }
    }

    #[inline]
    pub(crate) fn increase_indent(&mut self) {
        for _ in 0..self.indent_delta {
            self.current_indent.push(' ');
        }
    }

    #[inline]
    pub(crate) fn decrease_indent(&mut self) {
        let new_length = self.current_indent.len() - self.indent_delta;
        self.current_indent.truncate(new_length);
    }

    #[inline]
    pub(crate) fn indent_if_needed(
        &mut self,
    ) -> Result<(), <Self as IndentWrite<M>>::Error> {
        if self.last_was_newline {
            self.wrapped.write_str(&self.current_indent)?;
            self.last_was_newline = false;
        }
        Ok(())
    }
}

impl<M: IndentWriteMarker, W: IndentWrite<M>> IndentWrite<M>
    for IndentWriterImpl<'_, M, W>
{
    type Error = W::Error;

    #[inline]
    fn write_char(&mut self, c: char) -> Result<(), Self::Error> {
        self.indent_if_needed()?;
        self.wrapped.write_char(c)?;
        self.last_was_newline = c == '\n';
        Ok(())
    }

    #[inline]
    fn write_str(&mut self, str: &str) -> Result<(), Self::Error> {
        for c in str.chars() {
            self.write_char(c)?;
        }
        Ok(())
    }

    #[inline]
    fn flush(&mut self) -> Result<(), Self::Error> {
        self.wrapped.flush()
    }
}

/// Common API for indent writers.
pub trait IndentWriterCommon {
    /// Adds a level of indentation. The new indent takes effect upon the next
    /// newline.
    fn increase_indent(&mut self);

    /// Removes a level of indentation. The new indent takes effect upon the
    /// next newline.
    fn decrease_indent(&mut self);

    /// You will usually not need to call this function manually.
    fn indent_if_needed(&mut self);
}