1use super::Style;
2
3/// When printing out one colored string followed by another, use one of
4/// these rules to figure out which *extra* control codes need to be sent.
5#[derive(PartialEq, Clone, Copy, Debug)]
6pub enum Difference {
7 /// Print out the control codes specified by this style to end up looking
8 /// like the second string's styles.
9 ExtraStyles(Style),
10
11 /// Converting between these two is impossible, so just send a reset
12 /// command and then the second string's styles.
13 Reset,
14
15 /// The before style is exactly the same as the after style, so no further
16 /// control codes need to be printed.
17 Empty,
18}
19
20impl Difference {
21 /// Compute the 'style difference' required to turn an existing style into
22 /// the given, second style.
23 ///
24 /// For example, to turn green text into green bold text, it's redundant
25 /// to write a reset command then a second green+bold command, instead of
26 /// just writing one bold command. This method should see that both styles
27 /// use the foreground color green, and reduce it to a single command.
28 ///
29 /// This method returns an enum value because it's not actually always
30 /// possible to turn one style into another: for example, text could be
31 /// made bold and underlined, but you can't remove the bold property
32 /// without also removing the underline property. So when this has to
33 /// happen, this function returns None, meaning that the entire set of
34 /// styles should be reset and begun again.
35 pub fn between(first: &Style, next: &Style) -> Difference {
36 use self::Difference::*;
37
38 // XXX(Havvy): This algorithm is kind of hard to replicate without
39 // having the Plain/Foreground enum variants, so I'm just leaving
40 // it commented out for now, and defaulting to Reset.
41
42 if first == next {
43 return Empty;
44 }
45
46 // Cannot un-bold, so must Reset.
47 if first.is_bold && !next.is_bold {
48 return Reset;
49 }
50
51 if first.is_dimmed && !next.is_dimmed {
52 return Reset;
53 }
54
55 if first.is_italic && !next.is_italic {
56 return Reset;
57 }
58
59 // Cannot un-underline, so must Reset.
60 if first.is_underline && !next.is_underline {
61 return Reset;
62 }
63
64 if first.is_blink && !next.is_blink {
65 return Reset;
66 }
67
68 if first.is_reverse && !next.is_reverse {
69 return Reset;
70 }
71
72 if first.is_hidden && !next.is_hidden {
73 return Reset;
74 }
75
76 if first.is_strikethrough && !next.is_strikethrough {
77 return Reset;
78 }
79
80 // Cannot go from foreground to no foreground, so must Reset.
81 if first.foreground.is_some() && next.foreground.is_none() {
82 return Reset;
83 }
84
85 // Cannot go from background to no background, so must Reset.
86 if first.background.is_some() && next.background.is_none() {
87 return Reset;
88 }
89
90 let mut extra_styles = Style::default();
91
92 if first.is_bold != next.is_bold {
93 extra_styles.is_bold = true;
94 }
95
96 if first.is_dimmed != next.is_dimmed {
97 extra_styles.is_dimmed = true;
98 }
99
100 if first.is_italic != next.is_italic {
101 extra_styles.is_italic = true;
102 }
103
104 if first.is_underline != next.is_underline {
105 extra_styles.is_underline = true;
106 }
107
108 if first.is_blink != next.is_blink {
109 extra_styles.is_blink = true;
110 }
111
112 if first.is_reverse != next.is_reverse {
113 extra_styles.is_reverse = true;
114 }
115
116 if first.is_hidden != next.is_hidden {
117 extra_styles.is_hidden = true;
118 }
119
120 if first.is_strikethrough != next.is_strikethrough {
121 extra_styles.is_strikethrough = true;
122 }
123
124 if first.foreground != next.foreground {
125 extra_styles.foreground = next.foreground;
126 }
127
128 if first.background != next.background {
129 extra_styles.background = next.background;
130 }
131
132 ExtraStyles(extra_styles)
133 }
134}
135
136#[cfg(test)]
137mod test {
138 use super::Difference::*;
139 use super::*;
140 use crate::style::Color::*;
141 use crate::style::Style;
142
143 fn style() -> Style {
144 Style::new()
145 }
146
147 macro_rules! test {
148 ($name: ident: $first: expr; $next: expr => $result: expr) => {
149 #[test]
150 fn $name() {
151 assert_eq!($result, Difference::between(&$first, &$next));
152 }
153 };
154 }
155
156 test!(nothing: Green.normal(); Green.normal() => Empty);
157 test!(uppercase: Green.normal(); Green.bold() => ExtraStyles(style().bold()));
158 test!(lowercase: Green.bold(); Green.normal() => Reset);
159 test!(nothing2: Green.bold(); Green.bold() => Empty);
160
161 test!(color_change: Red.normal(); Blue.normal() => ExtraStyles(Blue.normal()));
162
163 test!(addition_of_blink: style(); style().blink() => ExtraStyles(style().blink()));
164 test!(addition_of_dimmed: style(); style().dimmed() => ExtraStyles(style().dimmed()));
165 test!(addition_of_hidden: style(); style().hidden() => ExtraStyles(style().hidden()));
166 test!(addition_of_reverse: style(); style().reverse() => ExtraStyles(style().reverse()));
167 test!(addition_of_strikethrough: style(); style().strikethrough() => ExtraStyles(style().strikethrough()));
168
169 test!(removal_of_strikethrough: style().strikethrough(); style() => Reset);
170 test!(removal_of_reverse: style().reverse(); style() => Reset);
171 test!(removal_of_hidden: style().hidden(); style() => Reset);
172 test!(removal_of_dimmed: style().dimmed(); style() => Reset);
173 test!(removal_of_blink: style().blink(); style() => Reset);
174}
175