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
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
use std::fmt;
use std::iter::FromIterator;
use std::marker::PhantomData;

use bytes::BytesMut;
use util::TryFromValues;
use HeaderValue;

// A single `HeaderValue` that can flatten multiple values with commas.
#[derive(Clone, PartialEq, Eq, Hash)]
pub(crate) struct FlatCsv<Sep = Comma> {
    pub(crate) value: HeaderValue,
    _marker: PhantomData<Sep>,
}

pub(crate) trait Separator {
    const BYTE: u8;
    const CHAR: char;
}

#[derive(Clone, Debug, PartialEq, Eq, Hash)]
pub(crate) enum Comma {}

impl Separator for Comma {
    const BYTE: u8 = b',';
    const CHAR: char = ',';
}

#[derive(Clone, Debug, PartialEq, Eq, Hash)]
pub(crate) enum SemiColon {}

impl Separator for SemiColon {
    const BYTE: u8 = b';';
    const CHAR: char = ';';
}

impl<Sep: Separator> FlatCsv<Sep> {
    pub(crate) fn iter(&self) -> impl Iterator<Item = &str> {
        self.value.to_str().ok().into_iter().flat_map(|value_str| {
            let mut in_quotes = false;
            value_str
                .split(move |c| {
                    if in_quotes {
                        if c == '"' {
                            in_quotes = false;
                        }
                        false // dont split
                    } else {
                        if c == Sep::CHAR {
                            true // split
                        } else {
                            if c == '"' {
                                in_quotes = true;
                            }
                            false // dont split
                        }
                    }
                })
                .map(|item| item.trim())
        })
    }
}

impl<Sep: Separator> TryFromValues for FlatCsv<Sep> {
    fn try_from_values<'i, I>(values: &mut I) -> Result<Self, ::Error>
    where
        I: Iterator<Item = &'i HeaderValue>,
    {
        let flat = values.collect();
        Ok(flat)
    }
}

impl<Sep> From<HeaderValue> for FlatCsv<Sep> {
    fn from(value: HeaderValue) -> Self {
        FlatCsv {
            value,
            _marker: PhantomData,
        }
    }
}

impl<'a, Sep> From<&'a FlatCsv<Sep>> for HeaderValue {
    fn from(flat: &'a FlatCsv<Sep>) -> HeaderValue {
        flat.value.clone()
    }
}

impl<Sep> fmt::Debug for FlatCsv<Sep> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        fmt::Debug::fmt(&self.value, f)
    }
}

impl<'a, Sep: Separator> FromIterator<&'a HeaderValue> for FlatCsv<Sep> {
    fn from_iter<I>(iter: I) -> Self
    where
        I: IntoIterator<Item = &'a HeaderValue>,
    {
        let mut values = iter.into_iter();

        // Common case is there is only 1 value, optimize for that
        if let (1, Some(1)) = values.size_hint() {
            return values
                .next()
                .expect("size_hint claimed 1 item")
                .clone()
                .into();
        }

        // Otherwise, there are multiple, so this should merge them into 1.
        let mut buf = values
            .next()
            .cloned()
            .map(|val| BytesMut::from(val.as_bytes()))
            .unwrap_or_else(|| BytesMut::new());

        for val in values {
            buf.extend_from_slice(&[Sep::BYTE, b' ']);
            buf.extend_from_slice(val.as_bytes());
        }

        let val = HeaderValue::from_maybe_shared(buf.freeze())
            .expect("comma separated HeaderValues are valid");

        val.into()
    }
}

// TODO: would be great if there was a way to de-dupe these with above
impl<Sep: Separator> FromIterator<HeaderValue> for FlatCsv<Sep> {
    fn from_iter<I>(iter: I) -> Self
    where
        I: IntoIterator<Item = HeaderValue>,
    {
        let mut values = iter.into_iter();

        // Common case is there is only 1 value, optimize for that
        if let (1, Some(1)) = values.size_hint() {
            return values.next().expect("size_hint claimed 1 item").into();
        }

        // Otherwise, there are multiple, so this should merge them into 1.
        let mut buf = values
            .next()
            .map(|val| BytesMut::from(val.as_bytes()))
            .unwrap_or_else(|| BytesMut::new());

        for val in values {
            buf.extend_from_slice(&[Sep::BYTE, b' ']);
            buf.extend_from_slice(val.as_bytes());
        }

        let val = HeaderValue::from_maybe_shared(buf.freeze())
            .expect("comma separated HeaderValues are valid");

        val.into()
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn comma() {
        let val = HeaderValue::from_static("aaa, b; bb, ccc");
        let csv = FlatCsv::<Comma>::from(val);

        let mut values = csv.iter();
        assert_eq!(values.next(), Some("aaa"));
        assert_eq!(values.next(), Some("b; bb"));
        assert_eq!(values.next(), Some("ccc"));
        assert_eq!(values.next(), None);
    }

    #[test]
    fn semicolon() {
        let val = HeaderValue::from_static("aaa; b, bb; ccc");
        let csv = FlatCsv::<SemiColon>::from(val);

        let mut values = csv.iter();
        assert_eq!(values.next(), Some("aaa"));
        assert_eq!(values.next(), Some("b, bb"));
        assert_eq!(values.next(), Some("ccc"));
        assert_eq!(values.next(), None);
    }

    #[test]
    fn quoted_text() {
        let val = HeaderValue::from_static("foo=\"bar,baz\", sherlock=holmes");
        let csv = FlatCsv::<Comma>::from(val);

        let mut values = csv.iter();
        assert_eq!(values.next(), Some("foo=\"bar,baz\""));
        assert_eq!(values.next(), Some("sherlock=holmes"));
        assert_eq!(values.next(), None);
    }
}