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
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
//! YAML serialization helpers.

use crate::char_traits;
use crate::yaml::{Hash, Yaml};
use std::convert::From;
use std::error::Error;
use std::fmt::{self, Display};

/// An error when emitting YAML.
#[derive(Copy, Clone, Debug)]
pub enum EmitError {
    /// A formatting error.
    FmtError(fmt::Error),
}

impl Error for EmitError {
    fn cause(&self) -> Option<&dyn Error> {
        None
    }
}

impl Display for EmitError {
    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            EmitError::FmtError(ref err) => Display::fmt(err, formatter),
        }
    }
}

impl From<fmt::Error> for EmitError {
    fn from(f: fmt::Error) -> Self {
        EmitError::FmtError(f)
    }
}

/// The YAML serializer.
///
/// ```
/// # use yaml_rust2::{YamlLoader, YamlEmitter};
/// let input_string = "a: b\nc: d";
/// let yaml = YamlLoader::load_from_str(input_string).unwrap();
///
/// let mut output = String::new();
/// YamlEmitter::new(&mut output).dump(&yaml[0]).unwrap();
///
/// assert_eq!(output, r#"---
/// a: b
/// c: d"#);
/// ```
#[allow(clippy::module_name_repetitions)]
pub struct YamlEmitter<'a> {
    writer: &'a mut dyn fmt::Write,
    best_indent: usize,
    compact: bool,
    level: isize,
    multiline_strings: bool,
}

/// A convenience alias for emitter functions that may fail without returning a value.
pub type EmitResult = Result<(), EmitError>;

// from serialize::json
fn escape_str(wr: &mut dyn fmt::Write, v: &str) -> Result<(), fmt::Error> {
    wr.write_str("\"")?;

    let mut start = 0;

    for (i, byte) in v.bytes().enumerate() {
        let escaped = match byte {
            b'"' => "\\\"",
            b'\\' => "\\\\",
            b'\x00' => "\\u0000",
            b'\x01' => "\\u0001",
            b'\x02' => "\\u0002",
            b'\x03' => "\\u0003",
            b'\x04' => "\\u0004",
            b'\x05' => "\\u0005",
            b'\x06' => "\\u0006",
            b'\x07' => "\\u0007",
            b'\x08' => "\\b",
            b'\t' => "\\t",
            b'\n' => "\\n",
            b'\x0b' => "\\u000b",
            b'\x0c' => "\\f",
            b'\r' => "\\r",
            b'\x0e' => "\\u000e",
            b'\x0f' => "\\u000f",
            b'\x10' => "\\u0010",
            b'\x11' => "\\u0011",
            b'\x12' => "\\u0012",
            b'\x13' => "\\u0013",
            b'\x14' => "\\u0014",
            b'\x15' => "\\u0015",
            b'\x16' => "\\u0016",
            b'\x17' => "\\u0017",
            b'\x18' => "\\u0018",
            b'\x19' => "\\u0019",
            b'\x1a' => "\\u001a",
            b'\x1b' => "\\u001b",
            b'\x1c' => "\\u001c",
            b'\x1d' => "\\u001d",
            b'\x1e' => "\\u001e",
            b'\x1f' => "\\u001f",
            b'\x7f' => "\\u007f",
            _ => continue,
        };

        if start < i {
            wr.write_str(&v[start..i])?;
        }

        wr.write_str(escaped)?;

        start = i + 1;
    }

    if start != v.len() {
        wr.write_str(&v[start..])?;
    }

    wr.write_str("\"")?;
    Ok(())
}

impl<'a> YamlEmitter<'a> {
    /// Create a new emitter serializing into `writer`.
    pub fn new(writer: &'a mut dyn fmt::Write) -> YamlEmitter {
        YamlEmitter {
            writer,
            best_indent: 2,
            compact: true,
            level: -1,
            multiline_strings: false,
        }
    }

    /// Set 'compact inline notation' on or off, as described for block
    /// [sequences](http://www.yaml.org/spec/1.2/spec.html#id2797382)
    /// and
    /// [mappings](http://www.yaml.org/spec/1.2/spec.html#id2798057).
    ///
    /// In this form, blocks cannot have any properties (such as anchors
    /// or tags), which should be OK, because this emitter doesn't
    /// (currently) emit those anyways.
    pub fn compact(&mut self, compact: bool) {
        self.compact = compact;
    }

    /// Determine if this emitter is using 'compact inline notation'.
    #[must_use]
    pub fn is_compact(&self) -> bool {
        self.compact
    }

    /// Render strings containing multiple lines in [literal style].
    ///
    /// # Examples
    ///
    /// ```rust
    /// use yaml_rust2::{Yaml, YamlEmitter, YamlLoader};
    ///
    /// let input = r#"{foo: "bar!\nbar!", baz: 42}"#;
    /// let parsed = YamlLoader::load_from_str(input).unwrap();
    /// eprintln!("{:?}", parsed);
    ///
    /// let mut output = String::new();
    /// let mut emitter = YamlEmitter::new(&mut output);
    /// emitter.multiline_strings(true);
    /// emitter.dump(&parsed[0]).unwrap();
    /// assert_eq!(output.as_str(), "\
    /// ---
    /// foo: |
    ///   bar!
    ///   bar!
    /// baz: 42");
    /// ```
    ///
    /// [literal style]: https://yaml.org/spec/1.2/spec.html#id2795688
    pub fn multiline_strings(&mut self, multiline_strings: bool) {
        self.multiline_strings = multiline_strings;
    }

    /// Determine if this emitter will emit multiline strings when appropriate.
    #[must_use]
    pub fn is_multiline_strings(&self) -> bool {
        self.multiline_strings
    }

    /// Dump Yaml to an output stream.
    /// # Errors
    /// Returns `EmitError` when an error occurs.
    pub fn dump(&mut self, doc: &Yaml) -> EmitResult {
        // write DocumentStart
        writeln!(self.writer, "---")?;
        self.level = -1;
        self.emit_node(doc)
    }

    fn write_indent(&mut self) -> EmitResult {
        if self.level <= 0 {
            return Ok(());
        }
        for _ in 0..self.level {
            for _ in 0..self.best_indent {
                write!(self.writer, " ")?;
            }
        }
        Ok(())
    }

    fn emit_node(&mut self, node: &Yaml) -> EmitResult {
        match *node {
            Yaml::Array(ref v) => self.emit_array(v),
            Yaml::Hash(ref h) => self.emit_hash(h),
            Yaml::String(ref v) => {
                if self.multiline_strings
                    && v.contains('\n')
                    && char_traits::is_valid_literal_block_scalar(v)
                {
                    write!(self.writer, "|")?;
                    self.level += 1;
                    for line in v.lines() {
                        writeln!(self.writer)?;
                        self.write_indent()?;
                        // It's literal text, so don't escape special chars.
                        write!(self.writer, "{line}")?;
                    }
                    self.level -= 1;
                } else if need_quotes(v) {
                    escape_str(self.writer, v)?;
                } else {
                    write!(self.writer, "{v}")?;
                }
                Ok(())
            }
            Yaml::Boolean(v) => {
                if v {
                    self.writer.write_str("true")?;
                } else {
                    self.writer.write_str("false")?;
                }
                Ok(())
            }
            Yaml::Integer(v) => {
                write!(self.writer, "{v}")?;
                Ok(())
            }
            Yaml::Real(ref v) => {
                write!(self.writer, "{v}")?;
                Ok(())
            }
            Yaml::Null | Yaml::BadValue => {
                write!(self.writer, "~")?;
                Ok(())
            }
            // XXX(chenyh) Alias
            Yaml::Alias(_) => Ok(()),
        }
    }

    fn emit_array(&mut self, v: &[Yaml]) -> EmitResult {
        if v.is_empty() {
            write!(self.writer, "[]")?;
        } else {
            self.level += 1;
            for (cnt, x) in v.iter().enumerate() {
                if cnt > 0 {
                    writeln!(self.writer)?;
                    self.write_indent()?;
                }
                write!(self.writer, "-")?;
                self.emit_val(true, x)?;
            }
            self.level -= 1;
        }
        Ok(())
    }

    fn emit_hash(&mut self, h: &Hash) -> EmitResult {
        if h.is_empty() {
            self.writer.write_str("{}")?;
        } else {
            self.level += 1;
            for (cnt, (k, v)) in h.iter().enumerate() {
                let complex_key = matches!(*k, Yaml::Hash(_) | Yaml::Array(_));
                if cnt > 0 {
                    writeln!(self.writer)?;
                    self.write_indent()?;
                }
                if complex_key {
                    write!(self.writer, "?")?;
                    self.emit_val(true, k)?;
                    writeln!(self.writer)?;
                    self.write_indent()?;
                    write!(self.writer, ":")?;
                    self.emit_val(true, v)?;
                } else {
                    self.emit_node(k)?;
                    write!(self.writer, ":")?;
                    self.emit_val(false, v)?;
                }
            }
            self.level -= 1;
        }
        Ok(())
    }

    /// Emit a yaml as a hash or array value: i.e., which should appear
    /// following a ":" or "-", either after a space, or on a new line.
    /// If `inline` is true, then the preceding characters are distinct
    /// and short enough to respect the compact flag.
    fn emit_val(&mut self, inline: bool, val: &Yaml) -> EmitResult {
        match *val {
            Yaml::Array(ref v) => {
                if (inline && self.compact) || v.is_empty() {
                    write!(self.writer, " ")?;
                } else {
                    writeln!(self.writer)?;
                    self.level += 1;
                    self.write_indent()?;
                    self.level -= 1;
                }
                self.emit_array(v)
            }
            Yaml::Hash(ref h) => {
                if (inline && self.compact) || h.is_empty() {
                    write!(self.writer, " ")?;
                } else {
                    writeln!(self.writer)?;
                    self.level += 1;
                    self.write_indent()?;
                    self.level -= 1;
                }
                self.emit_hash(h)
            }
            _ => {
                write!(self.writer, " ")?;
                self.emit_node(val)
            }
        }
    }
}

/// Check if the string requires quoting.
/// Strings starting with any of the following characters must be quoted.
/// :, &, *, ?, |, -, <, >, =, !, %, @
/// Strings containing any of the following characters must be quoted.
/// {, }, \[, t \], ,, #, `
///
/// If the string contains any of the following control characters, it must be escaped with double quotes:
/// \0, \x01, \x02, \x03, \x04, \x05, \x06, \a, \b, \t, \n, \v, \f, \r, \x0e, \x0f, \x10, \x11, \x12, \x13, \x14, \x15, \x16, \x17, \x18, \x19, \x1a, \e, \x1c, \x1d, \x1e, \x1f, \N, \_, \L, \P
///
/// Finally, there are other cases when the strings must be quoted, no matter if you're using single or double quotes:
/// * When the string is true or false (otherwise, it would be treated as a boolean value);
/// * When the string is null or ~ (otherwise, it would be considered as a null value);
/// * When the string looks like a number, such as integers (e.g. 2, 14, etc.), floats (e.g. 2.6, 14.9) and exponential numbers (e.g. 12e7, etc.) (otherwise, it would be treated as a numeric value);
/// * When the string looks like a date (e.g. 2014-12-31) (otherwise it would be automatically converted into a Unix timestamp).
#[allow(clippy::doc_markdown)]
fn need_quotes(string: &str) -> bool {
    fn need_quotes_spaces(string: &str) -> bool {
        string.starts_with(' ') || string.ends_with(' ')
    }

    string.is_empty()
        || need_quotes_spaces(string)
        || string.starts_with(|character: char| {
            matches!(
                character,
                '&' | '*' | '?' | '|' | '-' | '<' | '>' | '=' | '!' | '%' | '@'
            )
        })
        || string.contains(|character: char| {
            matches!(character, ':'
            | '{'
            | '}'
            | '['
            | ']'
            | ','
            | '#'
            | '`'
            | '\"'
            | '\''
            | '\\'
            | '\0'..='\x06'
            | '\t'
            | '\n'
            | '\r'
            | '\x0e'..='\x1a'
            | '\x1c'..='\x1f')
        })
        || [
            // http://yaml.org/type/bool.html
            // Note: 'y', 'Y', 'n', 'N', is not quoted deliberately, as in libyaml. PyYAML also parse
            // them as string, not booleans, although it is violating the YAML 1.1 specification.
            // See https://github.com/dtolnay/serde-yaml/pull/83#discussion_r152628088.
            "yes", "Yes", "YES", "no", "No", "NO", "True", "TRUE", "true", "False", "FALSE",
            "false", "on", "On", "ON", "off", "Off", "OFF",
            // http://yaml.org/type/null.html
            "null", "Null", "NULL", "~",
        ]
        .contains(&string)
        || string.starts_with('.')
        || string.starts_with("0x")
        || string.parse::<i64>().is_ok()
        || string.parse::<f64>().is_ok()
}

#[cfg(test)]
mod test {
    use super::YamlEmitter;
    use crate::YamlLoader;

    #[test]
    fn test_multiline_string() {
        let input = r#"{foo: "bar!\nbar!", baz: 42}"#;
        let parsed = YamlLoader::load_from_str(input).unwrap();
        let mut output = String::new();
        let mut emitter = YamlEmitter::new(&mut output);
        emitter.multiline_strings(true);
        emitter.dump(&parsed[0]).unwrap();
    }
}