sgf_parse/
parser.rs

1use std::ptr::NonNull;
2
3use crate::go;
4use crate::lexer::{tokenize, LexerError, Token};
5use crate::unknown_game;
6use crate::{GameTree, GameType, SgfNode, SgfProp};
7
8/// Returns the [`GameTree`] values parsed from the provided text using default parsing options.
9///
10/// This function will attempt to convert non-FF\[4\] files to FF\[4\] if possible. Check out
11/// [`parse_with_options`] if you want to change the default behavior.
12///
13/// # Errors
14/// If the text can't be parsed as an SGF FF\[4\] collection, then an error is returned.
15///
16/// # Examples
17/// ```
18/// use sgf_parse::{parse, GameType};
19///
20/// let sgf = "(;SZ[9]C[Some comment];B[de];W[fe])(;B[de];W[ff])";
21/// let gametrees = parse(sgf).unwrap();
22/// assert!(gametrees.len() == 2);
23/// assert!(gametrees.iter().all(|gametree| gametree.gametype() == GameType::Go));
24/// ```
25pub fn parse(text: &str) -> Result<Vec<GameTree>, SgfParseError> {
26    parse_with_options(text, &ParseOptions::default())
27}
28
29/// Returns the [`GameTree`] values parsed from the provided text.
30///
31/// # Errors
32/// If the text can't be parsed as an SGF FF\[4\] collection, then an error is returned.
33///
34/// # Examples
35/// ```
36/// use sgf_parse::{parse_with_options, ParseOptions, GameType, SgfParseError};
37///
38/// // Default options
39/// let sgf = "(;SZ[9]C[Some comment];B[de];W[fe])(;B[de];W[ff])";
40/// let gametrees = parse_with_options(sgf, &ParseOptions::default()).unwrap();
41/// assert!(gametrees.len() == 2);
42/// assert!(gametrees.iter().all(|gametree| gametree.gametype() == GameType::Go));
43///
44/// // Strict FF[4] identifiers
45/// let sgf = "(;SZ[9]CoPyright[Julian Andrews 2025];B[de];W[fe])(;B[de];W[ff])";
46/// let parse_options = ParseOptions {
47///     convert_mixed_case_identifiers: false,
48///     ..ParseOptions::default()
49/// };
50/// let result = parse_with_options(sgf, &parse_options);
51/// assert_eq!(result, Err(SgfParseError::InvalidFF4Property));
52/// ```
53pub fn parse_with_options(
54    text: &str,
55    options: &ParseOptions,
56) -> Result<Vec<GameTree>, SgfParseError> {
57    let text = text.trim();
58    let tokens = if options.lenient {
59        tokenize(text)
60            .take_while(Result::is_ok)
61            .map(|result| result.unwrap().0)
62            .collect()
63    } else {
64        tokenize(text)
65            .map(|result| match result {
66                Err(e) => Err(SgfParseError::LexerError(e)),
67                Ok((token, _span)) => Ok(token),
68            })
69            .collect::<Result<Vec<_>, _>>()?
70    };
71    split_by_gametree(&tokens, options.lenient)?
72        .into_iter()
73        .map(|tokens| match find_gametype(tokens)? {
74            GameType::Go => parse_gametree::<go::Prop>(tokens, options),
75            GameType::Unknown => parse_gametree::<unknown_game::Prop>(tokens, options),
76        })
77        .collect::<Result<_, _>>()
78}
79
80/// Options for parsing SGF files.
81///
82/// # Examples
83/// See [`parse_with_options`] for usage examples.
84pub struct ParseOptions {
85    /// Whether to allow conversion of FF\[3\] mixed case identifiers to FF\[4\].
86    ///
87    /// All lower case letters are dropped.
88    /// This should allow parsing any older files which are valid, but not valid FF\[4\].
89    pub convert_mixed_case_identifiers: bool,
90    /// Whether to use lenient parsing.
91    ///
92    /// In lenient mode, the parser should never return an error, but will instead parse the SGF
93    /// until it hits an error, and then return whatever it's managed to parse.
94    pub lenient: bool,
95}
96
97impl Default for ParseOptions {
98    fn default() -> Self {
99        ParseOptions {
100            convert_mixed_case_identifiers: true,
101            lenient: false,
102        }
103    }
104}
105
106/// Error type for failures parsing sgf from text.
107#[derive(Debug, Clone, Copy, PartialEq, Eq)]
108pub enum SgfParseError {
109    LexerError(LexerError),
110    UnexpectedGameTreeStart,
111    UnexpectedGameTreeEnd,
112    UnexpectedProperty,
113    UnexpectedEndOfData,
114    UnexpectedGameType,
115    InvalidFF4Property,
116}
117
118impl From<LexerError> for SgfParseError {
119    fn from(error: LexerError) -> Self {
120        Self::LexerError(error)
121    }
122}
123
124impl std::fmt::Display for SgfParseError {
125    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
126        match self {
127            SgfParseError::LexerError(e) => write!(f, "Error tokenizing: {e}"),
128            SgfParseError::UnexpectedGameTreeStart => write!(f, "Unexpected start of game tree"),
129            SgfParseError::UnexpectedGameTreeEnd => write!(f, "Unexpected end of game tree"),
130            SgfParseError::UnexpectedProperty => write!(f, "Unexpected property"),
131            SgfParseError::UnexpectedEndOfData => write!(f, "Unexpected end of data"),
132            SgfParseError::UnexpectedGameType => write!(f, "Unexpected game type"),
133            SgfParseError::InvalidFF4Property => {
134                write!(
135                    f,
136                    "Invalid FF[4] property without `convert_mixed_case_identifiers`"
137                )
138            }
139        }
140    }
141}
142
143impl std::error::Error for SgfParseError {}
144
145// Split the tokens up into individual gametrees.
146//
147// This will let us easily scan each gametree for GM properties.
148// Only considers StartGameTree/EndGameTree tokens.
149fn split_by_gametree(tokens: &[Token], lenient: bool) -> Result<Vec<&[Token]>, SgfParseError> {
150    let mut gametrees = vec![];
151    let mut gametree_depth: u64 = 0;
152    let mut slice_start = 0;
153    for (i, token) in tokens.iter().enumerate() {
154        match token {
155            Token::StartGameTree => gametree_depth += 1,
156            Token::EndGameTree => {
157                if gametree_depth == 0 {
158                    if lenient {
159                        break;
160                    } else {
161                        return Err(SgfParseError::UnexpectedGameTreeEnd);
162                    }
163                }
164                gametree_depth -= 1;
165                if gametree_depth == 0 {
166                    gametrees.push(&tokens[slice_start..=i]);
167                    slice_start = i + 1;
168                }
169            }
170            _ => {}
171        }
172    }
173    if gametree_depth != 0 {
174        if lenient {
175            // For lenient parsing assume all remaining tokens are part of the last gametree.
176            gametrees.push(&tokens[slice_start..]);
177        } else {
178            return Err(SgfParseError::UnexpectedEndOfData);
179        }
180    }
181
182    Ok(gametrees)
183}
184
185// Parse a single gametree of a known type.
186fn parse_gametree<Prop: SgfProp>(
187    tokens: &[Token],
188    options: &ParseOptions,
189) -> Result<GameTree, SgfParseError>
190where
191    SgfNode<Prop>: std::convert::Into<GameTree>,
192{
193    // TODO: Rewrite this without `unsafe`
194    let mut collection: Vec<SgfNode<Prop>> = vec![];
195    // //// Pointer to the `Vec` of children we're currently building.
196    let mut current_node_list_ptr = NonNull::new(&mut collection).unwrap();
197    // Stack of pointers to incomplete `Vec`s of children.
198    let mut incomplete_child_lists: Vec<NonNull<Vec<SgfNode<Prop>>>> = vec![];
199    //// Using pointers involves some unsafe calls, but should be ok here.
200    //// Since pointers are always initialized from real structs, and those structs
201    //// live for the whole function body, our only safety concern is dangling pointers.
202    ////
203    //// Since we build the tree traversing depth-first those structs shouldn't be
204    //// modified while the pointer is live. Heap-allocated contents of their
205    //// `children` may be modified, but that shouldn't change anything.
206
207    let mut tokens = tokens.iter().peekable();
208    while let Some(token) = tokens.next() {
209        match token {
210            Token::StartGameTree => {
211                // SGF game trees must have a root node.
212                if let Some(node_list_ptr) = incomplete_child_lists.last() {
213                    let node_list = unsafe { node_list_ptr.as_ref() };
214                    if node_list.is_empty() {
215                        if options.lenient {
216                            break;
217                        } else {
218                            return Err(SgfParseError::UnexpectedGameTreeStart);
219                        }
220                    }
221                }
222                incomplete_child_lists.push(current_node_list_ptr);
223            }
224            Token::EndGameTree => match incomplete_child_lists.pop() {
225                Some(node_list) => current_node_list_ptr = node_list,
226                None => {
227                    if options.lenient {
228                        break;
229                    } else {
230                        return Err(SgfParseError::UnexpectedGameTreeEnd);
231                    }
232                }
233            },
234            Token::StartNode => {
235                let mut new_node = SgfNode::default();
236                let mut prop_tokens = vec![];
237                while let Some(Token::Property(_)) = tokens.peek() {
238                    prop_tokens.push(tokens.next().unwrap());
239                }
240                for token in prop_tokens {
241                    match token {
242                        // TODO: Consider refactoring to consume tokens and clone of values.
243                        Token::Property((identifier, values)) => {
244                            let identifier = {
245                                if identifier.chars().all(|c| c.is_ascii_uppercase()) {
246                                    identifier.clone()
247                                } else if options.convert_mixed_case_identifiers {
248                                    identifier
249                                        .chars()
250                                        .filter(|c| c.is_ascii_uppercase())
251                                        .collect()
252                                } else if options.lenient {
253                                    break;
254                                } else {
255                                    return Err(SgfParseError::InvalidFF4Property);
256                                }
257                            };
258                            new_node
259                                .properties
260                                .push(Prop::new(identifier, values.clone()))
261                        }
262                        _ => unreachable!(),
263                    }
264                }
265                let node_list = unsafe { current_node_list_ptr.as_mut() };
266                node_list.push(new_node);
267                current_node_list_ptr =
268                    NonNull::new(&mut node_list.last_mut().unwrap().children).unwrap();
269            }
270            Token::Property(_) => {
271                if options.lenient {
272                    break;
273                } else {
274                    return Err(SgfParseError::UnexpectedProperty);
275                }
276            }
277        }
278    }
279
280    if !options.lenient && (!incomplete_child_lists.is_empty() || collection.len() != 1) {
281        return Err(SgfParseError::UnexpectedEndOfData);
282    }
283    let mut root_node = collection
284        .into_iter()
285        .next()
286        .ok_or(SgfParseError::UnexpectedEndOfData)?;
287    root_node.is_root = true;
288    Ok(root_node.into())
289}
290
291// Figure out which game to parse from a slice of tokens.
292//
293// This function is necessary because we need to know the game before we can do the parsing.
294fn find_gametype(tokens: &[Token]) -> Result<GameType, SgfParseError> {
295    match find_gametree_root_prop_values("GM", tokens)? {
296        None => Ok(GameType::Go),
297        Some(values) => {
298            if values.len() != 1 {
299                return Ok(GameType::Unknown);
300            }
301            match values[0].as_str() {
302                "1" => Ok(GameType::Go),
303                _ => Ok(GameType::Unknown),
304            }
305        }
306    }
307}
308
309// Find the property values for a given identifier in the root node from the gametree's tokens.
310//
311// We use this to determine key root properties (like GM and FF) before parsing.
312// Returns an error if there's more than one match.
313fn find_gametree_root_prop_values<'a>(
314    prop_ident: &'a str,
315    tokens: &'a [Token],
316) -> Result<Option<&'a Vec<String>>, SgfParseError> {
317    // Find the matching property values in the first node.
318    // Skip the initial StartGameTree, StartNode tokens; we'll handle any errors later.
319    let matching_tokens: Vec<&Vec<String>> = tokens
320        .iter()
321        .skip(2)
322        .take_while(|&token| matches!(token, Token::Property(_)))
323        .filter_map(move |token| match token {
324            Token::Property((ident, values)) if ident == prop_ident => Some(values),
325            _ => None,
326        })
327        .collect();
328
329    match matching_tokens.len() {
330        0 => Ok(None),
331        1 => Ok(Some(matching_tokens[0])),
332        _ => Err(SgfParseError::UnexpectedProperty),
333    }
334}
335
336#[cfg(test)]
337mod test {
338    use super::*;
339    use crate::{go, serialize};
340
341    fn load_test_sgf() -> Result<String, Box<dyn std::error::Error>> {
342        // See https://www.red-bean.com/sgf/examples/
343        let mut sgf_path = std::path::PathBuf::from(env!("CARGO_MANIFEST_DIR"));
344        sgf_path.push("resources/test/ff4_ex.sgf");
345        let data = std::fs::read_to_string(sgf_path)?;
346
347        Ok(data)
348    }
349
350    fn get_go_nodes() -> Result<Vec<SgfNode<go::Prop>>, Box<dyn std::error::Error>> {
351        let data = load_test_sgf()?;
352
353        Ok(go::parse(&data)?)
354    }
355
356    fn node_depth(mut sgf_node: &SgfNode<go::Prop>) -> u64 {
357        let mut depth = 1;
358        while sgf_node.children().count() > 0 {
359            depth += 1;
360            sgf_node = sgf_node.children().next().unwrap();
361        }
362        depth
363    }
364
365    #[test]
366    fn sgf_has_two_gametrees() {
367        let sgf_nodes = get_go_nodes().unwrap();
368        assert_eq!(sgf_nodes.len(), 2);
369    }
370
371    #[test]
372    fn gametree_one_has_five_variations() {
373        let sgf_nodes = get_go_nodes().unwrap();
374        let sgf_node = &sgf_nodes[0];
375        assert_eq!(sgf_node.children().count(), 5);
376    }
377
378    #[test]
379    fn gametree_one_has_size_19() {
380        let sgf_nodes = get_go_nodes().unwrap();
381        let sgf_node = &sgf_nodes[0];
382        match sgf_node.get_property("SZ") {
383            Some(go::Prop::SZ(size)) => assert_eq!(size, &(19, 19)),
384            _ => unreachable!("Expected size property"),
385        }
386    }
387
388    #[test]
389    fn gametree_variation_depths() {
390        let sgf_nodes = get_go_nodes().unwrap();
391        let sgf_node = &sgf_nodes[0];
392        let children: Vec<_> = sgf_node.children().collect();
393        assert_eq!(node_depth(children[0]), 13);
394        assert_eq!(node_depth(children[1]), 4);
395        assert_eq!(node_depth(children[2]), 4);
396    }
397
398    #[test]
399    fn gametree_two_has_one_variation() {
400        let sgf_nodes = get_go_nodes().unwrap();
401        let sgf_node = &sgf_nodes[1];
402        assert_eq!(sgf_node.children().count(), 1);
403    }
404
405    #[test]
406    fn serialize_then_parse() {
407        let data = load_test_sgf().unwrap();
408        let gametrees = parse(&data).unwrap();
409        let text = serialize(&gametrees);
410        assert_eq!(gametrees, parse(&text).unwrap());
411    }
412
413    #[test]
414    fn invalid_property() {
415        let input = "(;GM[1]W[rp.pmonpoqprpsornqmpm])";
416        let sgf_nodes = go::parse(input).unwrap();
417        let expected = vec![
418            go::Prop::GM(1),
419            go::Prop::Invalid("W".to_string(), vec!["rp.pmonpoqprpsornqmpm".to_string()]),
420        ];
421
422        assert_eq!(sgf_nodes.len(), 1);
423        let sgf_node = &sgf_nodes[0];
424        assert_eq!(sgf_node.properties().cloned().collect::<Vec<_>>(), expected);
425    }
426
427    #[test]
428    fn unknown_game() {
429        let input = "(;GM[37]W[rp.pmonpoqprpsornqmpm])";
430        let gametrees = parse(input).unwrap();
431        assert_eq!(gametrees.len(), 1);
432        assert_eq!(gametrees[0].gametype(), GameType::Unknown);
433        let sgf_node = match &gametrees[0] {
434            GameTree::Unknown(node) => node,
435            _ => panic!("Unexpected game type"),
436        };
437        let expected = vec![
438            unknown_game::Prop::GM(37),
439            unknown_game::Prop::W("rp.pmonpoqprpsornqmpm".into()),
440        ];
441
442        assert_eq!(sgf_node.properties().cloned().collect::<Vec<_>>(), expected);
443    }
444
445    #[test]
446    fn mixed_games() {
447        let input = "(;GM[1];W[dd])(;GM[37]W[rp.pmonpoqprpsornqmpm])";
448        let gametrees = parse(input).unwrap();
449        assert_eq!(gametrees.len(), 2);
450        assert_eq!(gametrees[0].gametype(), GameType::Go);
451        assert_eq!(gametrees[1].gametype(), GameType::Unknown);
452    }
453
454    #[test]
455    fn stack_overflow() {
456        // This input generated a stack overflow with the old code
457        let input = "(;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;)";
458        let result = parse(&input);
459        assert!(result.is_ok());
460    }
461
462    #[test]
463    fn converts_up_ff3_property() {
464        let input = "(;GM[1]FF[3]CoPyright[test])";
465        let expected = vec![
466            go::Prop::GM(1),
467            go::Prop::FF(3),
468            go::Prop::CP("test".into()),
469        ];
470
471        let sgf_nodes = go::parse(input).unwrap();
472
473        assert_eq!(sgf_nodes.len(), 1);
474        let properties = sgf_nodes[0].properties().cloned().collect::<Vec<_>>();
475        assert_eq!(properties, expected);
476    }
477
478    #[test]
479    fn doesnt_convert_if_not_allowed() {
480        let input = "(;GM[1]FF[3]CoPyright[test])";
481        let parse_options = ParseOptions {
482            convert_mixed_case_identifiers: false,
483            ..ParseOptions::default()
484        };
485        let result = parse_with_options(input, &parse_options);
486        assert_eq!(result, Err(SgfParseError::InvalidFF4Property));
487    }
488
489    #[test]
490    fn compressed_list_for_unknown_game() {
491        let input = "(;GM[]MA[a:b])";
492        let gametree = parse(&input).unwrap().pop().unwrap();
493        let node = match gametree {
494            GameTree::Unknown(node) => node,
495            _ => panic!("Expected Unknown Game type"),
496        };
497        match node.get_property("MA") {
498            Some(unknown_game::Prop::MA(values)) => {
499                assert_eq!(values.len(), 1);
500                assert!(values.contains("a:b"));
501            }
502            _ => panic!("MA prop not found"),
503        }
504    }
505
506    #[test]
507    fn strips_whitespace() {
508        let input = "\n(;GM[1];B[cc])";
509        let sgf_nodes = go::parse(&input).unwrap();
510        assert_eq!(sgf_nodes.len(), 1);
511    }
512
513    #[test]
514    fn lenient_parsing_unclosed_parens_ok() {
515        let input = "\n(;GM[1];B[cc]";
516        let parse_options = ParseOptions {
517            lenient: true,
518            ..ParseOptions::default()
519        };
520        let game_trees = parse_with_options(input, &parse_options).unwrap();
521        assert_eq!(game_trees.len(), 1);
522    }
523
524    #[test]
525    fn lenient_parsing_ignores_trailing_garbage() {
526        let input = "\n(;GM[1];B[cc]))";
527        let parse_options = ParseOptions {
528            lenient: true,
529            ..ParseOptions::default()
530        };
531        let game_trees = parse_with_options(input, &parse_options).unwrap();
532        assert_eq!(game_trees.len(), 1);
533    }
534
535    #[test]
536    fn lenient_parsing_handles_unescaped_property_end() {
537        let input = "(;B[cc];W[dd];C[username [12k]: foo])";
538        let parse_options = ParseOptions {
539            lenient: true,
540            ..ParseOptions::default()
541        };
542        let game_trees = parse_with_options(input, &parse_options).unwrap();
543        assert_eq!(game_trees.len(), 1);
544        let sgf_node = game_trees[0].as_go_node().unwrap();
545        // Should parse up through "[12k]" successfully
546        assert_eq!(sgf_node.main_variation().count(), 3);
547    }
548
549    #[test]
550    fn lenient_parsing_handles_unclosed_property_value() {
551        let input = "(;B[cc];W[dd];B[ee";
552        let parse_options = ParseOptions {
553            lenient: true,
554            ..ParseOptions::default()
555        };
556        let game_trees = parse_with_options(input, &parse_options).unwrap();
557        assert_eq!(game_trees.len(), 1);
558        let sgf_node = game_trees[0].as_go_node().unwrap();
559        // Should find 3 nodes. The last unfinished node has no properties since "B[ee" is unclosed.
560        assert_eq!(sgf_node.main_variation().count(), 3);
561        assert_eq!(
562            sgf_node.main_variation().last().unwrap().properties.len(),
563            0
564        );
565    }
566
567    #[test]
568    fn lenient_parsing_handles_missing_property_value() {
569        let input = "(;B[cc];W[dd];B";
570        let parse_options = ParseOptions {
571            lenient: true,
572            ..ParseOptions::default()
573        };
574        let game_trees = parse_with_options(input, &parse_options).unwrap();
575        assert_eq!(game_trees.len(), 1);
576        let sgf_node = game_trees[0].as_go_node().unwrap();
577        // Should find 3 nodes. The last node has no properties since "B" is missing its value
578        assert_eq!(sgf_node.main_variation().count(), 3);
579        assert_eq!(
580            sgf_node.main_variation().last().unwrap().properties.len(),
581            0
582        );
583    }
584}
sgf_parse/parser.rs

sgf_parse/
parser.rs
