    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

    // pest. The Elegant Parser
    // Copyright (c) 2018 Dragoș Tiselice
    //
    // Licensed under the Apache License, Version 2.0
    // <LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0> or the MIT
    // license <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
    // option. All files in the project carrying such notice may not be copied,
    // modified, or distributed except according to those terms.

    use alloc::rc::Rc;
    use alloc::vec::Vec;
    use core::fmt;

    use super::pair::{self, Pair};
    use super::queueable_token::QueueableToken;
    use super::tokens::{self, Tokens};
    use crate::RuleType;

    /// An iterator over [`Pair`]s. It is created by [`Pairs::flatten`].
    ///
    /// [`Pair`]: struct.Pair.html
    /// [`Pairs::flatten`]: struct.Pairs.html#method.flatten
    pub struct FlatPairs<'i, R> {
        /// # Safety
        ///
        /// All `QueueableToken`s' `input_pos` must be valid character boundary indices into `input`.
        queue: Rc<Vec<QueueableToken<R>>>,
        input: &'i str,
        start: usize,
        end: usize,
    }

    /// # Safety
    ///
    /// All `QueueableToken`s' `input_pos` must be valid character boundary indices into `input`.
    pub unsafe fn new<R: RuleType>(
        queue: Rc<Vec<QueueableToken<R>>>,
        input: &str,
        start: usize,
        end: usize,
    ) -> FlatPairs<'_, R> {
        FlatPairs {
            queue,
            input,
            start,
            end,
        }
    }

    impl<'i, R: RuleType> FlatPairs<'i, R> {
        /// Returns the `Tokens` for these pairs.
        ///
        /// # Examples
        ///
        /// ```
        /// # use std::rc::Rc;
        /// # use pest;
        /// # #[allow(non_camel_case_types)]
        /// # #[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
        /// enum Rule {
        ///     a
        /// }
        ///
        /// let input = "";
        /// let pairs = pest::state(input, |state| {
        ///     // generating Token pair with Rule::a ...
        /// #     state.rule(Rule::a, |s| Ok(s))
        /// }).unwrap();
        /// let tokens: Vec<_> = pairs.flatten().tokens().collect();
        ///
        /// assert_eq!(tokens.len(), 2);
        /// ```
        #[inline]
        pub fn tokens(self) -> Tokens<'i, R> {
            tokens::new(self.queue, self.input, self.start, self.end)
        }

        fn next_start(&mut self) {
            self.start += 1;

            while self.start < self.end && !self.is_start(self.start) {
                self.start += 1;
            }
        }

        fn next_start_from_end(&mut self) {
            self.end -= 1;

            while self.end >= self.start && !self.is_start(self.end) {
                self.end -= 1;
            }
        }

        fn is_start(&self, index: usize) -> bool {
            match self.queue[index] {
                QueueableToken::Start { .. } => true,
                QueueableToken::End { .. } => false,
            }
        }
    }

    impl<'i, R: RuleType> Iterator for FlatPairs<'i, R> {
        type Item = Pair<'i, R>;

        fn next(&mut self) -> Option<Self::Item> {
            if self.start >= self.end {
                return None;
            }

            let pair = unsafe { pair::new(Rc::clone(&self.queue), self.input, self.start) };

            self.next_start();

            Some(pair)
        }
    }

    impl<'i, R: RuleType> DoubleEndedIterator for FlatPairs<'i, R> {
        fn next_back(&mut self) -> Option<Self::Item> {
            if self.end <= self.start {
                return None;
            }

            self.next_start_from_end();

            let pair = unsafe { pair::new(Rc::clone(&self.queue), self.input, self.end) };

            Some(pair)
        }
    }

    impl<'i, R: RuleType> fmt::Debug for FlatPairs<'i, R> {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            f.debug_struct("FlatPairs")
                .field("pairs", &self.clone().collect::<Vec<_>>())
                .finish()
        }
    }

    impl<'i, R: Clone> Clone for FlatPairs<'i, R> {
        fn clone(&self) -> FlatPairs<'i, R> {
            FlatPairs {
                queue: Rc::clone(&self.queue),
                input: self.input,
                start: self.start,
                end: self.end,
            }
        }
    }

    #[cfg(test)]
    mod tests {
        use super::super::super::macros::tests::*;
        use super::super::super::Parser;
        use alloc::vec;
        use alloc::vec::Vec;

        #[test]
        fn iter_for_flat_pairs() {
            let pairs = AbcParser::parse(Rule::a, "abcde").unwrap();

            assert_eq!(
                pairs.flatten().map(|p| p.as_rule()).collect::<Vec<Rule>>(),
                vec![Rule::a, Rule::b, Rule::c]
            );
        }

        #[test]
        fn double_ended_iter_for_flat_pairs() {
            let pairs = AbcParser::parse(Rule::a, "abcde").unwrap();
            assert_eq!(
                pairs
                    .flatten()
                    .rev()
                    .map(|p| p.as_rule())
                    .collect::<Vec<Rule>>(),
                vec![Rule::c, Rule::b, Rule::a]
            );
        }
    }