squeeze-lib 0.5.0

use super::{Anchor, ByteSet, Finder, RunClass, RunRule};
use std::ops::Range;

#[derive(Default)]
pub struct Datetime {}

impl Datetime {
    fn try_date(input: &[u8], idx: usize) -> Option<Range<usize>> {
        // YYYY-MM-DD with optional time component
        if idx + 10 > input.len() {
            return None;
        }

        // Boundary before: not preceded by a digit. A preceding '-' is a
        // valid boundary when it is not glued to a digit run, so kebab names
        // like `backup-2024-01-15` match while `01-2024-01-15` stays vetoed.
        if idx > 0 {
            let prev = input[idx - 1];
            if prev.is_ascii_digit() {
                return None;
            }
            if prev == b'-' && idx >= 2 && input[idx - 2].is_ascii_digit() {
                return None;
            }
        }

        // YYYY
        if !Self::is_4_digits(input, idx) {
            return None;
        }
        let year = Self::parse_num(input, idx, 4);
        if !(1000..=9999).contains(&year) {
            return None;
        }

        if input[idx + 4] != b'-' {
            return None;
        }

        // MM
        if !Self::is_2_digits(input, idx + 5) {
            return None;
        }
        let month = Self::parse_num(input, idx + 5, 2);
        if !(1..=12).contains(&month) {
            return None;
        }

        if input[idx + 7] != b'-' {
            return None;
        }

        // DD
        if !Self::is_2_digits(input, idx + 8) {
            return None;
        }
        let day = Self::parse_num(input, idx + 8, 2);
        if !(1..=31).contains(&day) {
            return None;
        }

        let mut end = idx + 10;

        // Optional time component: T/t (RFC 3339) or space followed by HH:MM
        if end < input.len()
            && (input[end] == b'T' || input[end] == b't' || input[end] == b' ')
            && let Some(time_end) = Self::try_time(input, end + 1)
        {
            end = time_end;
        }

        // Boundary after: never followed by a digit. A trailing '-' is only a
        // veto when a digit follows and no timezone consumed it
        // (`2024-01-15-01` stays ambiguous), while `2024-01-15-my-post` is a
        // kebab-case boundary.
        if end < input.len() {
            let next = input[end];
            if next.is_ascii_digit() {
                return None;
            }
            if next == b'-' && end + 1 < input.len() && input[end + 1].is_ascii_digit() {
                return None;
            }
        }

        Some(idx..end)
    }

    fn try_time(input: &[u8], idx: usize) -> Option<usize> {
        // HH:MM[:SS[.fractional]]
        if idx + 5 > input.len() {
            return None;
        }

        if !Self::is_2_digits(input, idx) {
            return None;
        }
        let hour = Self::parse_num(input, idx, 2);
        if hour > 23 {
            return None;
        }

        if input[idx + 2] != b':' {
            return None;
        }

        if !Self::is_2_digits(input, idx + 3) {
            return None;
        }
        let minute = Self::parse_num(input, idx + 3, 2);
        if minute > 59 {
            return None;
        }

        let mut end = idx + 5;

        // Optional :SS
        if end + 3 <= input.len() && input[end] == b':' && Self::is_2_digits(input, end + 1) {
            let second = Self::parse_num(input, end + 1, 2);
            if second <= 60 {
                end += 3;

                // Optional fractional seconds: '.' or the ISO-preferred ','
                // (only consumed when at least one digit follows)
                if end < input.len() && (input[end] == b'.' || input[end] == b',') {
                    let frac_start = end + 1;
                    let mut frac_end = frac_start;
                    while frac_end < input.len() && input[frac_end].is_ascii_digit() {
                        frac_end += 1;
                    }
                    if frac_end > frac_start {
                        end = frac_end;
                    }
                }
            }
        }

        // Optional timezone (only ever after a time component): Z/z,
        // ±HH:MM, ±HHMM, or ±HH.
        if end < input.len() && (input[end] == b'Z' || input[end] == b'z') {
            end += 1;
        } else if end < input.len() && (input[end] == b'+' || input[end] == b'-') {
            // Count the digits directly after the sign (capped: 5 means
            // "5 or more", which is never a valid offset).
            let mut digits = 0;
            while digits < 5
                && end + 1 + digits < input.len()
                && input[end + 1 + digits].is_ascii_digit()
            {
                digits += 1;
            }
            if digits == 2 {
                if end + 6 <= input.len()
                    && input[end + 3] == b':'
                    && Self::is_2_digits(input, end + 4)
                {
                    end += 6; // ±HH:MM
                } else {
                    end += 3; // ±HH
                }
            } else if digits == 4 {
                end += 5; // ±HHMM
            }
            // Any other digit count: leave the sign unconsumed; the
            // boundary check in try_date decides what happens next.
        }

        Some(end)
    }

    fn is_2_digits(input: &[u8], pos: usize) -> bool {
        pos + 2 <= input.len() && input[pos].is_ascii_digit() && input[pos + 1].is_ascii_digit()
    }

    fn is_4_digits(input: &[u8], pos: usize) -> bool {
        pos + 4 <= input.len()
            && input[pos].is_ascii_digit()
            && input[pos + 1].is_ascii_digit()
            && input[pos + 2].is_ascii_digit()
            && input[pos + 3].is_ascii_digit()
    }

    fn parse_num(input: &[u8], pos: usize, len: usize) -> u32 {
        let mut n = 0u32;
        for i in 0..len {
            n = n * 10 + (input[pos + i] - b'0') as u32;
        }
        n
    }
}

impl Finder for Datetime {
    fn line_agnostic(&self) -> bool {
        // Matches never contain a line terminator and `\n`/`\r` end every
        // walk exactly like the end of the input does.
        true
    }

    fn id(&self) -> &'static str {
        "datetime"
    }

    fn dispatchable(&self) -> bool {
        true
    }

    fn could_start_at(&self, byte: u8) -> bool {
        byte.is_ascii_digit()
    }

    fn could_start_after(&self, prev: u8, _cur: u8) -> bool {
        !prev.is_ascii_digit()
    }

    fn could_continue_with(&self, _cur: u8, next: u8) -> bool {
        next.is_ascii_digit()
    }

    fn anchor(&self) -> Option<Anchor> {
        // `YYYY-MM-DD`: the dash after the month follows three bytes on.
        Some(
            Anchor::new(
                ByteSet::from_bytes(b"-"),
                ByteSet::from_fn(|b| b.is_ascii_digit()),
            )
            .confirm(b"-", &[3], b"-")
            .back(4),
        )
    }

    fn run_rules(&self) -> Vec<RunRule> {
        // `YYYY-MM-`.
        vec![
            RunRule::new(RunClass::Digit, 4, 4)
                .followed_by(b"-")
                .then(RunClass::Digit, 2, 2)
                .followed_by(b"-"),
        ]
    }

    fn try_at(&self, input: &[u8], pos: usize) -> Option<Range<usize>> {
        if !input[pos].is_ascii_digit() {
            return None;
        }
        Self::try_date(input, pos)
    }

    fn find(&self, s: &str) -> Option<Range<usize>> {
        let input = s.as_bytes();
        let mut idx = 0;

        while idx + 10 <= input.len() {
            if input[idx].is_ascii_digit()
                && let Some(range) = Self::try_date(input, idx)
            {
                return Some(range);
            }
            idx += 1;
        }

        None
    }
}

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

    #[test]
    fn id_should_return_datetime() {
        let finder = Datetime::default();
        assert_eq!("datetime", finder.id());
    }

    #[test]
    fn find_should_extract_date() {
        let finder = Datetime::default();
        let input = "created on 2024-01-15 by admin";
        let range = finder.find(input).unwrap();
        assert_eq!("2024-01-15", &input[range]);
    }

    #[test]
    fn find_should_extract_datetime_with_t() {
        let finder = Datetime::default();
        let input = "timestamp: 2024-01-15T10:30:00";
        let range = finder.find(input).unwrap();
        assert_eq!("2024-01-15T10:30:00", &input[range]);
    }

    #[test]
    fn find_should_extract_datetime_with_timezone_z() {
        let finder = Datetime::default();
        let input = "2024-01-15T10:30:00Z";
        let range = finder.find(input).unwrap();
        assert_eq!("2024-01-15T10:30:00Z", &input[range]);
    }

    #[test]
    fn find_should_extract_datetime_with_timezone_offset() {
        let finder = Datetime::default();
        let input = "2024-01-15T10:30:00+05:30";
        let range = finder.find(input).unwrap();
        assert_eq!("2024-01-15T10:30:00+05:30", &input[range]);
    }

    #[test]
    fn find_should_extract_datetime_with_negative_offset() {
        let finder = Datetime::default();
        let input = "2024-01-15T10:30:00-08:00";
        let range = finder.find(input).unwrap();
        assert_eq!("2024-01-15T10:30:00-08:00", &input[range]);
    }

    #[test]
    fn find_should_extract_datetime_with_fractional_seconds() {
        let finder = Datetime::default();
        let input = "2024-01-15T10:30:00.123Z";
        let range = finder.find(input).unwrap();
        assert_eq!("2024-01-15T10:30:00.123Z", &input[range]);
    }

    #[test]
    fn find_should_extract_datetime_with_fractional_and_offset() {
        let finder = Datetime::default();
        let input = "2024-01-15T10:30:00.123456+02:00";
        let range = finder.find(input).unwrap();
        assert_eq!("2024-01-15T10:30:00.123456+02:00", &input[range]);
    }

    #[test]
    fn find_should_extract_datetime_without_seconds() {
        let finder = Datetime::default();
        let input = "2024-01-15T10:30Z";
        let range = finder.find(input).unwrap();
        assert_eq!("2024-01-15T10:30Z", &input[range]);
    }

    #[test]
    fn find_should_extract_date_in_text() {
        let finder = Datetime::default();
        let input = "deployed on 2024-12-25 successfully";
        let range = finder.find(input).unwrap();
        assert_eq!("2024-12-25", &input[range]);
    }

    #[test]
    fn find_should_reject_invalid_month() {
        let finder = Datetime::default();
        assert!(finder.find("2024-13-01").is_none());
    }

    #[test]
    fn find_should_reject_invalid_day() {
        let finder = Datetime::default();
        assert!(finder.find("2024-01-32").is_none());
    }

    #[test]
    fn find_should_reject_month_zero() {
        let finder = Datetime::default();
        assert!(finder.find("2024-00-15").is_none());
    }

    #[test]
    fn find_should_reject_day_zero() {
        let finder = Datetime::default();
        assert!(finder.find("2024-01-00").is_none());
    }

    #[test]
    fn find_should_reject_preceded_by_digit() {
        let finder = Datetime::default();
        assert!(finder.find("x12024-01-15").is_none());
    }

    #[test]
    fn find_should_reject_followed_by_digit() {
        let finder = Datetime::default();
        assert!(finder.find("2024-01-155").is_none());
    }

    #[test]
    fn find_should_handle_empty_input() {
        let finder = Datetime::default();
        assert!(finder.find("").is_none());
    }

    #[test]
    fn find_should_extract_multiple_datetimes_iteratively() {
        let finder = Datetime::default();
        let input = "2024-01-15T10:00:00Z to 2024-01-16T12:00:00Z";

        let mut results = Vec::new();
        let mut idx = 0;
        while idx < input.len() {
            if let Some(range) = finder.find(&input[idx..]) {
                results.push(&input[idx + range.start..idx + range.end]);
                idx += range.end;
            } else {
                break;
            }
        }

        assert_eq!(
            vec!["2024-01-15T10:00:00Z", "2024-01-16T12:00:00Z"],
            results
        );
    }

    #[test]
    fn find_should_extract_date_at_start() {
        let finder = Datetime::default();
        let input = "2024-01-15 is the date";
        let range = finder.find(input).unwrap();
        assert_eq!("2024-01-15", &input[range]);
    }

    #[test]
    fn find_should_extract_date_at_end() {
        let finder = Datetime::default();
        let input = "the date is 2024-01-15";
        let range = finder.find(input).unwrap();
        assert_eq!("2024-01-15", &input[range]);
    }

    #[test]
    fn find_should_reject_invalid_hour() {
        let finder = Datetime::default();
        let input = "2024-01-15T25:00:00";
        let range = finder.find(input).unwrap();
        assert_eq!("2024-01-15", &input[range]);
    }

    #[test]
    fn find_should_reject_invalid_minute() {
        let finder = Datetime::default();
        let input = "2024-01-15T10:61:00";
        let range = finder.find(input).unwrap();
        assert_eq!("2024-01-15", &input[range]);
    }

    #[test]
    fn find_should_extract_datetime_with_space_separator() {
        let finder = Datetime::default();
        let input = "log: 2024-01-15 10:30:00";
        let range = finder.find(input).unwrap();
        assert_eq!("2024-01-15 10:30:00", &input[range]);
    }

    #[test]
    fn try_at_date_at_start() {
        let finder = Datetime::default();
        let input = b"2024-01-15 rest";
        assert_eq!(finder.try_at(input, 0), Some(0..10));
    }

    #[test]
    fn try_at_non_digit() {
        let finder = Datetime::default();
        let input = b"abc";
        assert!(finder.try_at(input, 0).is_none());
    }

    #[test]
    fn try_at_short_input() {
        let finder = Datetime::default();
        let input = b"2024";
        assert!(finder.try_at(input, 0).is_none());
    }

    #[test]
    fn try_at_preceded_by_digit() {
        let finder = Datetime::default();
        let input = b"12024-01-15";
        assert!(finder.try_at(input, 1).is_none());
    }

    #[test]
    fn find_boundary_year_1000() {
        let finder = Datetime::default();
        let input = "1000-01-01";
        assert!(finder.find(input).is_some());
    }

    #[test]
    fn find_boundary_year_9999() {
        let finder = Datetime::default();
        let input = "9999-12-31";
        assert!(finder.find(input).is_some());
    }

    #[test]
    fn find_leap_second() {
        let finder = Datetime::default();
        let input = "2024-06-30T23:59:60Z";
        let range = finder.find(input).unwrap();
        assert_eq!("2024-06-30T23:59:60Z", &input[range]);
    }

    #[test]
    fn find_fractional_seconds_many_digits() {
        let finder = Datetime::default();
        let input = "2024-01-15T10:30:00.123456789Z";
        let range = finder.find(input).unwrap();
        assert_eq!("2024-01-15T10:30:00.123456789Z", &input[range]);
    }

    #[test]
    fn find_single_digit_input() {
        let finder = Datetime::default();
        assert!(finder.find("1").is_none());
    }
}