ferro-rs 0.2.6

//! Cron expression parsing and due-checking
//!
//! Supports standard cron syntax with 5 fields:
//! `minute hour day-of-month month day-of-week`

use chrono::{Datelike, Local, Timelike};

/// Day of week enum for scheduling
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum DayOfWeek {
    /// Represents Sunday (cron value 0).
    Sunday = 0,
    /// Represents Monday (cron value 1).
    Monday = 1,
    /// Represents Tuesday (cron value 2).
    Tuesday = 2,
    /// Represents Wednesday (cron value 3).
    Wednesday = 3,
    /// Represents Thursday (cron value 4).
    Thursday = 4,
    /// Represents Friday (cron value 5).
    Friday = 5,
    /// Represents Saturday (cron value 6).
    Saturday = 6,
}

impl DayOfWeek {
    /// Convert from chrono Weekday
    pub fn from_chrono(weekday: chrono::Weekday) -> Self {
        match weekday {
            chrono::Weekday::Sun => DayOfWeek::Sunday,
            chrono::Weekday::Mon => DayOfWeek::Monday,
            chrono::Weekday::Tue => DayOfWeek::Tuesday,
            chrono::Weekday::Wed => DayOfWeek::Wednesday,
            chrono::Weekday::Thu => DayOfWeek::Thursday,
            chrono::Weekday::Fri => DayOfWeek::Friday,
            chrono::Weekday::Sat => DayOfWeek::Saturday,
        }
    }
}

/// Cron expression for scheduling tasks
///
/// Supports standard cron syntax with 5 fields:
/// `minute hour day-of-month month day-of-week`
///
/// # Examples
///
/// ```rust,ignore
/// use ferro_rs::CronExpression;
///
/// // Every minute
/// let expr = CronExpression::every_minute();
///
/// // Daily at 3:00 AM
/// let expr = CronExpression::daily_at("03:00");
///
/// // Custom cron expression
/// let expr = CronExpression::parse("0 */2 * * *").unwrap(); // Every 2 hours
/// ```
#[derive(Debug, Clone)]
pub struct CronExpression {
    raw: String,
    /// Minutes (0-59)
    minute: CronField,
    /// Hours (0-23)
    hour: CronField,
    /// Day of month (1-31)
    day_of_month: CronField,
    /// Month (1-12)
    month: CronField,
    /// Day of week (0-6, Sunday=0)
    day_of_week: CronField,
}

#[derive(Debug, Clone)]
enum CronField {
    Any,                // *
    Value(u32),         // 5
    Range(u32, u32),    // 1-5
    Step(u32),          // */5
    List(Vec<u32>),     // 1,3,5
    StepFrom(u32, u32), // 5/10 (start at 5, every 10)
}

impl CronField {
    fn matches(&self, value: u32) -> bool {
        match self {
            CronField::Any => true,
            CronField::Value(v) => *v == value,
            CronField::Range(start, end) => value >= *start && value <= *end,
            CronField::Step(step) => value.is_multiple_of(*step),
            CronField::StepFrom(start, step) => {
                value >= *start && (value - start).is_multiple_of(*step)
            }
            CronField::List(values) => values.contains(&value),
        }
    }

    fn parse(s: &str) -> Result<Self, String> {
        if s == "*" {
            return Ok(CronField::Any);
        }

        // Handle */N (every N)
        if let Some(step_str) = s.strip_prefix("*/") {
            let step: u32 = step_str
                .parse()
                .map_err(|_| format!("Invalid step value in '{s}'"))?;
            return Ok(CronField::Step(step));
        }

        // Handle N/M (starting at N, every M)
        if s.contains('/') && !s.starts_with('*') {
            let parts: Vec<&str> = s.split('/').collect();
            if parts.len() == 2 {
                let start: u32 = parts[0]
                    .parse()
                    .map_err(|_| format!("Invalid start value in '{s}'"))?;
                let step: u32 = parts[1]
                    .parse()
                    .map_err(|_| format!("Invalid step value in '{s}'"))?;
                return Ok(CronField::StepFrom(start, step));
            }
        }

        // Handle comma-separated list (1,3,5)
        if s.contains(',') {
            let values: Result<Vec<u32>, _> = s.split(',').map(|v| v.trim().parse()).collect();
            return Ok(CronField::List(
                values.map_err(|_| format!("Invalid list value in '{s}'"))?,
            ));
        }

        // Handle range (1-5)
        if s.contains('-') {
            let parts: Vec<&str> = s.split('-').collect();
            if parts.len() == 2 {
                let start: u32 = parts[0]
                    .parse()
                    .map_err(|_| format!("Invalid range start in '{s}'"))?;
                let end: u32 = parts[1]
                    .parse()
                    .map_err(|_| format!("Invalid range end in '{s}'"))?;
                return Ok(CronField::Range(start, end));
            }
        }

        // Handle single value
        let value: u32 = s.parse().map_err(|_| format!("Invalid value in '{s}'"))?;
        Ok(CronField::Value(value))
    }
}

impl std::fmt::Display for CronField {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            CronField::Any => write!(f, "*"),
            CronField::Value(v) => write!(f, "{v}"),
            CronField::Range(s, e) => write!(f, "{s}-{e}"),
            CronField::Step(s) => write!(f, "*/{s}"),
            CronField::StepFrom(start, step) => write!(f, "{start}/{step}"),
            CronField::List(l) => {
                let s: String = l
                    .iter()
                    .map(|v| v.to_string())
                    .collect::<Vec<_>>()
                    .join(",");
                write!(f, "{s}")
            }
        }
    }
}

impl CronExpression {
    /// Parse a cron expression string
    ///
    /// Format: `minute hour day-of-month month day-of-week`
    ///
    /// # Examples
    ///
    /// - `* * * * *` - Every minute
    /// - `0 * * * *` - Every hour
    /// - `0 3 * * *` - Daily at 3:00 AM
    /// - `0 0 * * 0` - Weekly on Sunday
    /// - `*/5 * * * *` - Every 5 minutes
    pub fn parse(expression: &str) -> Result<Self, String> {
        let parts: Vec<&str> = expression.split_whitespace().collect();

        if parts.len() != 5 {
            return Err(format!(
                "Cron expression must have 5 fields, got {}",
                parts.len()
            ));
        }

        Ok(Self {
            raw: expression.to_string(),
            minute: CronField::parse(parts[0])?,
            hour: CronField::parse(parts[1])?,
            day_of_month: CronField::parse(parts[2])?,
            month: CronField::parse(parts[3])?,
            day_of_week: CronField::parse(parts[4])?,
        })
    }

    /// Check if this expression is due now
    pub fn is_due(&self) -> bool {
        let now = Local::now();

        self.minute.matches(now.minute())
            && self.hour.matches(now.hour())
            && self.day_of_month.matches(now.day())
            && self.month.matches(now.month())
            && self
                .day_of_week
                .matches(now.weekday().num_days_from_sunday())
    }

    /// Get the raw cron expression string
    pub fn expression(&self) -> &str {
        &self.raw
    }

    /// Set the time component (modifies hour and minute)
    pub fn at(mut self, time: &str) -> Self {
        let parts: Vec<&str> = time.split(':').collect();
        if parts.len() == 2 {
            if let (Ok(hour), Ok(minute)) = (parts[0].parse::<u32>(), parts[1].parse::<u32>()) {
                self.hour = CronField::Value(hour);
                self.minute = CronField::Value(minute);
                self.raw = format!(
                    "{} {} {} {} {}",
                    minute, hour, self.day_of_month, self.month, self.day_of_week,
                );
            }
        }
        self
    }

    // =========================================================================
    // Factory Methods
    // =========================================================================

    /// Every minute: `* * * * *`
    pub fn every_minute() -> Self {
        Self::parse("* * * * *").expect("valid cron: every minute")
    }

    /// Every N minutes: `*/N * * * *`
    ///
    /// # Panics
    /// Panics if `n` is 0.
    pub fn every_n_minutes(n: u32) -> Self {
        assert!(n > 0, "interval must be > 0");
        Self::parse(&format!("*/{n} * * * *")).expect("valid cron: every N minutes")
    }

    /// Every hour at minute 0: `0 * * * *`
    pub fn hourly() -> Self {
        Self::parse("0 * * * *").expect("valid cron: hourly")
    }

    /// Every hour at specific minute: `M * * * *`
    ///
    /// # Panics
    /// Panics if `minute` >= 60.
    pub fn hourly_at(minute: u32) -> Self {
        assert!(minute < 60, "minute must be 0-59, got {minute}");
        Self::parse(&format!("{minute} * * * *")).expect("valid cron: hourly at")
    }

    /// Daily at midnight: `0 0 * * *`
    pub fn daily() -> Self {
        Self::parse("0 0 * * *").expect("valid cron: daily")
    }

    /// Daily at specific time: `M H * * *`
    ///
    /// Accepts `"HH:MM"` format. Falls back to midnight on invalid input.
    pub fn daily_at(time: &str) -> Self {
        let parts: Vec<&str> = time.split(':').collect();
        if parts.len() == 2 {
            let hour: u32 = parts[0].parse().unwrap_or(0);
            let minute: u32 = parts[1].parse().unwrap_or(0);
            Self::parse(&format!("{} {} * * *", minute.min(59), hour.min(23)))
                .expect("valid cron: daily at")
        } else {
            Self::daily()
        }
    }

    /// Weekly on Sunday at midnight: `0 0 * * 0`
    pub fn weekly() -> Self {
        Self::parse("0 0 * * 0").expect("valid cron: weekly")
    }

    /// Weekly on specific day at midnight: `0 0 * * D`
    pub fn weekly_on(day: DayOfWeek) -> Self {
        Self::parse(&format!("0 0 * * {}", day as u32)).expect("valid cron: weekly on")
    }

    /// On specific days of the week at midnight.
    ///
    /// # Panics
    /// Panics if `days` is empty.
    pub fn on_days(days: &[DayOfWeek]) -> Self {
        assert!(!days.is_empty(), "days must not be empty");
        let days_str: Vec<String> = days.iter().map(|d| (*d as u32).to_string()).collect();
        Self::parse(&format!("0 0 * * {}", days_str.join(","))).expect("valid cron: on days")
    }

    /// Monthly on the first day at midnight: `0 0 1 * *`
    pub fn monthly() -> Self {
        Self::parse("0 0 1 * *").expect("valid cron: monthly")
    }

    /// Monthly on specific day at midnight: `0 0 D * *`
    ///
    /// # Panics
    /// Panics if `day` is 0 or > 31.
    pub fn monthly_on(day: u32) -> Self {
        assert!((1..=31).contains(&day), "day must be 1-31, got {day}");
        Self::parse(&format!("0 0 {day} * *")).expect("valid cron: monthly on")
    }

    /// Quarterly on the first day of each quarter at midnight
    pub fn quarterly() -> Self {
        Self::parse("0 0 1 1,4,7,10 *").expect("valid cron: quarterly")
    }

    /// Yearly on January 1st at midnight: `0 0 1 1 *`
    pub fn yearly() -> Self {
        Self::parse("0 0 1 1 *").expect("valid cron: yearly")
    }

    /// On weekdays (Monday-Friday) at midnight
    pub fn weekdays() -> Self {
        Self::parse("0 0 * * 1-5").expect("valid cron: weekdays")
    }

    /// On weekends (Saturday-Sunday) at midnight
    pub fn weekends() -> Self {
        Self::parse("0 0 * * 0,6").expect("valid cron: weekends")
    }
}

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

    #[test]
    fn test_parse_every_minute() {
        let expr = CronExpression::parse("* * * * *").unwrap();
        assert_eq!(expr.expression(), "* * * * *");
    }

    #[test]
    fn test_parse_specific_time() {
        let expr = CronExpression::parse("30 14 * * *").unwrap();
        assert_eq!(expr.expression(), "30 14 * * *");
    }

    #[test]
    fn test_parse_invalid_expression() {
        let result = CronExpression::parse("* * *");
        assert!(result.is_err());
    }

    #[test]
    fn test_factory_methods() {
        assert_eq!(CronExpression::every_minute().expression(), "* * * * *");
        assert_eq!(CronExpression::hourly().expression(), "0 * * * *");
        assert_eq!(CronExpression::daily().expression(), "0 0 * * *");
        assert_eq!(CronExpression::weekly().expression(), "0 0 * * 0");
        assert_eq!(CronExpression::monthly().expression(), "0 0 1 * *");
    }

    #[test]
    fn test_daily_at() {
        let expr = CronExpression::daily_at("03:30");
        assert_eq!(expr.expression(), "30 3 * * *");
    }

    #[test]
    fn test_at_modifier() {
        let expr = CronExpression::daily().at("14:30");
        assert_eq!(expr.expression(), "30 14 * * *");
    }
}