rtc-hal 0.3.1

//! # DateTime Module
//!
//! This module defines a `DateTime` struct and helper functions for representing,
//! validating, and working with calendar date and time values in embedded systems.
//!
//! ## Features
//! - Stores year, month, day, hour, minute, second
//! - Built-in validation for all fields (including leap years and month lengths)
//! - Setter and getter methods that enforce validity
//! - Utility functions for leap year detection, days in a month, and weekday calculation
//!
//! ## Year Range
//! The default supported range is **year >= 1970**, which covers the widest set of
//! popular RTC chips. For example:
//!
//! - DS1307, DS3231: 2000-2099
//!
//! Drivers are responsible for checking and enforcing the *exact* year range of the
//! underlying hardware. The `DateTime` type itself only enforces the lower bound (1970)
//! to remain reusable in contexts outside RTCs.
//!
//! ## Weekday Format
//! - This module uses **1=Sunday to 7=Saturday**
//! - Drivers must handle conversion if required

/// Errors that can occur when working with DateTime
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[cfg_attr(feature = "defmt", derive(defmt::Format))]
pub enum DateTimeError {
    /// Invalid month value
    InvalidMonth,
    /// Invalid day value
    InvalidDay,
    /// Invalid hour value
    InvalidHour,
    /// Invalid minute value
    InvalidMinute,
    /// Invalid second value
    InvalidSecond,
    /// Invalid weekday value
    InvalidWeekday,
    /// Invalid Year value
    InvalidYear,
}

impl core::fmt::Display for DateTimeError {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        match self {
            DateTimeError::InvalidMonth => write!(f, "invalid month"),
            DateTimeError::InvalidDay => write!(f, "invalid day"),
            DateTimeError::InvalidHour => write!(f, "invalid hour"),
            DateTimeError::InvalidMinute => write!(f, "invalid minute"),
            DateTimeError::InvalidSecond => write!(f, "invalid second"),
            DateTimeError::InvalidWeekday => write!(f, "invalid weekday"),
            DateTimeError::InvalidYear => write!(f, "invalid year"),
        }
    }
}

impl core::error::Error for DateTimeError {}

/// Date and time representation used across RTC drivers.
///
/// This type represents calendar date and time in a general-purpose way,
/// independent of any specific RTC hardware.
///
/// - Validates that `year >= 1970`
/// - Other limits (e.g., 2000-2099) must be enforced by individual drivers
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct DateTime {
    /// Year (full year, e.g., 2024)
    year: u16,
    /// Month (1-12)
    month: u8,
    /// Day of the month (1-31 depending on month/year)
    day_of_month: u8,
    /// Hour (0-23)
    hour: u8,
    /// Minute (0-59)
    minute: u8,
    /// Second (0-59)
    second: u8,
}

impl DateTime {
    /// Create a new `DateTime` instance with validation.
    ///
    /// # Errors
    ///
    /// Returns a `DateTimeError` if any component is out of valid range.
    pub fn new(
        year: u16,
        month: u8,
        day_of_month: u8,
        hour: u8,
        minute: u8,
        second: u8,
    ) -> Result<Self, DateTimeError> {
        let dt = DateTime {
            year,
            month,
            day_of_month,
            hour,
            minute,
            second,
        };
        dt.validate()?;
        Ok(dt)
    }

    /// Validate all datetime components.
    ///
    /// # Errors
    ///
    /// Returns the first `DateTimeError` encountered.
    pub fn validate(&self) -> Result<(), DateTimeError> {
        Self::validate_year(self.year)?;
        Self::validate_month(self.month)?;
        Self::validate_day(self.year, self.month, self.day_of_month)?;
        Self::validate_hour(self.hour)?;
        Self::validate_minute(self.minute)?;
        Self::validate_second(self.second)?;
        Ok(())
    }

    /// Validate the year (must be >= 1970).
    fn validate_year(year: u16) -> Result<(), DateTimeError> {
        if year < 1970 {
            return Err(DateTimeError::InvalidYear);
        }
        Ok(())
    }

    /// Validate the month (must be 1-12).
    fn validate_month(month: u8) -> Result<(), DateTimeError> {
        if month == 0 || month > 12 {
            return Err(DateTimeError::InvalidMonth);
        }
        Ok(())
    }

    /// Validate the day (must be within the valid range for the month/year).
    fn validate_day(year: u16, month: u8, day: u8) -> Result<(), DateTimeError> {
        let max_day = days_in_month(year, month);
        if day == 0 || day > max_day {
            return Err(DateTimeError::InvalidDay);
        }
        Ok(())
    }

    /// Validate the hour (must be 0-23).
    fn validate_hour(hour: u8) -> Result<(), DateTimeError> {
        if hour > 23 {
            return Err(DateTimeError::InvalidHour);
        }
        Ok(())
    }

    /// Validate the minute (must be 0-59).
    fn validate_minute(minute: u8) -> Result<(), DateTimeError> {
        if minute > 59 {
            return Err(DateTimeError::InvalidMinute);
        }
        Ok(())
    }

    /// Validate the second (must be 0-59).
    fn validate_second(second: u8) -> Result<(), DateTimeError> {
        if second > 59 {
            return Err(DateTimeError::InvalidSecond);
        }
        Ok(())
    }

    /// Get the year (e.g. 2025).
    pub fn year(&self) -> u16 {
        self.year
    }

    /// Get the month number (1-12).
    pub fn month(&self) -> u8 {
        self.month
    }

    /// Get the day of the month (1-31).
    pub fn day_of_month(&self) -> u8 {
        self.day_of_month
    }

    /// Get the hour (0-23).
    pub fn hour(&self) -> u8 {
        self.hour
    }

    /// Get the minute (0-59).
    pub fn minute(&self) -> u8 {
        self.minute
    }

    /// Get the second (0-59).
    pub fn second(&self) -> u8 {
        self.second
    }

    /// Set year with validation.
    ///
    /// Re-validates the day in case of leap-year or February issues.
    pub fn set_year(&mut self, year: u16) -> Result<(), DateTimeError> {
        Self::validate_year(year)?;
        Self::validate_day(year, self.month, self.day_of_month)?;
        self.year = year;
        Ok(())
    }

    /// Set month with validation.
    ///
    /// Re-validates the day in case month/day mismatch occurs.
    pub fn set_month(&mut self, month: u8) -> Result<(), DateTimeError> {
        Self::validate_month(month)?;
        Self::validate_day(self.year, month, self.day_of_month)?;
        self.month = month;
        Ok(())
    }

    /// Set day with validation.
    pub fn set_day_of_month(&mut self, day_of_month: u8) -> Result<(), DateTimeError> {
        Self::validate_day(self.year, self.month, day_of_month)?;
        self.day_of_month = day_of_month;
        Ok(())
    }

    /// Set hour with validation.
    pub fn set_hour(&mut self, hour: u8) -> Result<(), DateTimeError> {
        Self::validate_hour(hour)?;
        self.hour = hour;
        Ok(())
    }

    /// Set minute with validation.
    pub fn set_minute(&mut self, minute: u8) -> Result<(), DateTimeError> {
        Self::validate_minute(minute)?;
        self.minute = minute;
        Ok(())
    }

    /// Set second with validation.
    pub fn set_second(&mut self, second: u8) -> Result<(), DateTimeError> {
        Self::validate_second(second)?;
        self.second = second;
        Ok(())
    }

    /// Calculate weekday for this DateTime
    pub fn calculate_weekday(&self) -> Result<Weekday, DateTimeError> {
        calculate_weekday(self.year, self.month, self.day_of_month)
    }
}

/// Day of the week (1 = Sunday .. 7 = Saturday)
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[repr(u8)]
pub enum Weekday {
    /// Sunday starts with 1
    Sunday = 1,
    /// Monday
    Monday = 2,
    /// Tuesday
    Tuesday = 3,
    /// Wednesday
    Wednesday = 4,
    /// Thursday
    Thursday = 5,
    /// Friday
    Friday = 6,
    /// Saturday
    Saturday = 7,
}

impl Weekday {
    /// Create a Weekday from a raw u8 (1 = Sunday .. 7 = Saturday).
    pub fn from_number(n: u8) -> Result<Self, DateTimeError> {
        match n {
            1 => Ok(Self::Sunday),
            2 => Ok(Self::Monday),
            3 => Ok(Self::Tuesday),
            4 => Ok(Self::Wednesday),
            5 => Ok(Self::Thursday),
            6 => Ok(Self::Friday),
            7 => Ok(Self::Saturday),
            _ => Err(DateTimeError::InvalidWeekday),
        }
    }

    /// Get the number form (1 = Sunday .. 7 = Saturday).
    pub fn to_number(self) -> u8 {
        self as u8
    }

    /// Get the weekday name as a string slice
    pub fn as_str(&self) -> &'static str {
        match self {
            Weekday::Sunday => "Sunday",
            Weekday::Monday => "Monday",
            Weekday::Tuesday => "Tuesday",
            Weekday::Wednesday => "Wednesday",
            Weekday::Thursday => "Thursday",
            Weekday::Friday => "Friday",
            Weekday::Saturday => "Saturday",
        }
    }
}

/// Check if a year is a leap year
pub fn is_leap_year(year: u16) -> bool {
    (year % 4 == 0) && (year % 100 != 0 || year % 400 == 0)
}

/// Get the number of days in a month
pub fn days_in_month(year: u16, month: u8) -> u8 {
    match month {
        1 | 3 | 5 | 7 | 8 | 10 | 12 => 31,
        4 | 6 | 9 | 11 => 30,
        2 => {
            if is_leap_year(year) {
                29
            } else {
                28
            }
        }
        _ => 0,
    }
}

/// Calculate the day of the week using Zeller's congruence algorithm
/// Returns 1=Sunday, 2=Monday, ..., 7=Saturday
pub fn calculate_weekday(year: u16, month: u8, day_of_month: u8) -> Result<Weekday, DateTimeError> {
    let (year, month) = if month < 3 {
        (year - 1, month + 12)
    } else {
        (year, month)
    };

    let k = year % 100;
    let j = year / 100;

    let h =
        (day_of_month as u16 + ((13 * (month as u16 + 1)) / 5) + k + (k / 4) + (j / 4) - 2 * j) % 7;

    // Convert Zeller's result (0=Saturday) to our format (1=Sunday)
    let weekday_num = ((h + 6) % 7) + 1;

    // This should never fail since we're calculating a valid weekday
    Weekday::from_number(weekday_num as u8)
}

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

    #[test]
    fn test_valid_datetime_creation() {
        let dt = DateTime::new(2024, 3, 15, 14, 30, 45).unwrap();
        assert_eq!(dt.year(), 2024);
        assert_eq!(dt.month(), 3);
        assert_eq!(dt.day_of_month(), 15);
        assert_eq!(dt.hour(), 14);
        assert_eq!(dt.minute(), 30);
        assert_eq!(dt.second(), 45);
    }

    #[test]
    fn test_invalid_year() {
        let result = DateTime::new(1969, 1, 1, 0, 0, 0);
        assert_eq!(result.unwrap_err(), DateTimeError::InvalidYear);
    }

    #[test]
    fn test_invalid_month() {
        assert_eq!(
            DateTime::new(2024, 0, 1, 0, 0, 0).unwrap_err(),
            DateTimeError::InvalidMonth
        );
        assert_eq!(
            DateTime::new(2024, 13, 1, 0, 0, 0).unwrap_err(),
            DateTimeError::InvalidMonth
        );
    }

    #[test]
    fn test_invalid_day() {
        // Test February 30th (invalid)
        assert_eq!(
            DateTime::new(2024, 2, 30, 0, 0, 0).unwrap_err(),
            DateTimeError::InvalidDay
        );

        // Test day 0
        assert_eq!(
            DateTime::new(2024, 1, 0, 0, 0, 0).unwrap_err(),
            DateTimeError::InvalidDay
        );

        // Test April 31st (invalid - April has 30 days)
        assert_eq!(
            DateTime::new(2024, 4, 31, 0, 0, 0).unwrap_err(),
            DateTimeError::InvalidDay
        );
    }

    #[test]
    fn test_invalid_hour() {
        assert_eq!(
            DateTime::new(2024, 1, 1, 24, 0, 0).unwrap_err(),
            DateTimeError::InvalidHour
        );
    }

    #[test]
    fn test_invalid_minute() {
        assert_eq!(
            DateTime::new(2024, 1, 1, 0, 60, 0).unwrap_err(),
            DateTimeError::InvalidMinute
        );
    }

    #[test]
    fn test_invalid_second() {
        assert_eq!(
            DateTime::new(2024, 1, 1, 0, 0, 60).unwrap_err(),
            DateTimeError::InvalidSecond
        );
    }

    #[test]
    fn test_leap_year_february_29() {
        // 2024 is a leap year - February 29th should be valid
        assert!(DateTime::new(2024, 2, 29, 0, 0, 0).is_ok());

        // 2023 is not a leap year - February 29th should be invalid
        assert_eq!(
            DateTime::new(2023, 2, 29, 0, 0, 0).unwrap_err(),
            DateTimeError::InvalidDay
        );
    }

    #[test]
    fn test_setters_with_validation() {
        let mut dt = DateTime::new(2024, 1, 1, 0, 0, 0).unwrap();

        // Valid operations
        assert!(dt.set_year(2025).is_ok());
        assert_eq!(dt.year(), 2025);

        assert!(dt.set_month(12).is_ok());
        assert_eq!(dt.month(), 12);

        assert!(dt.set_hour(23).is_ok());
        assert_eq!(dt.hour(), 23);

        // Invalid operations
        assert_eq!(dt.set_year(1969), Err(DateTimeError::InvalidYear));
        assert_eq!(dt.set_month(13), Err(DateTimeError::InvalidMonth));
        assert_eq!(dt.set_hour(24), Err(DateTimeError::InvalidHour));
    }

    #[test]
    fn test_leap_year_edge_cases_in_setters() {
        let mut dt = DateTime::new(2024, 2, 29, 0, 0, 0).unwrap(); // Leap year

        // Changing to non-leap year should fail because Feb 29 becomes invalid
        assert_eq!(dt.set_year(2023), Err(DateTimeError::InvalidDay));

        // Original value should remain unchanged after failed operation
        assert_eq!(dt.year(), 2024);
        assert_eq!(dt.day_of_month(), 29);
    }

    #[test]
    fn test_month_day_validation_in_setters() {
        let mut dt = DateTime::new(2024, 1, 31, 0, 0, 0).unwrap(); // January 31st

        // Changing to February should fail because Feb doesn't have 31 days
        assert_eq!(dt.set_month(2), Err(DateTimeError::InvalidDay));

        // Original value should remain unchanged
        assert_eq!(dt.month(), 1);
        assert_eq!(dt.day_of_month(), 31);

        // But changing to March should work (March has 31 days)
        assert!(dt.set_month(3).is_ok());
        assert_eq!(dt.month(), 3);
    }

    #[test]
    fn test_weekday_calculation() {
        let dt = DateTime::new(2024, 1, 1, 0, 0, 0).unwrap(); // New Year 2024
        let weekday = dt.calculate_weekday().unwrap();
        assert_eq!(weekday, Weekday::Monday); // January 1, 2024 was a Monday

        let dt = DateTime::new(2024, 12, 25, 0, 0, 0).unwrap();
        let weekday = dt.calculate_weekday().unwrap();
        assert_eq!(weekday, Weekday::Wednesday); // December 25, 2024 is a Wednesday
    }

    #[test]
    fn test_weekday_from_number() {
        assert_eq!(Weekday::from_number(1).unwrap(), Weekday::Sunday);
        assert_eq!(Weekday::from_number(2).unwrap(), Weekday::Monday);
        assert_eq!(Weekday::from_number(7).unwrap(), Weekday::Saturday);
        assert_eq!(Weekday::from_number(3).unwrap(), Weekday::Tuesday);

        assert_eq!(
            Weekday::from_number(0).unwrap_err(),
            DateTimeError::InvalidWeekday
        );
        assert_eq!(
            Weekday::from_number(8).unwrap_err(),
            DateTimeError::InvalidWeekday
        );
    }

    #[test]
    fn test_weekday_to_number() {
        assert_eq!(Weekday::Sunday.to_number(), 1);
        assert_eq!(Weekday::Monday.to_number(), 2);
        assert_eq!(Weekday::Saturday.to_number(), 7);
    }

    #[test]
    fn test_weekday_as_str() {
        assert_eq!(Weekday::Sunday.as_str(), "Sunday");
        assert_eq!(Weekday::Monday.as_str(), "Monday");
        assert_eq!(Weekday::Tuesday.as_str(), "Tuesday");
        assert_eq!(Weekday::Wednesday.as_str(), "Wednesday");
        assert_eq!(Weekday::Thursday.as_str(), "Thursday");
        assert_eq!(Weekday::Friday.as_str(), "Friday");
        assert_eq!(Weekday::Saturday.as_str(), "Saturday");
    }

    #[test]
    fn test_calculate_weekday_known_dates() {
        // Test some known dates
        assert_eq!(calculate_weekday(2000, 1, 1).unwrap(), Weekday::Saturday);
        assert_eq!(calculate_weekday(2024, 1, 1).unwrap(), Weekday::Monday);
        assert_eq!(calculate_weekday(2025, 8, 15).unwrap(), Weekday::Friday);

        // Test leap year boundary
        assert_eq!(calculate_weekday(2024, 2, 29).unwrap(), Weekday::Thursday); // Leap day 2024
    }

    #[test]
    fn test_is_leap_year() {
        // Regular leap years (divisible by 4)
        assert!(is_leap_year(2024));
        assert!(is_leap_year(2020));
        assert!(is_leap_year(1996));

        // Non-leap years
        assert!(!is_leap_year(2023));
        assert!(!is_leap_year(2021));
        assert!(!is_leap_year(1999));

        // Century years (divisible by 100 but not 400)
        assert!(!is_leap_year(1900));
        assert!(!is_leap_year(2100));

        // Century years divisible by 400
        assert!(is_leap_year(2000));
        assert!(is_leap_year(1600));
    }

    #[test]
    fn test_days_in_month() {
        // January (31 days)
        assert_eq!(days_in_month(2024, 1), 31);

        // February leap year (29 days)
        assert_eq!(days_in_month(2024, 2), 29);

        // February non-leap year (28 days)
        assert_eq!(days_in_month(2023, 2), 28);

        // April (30 days)
        assert_eq!(days_in_month(2024, 4), 30);

        // December (31 days)
        assert_eq!(days_in_month(2024, 12), 31);

        // Invalid month
        assert_eq!(days_in_month(2024, 13), 0);
        assert_eq!(days_in_month(2024, 0), 0);
    }

    #[test]
    fn test_setter_interdependency_edge_cases() {
        // January 31 → February (invalid because Feb max is 28/29)
        let mut dt = DateTime::new(2023, 1, 31, 0, 0, 0).unwrap();
        assert_eq!(dt.set_month(2), Err(DateTimeError::InvalidDay));

        // March 31 → April (invalid because April max is 30)
        let mut dt = DateTime::new(2023, 3, 31, 0, 0, 0).unwrap();
        assert_eq!(dt.set_month(4), Err(DateTimeError::InvalidDay));

        // Leap year Feb 29 → non-leap year
        let mut dt = DateTime::new(2024, 2, 29, 0, 0, 0).unwrap();
        assert_eq!(dt.set_year(2023), Err(DateTimeError::InvalidDay));

        // Non-leap year Feb 28 → leap year (should work)
        let mut dt = DateTime::new(2023, 2, 28, 0, 0, 0).unwrap();
        assert!(dt.set_year(2024).is_ok());
    }

    #[test]
    fn test_display_datetime_error() {
        assert_eq!(format!("{}", DateTimeError::InvalidMonth), "invalid month");
        assert_eq!(format!("{}", DateTimeError::InvalidDay), "invalid day");
        assert_eq!(format!("{}", DateTimeError::InvalidHour), "invalid hour");
        assert_eq!(
            format!("{}", DateTimeError::InvalidMinute),
            "invalid minute"
        );
        assert_eq!(
            format!("{}", DateTimeError::InvalidSecond),
            "invalid second"
        );
        assert_eq!(
            format!("{}", DateTimeError::InvalidWeekday),
            "invalid weekday"
        );
        assert_eq!(format!("{}", DateTimeError::InvalidYear), "invalid year");
    }

    #[test]
    fn test_datetime_error_trait() {
        let error = DateTimeError::InvalidMonth;
        let _: &dyn core::error::Error = &error;
    }

    #[test]
    fn test_boundary_values() {
        // Test minimum valid year
        assert!(DateTime::new(1970, 1, 1, 0, 0, 0).is_ok());

        // Test maximum valid time values
        assert!(DateTime::new(2024, 12, 31, 23, 59, 59).is_ok());

        // Test minimum valid day/month
        assert!(DateTime::new(2024, 1, 1, 0, 0, 0).is_ok());
    }

    #[test]
    fn test_february_edge_cases() {
        // Test February 28 in leap year
        assert!(DateTime::new(2024, 2, 28, 0, 0, 0).is_ok());

        // Test February 28 in non-leap year
        assert!(DateTime::new(2023, 2, 28, 0, 0, 0).is_ok());

        // Test February 29 in non-leap year (should fail)
        assert_eq!(
            DateTime::new(2023, 2, 29, 0, 0, 0).unwrap_err(),
            DateTimeError::InvalidDay
        );
    }

    #[test]
    fn test_all_month_max_days() {
        let year = 2023; // Non-leap year

        // 31-day months
        for month in [1, 3, 5, 7, 8, 10, 12] {
            assert!(DateTime::new(year, month, 31, 0, 0, 0).is_ok());
            assert_eq!(
                DateTime::new(year, month, 32, 0, 0, 0).unwrap_err(),
                DateTimeError::InvalidDay
            );
        }

        // 30-day months
        for month in [4, 6, 9, 11] {
            assert!(DateTime::new(year, month, 30, 0, 0, 0).is_ok());
            assert_eq!(
                DateTime::new(year, month, 31, 0, 0, 0).unwrap_err(),
                DateTimeError::InvalidDay
            );
        }
    }

    #[test]
    fn test_set_day_of_month() {
        let mut dt = DateTime::new(2024, 5, 15, 12, 30, 45).unwrap();

        assert!(dt.set_day_of_month(10).is_ok());
        assert_eq!(dt.day_of_month, 10);
    }

    #[test]
    fn test_all_setters_preserve_state_on_error() {
        let mut dt = DateTime::new(2024, 5, 15, 12, 30, 45).unwrap();
        let original = dt;

        // Test each setter preserves state when error occurs
        assert!(dt.set_day_of_month(40).is_err());
        assert_eq!(dt, original);

        assert!(dt.set_minute(70).is_err());
        assert_eq!(dt, original);

        assert!(dt.set_second(70).is_err());
        assert_eq!(dt, original);
    }

    #[test]
    fn test_set_minute() {
        let mut dt = DateTime::new(2024, 5, 15, 12, 30, 45).unwrap();

        assert!(dt.set_minute(10).is_ok());
        assert_eq!(dt.minute, 10);
    }

    #[test]
    fn test_set_second() {
        let mut dt = DateTime::new(2024, 5, 15, 12, 30, 45).unwrap();
        assert!(dt.set_second(10).is_ok());
        assert_eq!(dt.second, 10);
    }
}