use std::fmt;
use std::str::FromStr;
use chrono::{Datelike, Weekday};
use serde::{Deserialize, Deserializer, Serialize, Serializer};
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum RecurrenceFrequency {
Daily,
Weekly,
Monthly,
Yearly,
}
impl RecurrenceFrequency {
pub const fn as_str(self) -> &'static str {
match self {
Self::Daily => "daily",
Self::Weekly => "weekly",
Self::Monthly => "monthly",
Self::Yearly => "yearly",
}
}
pub fn parse(value: &str) -> Result<Self, InvalidRecurrenceFrequency> {
match value {
"daily" => Ok(Self::Daily),
"weekly" => Ok(Self::Weekly),
"monthly" => Ok(Self::Monthly),
"yearly" => Ok(Self::Yearly),
_ => Err(InvalidRecurrenceFrequency(value.to_string())),
}
}
}
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct InvalidRecurrenceFrequency(String);
impl fmt::Display for InvalidRecurrenceFrequency {
fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(formatter, "invalid recurrence frequency: {}", self.0)
}
}
impl std::error::Error for InvalidRecurrenceFrequency {}
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Default)]
pub struct WeekdaySet(u8);
impl WeekdaySet {
const MONDAY: u8 = 1 << 0;
const TUESDAY: u8 = 1 << 1;
const WEDNESDAY: u8 = 1 << 2;
const THURSDAY: u8 = 1 << 3;
const FRIDAY: u8 = 1 << 4;
const SATURDAY: u8 = 1 << 5;
const SUNDAY: u8 = 1 << 6;
pub fn from_weekdays(weekdays: impl IntoIterator<Item = Weekday>) -> Self {
let mut bits = 0;
for weekday in weekdays {
bits |= Self::bit(weekday);
}
Self(bits)
}
pub fn weekdays() -> Self {
Self(Self::MONDAY | Self::TUESDAY | Self::WEDNESDAY | Self::THURSDAY | Self::FRIDAY)
}
pub fn contains(self, weekday: Weekday) -> bool {
self.0 & Self::bit(weekday) != 0
}
pub fn is_empty(self) -> bool {
self.0 == 0
}
pub fn iter(self) -> impl DoubleEndedIterator<Item = Weekday> {
[
Weekday::Mon,
Weekday::Tue,
Weekday::Wed,
Weekday::Thu,
Weekday::Fri,
Weekday::Sat,
Weekday::Sun,
]
.into_iter()
.filter(move |weekday| self.contains(*weekday))
}
const fn bit(weekday: Weekday) -> u8 {
match weekday {
Weekday::Mon => Self::MONDAY,
Weekday::Tue => Self::TUESDAY,
Weekday::Wed => Self::WEDNESDAY,
Weekday::Thu => Self::THURSDAY,
Weekday::Fri => Self::FRIDAY,
Weekday::Sat => Self::SATURDAY,
Weekday::Sun => Self::SUNDAY,
}
}
}
impl fmt::Display for WeekdaySet {
fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
let mut separator = "";
for weekday in self.iter() {
formatter.write_str(separator)?;
formatter.write_str(weekday_name(weekday))?;
separator = ",";
}
Ok(())
}
}
impl FromStr for WeekdaySet {
type Err = &'static str;
fn from_str(value: &str) -> Result<Self, Self::Err> {
parse_weekday_set(value)
}
}
impl Serialize for WeekdaySet {
fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
where
S: Serializer,
{
serializer.serialize_str(&self.to_string())
}
}
impl<'de> Deserialize<'de> for WeekdaySet {
fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
where
D: Deserializer<'de>,
{
let value = String::deserialize(deserializer)?;
parse_weekday_set(&value).map_err(serde::de::Error::custom)
}
}
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize)]
pub struct RecurrenceRule {
frequency: RecurrenceFrequency,
interval: u32,
weekdays: WeekdaySet,
}
impl RecurrenceRule {
pub fn new(
frequency: RecurrenceFrequency,
interval: u32,
weekdays: WeekdaySet,
) -> Result<Self, InvalidRecurrenceRule> {
if interval == 0 {
return Err(InvalidRecurrenceRule::ZeroInterval);
}
match frequency {
RecurrenceFrequency::Weekly if weekdays.is_empty() => {
return Err(InvalidRecurrenceRule::EmptyWeekdays);
}
RecurrenceFrequency::Weekly => {}
_ if !weekdays.is_empty() => {
return Err(InvalidRecurrenceRule::NonWeeklyWeekdays);
}
_ => {}
}
Ok(Self {
frequency,
interval,
weekdays,
})
}
pub fn daily() -> Self {
Self::every_n_days(1).expect("one day is a valid recurrence interval")
}
pub fn every_n_days(interval: u32) -> Result<Self, InvalidRecurrenceRule> {
Self::new(RecurrenceFrequency::Daily, interval, WeekdaySet::default())
}
pub fn weekdays() -> Self {
Self {
frequency: RecurrenceFrequency::Weekly,
interval: 1,
weekdays: WeekdaySet::weekdays(),
}
}
pub fn monthly() -> Self {
Self::every_n_months(1).expect("one month is a valid recurrence interval")
}
pub fn every_n_months(interval: u32) -> Result<Self, InvalidRecurrenceRule> {
Self::new(
RecurrenceFrequency::Monthly,
interval,
WeekdaySet::default(),
)
}
pub fn yearly() -> Self {
Self::every_n_years(1).expect("one year is a valid recurrence interval")
}
pub fn every_n_years(interval: u32) -> Result<Self, InvalidRecurrenceRule> {
Self::new(RecurrenceFrequency::Yearly, interval, WeekdaySet::default())
}
pub fn weekly(weekday: Weekday) -> Self {
Self::weekly_on([weekday]).expect("one weekday is a valid weekly rule")
}
pub fn weekly_on(
weekdays: impl IntoIterator<Item = Weekday>,
) -> Result<Self, InvalidRecurrenceRule> {
Self::every_n_weeks_on(1, weekdays)
}
pub fn every_n_weeks_on(
interval: u32,
weekdays: impl IntoIterator<Item = Weekday>,
) -> Result<Self, InvalidRecurrenceRule> {
Self::new(
RecurrenceFrequency::Weekly,
interval,
WeekdaySet::from_weekdays(weekdays),
)
}
pub fn frequency(self) -> RecurrenceFrequency {
self.frequency
}
pub fn interval(self) -> u32 {
self.interval
}
pub fn weekdays_set(self) -> WeekdaySet {
self.weekdays
}
pub(crate) fn matches(self, start_on: chrono::NaiveDate, date: chrono::NaiveDate) -> bool {
if date < start_on {
return false;
}
match self.frequency {
RecurrenceFrequency::Daily => {
date.signed_duration_since(start_on).num_days() % i64::from(self.interval) == 0
}
RecurrenceFrequency::Weekly => {
let days_from_anchor = i64::from(start_on.weekday().num_days_from_monday())
+ date.signed_duration_since(start_on).num_days();
let weeks = days_from_anchor / 7;
weeks % i64::from(self.interval) == 0 && self.weekdays.contains(date.weekday())
}
RecurrenceFrequency::Monthly => {
matches_month_period(self.interval.into(), start_on, date)
}
RecurrenceFrequency::Yearly => {
matches_month_period(i64::from(self.interval) * 12, start_on, date)
}
}
}
}
impl<'de> Deserialize<'de> for RecurrenceRule {
fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
where
D: Deserializer<'de>,
{
#[derive(Deserialize)]
struct RuleWire {
frequency: RecurrenceFrequency,
interval: u32,
weekdays: WeekdaySet,
}
let wire = RuleWire::deserialize(deserializer)?;
Self::new(wire.frequency, wire.interval, wire.weekdays).map_err(serde::de::Error::custom)
}
}
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum InvalidRecurrenceRule {
ZeroInterval,
EmptyWeekdays,
NonWeeklyWeekdays,
}
impl fmt::Display for InvalidRecurrenceRule {
fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
formatter.write_str(match self {
Self::ZeroInterval => "recurrence interval must be greater than zero",
Self::EmptyWeekdays => "weekly recurrence must contain at least one weekday",
Self::NonWeeklyWeekdays => "weekday selections require weekly recurrence",
})
}
}
impl std::error::Error for InvalidRecurrenceRule {}
fn matches_month_period(period: i64, start_on: chrono::NaiveDate, date: chrono::NaiveDate) -> bool {
let start_month = i64::from(start_on.year()) * 12 + i64::from(start_on.month0());
let date_month = i64::from(date.year()) * 12 + i64::from(date.month0());
let month_difference = date_month - start_month;
month_difference >= 0
&& month_difference % period == 0
&& date.day() == start_on.day().min(last_day_of_month(date))
}
pub(crate) fn last_day_of_month(date: chrono::NaiveDate) -> u32 {
(28..=31)
.rev()
.find(|day| date.with_day(*day).is_some())
.expect("every calendar month has at least 28 days")
}
fn parse_weekday_set(value: &str) -> Result<WeekdaySet, &'static str> {
if value.is_empty() {
return Ok(WeekdaySet::default());
}
let mut weekdays = Vec::new();
for part in value.split(',') {
let weekday = match part {
"mon" => Weekday::Mon,
"tue" => Weekday::Tue,
"wed" => Weekday::Wed,
"thu" => Weekday::Thu,
"fri" => Weekday::Fri,
"sat" => Weekday::Sat,
"sun" => Weekday::Sun,
_ => return Err("weekday set must use canonical comma-separated weekday names"),
};
if weekdays.contains(&weekday) {
return Err("weekday set cannot contain duplicate weekdays");
}
weekdays.push(weekday);
}
let set = WeekdaySet::from_weekdays(weekdays);
if set.to_string() != value {
return Err("weekday set must be ordered from Monday through Sunday");
}
Ok(set)
}
const fn weekday_name(weekday: Weekday) -> &'static str {
match weekday {
Weekday::Mon => "mon",
Weekday::Tue => "tue",
Weekday::Wed => "wed",
Weekday::Thu => "thu",
Weekday::Fri => "fri",
Weekday::Sat => "sat",
Weekday::Sun => "sun",
}
}