shift-statistics 0.1.0

//! **Colleague mode**: find common rest days between two teams.
//!
//! The scenario: "I'm on team A, my friend/partner is on team B.
//! When can we both rest on the same day?"
//!
//! Ported from Flutter `colleague_mode.dart` and Android `colleague_mode.kt`.

use chrono::NaiveDate;
use serde::Serialize;
use shift_algorithm::{get_shift_type_for_date, ShiftCycleConfig};

/// Result of a colleague-mode query.
///
/// ```rust
/// use shift_algorithm::cycle::default_config;
/// use shift_statistics::colleague::find_common_rest_days;
/// use chrono::NaiveDate;
///
/// let config = default_config();
/// let today = NaiveDate::from_ymd_opt(2026, 5, 22).unwrap();
/// let result = find_common_rest_days(1, 3, today, 90, &config);
///
/// if let Some(date) = result.next_common_rest_date {
///     println!("下次共同休息: {}", date);
/// }
/// println!("未来30天: {} 次", result.count_in_30_days);
/// ```
#[derive(Debug, Clone, Serialize)]
pub struct CommonRestResult {
    /// First team ID (1-6).
    pub team_a_id: u32,
    /// Second team ID (1-6).
    pub team_b_id: u32,
    /// The next date when both teams rest.
    pub next_common_rest_date: Option<NaiveDate>,
    /// Days until the next common rest.
    pub days_until_next: Option<u32>,
    /// All common rest dates within the analysis window.
    pub common_rest_dates: Vec<NaiveDate>,
    /// Total common rest days found.
    pub total_count: u32,
    /// Common rests within the first 30 days.
    pub count_in_30_days: u32,
    /// Common rests within the first 60 days.
    pub count_in_60_days: u32,
}

/// Find common rest days between two teams.
///
/// For each day from `today` to `today + days_to_analyze`, computes the shift
/// for both teams. A day counts as "common rest" if both teams are on
/// [`Rest`](shift_algorithm::ShiftType::Rest) or [`Study`](shift_algorithm::ShiftType::Study).
///
/// ```rust
/// use shift_algorithm::cycle::default_config;
/// use shift_statistics::colleague::find_common_rest_days;
/// use chrono::NaiveDate;
///
/// let config = default_config();
/// let today = NaiveDate::from_ymd_opt(2026, 5, 22).unwrap();
/// let result = find_common_rest_days(1, 3, today, 60, &config);
///
/// assert_eq!(result.team_a_id, 1);
/// assert_eq!(result.team_b_id, 3);
/// assert!(result.count_in_30_days <= result.count_in_60_days);
/// ```
pub fn find_common_rest_days(
    team_a_id: u32,
    team_b_id: u32,
    today: NaiveDate,
    days_to_analyze: u32,
    config: &ShiftCycleConfig,
) -> CommonRestResult {
    let offset_a = config.team_phase_offset(team_a_id);
    let offset_b = config.team_phase_offset(team_b_id);

    let mut common_dates: Vec<NaiveDate> = Vec::new();
    let today_plus_30 = today + chrono::Duration::days(29); // match Dart: diff < 30
    let today_plus_60 = today + chrono::Duration::days(59); // match Dart: diff < 60

    for d in 0..days_to_analyze {
        let date = today + chrono::Duration::days(d as i64);
        let shift_a = get_shift_type_for_date(date, config, offset_a);
        let shift_b = get_shift_type_for_date(date, config, offset_b);

        if shift_a.is_rest() && shift_b.is_rest() {
            common_dates.push(date);
        }
    }

    let next = common_dates.first().copied();
    let days_until = next.map(|d| {
        let diff = (d - today).num_days();
        diff.max(0) as u32
    });

    let count_30 = common_dates
        .iter()
        .filter(|d| **d <= today_plus_30)
        .count() as u32;
    let count_60 = common_dates
        .iter()
        .filter(|d| **d <= today_plus_60)
        .count() as u32;

    CommonRestResult {
        team_a_id,
        team_b_id,
        next_common_rest_date: next,
        days_until_next: days_until,
        common_rest_dates: common_dates,
        total_count: count_60,
        count_in_30_days: count_30,
        count_in_60_days: count_60,
    }
}

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

    #[test]
    fn same_team_finds_all_rest_days() {
        let config = default_config();
        let today = NaiveDate::from_ymd_opt(2026, 5, 22).unwrap();
        let result = find_common_rest_days(1, 1, today, 42, &config);
        assert!(!result.common_rest_dates.is_empty());
        assert_eq!(result.team_a_id, result.team_b_id);
    }

    #[test]
    fn different_teams_produces_result() {
        let config = default_config();
        let today = NaiveDate::from_ymd_opt(2026, 5, 22).unwrap();
        let result = find_common_rest_days(1, 3, today, 90, &config);
        assert!(result.total_count <= 90);
        assert!(result.count_in_30_days <= result.count_in_60_days);
    }

    #[test]
    fn next_common_rest_is_in_future_or_none() {
        let config = default_config();
        let today = NaiveDate::from_ymd_opt(2026, 5, 22).unwrap();
        let result = find_common_rest_days(1, 4, today, 180, &config);
        if let Some(days) = result.days_until_next {
            assert!(days < 180);
        }
    }

    #[test]
    fn all_common_dates_are_within_window() {
        let config = default_config();
        let today = NaiveDate::from_ymd_opt(2026, 5, 22).unwrap();
        let window = 60u32;
        let result = find_common_rest_days(2, 5, today, window, &config);
        for date in &result.common_rest_dates {
            let diff = (*date - today).num_days();
            assert!(diff >= 0);
            assert!(diff < window as i64);
        }
        assert_eq!(result.total_count, result.common_rest_dates.len() as u32);
    }

    #[test]
    fn zero_day_window_returns_empty() {
        let config = default_config();
        let today = NaiveDate::from_ymd_opt(2026, 5, 22).unwrap();
        let result = find_common_rest_days(1, 2, today, 0, &config);
        assert!(result.common_rest_dates.is_empty());
        assert_eq!(result.total_count, 0);
        assert!(result.next_common_rest_date.is_none());
    }

    #[test]
    fn both_teams_all_rest_cycle_finds_every_day() {
        use shift_algorithm::ShiftType::*;
        let config = ShiftCycleConfig {
            cycle: vec![Rest; 7],
            cycle_length: 7,
            reference_date: shift_algorithm::cycle::default_reference_date(),
            total_teams: 2,
        };
        let today = NaiveDate::from_ymd_opt(2026, 5, 22).unwrap();
        let result = find_common_rest_days(1, 2, today, 10, &config);
        assert_eq!(result.total_count, 10);
        assert_eq!(result.common_rest_dates.len(), 10);
    }

    #[test]
    fn both_teams_all_work_cycle_finds_nothing() {
        use shift_algorithm::ShiftType::*;
        let config = ShiftCycleConfig {
            cycle: vec![Morning; 7],
            cycle_length: 7,
            reference_date: shift_algorithm::cycle::default_reference_date(),
            total_teams: 2,
        };
        let today = NaiveDate::from_ymd_opt(2026, 5, 22).unwrap();
        let result = find_common_rest_days(1, 2, today, 30, &config);
        assert_eq!(result.total_count, 0);
        assert!(result.common_rest_dates.is_empty());
    }

    #[test]
    fn counts_do_not_exceed_window() {
        let config = default_config();
        let today = NaiveDate::from_ymd_opt(2026, 5, 22).unwrap();
        let result = find_common_rest_days(1, 2, today, 20, &config);
        assert!(result.count_in_30_days <= result.common_rest_dates.len() as u32);
        assert!(result.count_in_60_days <= result.common_rest_dates.len() as u32);
    }
}