//! Cluster 4 — diary frequency / period primitives.
//! Tests the date math for ISO weeks, monthly, yearly periods.

use nuwiki_core::date::{
    DiaryCalendar, DiaryDate, DiaryFrequency, DiaryPeriod, WeekStart, WeeklyStyle,
};

#[test]
fn frequency_parses_canonical_strings() {
    assert_eq!(DiaryFrequency::parse("daily"), DiaryFrequency::Daily);
    assert_eq!(DiaryFrequency::parse("weekly"), DiaryFrequency::Weekly);
    assert_eq!(DiaryFrequency::parse("monthly"), DiaryFrequency::Monthly);
    assert_eq!(DiaryFrequency::parse("yearly"), DiaryFrequency::Yearly);
    assert_eq!(DiaryFrequency::parse("WeEkLy"), DiaryFrequency::Weekly);
    // Unknown falls back to Daily (mirrors vimwiki's permissive behaviour).
    assert_eq!(DiaryFrequency::parse("hourly"), DiaryFrequency::Daily);
    assert_eq!(DiaryFrequency::parse(""), DiaryFrequency::Daily);
}

#[test]
fn period_format_round_trips() {
    let cases = [
        (
            "2026-05-12",
            DiaryPeriod::Day(DiaryDate::from_ymd(2026, 5, 12).unwrap()),
        ),
        (
            "2026-W19",
            DiaryPeriod::Week {
                iso_year: 2026,
                iso_week: 19,
            },
        ),
        (
            "2026-05",
            DiaryPeriod::Month {
                year: 2026,
                month: 5,
            },
        ),
        ("2026", DiaryPeriod::Year { year: 2026 }),
    ];
    for (s, want) in cases {
        let parsed = DiaryPeriod::parse(s).unwrap_or_else(|| panic!("parse {s}"));
        assert_eq!(parsed, want, "parse({s})");
        assert_eq!(parsed.format(), s, "format({s})");
    }
}

#[test]
fn period_parse_rejects_garbage() {
    assert!(DiaryPeriod::parse("garbage").is_none());
    assert!(DiaryPeriod::parse("2026-W00").is_none());
    assert!(DiaryPeriod::parse("2026-13").is_none()); // month 13
    assert!(DiaryPeriod::parse("2026-").is_none());
}

#[test]
fn iso_week_jan_1_can_belong_to_prior_year() {
    // 2021-01-01 was a Friday → ISO week 53 of 2020.
    let d = DiaryDate::from_ymd(2021, 1, 1).unwrap();
    let p = DiaryPeriod::week_containing(d);
    assert_eq!(
        p,
        DiaryPeriod::Week {
            iso_year: 2020,
            iso_week: 53
        }
    );
}

#[test]
fn iso_week_dec_31_can_belong_to_next_year() {
    // 2024-12-30 (Monday) is in ISO week 1 of 2025.
    let d = DiaryDate::from_ymd(2024, 12, 30).unwrap();
    let p = DiaryPeriod::week_containing(d);
    assert_eq!(
        p,
        DiaryPeriod::Week {
            iso_year: 2025,
            iso_week: 1
        }
    );
}

#[test]
fn iso_week_mid_year_is_consistent() {
    // 2026-05-12 is a Tuesday in ISO week 20.
    let d = DiaryDate::from_ymd(2026, 5, 12).unwrap();
    let p = DiaryPeriod::week_containing(d);
    assert_eq!(
        p,
        DiaryPeriod::Week {
            iso_year: 2026,
            iso_week: 20
        }
    );
}

#[test]
fn week_next_and_prev_step_by_seven_days() {
    let p = DiaryPeriod::Week {
        iso_year: 2026,
        iso_week: 20,
    };
    assert_eq!(
        p.next(),
        DiaryPeriod::Week {
            iso_year: 2026,
            iso_week: 21
        }
    );
    assert_eq!(
        p.prev(),
        DiaryPeriod::Week {
            iso_year: 2026,
            iso_week: 19
        }
    );
}

#[test]
fn week_next_crosses_year_boundary() {
    // Week 53 of 2020 → week 53 ends; next should be week 1 of 2021.
    let p = DiaryPeriod::Week {
        iso_year: 2020,
        iso_week: 53,
    };
    assert_eq!(
        p.next(),
        DiaryPeriod::Week {
            iso_year: 2021,
            iso_week: 1
        }
    );
}

#[test]
fn month_next_wraps_to_january() {
    let dec = DiaryPeriod::Month {
        year: 2026,
        month: 12,
    };
    assert_eq!(
        dec.next(),
        DiaryPeriod::Month {
            year: 2027,
            month: 1
        }
    );
}

#[test]
fn month_prev_wraps_to_december() {
    let jan = DiaryPeriod::Month {
        year: 2026,
        month: 1,
    };
    assert_eq!(
        jan.prev(),
        DiaryPeriod::Month {
            year: 2025,
            month: 12
        }
    );
}

#[test]
fn year_next_and_prev_increment_by_one() {
    let y = DiaryPeriod::Year { year: 2026 };
    assert_eq!(y.next(), DiaryPeriod::Year { year: 2027 });
    assert_eq!(y.prev(), DiaryPeriod::Year { year: 2025 });
}

#[test]
fn day_next_and_prev_still_work() {
    let d = DiaryPeriod::Day(DiaryDate::from_ymd(2026, 5, 12).unwrap());
    assert_eq!(
        d.next(),
        DiaryPeriod::Day(DiaryDate::from_ymd(2026, 5, 13).unwrap())
    );
    assert_eq!(
        d.prev(),
        DiaryPeriod::Day(DiaryDate::from_ymd(2026, 5, 11).unwrap())
    );
}

// ===== DiaryCalendar — weekly naming styles + week-start =====
// 2026-05-25 is a Monday (so 2026-05-27 is a Wednesday, 2026-05-24 a Sunday).

fn day(y: i32, m: u8, d: u8) -> DiaryPeriod {
    DiaryPeriod::Day(DiaryDate::from_ymd(y, m, d).unwrap())
}

#[test]
fn weekly_style_and_week_start_parse() {
    assert_eq!(WeeklyStyle::parse("date"), WeeklyStyle::Date);
    assert_eq!(WeeklyStyle::parse("vimwiki"), WeeklyStyle::Date);
    assert_eq!(WeeklyStyle::parse("iso"), WeeklyStyle::Iso);
    assert_eq!(WeeklyStyle::parse(""), WeeklyStyle::Iso); // default
    assert_eq!(WeeklyStyle::parse("WEEK"), WeeklyStyle::Iso);
    // WeekStart::parse is exercised via the calendar tests below; unknown
    // names fall back to Monday.
    assert_eq!(WeekStart::parse("sunday"), WeekStart::parse("SUNDAY"));
    assert_eq!(WeekStart::parse("nonsense"), WeekStart::monday());
}

#[test]
fn date_mode_weekly_today_is_a_day() {
    let cal = DiaryCalendar::new(
        DiaryFrequency::Weekly,
        WeeklyStyle::Date,
        WeekStart::monday(),
    );
    assert!(matches!(cal.today(), DiaryPeriod::Day(_)));
}

#[test]
fn iso_mode_weekly_today_is_a_week() {
    let cal = DiaryCalendar::new(
        DiaryFrequency::Weekly,
        WeeklyStyle::Iso,
        WeekStart::monday(),
    );
    assert!(matches!(cal.today(), DiaryPeriod::Week { .. }));
}

#[test]
fn date_mode_weekly_steps_seven_days_from_the_week_start_monday() {
    let cal = DiaryCalendar::new(
        DiaryFrequency::Weekly,
        WeeklyStyle::Date,
        WeekStart::monday(),
    );
    // From a Wednesday: snap back to Mon 05-25, then ±7.
    assert_eq!(cal.next(day(2026, 5, 27)), day(2026, 6, 1));
    assert_eq!(cal.prev(day(2026, 5, 27)), day(2026, 5, 18));
    // From the Monday itself: no snap, just ±7.
    assert_eq!(cal.next(day(2026, 5, 25)), day(2026, 6, 1));
    assert_eq!(cal.prev(day(2026, 5, 25)), day(2026, 5, 18));
    // Stem is the plain date, like upstream.
    assert_eq!(cal.next(day(2026, 5, 27)).format(), "2026-06-01");
}

#[test]
fn date_mode_weekly_honours_a_sunday_week_start() {
    let cal = DiaryCalendar::new(
        DiaryFrequency::Weekly,
        WeeklyStyle::Date,
        WeekStart::parse("sunday"),
    );
    // Wed 05-27 snaps back to Sun 05-24, +7 = Sun 05-31.
    assert_eq!(cal.next(day(2026, 5, 27)), day(2026, 5, 31));
    assert_eq!(cal.prev(day(2026, 5, 27)), day(2026, 5, 17));
}

#[test]
fn iso_mode_weekly_delegates_to_iso_week_stepping() {
    let cal = DiaryCalendar::new(
        DiaryFrequency::Weekly,
        WeeklyStyle::Iso,
        WeekStart::monday(),
    );
    let wk = DiaryPeriod::week_containing(DiaryDate::from_ymd(2026, 5, 27).unwrap());
    assert_eq!(cal.next(wk), wk.next());
    assert_eq!(cal.prev(wk), wk.prev());
}

#[test]
fn daily_calendar_steps_one_day_regardless_of_weekly_fields() {
    let cal = DiaryCalendar::new(
        DiaryFrequency::Daily,
        WeeklyStyle::Date,
        WeekStart::parse("sunday"),
    );
    assert_eq!(cal.next(day(2026, 5, 27)), day(2026, 5, 28));
    assert_eq!(cal.prev(day(2026, 5, 27)), day(2026, 5, 26));
}