feat(views): lazy calendar-view iterators (days/weeks)

[AriajSarkar]

Summary

Add lazy DayIterator and WeekIterator to Calendar that yield pre-bucketed, owned event views — making it trivial to plug eventix into Rust UI frameworks (Yew, Leptos, Dioxus) for calendar rendering.

Closes #5

---

New Public API

// Forward day iteration — each DayView has events pre-bucketed
for day in cal.days(start).take(30) {
    let day = day?;
    println!("{}: {} events", day.date(), day.event_count());
    for event in day.events() {
        println!("  {} at {}", event.title(), event.occurrence_time);
    }
}

// Week iteration — each WeekView contains 7 contiguous DayViews (Mon–Sun)
for week in cal.weeks(start).take(4) {
    let week = week?;
    println!("Week of {}: {} events", week.start_date(), week.event_count());
}

// Backward iteration for scrolling into the past
let previous_days = cal.days_back(today).take(30);

// Jump to a specific date (resume after scroll)
let mut iter = cal.days(start);
iter.skip_to(target_date);

New Types

Type	Description
DayView	A single calendar day with all active intersecting events pre-bucketed
WeekView	Seven contiguous DayViews (Monday–Sunday)
OwnedEventOccurrence	Owned snapshot of an occurrence — no lifetime ties to Calendar
DayIterator	Lazy, fallible iterator over days (Item = Result)
WeekIterator	Lazy, fallible iterator over ISO weeks (Item = Result)

Key Design Decisions

• Owned data: DayView / OwnedEventOccurrence own their event data (Clone + PartialEq + Eq + Hash + Ord), so views can be freely moved into UI component props without lifetime issues.
• Fallible iteration: Iterators yield Result instead of silently stopping on errors — callers get full diagnostic info.
• Timezone-aware day boundaries: Day windows computed via local_day_window() respect DST transitions (a 25-hour day on fall-back is handled correctly).
• Intersection-based bucketing: Overnight/multi-day events appear on every day they span, not just the start day.
• ExactSizeIterator + FusedIterator: Both iterators formally advertise their exact remaining length and fused exhaustion.
• skip_to(date): Lets consumers jump the cursor for "load more" / infinite-scroll UIs.
• Additive only: No breaking changes to any existing API.

Framework Compatibility

Verified compatible with the prop/signal requirements of:

• Yew — Clone + PartialEq ✅
• Leptos — Clone + Send + Sync + 'static ✅ (NaiveDate is a perfect key)
• Dioxus — Clone + PartialEq ✅

Files Changed (12 files, +1210 / -68)

File	Change
src/views.rs	[NEW] Core module — all view types, iterators, helpers, 16 unit tests
ests/calendar_view_tests.rs	[NEW] Integration tests — overnight events, DST boundary, backward weeks, cancelled exclusion
examples/calendar_views.rs	[NEW] Runnable example demonstrating day/week iteration
src/calendar.rs	Added days(), days_back(), weeks(), weeks_back() methods
src/event.rs	Added PartialOrd + Ord + Hash to EventStatus
src/timezone.rs	Extracted
esolve_local(), added local_day_window()
src/recurrence.rs	Refactored to use shared
esolve_local from timezone module
src/lib.rs	Added �iews module, re-exports, NaiveDate re-export
README.md	Added Calendar Views section with usage examples
CHANGELOG.md	v0.5.0 entry
Cargo.toml	Version bump to 0.5.0
TODO.md	Marked feature as complete

Verification

• cargo test — 112 tests pass
• cargo test --doc — all doc tests pass
• cargo clippy --all-targets -- -D warnings — clean
• cargo run --example calendar_views — runs correctly
• Three rounds of code review (bugs fixed, edge cases handled, framework compatibility verified)

[greptile-apps]

Your free trial has ended. If you'd like to continue receiving code reviews, you can add a payment method here.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!