[CT-15] Implement on-chain Booking Conflict Detector for double-booking prevention in Rust

[devwums]

Problem

Double-booking is prevented only in the NestJS backend. There is no on-chain validation, meaning a malicious actor can bypass the backend and submit duplicate booking transactions directly to the contract.

Proposed Solution

Create contracts/cntr/booking_conflict.rs defining pub struct BookingSlot { pub booking_id: String, pub start_ts: u64, pub end_ts: u64 } and implementing pub fn find_conflicts(new_slot: &BookingSlot, existing_slots: &[BookingSlot]) -> Vec<String> returning the booking_id of each conflicting slot. Overlap condition: new.start_ts < existing.end_ts && new.end_ts > existing.start_ts. Adjacent slots (touching endpoints) are NOT conflicts. All implementation must live inside contracts/cntr/.

Acceptance Criteria

• File at contracts/cntr/booking_conflict.rs
• Returns empty Vec when no conflicts exist
• Detects full overlap, partial overlap (start inside), and containment
• Adjacent bookings (one ends exactly when other starts) are not flagged
• Returns only the booking_id strings of conflicting slots
• At least 7 unit tests
• Compiles with cargo test

[Jujukoder]

@Jujukoder has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Good Morning Ser, I'm an experienced rust dev, and I can solve this issue. Please assign it to me.

Thank you as you grant my request.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Jujukoder to this issue.

[Hassan-oladipupo]

@Hassan-oladipupo has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

can i take this

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Hassan-oladipupo to this issue.

[drips-wave]

Congratulations, @Hassan-oladipupo! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 2, 2026.

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