[Contract]-Prize pool escrow + configurable top-N reward split

[grantfox-oss]

event::create_event (src/event.rs) only charges a flat creation_fee that
goes to the global treasury (event.rs:99-101) — this is a platform
anti-spam fee, not a prize pool. There is currently no way for a creator to
fund a prize pool or define how it's split among winners. src/token.rs has
unused helpers (collect_entry_fee, distribute_winnings,
calculate_winnings) that hint this was planned but never wired up.

Goal

Let a creator deposit an XLM prize pool when creating an event, and define what
percentage of it each leaderboard rank receives (e.g. [40, 30, 20, 5, 5] for
top 5).

Requirements

1. Event struct gains:

   pub prize_pool: i128,
   pub reward_distribution: Vec<u32>, // percentages, 1-based rank order, sum == 100 when prize_pool > 0
   pub is_finalized: bool,

2. New constants in src/storage_types.rs:

   pub const MAX_REWARD_RANKS: u32 = 5;
   pub const REWARD_PERCENT_TOTAL: u32 = 100;

3. event::create_event signature gains:

   prize_pool: i128,
   reward_distribution: Vec<u32>,

4. New EventError variants:

   • InvalidPrizePool = 13 — prize_pool < 0
   • InvalidRewardDistribution = 14 — any of:
     • prize_pool > 0 and reward_distribution.is_empty()
     • reward_distribution.len() > MAX_REWARD_RANKS
     • any entry == 0 or > 100
     • sum(reward_distribution) != 100 (only enforced when prize_pool > 0;
       if prize_pool == 0, reward_distribution must be empty — this is a
       "fun event", no payouts)
   • InsufficientPrizePoolFunds = 15 — creator's XLM balance < prize_pool

5. Flow changes in create_event:

   • Validate reward_distribution as above.
   • If prize_pool > 0: transfer prize_pool from creator to
     env.current_contract_address() (escrow) — this is a second,
     separate transfer from the existing creation_fee → treasury transfer.
     Do not conflate the two.
   • Store prize_pool, reward_distribution, is_finalized: false on Event.
   • Emit (Symbol("event"), Symbol("prize_pool_funded")) with
     (event_id, prize_pool, reward_distribution).

6. New read-only views (src/views.rs + lib.rs):

   pub fn get_event_prize_pool(env: Env, event_id: u64) -> i128;
   pub fn get_event_reward_distribution(env: Env, event_id: u64) -> Vec<u32>;

Acceptance criteria

• Creator can specify prize_pool and reward_distribution at creation
• prize_pool XLM moves from creator to the contract address (verify
  via TokenClient::balance in tests), separate from the creation fee
• All InvalidRewardDistribution cases are rejected with clear errors
• prize_pool == 0 requires an empty reward_distribution (fun events with no payout)

Testing checklist (tests/event_tests.rs)

• test_create_event_with_prize_pool_escrows_funds — assert contract's XLM
  balance increases by prize_pool and creator's decreases by
  creation_fee + prize_pool
• test_create_event_reward_distribution_must_sum_to_100 — [50, 30, 10] → error
• test_create_event_too_many_reward_ranks — 6 entries → error
• test_create_event_zero_entry_in_distribution_rejected — [100, 0] → error
• test_create_event_insufficient_balance_for_prize_pool
• test_create_event_zero_prize_pool_requires_empty_distribution
• test_get_event_prize_pool_and_distribution_views

[Obiajulu-gif]

Hi Maintainer, I’d like to work on this issue: Prize pool escrow + configurable top-N reward split.

I understand this is a core contract feature because event creation currently only supports a platform creation fee, but not creator-funded prize pools or winner reward distribution. I can update the Event struct, add prize pool and reward distribution validation, escrow the XLM prize pool separately from the treasury fee, expose the new read-only views, and emit the required funding event.

I’ll also add full tests covering escrow balance changes, invalid reward splits, too many ranks, zero entries, insufficient balance, fun events with no payout, and the new prize pool/distribution views. I’ll keep the implementation secure, clean, and aligned with the existing contract style. Please assign this issue to me.

[binayyub4211]

Hey maintainer kindly assign me I want to work on this issues

[DevSolex]

Hi Maintainer,

I’m a smart contract and full-stack developer and would love to contribute to this issue. I’m an experienced contributor with hands-on expertise in Rust, Soroban, Cairo, and TypeScript.

I’m passionate about building secure, scalable blockchain solutions, with a strong emphasis on writing clean and maintainable code. Based on the scope of this issue, I’m confident I can deliver a complete solution within 24 hours of assignment.

I’d greatly appreciate the opportunity to contribute and help move this forward.

[Fatimasanusi]

I would like to work on this as a professional full stack developer and i'm an expect in solving complex smart contract problem

[grantfox-oss]

🦊 GrantFox — @tech-adrian has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #968)
2. Your PR will be reviewed by the Arena1X maintainers

Good luck! Track your progress on GrantFox.

[grantfox-oss]

🦊 GrantFox — @Obiajulu-gif has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #968)
2. Your PR will be reviewed by the Arena1X maintainers

Good luck! Track your progress on GrantFox.

[Olowodarey]

@Obiajulu-gif good day sir pls your issues need too be done with time we have other issues depending on it thank you