implement Prize pool escrow + configurable top-N reward split

[AJtheManager]

create_event previously only charged a flat creation_fee that went to the
global treasury — a platform anti-spam fee, not a prize pool. There was no way
for a creator to fund a prize pool or define how it is split among winners
(the unused token.rs helpers hinted this was planned but never wired up).

This PR lets 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 the top 5). The prize pool is escrowed in the contract
address, separately from the creation-fee → treasury transfer.

Changes

src/storage_types.rs

• New constants:
  • MAX_REWARD_RANKS: u32 = 5
  • REWARD_PERCENT_TOTAL: u32 = 100
• Event struct gains:
  • prize_pool: i128
  • reward_distribution: Vec<u32> — percentages, 1-based rank order
  • is_finalized: bool
• Event::new takes prize_pool and reward_distribution and always
  initializes is_finalized: false.

src/event.rs

• New EventError variants:
  • InvalidPrizePool = 13 — prize_pool < 0
  • InvalidRewardDistribution = 14 — empty when funded, more than
    MAX_REWARD_RANKS entries, any entry == 0 or > 100, sum != 100 (when
    funded), or a non-empty distribution on an unfunded event
  • InsufficientPrizePoolFunds = 15 — creator cannot cover
    creation_fee + prize_pool
• New validate_prize_pool() helper enforcing all of the above. A
  prize_pool == 0 "fun event" requires an empty reward_distribution and has
  no payouts.
• create_event signature gains prize_pool: i128 and
  reward_distribution: Vec<u32>. Flow:
  1. Validate the reward distribution.
  2. Verify the creator can cover fee + prize_pool before any transfer, so
     we never move only the fee.
  3. Transfer the creation fee to the treasury (unchanged).
  4. If prize_pool > 0, escrow prize_pool from creator to
     env.current_contract_address() — a separate transfer from the
     creation-fee transfer.
  5. Persist prize_pool, reward_distribution, and is_finalized: false.
  6. Emit (Symbol("event"), Symbol("prize_pool_funded")) with
     (event_id, prize_pool, reward_distribution) when funded.

src/views.rs + src/lib.rs

• New read-only views:
  • get_event_prize_pool(env, event_id) -> i128
  • get_event_reward_distribution(env, event_id) -> Vec<u32>
• lib.rs wires these through (panicking event_not_found on a missing event)
  and maps the three new errors to invalid_prize_pool,
  invalid_reward_distribution, and insufficient_prize_pool_funds.

Acceptance criteria

• Creator can specify prize_pool and reward_distribution at creation.
• prize_pool XLM moves from creator to the contract address (verified via
  TokenClient::balance), 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).

Tests (tests/event_tests.rs)

• test_create_event_with_prize_pool_escrows_funds — contract XLM balance
  increases by prize_pool; 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 → error.
• test_create_event_zero_prize_pool_requires_empty_distribution → error.
• test_get_event_prize_pool_and_distribution_views — views + stored fields.
• test_get_event_prize_pool_zero_for_fun_event — fun-event view defaults.

The new create_event / Event::new signatures rippled across the suite; all
existing call sites were updated (fun events pass 0 / an empty Vec).

Verification

• cargo test — all suites pass, 0 failures (including the 8 new tests).
• cargo build --release --target wasm32-unknown-unknown — deploy artifact
  compiles cleanly.

Notes / Follow-ups

• This is a breaking ABI change to create_event (two new positional
  args). Off-chain callers (frontend, backend indexer) must pass prize_pool
  and reward_distribution, and the indexer should handle the new
  prize_pool_funded event and prize_pool / reward_distribution fields.
• Payout/distribution of the escrowed pool to winners (using is_finalized) is
  intentionally out of scope here and left for a follow-up.

closes #968

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Project	Deployment	Actions	Updated (UTC)
insight-arena-4rll	Ready	Preview, Comment	Jun 18, 2026 7:33am

[Olowodarey]

@AJtheManager clean job thank you for taking this with urgency