Mission Engine

The Mission Engine is the core coordination mechanism of Horizon Protocol.

Overview

A mission represents a real-world task with:

• Escrow: USDC locked until completion
• Location: Optional geofenced area
• Deadline: Expiration timestamp
• Proof: Evidence of completion

Lifecycle States

stateDiagram-v2
    [*] --> Open: Create Mission
    Open --> Accepted: Performer accepts
    Open --> Cancelled: Poster cancels
    Open --> [*]: Expired (auto)
    Accepted --> Submitted: Submit proof
    Submitted --> Completed: Poster approves
    Submitted --> Disputed: Either party disputes
    Disputed --> Resolved: Resolver decides
    Completed --> [*]
    Cancelled --> [*]
    Resolved --> [*]

State Details

Open

Initial state after mission creation.

Properties:

• Funds escrowed in contract
• Any eligible user can accept
• Poster can cancel (full refund)
• Auto-expires at deadline

Transitions:

• acceptMission() → Accepted
• cancelMission() → Cancelled
• Time-based → Expired

Accepted

Performer has committed to the mission.

Properties:

• Performer address locked
• Countdown to deadline begins
• Cannot be cancelled by poster

Transitions:

• submitProof() → Submitted

Submitted

Performer has submitted proof of completion.

Properties:

• Proof hash stored on-chain
• Poster must review
• Either party can dispute

Transitions:

• approveCompletion() → Completed
• raiseDispute() → Disputed

Completed

Mission successfully completed.

Properties:

• Escrow settled via PaymentRouter
• 5-way fee split executed
• Reputation attestations emitted

Disputed

Mission in dispute resolution.

Properties:

• DDR deposits required
• Resolver assigned
• Evidence collection period

Transitions:

• resolveDispute() → Resolved

Mission Parameters

Immutable (set at creation)

Parameter	Type	Description
rewardAmount	uint256	USDC reward (6 decimals)
expiresAt	uint256	Unix timestamp deadline
poster	address	Creator's address
guild	address	Associated guild (optional)
metadataHash	bytes32	IPFS hash of details
locationHash	bytes32	IPFS hash of encrypted location

Runtime (mutable)

Parameter	Type	Description
performer	address	Acceptor's address
state	enum	Current state
proofHash	bytes32	IPFS hash of proof
disputeRaised	bool	Dispute flag

Location Requirements

Geofence Types

Precision	Revealed	Use Case
Exact (0)	Full address after accept	Specific delivery
Block (1)	Street block	Area-based tasks
Neighborhood (2)	District only	Privacy-sensitive

Presence Verification

Performers can verify their location:

POST /missions/:id/verify-presence
{
  "latitude": 38.7225,
  "longitude": -9.1395,
  "accuracy": 10
}

Response indicates if within geofence radius + GPS grace period.

XP Rewards

Action	XP Award
Complete mission	10-50 XP (based on reward)
First mission	+25 XP bonus
Perfect rating	+10 XP bonus
Mission streak (5+)	+15% XP bonus

Security Invariants

1. Funds are immutable: rewardAmount cannot change
2. Performer is locked: Once accepted, cannot change
3. State transitions are ordered: Follow state machine strictly
4. Escrow is non-custodial: Service cannot modify funds