Create `PaymentStream` type for usage-based billing

[rz1989s]

Context

Part of Phase 10.4: AI Agent Infrastructure (Roadmap)

AI agents need continuous payment streams for usage-based billing.

Description

Create a PaymentStream type for representing continuous, metered payments:

• Real-time balance updates
• Rate-based streaming
• Pause/resume capability
• Automatic settlement triggers

Example

#[solana]
#[account]
struct AIServiceSubscription {
    subscriber: PublicKey,
    provider: PublicKey,
    stream: PaymentStream,
    total_requests: u64,
}

Type Definition

struct PaymentStream {
    /// Lamports per second (or per unit)
    rate: u64,
    /// Stream start timestamp
    started_at: i64,
    /// Last settlement timestamp
    last_settled_at: i64,
    /// Total settled amount
    total_settled: u64,
    /// Deposited balance
    deposit: u64,
    /// Stream status
    status: StreamStatus,
}

enum StreamStatus {
    Active,
    Paused,
    Depleted,
    Cancelled,
}

Generated Helpers

Rust:

impl PaymentStream {
    pub fn accrued(&self) -> u64;
    pub fn remaining_time(&self) -> i64;
    pub fn settle(&mut self) -> u64;
    pub fn pause(&mut self);
    pub fn resume(&mut self);
}

TypeScript:

class PaymentStream {
    accrued(): bigint;
    remainingTime(): number;
    estimateEndTime(): Date;
    isActive(): boolean;
}

Acceptance Criteria

• PaymentStream recognized as built-in type
• StreamStatus enum generated
• Generates Rust struct with stream methods
• Generates TypeScript class with real-time helpers
• Time-based calculations using Solana Clock
• Unit tests for stream arithmetic
• Documentation with streaming payment patterns