Enum Draw 

pub enum Draw {
    Ok,
    Halted,
}

The outcome of drawing token spend against the ledger.

use io_harness::{Containment, Draw, Ledger, Usage};

let ledger = Ledger::new(&Containment::new(4, 2, 1, 5_000));
let usage = Usage {
    prompt_tokens: 4_000,
    completion_tokens: 800,
    total_tokens: 4_800,
    ..Default::default()
};

// What the run loop does with a completion's usage: draw it, then branch. This
// is the only place the tree's ceiling is checked, so ignoring the return is
// how a tree overspends.
match ledger.draw_tokens(usage.total_tokens) {
    Draw::Ok => { /* take another step */ }
    Draw::Halted => unreachable!("4,800 fits under 5,000"),
}

// The next step does not fit. `Halted` stops the whole tree, not just this
// agent — and the rejected draw is not recorded, so the total never drifts
// above the ceiling even though the provider did charge for that step.
assert_eq!(ledger.draw_tokens(usage.total_tokens), Draw::Halted);
assert_eq!(ledger.spent_tokens(), 4_800);

Variants

Ok

The draw was within the ceiling; the tree may continue.

Halted

This draw crossed the aggregate ceiling. The spend is still recorded (a step already happened and its tokens were spent), but the tree must halt as a whole — no agent gets another step.

Trait Implementations

impl Clone for Draw

fn clone(&self) -> Draw

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for Draw

impl Debug for Draw

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for Draw

impl PartialEq for Draw

fn eq(&self, other: &Draw) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for Draw