import assert from 'node:assert/strict'
import { test } from 'node:test'
import fc from 'fast-check'
import {
  type BudgetState,
  canSpend,
  DEFAULT_BUDGET,
  emptyBudgetState,
  rollover,
  spend,
} from './budget.ts'
import { fixedClock } from './time.ts'

const cfg = { dailyCapCalls: 10, recoveryReserveFraction: 0.2 }

test('ordinary calls stop at cap minus reserve', () => {
  let s: BudgetState = { day: '2026-09-12', used: 0, usedRecovery: 0 }
  for (let i = 0; i < 8; i++) s = spend(cfg, s, 'chat')
  assert.equal(canSpend(cfg, s, 'chat'), false)
  assert.equal(canSpend(cfg, s, 'deploy_failure'), true)
})

test('recovery calls draw from the reserve only', () => {
  let s: BudgetState = { day: '2026-09-12', used: 0, usedRecovery: 0 }
  for (let i = 0; i < 2; i++) s = spend(cfg, s, 'recovery')
  assert.equal(canSpend(cfg, s, 'recovery'), false)
  assert.equal(canSpend(cfg, s, 'chat'), true)
})

test('zero cap disables limiting', () => {
  const s = { day: '2026-09-12', used: 9999, usedRecovery: 0 }
  assert.equal(canSpend({ dailyCapCalls: 0, recoveryReserveFraction: 0.1 }, s, 'chat'), true)
})

test('state rolls over on a new day', () => {
  const clock = fixedClock('2026-09-13T00:00:30Z')
  const s = rollover({ day: '2026-09-12', used: 5, usedRecovery: 1 }, clock)
  assert.deepEqual(s, emptyBudgetState(clock))
})

test('property: total allowed recovery calls per day equals reserve', () => {
  fc.assert(
    fc.property(fc.nat({ max: 1000 }), fc.nat({ max: 900 }), (cap, fractionPermille) => {
      const config = {
        dailyCapCalls: cap,
        recoveryReserveFraction: fractionPermille / 1000,
      }
      let s = emptyBudgetState(fixedClock('2026-09-12T10:00:00Z'))
      let recoveryCalls = 0
      while (recoveryCalls < 100_000 && canSpend(config, s, 'recovery')) {
        s = spend(config, s, 'recovery')
        recoveryCalls++
      }
      const reserve = Math.floor(config.dailyCapCalls * config.recoveryReserveFraction)
      assert.equal(recoveryCalls, config.dailyCapCalls === 0 ? 100_000 : reserve)
    }),
  )
})

test('default budget exists and is sane', () => {
  assert.ok(DEFAULT_BUDGET.dailyCapCalls > 0)
  assert.ok(
    DEFAULT_BUDGET.recoveryReserveFraction > 0 && DEFAULT_BUDGET.recoveryReserveFraction < 1,
  )
})