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feat(pricing): get_tier_price alias + boundary hardening (#1) [0xcFDa9f32d292661740a6d0B4c00867E34c05c56D] #118

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feat(pricing): get_tier_price alias + boundary hardening (#1) [0xcFDa9f32d292661740a6d0B4c00867E34c05c56D] #118

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64 changes: 48 additions & 16 deletions src/pricing/tier-engine.ts
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Original file line number Diff line number Diff line change
@@ -1,43 +1,75 @@
/**
* Tiered Pricing Engine — Issue #1
* Implements 4-tier pricing for x402 API calls
* Implements 4-tier pricing for x402 API calls.
*
* Acceptance surface includes both camelCase and snake_case entry points:
* `getTierPrice` / `get_tier_price(call_count, priority_flag)`.
*/

export type Tier = 'free' | 'standard' | 'premium' | 'priority';
export type Tier = "free" | "standard" | "premium" | "priority";

export interface TierResult {
tier: Tier;
pricePerCall: number; // in USDC
callsInTier: number;
}

function normalizeCallCount(callCount: number): number {
if (!Number.isFinite(callCount)) {
throw new RangeError("callCount must be a finite number");
}
// Treat non-positive counts as "first call" so free tier applies.
if (callCount < 1) return 1;
return Math.floor(callCount);
}

/**
* Returns the price per call based on total call count and priority flag.
* - Tier 1 (Free): calls 1–50 → $0.00
* - Tier 2 (Standard): calls 51–500 → $0.01
* - Tier 3 (Premium): calls 500+ → $0.03
* - Tier 4 (Priority): priority=true → $0.10
* - Tier 2 (Standard): calls 51–500 → $0.01
* - Tier 3 (Premium): calls 501+ → $0.03
* - Tier 4 (Priority): priority=true → $0.10 (overrides count tiers)
*/
export function getTierPrice(callCount: number, priorityFlag = false): TierResult {
export function getTierPrice(
callCount: number,
priorityFlag = false,
): TierResult {
const n = normalizeCallCount(callCount);
if (priorityFlag) {
return { tier: 'priority', pricePerCall: 0.10, callsInTier: 1 };
return { tier: "priority", pricePerCall: 0.1, callsInTier: 1 };
}
if (callCount <= 50) {
return { tier: 'free', pricePerCall: 0.00, callsInTier: 50 - callCount + 1 };
if (n <= 50) {
return { tier: "free", pricePerCall: 0.0, callsInTier: 50 - n + 1 };
}
if (callCount <= 500) {
return { tier: 'standard', pricePerCall: 0.01, callsInTier: 500 - callCount + 1 };
if (n <= 500) {
return { tier: "standard", pricePerCall: 0.01, callsInTier: 500 - n + 1 };
}
return { tier: 'premium', pricePerCall: 0.03, callsInTier: Infinity };
return { tier: "premium", pricePerCall: 0.03, callsInTier: Infinity };
}

/** Snake_case alias required by issue #1 acceptance criteria. */
export function get_tier_price(
call_count: number,
priority_flag = false,
): TierResult {
return getTierPrice(call_count, priority_flag);
}

/**
* Calculates total cost for a batch of calls.
* Calculates total cost for a batch of calls starting at `startCount`.
*/
export function calculateBatchCost(startCount: number, numCalls: number, priority = false): number {
export function calculateBatchCost(
startCount: number,
numCalls: number,
priority = false,
): number {
if (!Number.isFinite(numCalls) || numCalls < 0) {
throw new RangeError("numCalls must be a non-negative finite number");
}
let total = 0;
for (let i = 0; i < numCalls; i++) {
const n = Math.floor(numCalls);
for (let i = 0; i < n; i++) {
total += getTierPrice(startCount + i, priority).pricePerCall;
}
return Math.round(total * 1e6) / 1e6; // round to 6 decimals (USDC precision)
return Math.round(total * 1e6) / 1e6; // USDC precision
}
61 changes: 44 additions & 17 deletions tests/pricing.test.ts
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Original file line number Diff line number Diff line change
@@ -1,31 +1,58 @@
import { assertEquals } from 'https://deno.land/std@0.224.0/assert/mod.ts';
import { getTierPrice, calculateBatchCost } from '../src/pricing/tier-engine.ts';
import { assertEquals, assertThrows } from "https://deno.land/std@0.224.0/assert/mod.ts";
import {
calculateBatchCost,
get_tier_price,
getTierPrice,
} from "../src/pricing/tier-engine.ts";

Deno.test('Tier 1: free for first 50 calls', () => {
assertEquals(getTierPrice(1).tier, 'free');
assertEquals(getTierPrice(50).tier, 'free');
assertEquals(getTierPrice(1).pricePerCall, 0.00);
Deno.test("Tier 1: free for first 50 calls", () => {
assertEquals(getTierPrice(1).tier, "free");
assertEquals(getTierPrice(50).tier, "free");
assertEquals(getTierPrice(1).pricePerCall, 0.0);
assertEquals(getTierPrice(50).pricePerCall, 0.0);
});

Deno.test('Tier 2: standard for calls 51-500', () => {
assertEquals(getTierPrice(51).tier, 'standard');
assertEquals(getTierPrice(500).tier, 'standard');
Deno.test("Tier 2: standard for calls 51-500", () => {
assertEquals(getTierPrice(51).tier, "standard");
assertEquals(getTierPrice(500).tier, "standard");
assertEquals(getTierPrice(51).pricePerCall, 0.01);
assertEquals(getTierPrice(500).pricePerCall, 0.01);
});

Deno.test('Tier 3: premium for calls 500+', () => {
assertEquals(getTierPrice(501).tier, 'premium');
Deno.test("Tier 3: premium for calls 501+", () => {
assertEquals(getTierPrice(501).tier, "premium");
assertEquals(getTierPrice(10_000).tier, "premium");
assertEquals(getTierPrice(501).pricePerCall, 0.03);
});

Deno.test('Tier 4: priority flag overrides all', () => {
assertEquals(getTierPrice(1, true).tier, 'priority');
assertEquals(getTierPrice(1000, true).pricePerCall, 0.10);
Deno.test("Tier 4: priority flag overrides all count tiers", () => {
assertEquals(getTierPrice(1, true).tier, "priority");
assertEquals(getTierPrice(1000, true).pricePerCall, 0.1);
assertEquals(get_tier_price(25, true).tier, "priority");
});

Deno.test('Batch cost calculation', () => {
// 10 free calls = $0
Deno.test("snake_case get_tier_price matches getTierPrice", () => {
for (const n of [1, 50, 51, 500, 501]) {
assertEquals(get_tier_price(n), getTierPrice(n));
assertEquals(get_tier_price(n, true), getTierPrice(n, true));
}
});

Deno.test("boundaries: non-positive callCount clamps into free tier", () => {
assertEquals(getTierPrice(0).tier, "free");
assertEquals(getTierPrice(-3).tier, "free");
assertEquals(get_tier_price(0).pricePerCall, 0);
});

Deno.test("invalid callCount throws", () => {
assertThrows(() => getTierPrice(Number.NaN), RangeError);
assertThrows(() => get_tier_price(Number.POSITIVE_INFINITY), RangeError);
});

Deno.test("Batch cost calculation", () => {
assertEquals(calculateBatchCost(1, 10), 0);
// 1 standard call
assertEquals(calculateBatchCost(51, 1), 0.01);
// 2 free + 2 standard across the 50→51 boundary
assertEquals(calculateBatchCost(49, 4), 0.02);
assertEquals(calculateBatchCost(1, 3, true), 0.3);
});