# Pricing & Calculation

Browse available strikes, calculate exact loan costs, and check promotional pricing eligibility.

## Fetch Strike Options

`getStrikeOptions()` fetches live pricing from the Deribit-style API, filters for valid OTM put options, calculates estimated APRs, and groups results by expiry date.

```typescript
import { ThetanutsClient } from '@thetanuts-finance/thetanuts-client';

const client = new ThetanutsClient({ chainId: 8453, provider });

// ETH strikes with default settings
const groups = await client.loan.getStrikeOptions('ETH');

// BTC strikes with custom filters
const btcGroups = await client.loan.getStrikeOptions('BTC', {
  minDurationDays: 30,   // At least 30 days to expiry
  maxStrikes: 5,         // Top 5 strikes per expiry
  sortOrder: 'highestStrike',
  maxApr: 15,            // Borrowing rate for cost estimation
});
```

### Strike Settings

| Setting           | Default           | Description                                                                |
| ----------------- | ----------------- | -------------------------------------------------------------------------- |
| `minDurationDays` | `7`               | Minimum days until expiry                                                  |
| `maxStrikes`      | `20`              | Maximum strikes per expiry group                                           |
| `sortOrder`       | `'highestStrike'` | `'highestStrike'`, `'lowestStrike'`, `'nearestExpiry'`, `'furthestExpiry'` |
| `maxApr`          | `20`              | Borrowing APR used for cost estimation (not a filter)                      |

### Strike Option Fields

Each option in a group contains:

| Field               | Type      | Description                               |
| ------------------- | --------- | ----------------------------------------- |
| `strike`            | `number`  | Strike price in USD                       |
| `strikeFormatted`   | `string`  | `"$1,600"`                                |
| `expiry`            | `number`  | Unix timestamp                            |
| `expiryFormatted`   | `string`  | `"Fri, March 28, 2025"`                   |
| `expiryLabel`       | `string`  | Deribit format: `"28MAR25"`               |
| `underlyingPrice`   | `number`  | Current underlying price                  |
| `askPrice`          | `number`  | Option ask price (fraction of underlying) |
| `impliedLoanAmount` | `number`  | Estimated receive per unit of collateral  |
| `effectiveApr`      | `number`  | All-in APR including all costs            |
| `isPromo`           | `boolean` | Promotional pricing eligible              |

***

## Calculate Loan Costs

`calculateLoan()` is synchronous — pure BigInt math, no network calls. Use it after selecting a strike from `getStrikeOptions()`.

```typescript
const calc = client.loan.calculateLoan({
  depositAmount: '2.5',       // 2.5 ETH
  underlying: 'ETH',
  strike: 1800,               // $1,800 strike
  expiryTimestamp: 1780041600, // Unix seconds
  askPrice: 0.007,             // from strike option
  underlyingPrice: 2500,       // from strike option
  maxApr: 20,                  // borrowing rate (default: 20)
});

if (calc) {
  // Raw BigInt values (USDC, 6 decimals)
  console.log(calc.owe);             // Total owed at expiry
  console.log(calc.optionCost);      // Option premium
  console.log(calc.capitalCost);     // Borrowing fee
  console.log(calc.protocolFee);     // Protocol fee (4 bps)
  console.log(calc.totalCosts);      // Sum of all costs
  console.log(calc.finalLoanAmount); // What you receive

  // Formatted strings
  console.log(calc.formatted.receive);    // "4198.23"
  console.log(calc.formatted.repay);      // "4500.00"
  console.log(calc.formatted.optionCost); // "43.7500"
  console.log(calc.formatted.capitalCost);// "98.6301"
  console.log(calc.formatted.protocolFee);// "1.8000"
  console.log(calc.formatted.apr);        // "14.52"

  // Use finalLoanAmount as minSettlementAmount in requestLoan()
  await client.loan.requestLoan({
    underlying: 'ETH',
    collateralAmount: '2.5',
    strike: 1800,
    expiryTimestamp: 1780041600,
    minSettlementAmount: calc.finalLoanAmount,
  });
}
```

Returns `null` if inputs are invalid (zero deposit, zero strike, etc.) or if the final loan amount would be negative.

***

## Promotional Pricing

Check if a specific strike qualifies for promotional rates:

```typescript
const isPromo = client.loan.isPromoOption(
  1200,           // strike price in USD
  2500,           // current underlying price
  1790041600,     // expiry timestamp
  50000,          // estimated loan amount in USD (optional, for $250k cap)
);

console.log(isPromo); // true if eligible
```

### Promo Eligibility Rules

| Condition      | Requirement                         |
| -------------- | ----------------------------------- |
| Days to expiry | > 90 days                           |
| LTV ratio      | < 50% (strike / underlyingPrice)    |
| Loan amount    | < $250,000 per person               |
| Total pool     | < $2,000,000 across all promo loans |

When promo applies:

* Option premium is waived (`optionCost = 0`)
* Borrowing APR is fixed at 5.68%

***

## Raw Pricing Data

Access the underlying Deribit-style pricing API directly:

```typescript
const pricing = await client.loan.fetchPricing();

// pricing['ETH']['ETH-28MAR25-3000-P'] = {
//   underlying_price: 2500,
//   ask_price: 0.007,
//   mark_price: 0.0065,
// }

// Cached for 30 seconds — subsequent calls return cached data
const cached = await client.loan.fetchPricing(); // instant if < 30s
```

***

## See Also

* [Overview](/sdk/loan/overview.md) — Module overview and cost formula
* [Borrowing](/sdk/loan/borrowing.md) — Full borrowing workflow
* [Lending](/sdk/loan/lending.md) — Fill limit orders and earn yield


---

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