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# Price Authority

A priceAuthority can be used in contracts (usually specified in the terms of a contract) to provide a price feed, on-demand quotes, and wakeups for various time and price conditions.

# Examples

To see a priceAuthority in use, see the Loan contract(opens new window) and the Call Spread contract(opens new window) .

# Receiving a quote

A priceAuthority has a number of different methods that will return official priceQuotes. A priceQuote is an amount, payment pair, where the amount is also the current balance of the payment:

const { quoteAmount, quotePayment } = priceQuote;

Because these are ERTP amounts and payments, they have issuers. And the payments are minted by an ERTP mint. A quote issuer and mint may be shared by several priceAuthorities, and a priceAuthority may use several quoteIssuers.

Importantly, you can confirm the brand of a quote and that it was minted by the mint associated with the quoteIssuer by using the quoteIssuer to obtain the quoteAmount of the quotePayment:

const verifiedQuoteAmount = await E(quoteIssuer).getAmountOf(quotePayment);

Once you have a quoteAmount (or a verifiedQuoteAmount), you can extract the quoted amounts:

const [{ value: { amountIn, amountOut, timestamp, timer }] = quoteAmount;

This means that the priceAuthority asserts that when timestamp according to timer happened, you could sell amountIn and receive amountOut for it. amountIn and amountOut are ERTP amounts for the brandIn and brandOut you requested.

# PriceAuthority Methods

# getQuoteIssuer(brandIn, brandOut)

  • brandIn: { Brand }
  • brandOut: { Brand }
  • Returns: { Issuer | Promise<Issuer> }
  • Gets the ERTP Issuer of PriceQuotes for a given brandIn/brandOut pair.

# getTimerService(brandIn, brandOut)

  • brandIn: { Brand }
  • brandOut: { Brand }
  • Returns: { TimerService | Promise<TimerService> }
  • Gets the timer used in PriceQuotes for a given brandIn/brandOut pair.

# makeQuoteNotifier(amountIn, brandOut)

  • amountIn: { Amount }
  • brandOut: { Brand }
  • Returns: { ERef<Notifier<PriceQuote>> }
  • Be notified of the latest PriceQuotes for a given amountIn. The rate at which these are issued may be very different between priceAuthorities.

# quoteAtTime(deadline, amountIn, brandOut)

  • deadline: { Timestamp }
  • amountIn: { Amount }
  • brandOut: { Brand }
  • Returns: { Promise<PriceQuote> }
  • Resolves after deadline passes on the priceAuthority’s timerService with the price quote of amountIn at that time.

# quoteGiven(amountIn, brandOut)

  • amountIn:{ Amount }`
  • brandOut:{ Brand }`
  • Returns: { Promise<PriceQuote> }
  • Get a quote on demand corresponding to amountIn.

# quoteWanted(brandIn, amountOut)

  • brandIn: { Brand }
  • amountOut: { Amount }
  • Returns: { Promise<PriceQuote> }
  • Get a quote on demand corresponding to amountOut.

# quoteWhenGT(amountIn, amountOutLimit)

  • amountIn: { Amount }
  • amountOutLimit: { Amount }
  • Returns: { Promise<PriceQuote> }
  • Resolves when a price quote of amountIn exceeds amountOutLimit.

# quoteWhenGTE(amountIn, amountOutLimit)

  • amountIn: { Amount }
  • amountOutLimit: { Amount }
  • Returns: { Promise<PriceQuote> }
  • Resolves when a price quote of amountIn reaches or exceeds amountOutLimit.

# quoteWhenLT(amountIn, amountOutLimit)

  • amountIn: { Amount }
  • amountOutLimit: { Amount }
  • Returns: { Promise<PriceQuote> }
  • Resolves when a price quote of amountIn drops below amountOutLimit.

# quoteWhenLTE(amountIn, amountOutLimit)

  • amountIn: { Amount }
  • amountOutLimit: { Amount }
  • Returns: { Promise<PriceQuote> }
  • Resolves when a price quote of amountIn reaches or drops below amountOutLimit.

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