Market Resolution API (#600)

* Add market resolution API

* Add additional free market resolution validation

* Address review comments

* Refactor resolution validation code somewhat

Co-authored-by: Marshall Polaris <marshall@pol.rs>

docs/docs/api.md

@@ -456,7 +456,6 @@ Requires no authorization.
   }
   ```
 
-
 ### `POST /v0/bet`
 
 Places a new bet on behalf of the authorized user.
@@ -514,6 +513,60 @@ $ curl https://manifold.markets/api/v0/market -X POST -H 'Content-Type: applicat
                  "initialProb":25}'
 ```
 
+### `POST /v0/market/[marketId]/resolve`
+
+Resolves a market on behalf of the authorized user.
+
+Parameters:
+
+For binary markets:
+
+- `outcome`: Required. One of `YES`, `NO`, `MKT`, or `CANCEL`.
+- `probabilityInt`: Optional. The probability to use for `MKT` resolution.
+
+For free response markets:
+
+- `outcome`: Required. One of `MKT`, `CANCEL`, or a `number` indicating the Free Response outcome ID.
+- `resolutions`: A map of from outcome => number to use as the weights for resolving in favor of multiple free response options. Can only be set with `MKT` outcome.
+
+For numeric markets:
+
+- `outcome`: Required. One of `CANCEL`, or a `number` indicating the selected numeric bucket ID.
+- `value`: The value that the market may resolves to.
+
+Example request:
+
+```
+# Resolve a binary market
+$ curl https://manifold.markets/api/v0/market -X POST -H 'Content-Type: application/json' \
+    -H 'Authorization: Key {...}'
+    --data-raw '{"contractId":"{...}", \
+                 "outcome":"YES"}'
+
+# Resolve a binary market with a specified probability
+$ curl https://manifold.markets/api/v0/market -X POST -H 'Content-Type: application/json' \
+    -H 'Authorization: Key {...}'
+    --data-raw '{"contractId":"{...}", \
+                 "outcome":"MKT",
+                 "probabilityInt": 75}'
+
+# Resolve a free response market with a single answer chosen
+$ curl https://manifold.markets/api/v0/market -X POST -H 'Content-Type: application/json' \
+    -H 'Authorization: Key {...}'
+    --data-raw '{"contractId":"{...}", \
+                 "outcome":"{...}"}'
+
+# Resolve a free response market with multiple answers chosen
+$ curl https://manifold.markets/api/v0/market -X POST -H 'Content-Type: application/json' \
+    -H 'Authorization: Key {...}'
+    --data-raw '{"contractId":"{...}", \
+                 "outcome":"MKT",
+                 "resolutions": {
+                   "{...}": 1,
+                   "{...}": 2,
+                 }}'
+```
+
 ## Changelog
 
 - 2022-06-08: Add paging to markets endpoint

functions/src/resolve-market.ts

@@ -2,7 +2,11 @@ import * as admin from 'firebase-admin'
 import { z } from 'zod'
 import { difference, uniq, mapValues, groupBy, sumBy } from 'lodash'
 
-import { Contract, RESOLUTIONS } from '../../common/contract'
+import {
+  Contract,
+  FreeResponseContract,
+  RESOLUTIONS,
+} from '../../common/contract'
 import { User } from '../../common/user'
 import { Bet } from '../../common/bet'
 import { getUser, isProd, payUser } from './utils'
@@ -59,10 +63,10 @@ export const resolvemarket = newEndpoint(opts, async (req, auth) => {
   if (!contractSnap.exists)
     throw new APIError(404, 'No contract exists with the provided ID')
   const contract = contractSnap.data() as Contract
-  const { creatorId, outcomeType, closeTime } = contract
+  const { creatorId, closeTime } = contract
 
   const { value, resolutions, probabilityInt, outcome } = getResolutionParams(
-    outcomeType,
+    contract,
     req.body
   )
 
@@ -215,7 +219,8 @@ const sendResolutionEmails = async (
   )
 }
 
-function getResolutionParams(outcomeType: string, body: string) {
+function getResolutionParams(contract: Contract, body: string) {
+  const { outcomeType } = contract
   if (outcomeType === 'NUMERIC') {
     return {
       ...validate(numericSchema, body),
@@ -225,19 +230,39 @@ function getResolutionParams(outcomeType: string, body: string) {
   } else if (outcomeType === 'FREE_RESPONSE') {
     const freeResponseParams = validate(freeResponseSchema, body)
     const { outcome } = freeResponseParams
-    const resolutions =
-      'resolutions' in freeResponseParams
-        ? Object.fromEntries(
-            freeResponseParams.resolutions.map((r) => [r.answer, r.pct])
-          )
-        : undefined
-    return {
-      // Free Response outcome IDs are numbers by convention,
-      // but treated as strings everywhere else.
-      outcome: outcome.toString(),
-      resolutions,
-      value: undefined,
-      probabilityInt: undefined,
+    switch (outcome) {
+      case 'CANCEL':
+        return {
+          outcome: outcome.toString(),
+          resolutions: undefined,
+          value: undefined,
+          probabilityInt: undefined,
+        }
+      case 'MKT': {
+        const { resolutions } = freeResponseParams
+        resolutions.forEach(({ answer }) => validateAnswer(contract, answer))
+        const pctSum = sumBy(resolutions, ({ pct }) => pct)
+        if (Math.abs(pctSum - 100) > 0.1) {
+          throw new APIError(400, 'Resolution percentages must sum to 100')
+        }
+        return {
+          outcome: outcome.toString(),
+          resolutions: Object.fromEntries(
+            resolutions.map((r) => [r.answer, r.pct])
+          ),
+          value: undefined,
+          probabilityInt: undefined,
+        }
+      }
+      default: {
+        validateAnswer(contract, outcome)
+        return {
+          outcome: outcome.toString(),
+          resolutions: undefined,
+          value: undefined,
+          probabilityInt: undefined,
+        }
+      }
     }
   } else if (outcomeType === 'BINARY') {
     return {
@@ -249,4 +274,11 @@ function getResolutionParams(outcomeType: string, body: string) {
   throw new APIError(500, `Invalid outcome type: ${outcomeType}`)
 }
 
+function validateAnswer(contract: FreeResponseContract, answer: number) {
+  const validIds = contract.answers.map((a) => a.id)
+  if (!validIds.includes(answer.toString())) {
+    throw new APIError(400, `${answer} is not a valid answer ID`)
+  }
+}
+
 const firestore = admin.firestore()

web/lib/api/proxy.ts

@@ -41,7 +41,12 @@ export const fetchBackend = (req: NextApiRequest, name: string) => {
     'Origin',
   ])
   const hasBody = req.method != 'HEAD' && req.method != 'GET'
-  const opts = { headers, method: req.method, body: hasBody ? req : undefined }
+  const body = req.body ? JSON.stringify(req.body) : req
+  const opts = {
+    headers,
+    method: req.method,
+    body: hasBody ? body : undefined,
+  }
   return fetch(url, opts)
 }
 

web/pages/api/v0/market/[id]/index.ts

@@ -3,7 +3,7 @@ import { listAllBets } from 'web/lib/firebase/bets'
 import { listAllComments } from 'web/lib/firebase/comments'
 import { getContractFromId } from 'web/lib/firebase/contracts'
 import { applyCorsHeaders, CORS_UNRESTRICTED } from 'web/lib/api/cors'
-import { FullMarket, ApiError, toFullMarket } from '../_types'
+import { FullMarket, ApiError, toFullMarket } from '../../_types'
 
 export default async function handler(
   req: NextApiRequest,

web/pages/api/v0/market/[id]/resolve.ts

@@ -0,0 +1,28 @@
+import { NextApiRequest, NextApiResponse } from 'next'
+import {
+  CORS_ORIGIN_MANIFOLD,
+  CORS_ORIGIN_LOCALHOST,
+} from 'common/envs/constants'
+import { applyCorsHeaders } from 'web/lib/api/cors'
+import { fetchBackend, forwardResponse } from 'web/lib/api/proxy'
+
+export const config = { api: { bodyParser: true } }
+
+export default async function route(req: NextApiRequest, res: NextApiResponse) {
+  await applyCorsHeaders(req, res, {
+    origin: [CORS_ORIGIN_MANIFOLD, CORS_ORIGIN_LOCALHOST],
+    methods: 'POST',
+  })
+
+  const { id } = req.query
+  const contractId = id as string
+
+  if (req.body) req.body.contractId = contractId
+  try {
+    const backendRes = await fetchBackend(req, 'resolvemarket')
+    await forwardResponse(res, backendRes)
+  } catch (err) {
+    console.error('Error talking to cloud function: ', err)
+    res.status(500).json({ message: 'Error communicating with backend.' })
+  }
+}