feat: mastodon follow challenge

app/src/app/api/challenges/[id]/webhook/route.ts

@@ -41,6 +41,10 @@ export async function POST(request: Request, { params }: { params: Promise<{ id:
     // Use the path from webhookUrl but resolve it against the local origin,
     // so we always hit our own API regardless of what host is stored in Sanity.
     const { pathname, search } = new URL(challenge.webhookUrl)
+    if (!pathname.startsWith("/api/webhook/")) {
+      return NextResponse.json({ message: "Invalid webhook path" }, { status: 400 })
+    }
+
     const { origin } = new URL(request.url)
     const localWebhookUrl = `${origin}${pathname}${search}`
 
@@ -54,6 +58,15 @@ export async function POST(request: Request, { params }: { params: Promise<{ id:
       }),
     })
 
+    const contentType = webhookResponse.headers.get("content-type") ?? ""
+    if (!contentType.includes("application/json")) {
+      const text = await webhookResponse.text()
+      console.error("Webhook returned non-JSON response:", text)
+      return NextResponse.json(
+        { message: "Webhook returned an unexpected response" },
+        { status: 502 },
+      )
+    }
     const data = await webhookResponse.json()
     return NextResponse.json(data, { status: webhookResponse.status })
   } catch (error) {

app/src/app/api/webhook/mastodon/route.ts

@@ -0,0 +1,244 @@
+import { NextResponse } from "next/server"
+import { completeChallenge, findPlayerAndChallenge, findChallenge } from "@/lib/sanity.queries"
+
+// Maximum number of following-list pages to walk before giving up.
+// Each page returns up to 80 accounts, so 12 pages ≈ 960 checked entries.
+const MAX_FOLLOWING_PAGES = 12
+
+interface MastodonAccount {
+  id: string
+  acct: string
+  url: string
+}
+
+/**
+ * Resolve a Mastodon username to an account object via the lookup API.
+ *
+ * Uses GET /api/v1/accounts/lookup which works without authentication and
+ * directly returns the account for a given acct handle on the instance.
+ *
+ * @param username The bare username (no @ prefix, no domain) entered by the player.
+ * @param instance The Mastodon instance derived from the challenge's callToAction URL.
+ */
+async function resolveAccount(username: string, instance: string): Promise<MastodonAccount | null> {
+  const lookupUrl = `https://${instance}/api/v1/accounts/lookup?acct=${encodeURIComponent(username)}`
+
+  const response = await fetch(lookupUrl, { headers: { Accept: "application/json" } })
+
+  if (response.status === 404) return null
+
+  if (!response.ok) {
+    throw new Error(
+      `Mastodon account lookup failed on ${instance}: ${response.status} ${response.statusText}`,
+    )
+  }
+
+  return (await response.json()) as MastodonAccount
+}
+
+/**
+ * Parse the Mastodon instance and username from a profile URL.
+ *
+ * Supports:
+ *  - https://mastodon.social/@nephila       → { instance: "mastodon.social", username: "nephila" }
+ *  - https://fosstodon.org/users/fosstodon  → { instance: "fosstodon.org",  username: "fosstodon" }
+ */
+function parseProfileUrl(url: string): { instance: string; username: string } | null {
+  try {
+    const parsed = new URL(url)
+    const instance = parsed.hostname
+    // Handles both "/@username" and "/users/username" forms
+    const match = parsed.pathname.match(/^\/(?:@|users\/)([^/]+)/)
+    if (!match) return null
+    return { instance, username: match[1] }
+  } catch {
+    return null
+  }
+}
+
+/**
+ * Check whether `followerAccount` (identified by its Mastodon ID on `instance`)
+ * is following `targetAcct` (the full qualified acct, e.g. "nephila@mastodon.social"
+ * or just "nephila" if on the same instance).
+ *
+ * Paginates through the follower's following list up to MAX_FOLLOWING_PAGES pages.
+ */
+async function checkIsFollowing(
+  instance: string,
+  followerId: string,
+  targetAcct: string,
+): Promise<boolean> {
+  // Normalise targetAcct for comparison — strip leading @
+  const normTarget = targetAcct.replace(/^@/, "").toLowerCase()
+
+  let url: string | null = `https://${instance}/api/v1/accounts/${followerId}/following?limit=80`
+  let pages = 0
+
+  while (url !== null && pages < MAX_FOLLOWING_PAGES) {
+    const currentUrl: string = url
+    url = null
+
+    const response: Response = await fetch(currentUrl, { headers: { Accept: "application/json" } })
+
+    if (!response.ok) {
+      throw new Error(
+        `Mastodon following-list fetch failed: ${response.status} ${response.statusText}`,
+      )
+    }
+
+    const followingPage = (await response.json()) as MastodonAccount[]
+
+    for (const account of followingPage) {
+      const acct = account.acct.toLowerCase()
+      // Match "nephila" or "nephila@mastodon.social"
+      if (acct === normTarget || acct.split("@")[0] === normTarget.split("@")[0]) {
+        // Confirm the instance also matches when both sides have a domain
+        const acctDomain = acct.split("@")[1] ?? instance
+        const targetDomain = normTarget.split("@")[1] ?? instance
+        if (acctDomain === targetDomain) return true
+      }
+    }
+
+    // Mastodon uses Link headers for cursor-based pagination
+    const linkHeader: string | null = response.headers.get("link")
+    if (linkHeader) {
+      const nextMatch: RegExpMatchArray | null = linkHeader.match(/<([^>]+)>;\s*rel="next"/)
+      if (nextMatch) url = nextMatch[1]
+    }
+
+    pages++
+  }
+
+  return false
+}
+
+export async function POST(request: Request) {
+  try {
+    const body = await request.json()
+    const {
+      challengeId,
+      playerEmail,
+      verificationData,
+    }: {
+      challengeId?: string
+      playerEmail?: string
+      verificationData?: Record<string, string>
+    } = body
+
+    if (!challengeId || !playerEmail || !verificationData) {
+      return NextResponse.json(
+        { message: "Missing required fields", success: false },
+        { status: 400 },
+      )
+    }
+
+    const mastodonUsername = verificationData.username?.trim().replace(/^@/, "").split("@")[0]
+    if (!mastodonUsername) {
+      return NextResponse.json(
+        { message: "Mastodon username is required", success: false },
+        { status: 400 },
+      )
+    }
+
+    // Load the challenge so we can extract the target account from callToAction.url
+    const challenge = await findChallenge(challengeId)
+    if (!challenge) {
+      return NextResponse.json({ message: "Challenge not found", success: false }, { status: 404 })
+    }
+
+    const callToActionUrl: string | undefined = challenge.callToAction?.url
+    if (!callToActionUrl) {
+      return NextResponse.json(
+        { message: "Challenge has no callToAction URL configured", success: false },
+        { status: 500 },
+      )
+    }
+
+    const targetParsed = parseProfileUrl(callToActionUrl)
+    if (!targetParsed) {
+      return NextResponse.json(
+        { message: "Could not parse target Mastodon profile URL", success: false },
+        { status: 500 },
+      )
+    }
+
+    const { instance: targetInstance, username: targetUsername } = targetParsed
+    // Full qualified acct used for comparison
+    const targetAcct = `${targetUsername}@${targetInstance}`
+
+    // Verify the player hasn't already completed this challenge
+    const player = await findPlayerAndChallenge(playerEmail, challengeId)
+    if (!player) {
+      return NextResponse.json(
+        { message: "Player not found or challenge already completed", success: false },
+        { status: 404 },
+      )
+    }
+
+    // Resolve the submitting user's Mastodon account.
+    // We search on the target instance (mastodon.social) which can WebFinger-resolve
+    // remote accounts — so cross-instance users are handled correctly.
+    let followerAccount: MastodonAccount | null
+    try {
+      followerAccount = await resolveAccount(mastodonUsername, targetInstance)
+    } catch (error) {
+      console.error("Mastodon account resolution error:", error)
+      return NextResponse.json(
+        {
+          message: `Could not resolve Mastodon account "${mastodonUsername}". Make sure you entered the correct username`,
+          success: false,
+        },
+        { status: 422 },
+      )
+    }
+
+    if (!followerAccount) {
+      return NextResponse.json(
+        {
+          message: `Mastodon account "${mastodonUsername}" not found.`,
+          success: false,
+        },
+        { status: 404 },
+      )
+    }
+
+    // Check following list
+    let isFollowing: boolean
+    try {
+      isFollowing = await checkIsFollowing(targetInstance, followerAccount.id, targetAcct)
+    } catch (error) {
+      console.error("Mastodon following-check error:", error)
+      return NextResponse.json(
+        {
+          message: "Failed to verify Mastodon follow status. Please try again later.",
+          success: false,
+        },
+        { status: 500 },
+      )
+    }
+
+    if (!isFollowing) {
+      return NextResponse.json(
+        {
+          message: `@${followerAccount.acct} does not appear to be following @${targetAcct}. Make sure you follow the account and try again.`,
+          success: false,
+        },
+        { status: 422 },
+      )
+    }
+
+    // Follow confirmed — mark the challenge as completed
+    await completeChallenge(player._id, challengeId, {
+      ...verificationData,
+      mastodon_username: followerAccount.acct,
+    })
+
+    return NextResponse.json({
+      message: `Follow verified! @${followerAccount.acct} is following @${targetAcct}.`,
+      success: true,
+    })
+  } catch (error) {
+    console.error("Mastodon webhook error:", error)
+    return NextResponse.json({ message: "Internal server error", success: false }, { status: 500 })
+  }
+}

app/src/app/page.tsx

@@ -46,9 +46,9 @@ export default function HomePage() {
           </div>
 
           <p className="text-center mb-8 filter text-lg font-bold">
-            {eventCode
-              ? `Join the ${capitalize(eventCode)} challenge and collect points through exciting activities! Unlock exclusive rewards with your earned points!`
-              : `Join the ${eventCode ? capitalize(eventCode) : ""} challenge and collect points through exciting activities! Unlock exclusive rewards with your earned points!`}
+            Join the {eventCode ? capitalize(eventCode) : ""}
+            challenge and collect points through exciting activities! Unlock exclusive rewards with
+            your earned points!
           </p>
 
           <div

app/src/components/ChallengeDetail.tsx

@@ -110,9 +110,15 @@ export function ChallengeDetail({ challenge }: Props) {
         })
 
         if (!response.ok) {
-          const errorData = await response.json()
+          let errorMessage = "Unknown error"
+          try {
+            const errorData = await response.json()
+            errorMessage = errorData.message ?? errorMessage
+          } catch {
+            errorMessage = await response.text().catch(() => errorMessage)
+          }
           throw new Error(
-            `Failed to verify the challenge: ${errorData.message}. If the problem persists, please contact the staff.`,
+            `Failed to verify the challenge: ${errorMessage}. If the problem persists, please contact the staff.`,
           )
         }
       } catch (error) {
@@ -243,20 +249,19 @@ export function ChallengeDetail({ challenge }: Props) {
             </div>
           )}
           <form>
-            {challenge.verificationConfigJSON &&
-              challenge.verificationConfigJSON.fields.map((field) => (
-                <div key={field.name}>
-                  {field.type === "hidden" ? null : (
-                    <h3 className="font-semibold mb-2">{field.title}:</h3>
-                  )}
-                  {field.type === "hidden" ? null : (
-                    <label htmlFor={field.name} className="text-sm text-neutral-600 mb-2">
-                      {field.description}
-                    </label>
-                  )}
-                  <Input type={field.type} name={field.name} defaultValue={field?.value || ""} />
-                </div>
-              ))}
+            {challenge.verificationConfigJSON?.fields?.map((field) => (
+              <div key={field.name}>
+                {field.type === "hidden" ? null : (
+                  <h3 className="font-semibold mb-2">{field.title}:</h3>
+                )}
+                {field.type === "hidden" ? null : (
+                  <label htmlFor={field.name} className="text-sm text-neutral-600 mb-2">
+                    {field.description}
+                  </label>
+                )}
+                <Input type={field.type} name={field.name} defaultValue={field?.value || ""} />
+              </div>
+            ))}
           </form>
 
           {!challenge.isOnline && (

app/src/types/index.ts

@@ -51,13 +51,15 @@ export interface Challenge {
   }
   verificationConfigJSON?: {
     type: string
-    fields: {
-      type: string
-      title: string
-      name: string
-      description: string
-      value?: string
-    }[]
+    fields:
+      | {
+          type: string
+          title: string
+          name: string
+          description: string
+          value?: string
+        }[]
+      | null
   }
   event: {
     _type: "reference"