Added solutions

src/contributors/GitHubService.kt

@@ -25,6 +25,17 @@ interface GitHubService {
         @Path("owner") owner: String,
         @Path("repo") repo: String
     ): Call<List<User>>
+
+    @GET("orgs/{org}/repos?per_page=100")
+    suspend fun getOrgRepos(
+        @Path("org") org: String
+    ): Response<List<Repo>>
+
+    @GET("repos/{owner}/{repo}/contributors?per_page=100")
+    suspend fun getRepoContributors(
+        @Path("owner") owner: String,
+        @Path("repo") repo: String
+    ): Response<List<User>>
 }
 
 @Serializable

src/tasks/Aggregation.kt

@@ -15,4 +15,6 @@ TODO: Write aggregation code.
  You can use 'Navigate | Test' menu action (note the shortcut) to navigate to the test.
 */
 fun List<User>.aggregate(): List<User> =
-    this
+    groupBy { it.login }
+        .map { (login, group) -> User(login, group.sumBy { it.contributions }) }
+        .sortedByDescending { it.contributions }

src/tasks/Request2Background.kt

@@ -7,6 +7,6 @@ import kotlin.concurrent.thread
 
 fun loadContributorsBackground(service: GitHubService, req: RequestData, updateResults: (List<User>) -> Unit) {
     thread {
-        loadContributorsBlocking(service, req)
+        updateResults(loadContributorsBlocking(service, req))
     }
 }

src/tasks/Request3Callbacks.kt

@@ -11,16 +11,18 @@ fun loadContributorsCallbacks(service: GitHubService, req: RequestData, updateRe
     service.getOrgReposCall(req.org).onResponse { responseRepos ->
         logRepos(req, responseRepos)
         val repos = responseRepos.bodyList()
-        val allUsers = mutableListOf<User>()
+        val allUsers = Collections.synchronizedList(mutableListOf<User>())
+        val numberOfProcessed = AtomicInteger(0)
         for (repo in repos) {
             service.getRepoContributorsCall(req.org, repo.name).onResponse { responseUsers ->
                 logUsers(repo, responseUsers)
                 val users = responseUsers.bodyList()
                 allUsers += users
+                if (numberOfProcessed.incrementAndGet() == repos.size) {
+                    updateResults(allUsers.aggregate())
+                }
             }
         }
-        // TODO: Why this code doesn't work? How to fix that?
-        updateResults(allUsers.aggregate())
     }
 }
 

src/tasks/Request4Suspend.kt

@@ -3,5 +3,14 @@ package tasks
 import contributors.*
 
 suspend fun loadContributorsSuspend(service: GitHubService, req: RequestData): List<User> {
-    TODO()
+    val repos = service
+        .getOrgRepos(req.org)
+        .also { logRepos(req, it) }
+        .bodyList()
+
+    return repos.flatMap { repo ->
+        service.getRepoContributors(req.org, repo.name)
+            .also { logUsers(repo, it) }
+            .bodyList()
+    }.aggregate()
 }

src/tasks/Request5Concurrent.kt

@@ -4,5 +4,17 @@ import contributors.*
 import kotlinx.coroutines.*
 
 suspend fun loadContributorsConcurrent(service: GitHubService, req: RequestData): List<User> = coroutineScope {
-    TODO()
+    val repos = service
+        .getOrgRepos(req.org)
+        .also { logRepos(req, it) }
+        .bodyList()
+
+    val deferreds: List<Deferred<List<User>>> = repos.map { repo ->
+        async {
+            service.getRepoContributors(req.org, repo.name)
+                .also { logUsers(repo, it) }
+                .bodyList()
+        }
+    }
+    deferreds.awaitAll().flatten().aggregate()
 }

src/tasks/Request5NotCancellable.kt

@@ -5,5 +5,19 @@ import kotlinx.coroutines.*
 import kotlin.coroutines.coroutineContext
 
 suspend fun loadContributorsNotCancellable(service: GitHubService, req: RequestData): List<User> {
-    TODO()
+    val repos = service
+        .getOrgRepos(req.org)
+        .also { logRepos(req, it) }
+        .bodyList()
+
+    val deferreds: List<Deferred<List<User>>> = repos.map { repo ->
+        GlobalScope.async(Dispatchers.Default) {
+            log("starting loading for ${repo.name}")
+            delay(3000)
+            service.getRepoContributors(req.org, repo.name)
+                .also { logUsers(repo, it) }
+                .bodyList()
+        }
+    }
+    return deferreds.awaitAll().flatten().aggregate()
 }

src/tasks/Request6Progress.kt

@@ -7,5 +7,18 @@ suspend fun loadContributorsProgress(
     req: RequestData,
     updateResults: suspend (List<User>, completed: Boolean) -> Unit
 ) {
-    TODO()
+    val repos = service
+        .getOrgRepos(req.org)
+        .also { logRepos(req, it) }
+        .bodyList()
+
+    var allUsers = emptyList<User>()
+    for ((index, repo) in repos.withIndex()) {
+        val users = service.getRepoContributors(req.org, repo.name)
+            .also { logUsers(repo, it) }
+            .bodyList()
+
+        allUsers = (allUsers + users).aggregate()
+        updateResults(allUsers, index == repos.lastIndex)
+    }
 }

src/tasks/Request7Channels.kt

@@ -9,8 +9,25 @@ suspend fun loadContributorsChannels(
     service: GitHubService,
     req: RequestData,
     updateResults: suspend (List<User>, completed: Boolean) -> Unit
-) {
-    coroutineScope {
-        TODO()
+) = coroutineScope {
+    val repos = service
+        .getOrgRepos(req.org)
+        .also { logRepos(req, it) }
+        .bodyList()
+
+    val channel = Channel<List<User>>()
+    for (repo in repos) {
+        launch {
+            val users = service.getRepoContributors(req.org, repo.name)
+                .also { logUsers(repo, it) }
+                .bodyList()
+            channel.send(users)
+        }
+    }
+    var allUsers = emptyList<User>()
+    repeat(repos.size) {
+        val users = channel.receive()
+        allUsers = (allUsers + users).aggregate()
+        updateResults(allUsers, it == repos.lastIndex)
     }
 }

test/contributors/MockGithubService.kt

@@ -14,9 +14,6 @@ object MockGithubService : GitHubService {
         return Calls.response(reposMap.getValue(repo).users)
     }
 
-/*
-    // Uncomment the following implementations after adding these methods to GitHubService:
-
     override suspend fun getOrgRepos(org: String): Response<List<Repo>> {
         delay(reposDelay)
         return Response.success(repos)
@@ -27,5 +24,4 @@ object MockGithubService : GitHubService {
         delay(testRepo.delay)
         return Response.success(testRepo.users)
     }
-*/
 }