Initial library implementations and tests (#1)
Main Workflow / Lint and test library (push) Successful in 16m40s
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Main Workflow / Lint and test library (push) Successful in 16m40s
Details
- [x] Implements library according to instructions, with tests. - [x] GitHub Actions workflow to lint and test library. Reviewed-on: #1
This commit is contained in:
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name: Main Workflow
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on:
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pull_request:
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branches:
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- main
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push:
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branches:
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- main
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jobs:
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lint-and-test:
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name: Lint and test library
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runs-on: ubuntu-latest
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steps:
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- uses: actions/checkout@v4
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- name: Set up Java
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uses: actions/setup-java@v3
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with:
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distribution: 'adopt'
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java-version: 17
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- name: Verify Gradle wrapper
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uses: gradle/wrapper-validation-action@v1
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- name: Setup Gradle
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uses: gradle/gradle-build-action@v2
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- name: Run checks
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run: ./gradlew check
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@ -1,9 +1,11 @@
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<?xml version="1.0" encoding="UTF-8"?>
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<project version="4">
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<component name="GradleMigrationSettings" migrationVersion="1" />
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<component name="GradleSettings">
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<option name="linkedExternalProjectsSettings">
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<GradleProjectSettings>
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<option name="externalProjectPath" value="$PROJECT_DIR$" />
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<option name="gradleJvm" value="corretto-19" />
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<option name="modules">
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<set>
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<option value="$PROJECT_DIR$" />
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@ -4,7 +4,11 @@
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<component name="FrameworkDetectionExcludesConfiguration">
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<file type="web" url="file://$PROJECT_DIR$" />
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</component>
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<component name="ProjectRootManager" version="2" languageLevel="JDK_1_8" project-jdk-name="corretto-19" project-jdk-type="JavaSDK">
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<component name="PWA">
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<option name="enabled" value="true" />
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<option name="wasEnabledAtLeastOnce" value="true" />
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</component>
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<component name="ProjectRootManager" version="2" languageLevel="JDK_17" project-jdk-name="openjdk-21" project-jdk-type="JavaSDK">
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<output url="file://$PROJECT_DIR$/out" />
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</component>
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</project>
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@ -3,6 +3,8 @@
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This is a small project to implement a subset of git's functionality in Kotlin and was created using the instructions
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below as part of my application to the JetBrains internship project "TeamCity support for Gitea".
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The package is named `tinyvm` for 'tiny version manager'.
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## Assumptions
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Since this is an internship application project, I have assumed that a minimal usage of external libraries is preferred,
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plugins {
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kotlin("jvm") version "1.9.21"
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id("org.jmailen.kotlinter") version "4.1.0"
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}
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group = "net.koval"
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@ -18,5 +19,5 @@ tasks.test {
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}
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kotlin {
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jvmToolchain(8)
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jvmToolchain(17)
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}
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package tinyvm
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import java.security.MessageDigest
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import java.time.Instant
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abstract class Object(
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val type: String,
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) {
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abstract val data: String
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fun hash(): String =
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MessageDigest
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.getInstance("SHA-1")
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.digest("$type ${data.length}\u0000$data".toByteArray())
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.toHex()
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}
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class Commit(
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val tree: Tree,
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val author: Author,
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val message: String,
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val timestamp: Instant,
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) : Object("commit") {
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// Use \n\n for end of header in-case additional metadata is implemented in the future.
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override val data: String
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get() = "tree ${tree.hash()}\nauthor $author\ntimestamp ${timestamp.epochSecond}\n\n$message"
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}
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data class Author(
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val name: String,
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val email: String,
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) {
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override fun toString(): String = "$name <$email>"
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}
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package tinyvm
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import java.util.HexFormat
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fun ByteArray.toHex(): String = HexFormat.of().formatHex(this)
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package tinyvm
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class HashCollisionException(hash: String) : Exception("Different object types with identical hash '$hash'")
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class CommitTimeComparator : Comparator<Commit> {
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override fun compare(
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o1: Commit,
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o2: Commit,
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): Int = (o1.timestamp.epochSecond - o2.timestamp.epochSecond).toInt()
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}
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class Repository {
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private val commits = sortedSetOf(CommitTimeComparator())
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// Store all objects in one map like git does. This would simplify the data persistence implementation (if there was
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// one) and allows for other objects to be added in the future without modifying the data persistence implementation
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// at all.
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private val objects = mutableMapOf<String, Object>()
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/**
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* (Deep) get or put a commit object into the repository.
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* This will also get or put all child trees and blobs.
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*/
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fun commit(commit: Commit): Commit {
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val hash = commit.hash()
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val obj = findObject<Commit>(hash)
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if (obj != null) return obj
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val newCommit =
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Commit(
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tree = addTree(commit.tree),
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author = commit.author,
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message = commit.message,
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timestamp = commit.timestamp,
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)
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objects[hash] = newCommit
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commits.add(newCommit)
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return newCommit
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}
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/**
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* Get a commit by its hash.
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*/
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fun getCommit(hash: String): Commit? = findObject<Commit>(hash)
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/**
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* List all commits.
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*/
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fun listCommits(): List<Commit> = commits.toList()
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/**
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* Find commit.
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*/
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fun findCommit(predicate: (Commit) -> Boolean): Commit? = commits.find(predicate)
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/**
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* Dump repository objects
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*/
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fun dumpObjects(): Map<String, Object> = objects
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/**
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* (Deep) get or put a tree object into the repository.
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* This will also get or put all child trees and blobs.
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*/
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private fun addTree(tree: Tree): Tree {
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val hash = tree.hash()
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val obj = findObject<Tree>(hash)
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if (obj != null) return obj
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val newTree =
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Tree(
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tree.nodes.map { (name, node) ->
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when (node) {
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is Tree -> name to addTree(node)
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is Blob -> name to addObject(node)
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}
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}.toMap(),
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)
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objects[hash] = newTree
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return tree
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}
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/**
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* (Shallow) get or put an object into the repository.
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*/
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private inline fun <reified T : Object> addObject(obj: T): T =
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objects.getOrPut(obj.hash()) { obj } as? T ?: throw HashCollisionException(obj.hash())
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/**
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* Find an object in the repository by its hash.
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*/
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private inline fun <reified T : Object> findObject(hash: String): T? =
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objects[hash]?.let { it as? T ?: throw HashCollisionException(hash) }
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}
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package tinyvm
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sealed class Node(type: String) : Object(type)
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class Tree(val nodes: Map<String, Node>) : Node("tree") {
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// For simplicity just use the hex-formatted hash, not the actual value like git does.
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override val data: String
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get() =
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nodes.map { (name, node) ->
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"${node.type} $name\u0000${node.hash()}"
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}.sorted().joinToString()
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}
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class Blob(override val data: String) : Node("blob")
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package tinyvm
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import java.time.Instant
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import kotlin.test.Test
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import kotlin.test.assertEquals
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internal class RepositoryTest {
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private val repository = Repository()
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private val commits =
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listOf(
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Commit(
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tree = Tree(mapOf("test1.txt" to Blob("Hello World!"))),
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author = Author("Gleb Koval", "gleb@koval.net"),
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message = "Add test1.txt",
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timestamp = Instant.ofEpochSecond(0),
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),
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Commit(
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tree =
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Tree(
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mapOf(
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"dir1" to
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Tree(
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mapOf(
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"test1.txt" to Blob("Hello World!"),
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),
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),
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"dir2" to
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Tree(
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mapOf(
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"test2.txt" to Blob("This is a second file"),
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),
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),
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),
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),
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author = Author("Gleb Koval", "gleb@koval.net"),
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message = "Move test1.txt and add dir2/test2.txt",
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timestamp = Instant.ofEpochSecond(50),
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),
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Commit(
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tree =
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Tree(
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mapOf(
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"dir1" to
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Tree(
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mapOf(
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"test1.txt" to Blob("Hello World!"),
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),
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),
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"dir2" to
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Tree(
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mapOf(
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"test2.txt" to Blob("This is a second file"),
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),
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),
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"README.md" to Blob("# This is a test repo!"),
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),
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),
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author = Author("Gleb Koval", "gleb@koval.net"),
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message = "Add README.md",
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timestamp = Instant.ofEpochSecond(100),
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),
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)
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@Test
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fun `can commit`() {
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val committed = repository.commit(commits[0])
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assertEquals(commits[0].hash(), committed.hash())
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assertEquals(1, repository.listCommits().size)
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assertEquals(3, repository.dumpObjects().size)
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}
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@Test
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fun `can deduplicate commit`() {
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repository.commit(commits[0])
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assertEquals(1, repository.listCommits().size)
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val committed = repository.commit(commits[0])
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assertEquals(1, repository.listCommits().size)
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assertEquals(3, repository.dumpObjects().size)
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assertEquals(commits[0].hash(), committed.hash())
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}
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@Test
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fun `can commit twice and deduplicate objects`() {
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repository.commit(commits[0])
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val committed = repository.commit(commits[1])
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assertEquals(2, repository.listCommits().size)
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assertEquals(7, repository.dumpObjects().size)
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assertEquals(commits[1].hash(), committed.hash())
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assertEquals(commits.take(2).map { it.hash() }, repository.listCommits().map { it.hash() })
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}
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@Test
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fun `can commit in-between existing commits`() {
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repository.commit(commits[0])
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repository.commit(commits[2])
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val committed = repository.commit(commits[1])
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assertEquals(3, repository.listCommits().size)
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assertEquals(10, repository.dumpObjects().size)
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assertEquals(commits[1].hash(), committed.hash())
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assertEquals(commits.map { it.hash() }, repository.listCommits().map { it.hash() })
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}
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@Test
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fun `can get commit by hash`() {
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repository.commit(commits[0])
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val committed = repository.commit(commits[1])
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repository.commit(commits[2])
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assertEquals(committed, repository.getCommit(commits[1].hash()))
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assertEquals(null, repository.getCommit("00000000000000000000"))
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}
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@Test
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fun `can find commit by predicate`() {
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repository.commit(commits[0])
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val committed = repository.commit(commits[1])
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repository.commit(commits[2])
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assertEquals(committed, repository.findCommit { it.message.matches("Move.*".toRegex()) })
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assertEquals(null, repository.getCommit("00000000000000000000"))
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}
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}
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