Gleb Koval
e2764a5473
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- [x] Implements library according to instructions, with tests. - [x] GitHub Actions workflow to lint and test library. Reviewed-on: #1
92 lines
2.8 KiB
Kotlin
92 lines
2.8 KiB
Kotlin
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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} |