Prefix maven modules

simplenotes-domain/src/main/kotlin/DomainModule.kt

@@ -0,0 +1,37 @@
+package be.simplenotes.domain
+
+import be.simplenotes.domain.security.BcryptPasswordHash
+import be.simplenotes.domain.security.JwtPayloadExtractor
+import be.simplenotes.domain.security.PasswordHash
+import be.simplenotes.domain.security.SimpleJwt
+import be.simplenotes.domain.usecases.NoteService
+import be.simplenotes.domain.usecases.UserService
+import be.simplenotes.domain.usecases.export.ExportUseCase
+import be.simplenotes.domain.usecases.export.ExportUseCaseImpl
+import be.simplenotes.domain.usecases.markdown.MarkdownConverter
+import be.simplenotes.domain.usecases.markdown.MarkdownConverterImpl
+import be.simplenotes.domain.usecases.users.delete.DeleteUseCase
+import be.simplenotes.domain.usecases.users.delete.DeleteUseCaseImpl
+import be.simplenotes.domain.usecases.users.login.LoginUseCase
+import be.simplenotes.domain.usecases.users.login.LoginUseCaseImpl
+import be.simplenotes.domain.usecases.users.register.RegisterUseCase
+import be.simplenotes.domain.usecases.users.register.RegisterUseCaseImpl
+import org.koin.dsl.module
+
+val domainModule = module {
+    single<LoginUseCase> { LoginUseCaseImpl(get(), get(), get()) }
+    single<RegisterUseCase> { RegisterUseCaseImpl(get(), get()) }
+    single<DeleteUseCase> { DeleteUseCaseImpl(get(), get(), get()) }
+    single { UserService(get(), get(), get(), get()) }
+    single<PasswordHash> { BcryptPasswordHash() }
+    single { SimpleJwt(get()) }
+    single { JwtPayloadExtractor(get()) }
+    single {
+        NoteService(get(), get(), get(), get()).apply {
+            dropAllIndexes()
+            indexAll()
+        }
+    }
+    single<MarkdownConverter> { MarkdownConverterImpl() }
+    single<ExportUseCase> { ExportUseCaseImpl(get(), get()) }
+}

simplenotes-domain/src/main/kotlin/model/Note.kt

@@ -0,0 +1,47 @@
+package be.simplenotes.domain.model
+
+import kotlinx.serialization.Contextual
+import kotlinx.serialization.Serializable
+import java.time.LocalDateTime
+import java.util.*
+
+@Serializable
+data class NoteMetadata(
+    val title: String,
+    val tags: List<String>,
+)
+
+@Serializable
+data class PersistedNoteMetadata(
+    val title: String,
+    val tags: List<String>,
+    @Contextual val updatedAt: LocalDateTime,
+    @Contextual val uuid: UUID,
+)
+
+@Serializable
+data class Note(
+    val meta: NoteMetadata,
+    val markdown: String,
+    val html: String,
+)
+
+@Serializable
+data class PersistedNote(
+    val meta: NoteMetadata,
+    val markdown: String,
+    val html: String,
+    @Contextual val updatedAt: LocalDateTime,
+    @Contextual val uuid: UUID,
+    val public: Boolean,
+)
+
+@Serializable
+data class ExportedNote(
+    val title: String,
+    val tags: List<String>,
+    val markdown: String,
+    val html: String,
+    @Contextual val updatedAt: LocalDateTime,
+    val trash: Boolean,
+)

simplenotes-domain/src/main/kotlin/model/User.kt

@@ -0,0 +1,4 @@
+package be.simplenotes.domain.model
+
+data class User(val username: String, val password: String)
+data class PersistedUser(val username: String, val password: String, val id: Int)

simplenotes-domain/src/main/kotlin/security/HtmlSanitizer.kt

@@ -0,0 +1,20 @@
+package be.simplenotes.domain.security
+
+import org.owasp.html.HtmlPolicyBuilder
+
+object HtmlSanitizer {
+    private val htmlPolicy = HtmlPolicyBuilder()
+        .allowElements("a")
+        .allowCommonBlockElements()
+        .allowCommonInlineFormattingElements()
+        .allowElements("pre")
+        .allowAttributes("class").onElements("code")
+        .allowUrlProtocols("http", "https")
+        .allowAttributes("href").onElements("a")
+        .allowElements("input")
+        .allowAttributes("type", "checked", "disabled", "readonly").onElements("input")
+        .requireRelNofollowOnLinks()
+        .toFactory()!!
+
+    fun sanitize(unsafeHtml: String) = htmlPolicy.sanitize(unsafeHtml)!!
+}

simplenotes-domain/src/main/kotlin/security/JwtPayload.kt

@@ -0,0 +1,21 @@
+package be.simplenotes.domain.security
+
+import be.simplenotes.domain.model.PersistedUser
+import com.auth0.jwt.exceptions.JWTVerificationException
+
+data class JwtPayload(val userId: Int, val username: String) {
+    constructor(user: PersistedUser) : this(user.id, user.username)
+}
+
+class JwtPayloadExtractor(private val jwt: SimpleJwt) {
+    operator fun invoke(token: String): JwtPayload? = try {
+        val decodedJWT = jwt.verifier.verify(token)
+        val id = decodedJWT.getClaim(userIdField).asInt() ?: null
+        val username = decodedJWT.getClaim(usernameField).asString() ?: null
+        id?.let { username?.let { JwtPayload(id, username) } }
+    } catch (e: JWTVerificationException) {
+        null
+    } catch (e: IllegalArgumentException) {
+        null
+    }
+}

simplenotes-domain/src/main/kotlin/security/PasswordHash.kt

@@ -0,0 +1,14 @@
+package be.simplenotes.domain.security
+
+import org.mindrot.jbcrypt.BCrypt
+
+internal interface PasswordHash {
+    fun crypt(password: String): String
+    fun verify(password: String, hashedPassword: String): Boolean
+}
+
+internal class BcryptPasswordHash(test: Boolean = false) : PasswordHash {
+    private val rounds = if (test) 4 else 10
+    override fun crypt(password: String) = BCrypt.hashpw(password, BCrypt.gensalt(rounds))!!
+    override fun verify(password: String, hashedPassword: String) = BCrypt.checkpw(password, hashedPassword)
+}

simplenotes-domain/src/main/kotlin/security/SimpleJwt.kt

@@ -0,0 +1,25 @@
+package be.simplenotes.domain.security
+
+import be.simplenotes.shared.config.JwtConfig
+import com.auth0.jwt.JWT
+import com.auth0.jwt.JWTVerifier
+import com.auth0.jwt.algorithms.Algorithm
+import java.util.*
+import java.util.concurrent.TimeUnit
+
+internal const val userIdField = "i"
+internal const val usernameField = "u"
+
+class SimpleJwt(jwtConfig: JwtConfig) {
+    private val validityInMs = TimeUnit.MILLISECONDS.convert(jwtConfig.validity, jwtConfig.timeUnit)
+    private val algorithm = Algorithm.HMAC256(jwtConfig.secret)
+
+    val verifier: JWTVerifier = JWT.require(algorithm).build()
+    fun sign(jwtPayload: JwtPayload): String = JWT.create()
+        .withClaim(userIdField, jwtPayload.userId)
+        .withClaim(usernameField, jwtPayload.username)
+        .withExpiresAt(getExpiration())
+        .sign(algorithm)
+
+    private fun getExpiration() = Date(System.currentTimeMillis() + validityInMs)
+}

simplenotes-domain/src/main/kotlin/usecases/NoteService.kt

@@ -0,0 +1,97 @@
+package be.simplenotes.domain.usecases
+
+import arrow.core.Either
+import arrow.core.extensions.fx
+import be.simplenotes.domain.model.Note
+import be.simplenotes.domain.model.PersistedNote
+import be.simplenotes.domain.model.PersistedNoteMetadata
+import be.simplenotes.domain.security.HtmlSanitizer
+import be.simplenotes.domain.usecases.markdown.MarkdownConverter
+import be.simplenotes.domain.usecases.markdown.MarkdownParsingError
+import be.simplenotes.domain.usecases.repositories.NoteRepository
+import be.simplenotes.domain.usecases.repositories.UserRepository
+import be.simplenotes.domain.usecases.search.NoteSearcher
+import be.simplenotes.domain.usecases.search.SearchTerms
+import java.util.*
+
+class NoteService(
+    private val markdownConverter: MarkdownConverter,
+    private val noteRepository: NoteRepository,
+    private val userRepository: UserRepository,
+    private val searcher: NoteSearcher,
+) {
+
+    fun create(userId: Int, markdownText: String) = Either.fx<MarkdownParsingError, PersistedNote> {
+        val persistedNote = !markdownConverter.renderDocument(markdownText)
+            .map { it.copy(html = HtmlSanitizer.sanitize(it.html)) }
+            .map { Note(it.metadata, markdown = markdownText, html = it.html) }
+            .map { noteRepository.create(userId, it) }
+
+        searcher.indexNote(userId, persistedNote)
+        persistedNote
+    }
+
+    fun update(userId: Int, uuid: UUID, markdownText: String) = Either.fx<MarkdownParsingError, PersistedNote?> {
+        val persistedNote = !markdownConverter.renderDocument(markdownText)
+            .map { it.copy(html = HtmlSanitizer.sanitize(it.html)) }
+            .map { Note(it.metadata, markdown = markdownText, html = it.html) }
+            .map { noteRepository.update(userId, uuid, it) }
+
+        persistedNote?.let { searcher.updateIndex(userId, it) }
+        persistedNote
+    }
+
+    fun paginatedNotes(
+        userId: Int,
+        page: Int,
+        itemsPerPage: Int = 20,
+        tag: String? = null,
+        deleted: Boolean = false,
+    ): PaginatedNotes {
+        val count = noteRepository.count(userId, tag, deleted)
+        val offset = (page - 1) * itemsPerPage
+        val numberOfPages = (count / itemsPerPage) + 1
+        val notes = if (count == 0) emptyList() else noteRepository.findAll(userId, itemsPerPage, offset, tag, deleted)
+        return PaginatedNotes(numberOfPages, notes)
+    }
+
+    fun find(userId: Int, uuid: UUID) = noteRepository.find(userId, uuid)
+
+    fun trash(userId: Int, uuid: UUID): Boolean {
+        val res = noteRepository.delete(userId, uuid, permanent = false)
+        if (res) searcher.deleteIndex(userId, uuid)
+        return res
+    }
+
+    fun restore(userId: Int, uuid: UUID): Boolean {
+        val res = noteRepository.restore(userId, uuid)
+        if (res) find(userId, uuid)?.let { note -> searcher.indexNote(userId, note) }
+        return res
+    }
+
+    fun delete(userId: Int, uuid: UUID): Boolean {
+        val res = noteRepository.delete(userId, uuid, permanent = true)
+        if (res) searcher.deleteIndex(userId, uuid)
+        return res
+    }
+
+    fun countDeleted(userId: Int) = noteRepository.count(userId, deleted = true)
+
+    fun indexAll() {
+        val userIds = userRepository.findAll()
+        userIds.forEach { id ->
+            val notes = noteRepository.findAllDetails(id)
+            searcher.indexNotes(id, notes)
+        }
+    }
+
+    fun search(userId: Int, searchTerms: SearchTerms) = searcher.search(userId, searchTerms)
+
+    fun dropAllIndexes() = searcher.dropAll()
+
+    fun makePublic(userId: Int, uuid: UUID) = noteRepository.makePublic(userId, uuid)
+    fun makePrivate(userId: Int, uuid: UUID) = noteRepository.makePrivate(userId, uuid)
+    fun findPublic(uuid: UUID) = noteRepository.findPublic(uuid)
+}
+
+data class PaginatedNotes(val pages: Int, val notes: List<PersistedNoteMetadata>)

simplenotes-domain/src/main/kotlin/usecases/UserService.kt

@@ -0,0 +1,16 @@
+package be.simplenotes.domain.usecases
+
+import be.simplenotes.domain.usecases.export.ExportUseCase
+import be.simplenotes.domain.usecases.users.delete.DeleteUseCase
+import be.simplenotes.domain.usecases.users.login.LoginUseCase
+import be.simplenotes.domain.usecases.users.register.RegisterUseCase
+
+class UserService(
+    loginUseCase: LoginUseCase,
+    registerUseCase: RegisterUseCase,
+    deleteUseCase: DeleteUseCase,
+    exportUseCase: ExportUseCase,
+) : LoginUseCase by loginUseCase,
+    RegisterUseCase by registerUseCase,
+    DeleteUseCase by deleteUseCase,
+    ExportUseCase by exportUseCase

simplenotes-domain/src/main/kotlin/usecases/export/ExportUseCase.kt

@@ -0,0 +1,8 @@
+package be.simplenotes.domain.usecases.export
+
+import java.io.InputStream
+
+interface ExportUseCase {
+    fun exportAsJson(userId: Int): String
+    fun exportAsZip(userId: Int): InputStream
+}

simplenotes-domain/src/main/kotlin/usecases/export/ExportUseCaseImpl.kt

@@ -0,0 +1,50 @@
+package be.simplenotes.domain.usecases.export
+
+import be.simplenotes.domain.model.ExportedNote
+import be.simplenotes.domain.usecases.repositories.NoteRepository
+import kotlinx.serialization.builtins.ListSerializer
+import kotlinx.serialization.json.Json
+import org.apache.commons.compress.archivers.zip.ZipArchiveEntry
+import org.apache.commons.compress.archivers.zip.ZipArchiveOutputStream
+import java.io.ByteArrayInputStream
+import java.io.ByteArrayOutputStream
+import java.io.InputStream
+
+internal class ExportUseCaseImpl(private val noteRepository: NoteRepository, private val json: Json) : ExportUseCase {
+    override fun exportAsJson(userId: Int): String {
+        val notes = noteRepository.export(userId)
+        return json.encodeToString(ListSerializer(ExportedNote.serializer()), notes)
+    }
+
+    private fun sanitizeFilename(inputName: String): String = inputName.replace("[^a-zA-Z0-9-_.]".toRegex(), "_")
+
+    override fun exportAsZip(userId: Int): InputStream {
+        val notes = noteRepository.export(userId)
+        val zipOutput = ZipOutput()
+        zipOutput.use { zip ->
+            notes.forEach {
+                val name = sanitizeFilename(it.title)
+                zip.write("notes/$name.md", it.markdown)
+            }
+        }
+        return ByteArrayInputStream(zipOutput.outputStream.toByteArray())
+    }
+}
+
+
+class ZipOutput : AutoCloseable {
+    val outputStream = ByteArrayOutputStream()
+    private val zipOutputStream = ZipArchiveOutputStream(outputStream)
+
+    fun write(path: String, content: String) {
+        val entry = ZipArchiveEntry(path)
+        zipOutputStream.putArchiveEntry(entry)
+        zipOutputStream.write(content.toByteArray())
+        zipOutputStream.closeArchiveEntry()
+    }
+
+    override fun close() {
+        zipOutputStream.finish()
+        zipOutputStream.close()
+    }
+}

simplenotes-domain/src/main/kotlin/usecases/markdown/MarkdownConverter.kt

@@ -0,0 +1,83 @@
+package be.simplenotes.domain.usecases.markdown
+
+import arrow.core.Either
+import arrow.core.extensions.fx
+import arrow.core.left
+import arrow.core.right
+import be.simplenotes.domain.model.NoteMetadata
+import be.simplenotes.domain.validation.NoteValidations
+import com.vladsch.flexmark.ext.gfm.tasklist.TaskListExtension
+import com.vladsch.flexmark.html.HtmlRenderer
+import com.vladsch.flexmark.parser.Parser
+import com.vladsch.flexmark.util.data.MutableDataSet
+import io.konform.validation.ValidationErrors
+import org.yaml.snakeyaml.Yaml
+import org.yaml.snakeyaml.parser.ParserException
+import org.yaml.snakeyaml.scanner.ScannerException
+
+sealed class MarkdownParsingError
+object MissingMeta : MarkdownParsingError()
+object InvalidMeta : MarkdownParsingError()
+class ValidationError(val validationErrors: ValidationErrors) : MarkdownParsingError()
+
+data class Document(val metadata: NoteMetadata, val html: String)
+
+typealias MetaMdPair = Pair<String, String>
+
+interface MarkdownConverter {
+    fun renderDocument(input: String): Either<MarkdownParsingError, Document>
+}
+
+internal class MarkdownConverterImpl : MarkdownConverter {
+    private val yamlBoundPattern = "-{3}".toRegex()
+    private fun splitMetaFromDocument(input: String): Either<MissingMeta, MetaMdPair> {
+        val split = input.split(yamlBoundPattern, 3)
+        if (split.size < 3) return MissingMeta.left()
+        return (split[1].trim() to split[2].trim()).right()
+    }
+
+    private val yaml = Yaml()
+    private fun parseMeta(input: String): Either<InvalidMeta, NoteMetadata> {
+        val load: Map<String, Any> = try {
+            yaml.load(input)
+        } catch (e: ParserException) {
+            return InvalidMeta.left()
+        } catch (e: ScannerException) {
+            return InvalidMeta.left()
+        }
+
+        val title = when (val titleNode = load["title"]) {
+            is String, is Number -> titleNode.toString()
+            else -> return InvalidMeta.left()
+        }
+
+        val tagsNode = load["tags"]
+        val tags = if (tagsNode !is List<*>)
+            emptyList()
+        else
+            tagsNode.map { it.toString() }
+
+        return NoteMetadata(title, tags).right()
+    }
+
+    private val parser: Parser
+    private val renderer: HtmlRenderer
+
+    init {
+        val options = MutableDataSet()
+        options.set(Parser.EXTENSIONS, listOf(TaskListExtension.create()))
+        options.set(HtmlRenderer.SOFT_BREAK, "<br>")
+        parser = Parser.builder(options).build()
+        renderer = HtmlRenderer.builder(options).build()
+    }
+
+    private fun renderMarkdown(markdown: String) = parser.parse(markdown).run(renderer::render)
+
+    override fun renderDocument(input: String) = Either.fx<MarkdownParsingError, Document> {
+        val (meta, md) = !splitMetaFromDocument(input)
+        val parsedMeta = !parseMeta(meta)
+        !NoteValidations.validateMetadata(parsedMeta).toEither { }.swap()
+        val html = renderMarkdown(md)
+        Document(parsedMeta, html)
+    }
+}

simplenotes-domain/src/main/kotlin/usecases/repositories/NoteRepository.kt

@@ -0,0 +1,35 @@
+package be.simplenotes.domain.usecases.repositories
+
+import be.simplenotes.domain.model.ExportedNote
+import be.simplenotes.domain.model.Note
+import be.simplenotes.domain.model.PersistedNote
+import be.simplenotes.domain.model.PersistedNoteMetadata
+import java.util.*
+
+interface NoteRepository {
+
+    fun findAll(
+        userId: Int,
+        limit: Int = 20,
+        offset: Int = 0,
+        tag: String? = null,
+        deleted: Boolean = false
+    ): List<PersistedNoteMetadata>
+
+    fun count(userId: Int, tag: String? = null, deleted: Boolean = false): Int
+    fun delete(userId: Int, uuid: UUID, permanent: Boolean = false): Boolean
+    fun restore(userId: Int, uuid: UUID): Boolean
+
+    // These methods only access notes where `Notes.deleted = false`
+    fun getTags(userId: Int): List<String>
+    fun exists(userId: Int, uuid: UUID): Boolean
+    fun create(userId: Int, note: Note): PersistedNote
+    fun find(userId: Int, uuid: UUID): PersistedNote?
+    fun update(userId: Int, uuid: UUID, note: Note): PersistedNote?
+    fun export(userId: Int): List<ExportedNote>
+    fun findAllDetails(userId: Int): List<PersistedNote>
+
+    fun makePublic(userId: Int, uuid: UUID): Boolean
+    fun makePrivate(userId: Int, uuid: UUID): Boolean
+    fun findPublic(uuid: UUID): PersistedNote?
+}

simplenotes-domain/src/main/kotlin/usecases/repositories/UserRepository.kt

@@ -0,0 +1,14 @@
+package be.simplenotes.domain.usecases.repositories
+
+import be.simplenotes.domain.model.PersistedUser
+import be.simplenotes.domain.model.User
+
+interface UserRepository {
+    fun create(user: User): PersistedUser?
+    fun find(username: String): PersistedUser?
+    fun find(id: Int): PersistedUser?
+    fun exists(username: String): Boolean
+    fun exists(id: Int): Boolean
+    fun delete(id: Int): Boolean
+    fun findAll(): List<Int>
+}

simplenotes-domain/src/main/kotlin/usecases/search/SearchUseCase.kt

@@ -0,0 +1,17 @@
+package be.simplenotes.domain.usecases.search
+
+import be.simplenotes.domain.model.PersistedNote
+import be.simplenotes.domain.model.PersistedNoteMetadata
+import java.util.*
+
+data class SearchTerms(val title: String?, val tag: String?, val content: String?, val all: String?)
+
+interface NoteSearcher {
+    fun indexNote(userId: Int, note: PersistedNote)
+    fun indexNotes(userId: Int, notes: List<PersistedNote>)
+    fun deleteIndex(userId: Int, uuid: UUID)
+    fun updateIndex(userId: Int, note: PersistedNote)
+    fun search(userId: Int, terms: SearchTerms): List<PersistedNoteMetadata>
+    fun dropIndex(userId: Int)
+    fun dropAll()
+}

simplenotes-domain/src/main/kotlin/usecases/users/delete/DeleteUseCaseImpl.kt

@@ -0,0 +1,27 @@
+package be.simplenotes.domain.usecases.users.delete
+
+import arrow.core.Either
+import arrow.core.extensions.fx
+import arrow.core.rightIfNotNull
+import be.simplenotes.domain.security.PasswordHash
+import be.simplenotes.domain.usecases.repositories.UserRepository
+import be.simplenotes.domain.usecases.search.NoteSearcher
+import be.simplenotes.domain.validation.UserValidations
+
+internal class DeleteUseCaseImpl(
+    private val userRepository: UserRepository,
+    private val passwordHash: PasswordHash,
+    private val searcher: NoteSearcher,
+    ) : DeleteUseCase {
+    override fun delete(form: DeleteForm) = Either.fx<DeleteError, Unit> {
+        val user = !UserValidations.validateDelete(form)
+        val persistedUser = !userRepository.find(user.username).rightIfNotNull { DeleteError.Unregistered }
+        !Either.cond(
+            passwordHash.verify(user.password, persistedUser.password),
+            { Unit },
+            { DeleteError.WrongPassword }
+        )
+        !Either.cond(userRepository.delete(persistedUser.id), { Unit }, { DeleteError.Unregistered })
+        searcher.dropIndex(persistedUser.id)
+    }
+}

simplenotes-domain/src/main/kotlin/usecases/users/delete/DeleteUsecase.kt

@@ -0,0 +1,16 @@
+package be.simplenotes.domain.usecases.users.delete
+
+import arrow.core.Either
+import io.konform.validation.ValidationErrors
+
+sealed class DeleteError {
+    object Unregistered : DeleteError()
+    object WrongPassword : DeleteError()
+    class InvalidForm(val validationErrors: ValidationErrors) : DeleteError()
+}
+
+data class DeleteForm(val username: String?, val password: String?, val checked: Boolean)
+
+interface DeleteUseCase {
+    fun delete(form: DeleteForm): Either<DeleteError, Unit>
+}

simplenotes-domain/src/main/kotlin/usecases/users/login/LoginUseCaseImpl.kt

@@ -0,0 +1,25 @@
+package be.simplenotes.domain.usecases.users.login
+
+import arrow.core.Either
+import arrow.core.extensions.fx
+import arrow.core.filterOrElse
+import arrow.core.rightIfNotNull
+import be.simplenotes.domain.security.JwtPayload
+import be.simplenotes.domain.security.PasswordHash
+import be.simplenotes.domain.security.SimpleJwt
+import be.simplenotes.domain.usecases.repositories.UserRepository
+import be.simplenotes.domain.validation.UserValidations
+
+internal class LoginUseCaseImpl(
+    private val userRepository: UserRepository,
+    private val passwordHash: PasswordHash,
+    private val jwt: SimpleJwt
+) : LoginUseCase {
+    override fun login(form: LoginForm) = Either.fx<LoginError, Token> {
+        val user = !UserValidations.validateLogin(form)
+        !userRepository.find(user.username)
+            .rightIfNotNull { Unregistered }
+            .filterOrElse({ passwordHash.verify(form.password!!, it.password) }, { WrongPassword })
+            .map { jwt.sign(JwtPayload(it)) }
+    }
+}

simplenotes-domain/src/main/kotlin/usecases/users/login/LoginUsecase.kt

@@ -0,0 +1,19 @@
+package be.simplenotes.domain.usecases.users.login
+
+import arrow.core.Either
+import io.konform.validation.ValidationErrors
+import kotlinx.serialization.Serializable
+
+sealed class LoginError
+object Unregistered : LoginError()
+object WrongPassword : LoginError()
+class InvalidLoginForm(val validationErrors: ValidationErrors) : LoginError()
+
+typealias Token = String
+
+@Serializable
+data class LoginForm(val username: String?, val password: String?)
+
+interface LoginUseCase {
+    fun login(form: LoginForm): Either<LoginError, Token>
+}

simplenotes-domain/src/main/kotlin/usecases/users/register/RegisterUseCaseImpl.kt

@@ -0,0 +1,22 @@
+package be.simplenotes.domain.usecases.users.register
+
+import arrow.core.Either
+import arrow.core.filterOrElse
+import arrow.core.leftIfNull
+import be.simplenotes.domain.model.PersistedUser
+import be.simplenotes.domain.security.PasswordHash
+import be.simplenotes.domain.usecases.repositories.UserRepository
+import be.simplenotes.domain.validation.UserValidations
+
+internal class RegisterUseCaseImpl(
+    private val userRepository: UserRepository,
+    private val passwordHash: PasswordHash
+) : RegisterUseCase {
+    override fun register(form: RegisterForm): Either<RegisterError, PersistedUser> {
+        return UserValidations.validateRegister(form)
+            .filterOrElse({ !userRepository.exists(it.username) }, { UserExists })
+            .map { it.copy(password = passwordHash.crypt(it.password)) }
+            .map { userRepository.create(it) }
+            .leftIfNull { UserExists }
+    }
+}

simplenotes-domain/src/main/kotlin/usecases/users/register/RegisterUsecase.kt

@@ -0,0 +1,16 @@
+package be.simplenotes.domain.usecases.users.register
+
+import arrow.core.Either
+import be.simplenotes.domain.model.PersistedUser
+import be.simplenotes.domain.usecases.users.login.LoginForm
+import io.konform.validation.ValidationErrors
+
+sealed class RegisterError
+object UserExists : RegisterError()
+class InvalidRegisterForm(val validationErrors: ValidationErrors) : RegisterError()
+
+typealias RegisterForm = LoginForm
+
+interface RegisterUseCase {
+    fun register(form: RegisterForm): Either<RegisterError, PersistedUser>
+}

simplenotes-domain/src/main/kotlin/validation/NoteValidations.kt

@@ -0,0 +1,36 @@
+package be.simplenotes.domain.validation
+
+import arrow.core.*
+import be.simplenotes.domain.model.NoteMetadata
+import be.simplenotes.domain.usecases.markdown.ValidationError
+import io.konform.validation.Validation
+import io.konform.validation.jsonschema.maxItems
+import io.konform.validation.jsonschema.maxLength
+import io.konform.validation.jsonschema.uniqueItems
+
+internal object NoteValidations {
+    private val metaValidator = Validation<NoteMetadata> {
+        NoteMetadata::title required {
+            addConstraint("must not be blank") { it.isNotBlank() }
+            maxLength(50)
+        }
+        NoteMetadata::tags required {
+            maxItems(5)
+            uniqueItems(true)
+        }
+
+        NoteMetadata::tags onEach {
+            maxLength(15)
+            addConstraint("must not be blank") { it.isNotBlank() }
+            addConstraint("must only contain alphanumeric characters, `-` and `_`") {
+                it.matches("^[a-zA-Z0-9-_]+\$".toRegex())
+            }
+        }
+    }
+
+    fun validateMetadata(meta: NoteMetadata): Option<ValidationError> {
+        val errors = metaValidator.validate(meta).errors
+        return if (errors.isEmpty()) none()
+        else return ValidationError(errors).some()
+    }
+}

simplenotes-domain/src/main/kotlin/validation/UserValidations.kt

@@ -0,0 +1,60 @@
+package be.simplenotes.domain.validation
+
+import arrow.core.Either
+import arrow.core.left
+import arrow.core.right
+import be.simplenotes.domain.model.User
+import be.simplenotes.domain.usecases.users.delete.DeleteError
+import be.simplenotes.domain.usecases.users.delete.DeleteForm
+import be.simplenotes.domain.usecases.users.login.InvalidLoginForm
+import be.simplenotes.domain.usecases.users.login.LoginForm
+import be.simplenotes.domain.usecases.users.register.InvalidRegisterForm
+import be.simplenotes.domain.usecases.users.register.RegisterForm
+import io.konform.validation.Validation
+import io.konform.validation.jsonschema.maxLength
+import io.konform.validation.jsonschema.minLength
+
+internal object UserValidations {
+    private val loginValidator = Validation<LoginForm> {
+        LoginForm::username required {
+            minLength(3)
+            maxLength(50)
+        }
+        LoginForm::password required {
+            minLength(8)
+            maxLength(72) // jbcrypt limit, see https://security.stackexchange.com/a/39851
+        }
+    }
+
+    fun validateLogin(form: LoginForm): Either<InvalidLoginForm, User> {
+        val errors = loginValidator.validate(form).errors
+        return if (errors.isEmpty()) User(form.username!!, form.password!!).right()
+        else return InvalidLoginForm(errors).left()
+    }
+
+    fun validateRegister(form: RegisterForm): Either<InvalidRegisterForm, User> {
+        val errors = loginValidator.validate(form).errors
+        return if (errors.isEmpty()) User(form.username!!, form.password!!).right()
+        else return InvalidRegisterForm(errors).left()
+    }
+
+    private val deleteValidator = Validation<DeleteForm> {
+        DeleteForm::username required {
+            minLength(3)
+            maxLength(50)
+        }
+        DeleteForm::password required {
+            minLength(8)
+            maxLength(72)
+        }
+        DeleteForm::checked required {
+            addConstraint("Should be checked") { it }
+        }
+    }
+
+    fun validateDelete(form: DeleteForm): Either<DeleteError.InvalidForm, User> {
+        val errors = deleteValidator.validate(form).errors
+        return if (errors.isEmpty()) User(form.username!!, form.password!!).right()
+        else return DeleteError.InvalidForm(errors).left()
+    }
+}

simplenotes-domain/src/test/kotlin/Empty.kt

@@ -0,0 +1,5 @@
+package be.simplenotes.domain
+
+/**
+ * Empty file @see [root-package-declaration](https://discuss.kotlinlang.org/t/root-package-declaration-to-reduce-folder-clutter/2247/4)
+ */

simplenotes-domain/src/test/kotlin/security/JwtPayloadExtractorTest.kt

@@ -0,0 +1,50 @@
+package be.simplenotes.domain.security
+
+import be.simplenotes.domain.usecases.users.login.Token
+import be.simplenotes.shared.config.JwtConfig
+import com.auth0.jwt.JWT
+import com.auth0.jwt.algorithms.Algorithm
+import com.natpryce.hamkrest.absent
+import com.natpryce.hamkrest.assertion.assertThat
+import com.natpryce.hamkrest.equalTo
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.params.ParameterizedTest
+import org.junit.jupiter.params.provider.MethodSource
+import java.util.concurrent.TimeUnit
+import java.util.stream.Stream
+
+internal class JwtPayloadExtractorTest {
+    private val jwtConfig = JwtConfig("a secret", 1, TimeUnit.HOURS)
+    private val simpleJwt = SimpleJwt(jwtConfig)
+    private val jwtPayloadExtractor = JwtPayloadExtractor(simpleJwt)
+
+    private fun createToken(username: String? = null, id: Int? = null, secret: String = jwtConfig.secret): Token {
+        val algo = Algorithm.HMAC256(secret)
+        return JWT.create().apply {
+            username?.let { withClaim(usernameField, it) }
+            id?.let { withClaim(userIdField, it) }
+        }.sign(algo)
+    }
+
+    @Suppress("Unused")
+    private fun invalidTokens() = Stream.of(
+        createToken(id = 1),
+        createToken(username = "user"),
+        createToken(),
+        createToken(username = "user", id = 1, secret = "not the correct secret"),
+        createToken(username = "user", id = 1) + "\"efesfsef",
+        "something that is not even a token"
+    )
+
+    @ParameterizedTest(name = "[{index}] token `{0}` should be invalid")
+    @MethodSource("invalidTokens")
+    fun `parse invalid tokens`(token: String) {
+        assertThat(jwtPayloadExtractor(token), absent())
+    }
+
+    @Test
+    fun `parse valid token`() {
+        val token = createToken(username = "someone", id = 1)
+        assertThat(jwtPayloadExtractor(token), equalTo(JwtPayload(1, "someone")))
+    }
+}

simplenotes-domain/src/test/kotlin/usecases/users/login/LoginUseCaseImplTest.kt

@@ -0,0 +1,64 @@
+package be.simplenotes.domain.usecases.users.login
+
+import be.simplenotes.domain.model.PersistedUser
+import be.simplenotes.domain.security.BcryptPasswordHash
+import be.simplenotes.domain.security.SimpleJwt
+import be.simplenotes.domain.usecases.repositories.UserRepository
+import be.simplenotes.shared.config.JwtConfig
+import be.simplenotes.shared.testutils.assertions.isLeftOfType
+import be.simplenotes.shared.testutils.assertions.isRight
+import com.natpryce.hamkrest.assertion.assertThat
+import io.mockk.*
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import java.util.concurrent.TimeUnit
+
+internal class LoginUseCaseImplTest {
+    // region setup
+    private val mockUserRepository = mockk<UserRepository>()
+    private val passwordHash = BcryptPasswordHash(test = true)
+    private val jwtConfig = JwtConfig("a secret", 1, TimeUnit.HOURS)
+    private val simpleJwt = SimpleJwt(jwtConfig)
+    private val loginUseCase = LoginUseCaseImpl(mockUserRepository, passwordHash, simpleJwt)
+
+    @BeforeEach
+    fun resetMocks() {
+        clearMocks(mockUserRepository)
+    }
+    // endregion
+
+    @Test
+    fun `Login should fail with invalid form`() {
+        val form = LoginForm("", "a")
+        assertThat(loginUseCase.login(form), isLeftOfType<InvalidLoginForm>())
+        verify { mockUserRepository wasNot called }
+    }
+
+    @Test
+    fun `Login should fail with non existing user`() {
+        val form = LoginForm("someusername", "somepassword")
+        every { mockUserRepository.find(form.username!!) } returns null
+        assertThat(loginUseCase.login(form), isLeftOfType<Unregistered>())
+    }
+
+    @Test
+    fun `Login should fail with wrong password`() {
+        val form = LoginForm("someusername", "wrongpassword")
+
+        every { mockUserRepository.find(form.username!!) } returns
+            PersistedUser(form.username!!, passwordHash.crypt("right password"), 1)
+
+        assertThat(loginUseCase.login(form), isLeftOfType<WrongPassword>())
+    }
+
+    @Test
+    fun `Login should succeed with existing user and correct password`() {
+        val loginForm = LoginForm("someusername", "somepassword")
+
+        every { mockUserRepository.find(loginForm.username!!) } returns
+            PersistedUser(loginForm.username!!, passwordHash.crypt(loginForm.password!!), 1)
+
+        val res = loginUseCase.login(loginForm)
+        assertThat(res, isRight())
+    }
+}

simplenotes-domain/src/test/kotlin/usecases/users/register/RegisterUseCaseImplTest.kt

@@ -0,0 +1,50 @@
+package be.simplenotes.domain.usecases.users.register
+
+import be.simplenotes.domain.model.PersistedUser
+import be.simplenotes.domain.security.BcryptPasswordHash
+import be.simplenotes.domain.usecases.repositories.UserRepository
+import be.simplenotes.shared.testutils.assertions.isLeftOfType
+import be.simplenotes.shared.testutils.assertions.isRight
+import com.natpryce.hamkrest.assertion.assertThat
+import com.natpryce.hamkrest.equalTo
+import io.mockk.*
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+
+internal class RegisterUseCaseImplTest {
+
+    // region setup
+    private val mockUserRepository = mockk<UserRepository>()
+    private val passwordHash = BcryptPasswordHash(test = true)
+    private val registerUseCase = RegisterUseCaseImpl(mockUserRepository, passwordHash)
+
+    @BeforeEach
+    fun resetMocks() {
+        clearMocks(mockUserRepository)
+    }
+    // endregion
+
+    @Test
+    fun `register should fail with invalid form`() {
+        val form = RegisterForm("", "a".repeat(10))
+        assertThat(registerUseCase.register(form), isLeftOfType<InvalidRegisterForm>())
+        verify { mockUserRepository wasNot called }
+    }
+
+    @Test
+    fun `Register should fail with existing username`() {
+        val form = RegisterForm("someuser", "somepassword")
+        every { mockUserRepository.exists(form.username!!) } returns true
+        assertThat(registerUseCase.register(form), isLeftOfType<UserExists>())
+    }
+
+    @Test
+    fun `Register should succeed with new user`() {
+        val form = RegisterForm("someuser", "somepassword")
+        every { mockUserRepository.exists(form.username!!) } returns false
+        every { mockUserRepository.create(any()) } returns PersistedUser(form.username!!, form.password!!, 1)
+        val res = registerUseCase.register(form)
+        assertThat(res, isRight())
+        res.map { assertThat(it.username, equalTo(form.username)) }
+    }
+}

simplenotes-domain/src/test/kotlin/validation/UserValidationsTest.kt

@@ -0,0 +1,77 @@
+package be.simplenotes.domain.validation
+
+import be.simplenotes.domain.usecases.users.login.InvalidLoginForm
+import be.simplenotes.domain.usecases.users.login.LoginForm
+import be.simplenotes.domain.usecases.users.register.RegisterForm
+import be.simplenotes.shared.testutils.assertions.isLeftOfType
+import be.simplenotes.shared.testutils.assertions.isRight
+import com.natpryce.hamkrest.assertion.assertThat
+import org.junit.jupiter.api.Nested
+import org.junit.jupiter.params.ParameterizedTest
+import org.junit.jupiter.params.provider.MethodSource
+import java.util.stream.Stream
+
+internal class UserValidationsTest {
+
+    @Nested
+    inner class Login {
+
+        @Suppress("Unused")
+        fun invalidLoginForms(): Stream<LoginForm> = Stream.of(
+            LoginForm(username = null, password = null),
+            LoginForm(username = "", password = ""),
+            LoginForm(username = "a", password = "aaaa"),
+            LoginForm(username = "a".repeat(51), password = "a".repeat(8)),
+            LoginForm(username = "a".repeat(10), password = "a".repeat(7))
+        )
+
+        @ParameterizedTest
+        @MethodSource("invalidLoginForms")
+        fun `validate invalid logins`(form: LoginForm) {
+            assertThat(UserValidations.validateLogin(form), isLeftOfType<InvalidLoginForm>())
+        }
+
+        @Suppress("Unused")
+        fun validLoginForms(): Stream<LoginForm> = Stream.of(
+            LoginForm(username = "a".repeat(50), password = "a".repeat(72)),
+            LoginForm(username = "a".repeat(3), password = "a".repeat(8))
+        )
+
+        @ParameterizedTest
+        @MethodSource("validLoginForms")
+        fun `validate valid logins`(form: LoginForm) {
+            assertThat(UserValidations.validateLogin(form), isRight())
+        }
+    }
+
+    @Nested
+    inner class Register {
+
+        @Suppress("Unused")
+        fun invalidRegisterForms(): Stream<RegisterForm> = Stream.of(
+            RegisterForm(username = null, password = null),
+            RegisterForm(username = "", password = ""),
+            RegisterForm(username = "a", password = "aaaa"),
+            RegisterForm(username = "a".repeat(51), password = "a".repeat(8)),
+            RegisterForm(username = "a".repeat(10), password = "a".repeat(7))
+        )
+
+        @ParameterizedTest
+        @MethodSource("invalidRegisterForms")
+        fun `validate invalid register`(form: LoginForm) {
+            assertThat(UserValidations.validateLogin(form), isLeftOfType<InvalidLoginForm>())
+        }
+
+        @Suppress("Unused")
+        fun validRegisterForms(): Stream<RegisterForm> = Stream.of(
+            RegisterForm(username = "a".repeat(50), password = "a".repeat(72)),
+            RegisterForm(username = "a".repeat(3), password = "a".repeat(8))
+        )
+
+        @ParameterizedTest
+        @MethodSource("validRegisterForms")
+        fun `validate valid register`(form: LoginForm) {
+            assertThat(UserValidations.validateLogin(form), isRight())
+        }
+    }
+}