Add ReserveSlotUseCase

Implemented second use case responsible for slot reservation.
Implemented reservation-rules in domain model.

src/main/kotlin/eu/kowalcze/michal/arch/clean/example/domain/model/DaySchedule.kt

@@ -7,16 +7,44 @@ import java.time.LocalTime
 data class DaySchedule(
     val day: LocalDate,
     val slots: List<Slot>,
-)
+) {
+
+    fun reserveSlot(index: Int): DaySchedule {
+        verifyIndexIsValid(index)
+
+        if (slots[index].reserved) {
+            throw SlotAlreadyReservedException(index)
+        }
+
+        val modifiedSlots = slots.toMutableList()
+        modifiedSlots.set(index, slots[index].makeReservation())
+        return copy(slots = modifiedSlots)
+    }
+
+    private fun verifyIndexIsValid(index: Int) {
+        if (index < 0 || index >= slots.size) {
+            throw InvalidSlotIndexException(index, slots.size)
+        }
+    }
+
+
+}
 
 data class Slot(
-    val occupied: Boolean,
+    val reserved: Boolean,
     val start: LocalTime,
     val end: LocalTime,
-)
+) {
+    fun makeReservation(): Slot = copy(reserved = true)
+}
 
 
 data class SlotId(
     val day: LocalDate,
     val index: Int,
-)
+)
+
+class InvalidSlotIndexException(index: Int, slotsCount: Int) :
+    IllegalArgumentException("Slot[$index] is not available. Slots count is: $slotsCount")
+
+class SlotAlreadyReservedException(index: Int) : IllegalStateException("Slot[$index] is already reserved")

src/main/kotlin/eu/kowalcze/michal/arch/clean/example/domain/usecase/ReserveSlotUseCase.kt

@@ -0,0 +1,20 @@
+package eu.kowalcze.michal.arch.clean.example.domain.usecase
+
+import eu.kowalcze.michal.arch.clean.example.domain.model.DaySchedule
+import eu.kowalcze.michal.arch.clean.example.domain.model.SlotId
+import eu.kowalcze.michal.arch.clean.example.domain.repository.DayScheduleRepository
+
+class ReserveSlotUseCase(
+    private val dayScheduleRepository: DayScheduleRepository,
+    private val getScheduleUseCase: GetScheduleUseCase,
+) {
+
+    fun reserve(slotId: SlotId): DaySchedule {
+        val daySchedule = getScheduleUseCase.getSchedule(scheduleDay = slotId.day)
+
+        val modifiedSchedule = daySchedule.reserveSlot(slotId.index)
+
+        return dayScheduleRepository.save(modifiedSchedule)
+    }
+}
+

src/test/kotlin/eu/kowalcze/michal/arch/clean/example/domain/model/DayScheduleTest.kt

@@ -0,0 +1,53 @@
+package eu.kowalcze.michal.arch.clean.example.domain.model
+
+import io.kotest.assertions.throwables.shouldThrow
+import io.kotest.matchers.shouldBe
+import org.junit.jupiter.api.Test
+import java.time.LocalDate
+import java.time.LocalTime
+
+internal class DayScheduleTest {
+
+    @Test
+    fun `Should reserve a slot`() {
+        // given
+        val today = LocalDate.now()
+        val givenSchedule =
+            DaySchedule(today, listOf(Slot(reserved = false, start = LocalTime.MIN, end = LocalTime.MAX)))
+
+
+        // when
+        val daySchedule = givenSchedule.reserveSlot(0)
+
+        // then
+        daySchedule.slots[0].reserved shouldBe true
+    }
+
+    @Test
+    fun `Should fail when slot is already reserved`() {
+        // given
+        val today = LocalDate.now()
+        val givenSchedule =
+            DaySchedule(today, listOf(Slot(reserved = true, start = LocalTime.MIN, end = LocalTime.MAX)))
+
+        // expect
+        val exception =
+            shouldThrow<SlotAlreadyReservedException> { givenSchedule.reserveSlot(0) }
+
+        exception.message shouldBe "Slot[0] is already reserved"
+    }
+
+    @Test
+    fun `Should fail when slot index is out of `() {
+        // given
+        val today = LocalDate.now()
+        val givenSchedule =
+            DaySchedule(today, listOf(Slot(reserved = true, start = LocalTime.MIN, end = LocalTime.MAX)))
+
+        // expect
+        val exception =
+            shouldThrow<InvalidSlotIndexException> { givenSchedule.reserveSlot(1) }
+
+        exception.message shouldBe "Slot[1] is not available. Slots count is: 1"
+    }
+}

src/test/kotlin/eu/kowalcze/michal/arch/clean/example/domain/usecase/ReserveSlotUseCaseTest.kt

@@ -0,0 +1,48 @@
+package eu.kowalcze.michal.arch.clean.example.domain.usecase
+
+import eu.kowalcze.michal.arch.clean.example.domain.model.DaySchedule
+import eu.kowalcze.michal.arch.clean.example.domain.model.DayScheduleCreator
+import eu.kowalcze.michal.arch.clean.example.domain.model.Slot
+import eu.kowalcze.michal.arch.clean.example.domain.model.SlotId
+import eu.kowalcze.michal.arch.clean.example.infrastructure.InMemoryDayScheduleRepository
+import io.kotest.matchers.shouldBe
+import io.kotest.matchers.types.shouldBeSameInstanceAs
+import io.mockk.every
+import io.mockk.mockk
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import java.time.LocalDate
+import java.time.LocalTime
+
+internal class ReserveSlotUseCaseTest {
+    private lateinit var daySchedulerRepository: InMemoryDayScheduleRepository
+    private lateinit var dayScheduleCreator: DayScheduleCreator
+    private lateinit var getScheduleUseCase: GetScheduleUseCase
+    private lateinit var reserveSlotUseCase: ReserveSlotUseCase
+
+    @BeforeEach
+    fun setup() {
+        dayScheduleCreator = mockk(relaxed = true)
+        daySchedulerRepository = InMemoryDayScheduleRepository()
+        getScheduleUseCase = GetScheduleUseCase(daySchedulerRepository, dayScheduleCreator)
+        reserveSlotUseCase = ReserveSlotUseCase(daySchedulerRepository, getScheduleUseCase)
+    }
+
+    @Test
+    fun `Should reserve a slot`() {
+        // given
+        val today = LocalDate.now()
+        val givenSchedule =
+            DaySchedule(today, listOf(Slot(reserved = false, start = LocalTime.MIN, end = LocalTime.MAX)))
+        every { dayScheduleCreator.create(today) }.returns(givenSchedule)
+
+        // when
+        val daySchedule = reserveSlotUseCase.reserve(SlotId(today, index = 0))
+
+        // then
+        daySchedule.slots[0].reserved shouldBe true
+        daySchedulerRepository.itemsCount() shouldBe 1
+        daySchedulerRepository.get(today) shouldBeSameInstanceAs daySchedule
+    }
+
+}