OrderBookService implemented and tested

src/main/kotlin/com/frankenergie/smartasset/domain/OrderBook.kt

@@ -0,0 +1,92 @@
+package com.frankenergie.smartasset.domain
+
+import com.frankenergie.smartasset.model.DeliveryPeriod
+import com.frankenergie.smartasset.model.OrderSide
+import java.math.BigDecimal
+import java.util.TreeMap
+import java.util.concurrent.ConcurrentHashMap
+
+data class PriceLevel(
+    val price: BigDecimal,
+    val quantity: BigDecimal
+)
+
+class OrderBook {
+
+    private val bidsPerPeriod: ConcurrentHashMap<DeliveryPeriod, TreeMap<BigDecimal, BigDecimal>> = ConcurrentHashMap()
+    private val asksPerPeriod: ConcurrentHashMap<DeliveryPeriod, TreeMap<BigDecimal, BigDecimal>> = ConcurrentHashMap()
+
+    fun processOrder(period: DeliveryPeriod, side: OrderSide, quantity: BigDecimal, price: BigDecimal): BigDecimal {
+        val bids = bidsPerPeriod.computeIfAbsent(period) { TreeMap(Comparator.reverseOrder()) }
+        val asks = asksPerPeriod.computeIfAbsent(period) { TreeMap() }
+
+        return when (side) {
+            OrderSide.BUY -> processBuyOrder(bids, asks, quantity, price)
+            OrderSide.SELL -> processSellOrder(bids, asks, quantity, price)
+        }
+    }
+
+    private fun processBuyOrder(
+        bids: TreeMap<BigDecimal, BigDecimal>,
+        asks: TreeMap<BigDecimal, BigDecimal>,
+        quantity: BigDecimal,
+        price: BigDecimal
+    ): BigDecimal {
+        var remaining = quantity
+
+        val iterator = asks.entries.iterator()
+        while (iterator.hasNext() && remaining > BigDecimal.ZERO) {
+            val (askPrice, askQty) = iterator.next()
+            if (askPrice > price) break
+
+            val matched = remaining.min(askQty)
+            remaining -= matched
+            val newQty = askQty - matched
+            if (newQty <= BigDecimal.ZERO) iterator.remove() else asks[askPrice] = newQty
+        }
+
+        if (remaining > BigDecimal.ZERO) {
+            bids.merge(price, remaining) { old, new -> old + new }
+        }
+
+        return quantity - remaining
+    }
+
+    private fun processSellOrder(
+        bids: TreeMap<BigDecimal, BigDecimal>,
+        asks: TreeMap<BigDecimal, BigDecimal>,
+        quantity: BigDecimal,
+        price: BigDecimal
+    ): BigDecimal {
+        var remaining = quantity
+
+        val iterator = bids.entries.iterator()
+        while (iterator.hasNext() && remaining > BigDecimal.ZERO) {
+            val (bidPrice, bidQty) = iterator.next()
+            if (bidPrice < price) break
+
+            val matched = remaining.min(bidQty)
+            remaining -= matched
+            val newQty = bidQty - matched
+            if (newQty <= BigDecimal.ZERO) iterator.remove() else bids[bidPrice] = newQty
+        }
+
+        if (remaining > BigDecimal.ZERO) {
+            asks.merge(price, remaining) { old, new -> old + new }
+        }
+
+        return quantity - remaining
+    }
+
+    fun getBids(period: DeliveryPeriod): Map<BigDecimal, BigDecimal> = bidsPerPeriod[period]?.toMap() ?: emptyMap()
+
+    fun getAsks(period: DeliveryPeriod): Map<BigDecimal, BigDecimal> = asksPerPeriod[period]?.toMap() ?: emptyMap()
+
+    fun getBestBid(period: DeliveryPeriod): PriceLevel? =
+        bidsPerPeriod[period]?.firstEntry()?.let { PriceLevel(it.key, it.value) }
+
+    fun getBestAsk(period: DeliveryPeriod): PriceLevel? =
+        asksPerPeriod[period]?.firstEntry()?.let { PriceLevel(it.key, it.value) }
+
+    fun getAllPeriods(): Set<DeliveryPeriod> = bidsPerPeriod.keys + asksPerPeriod.keys
+}

src/main/kotlin/com/frankenergie/smartasset/model/DeliveryPeriod.kt

@@ -0,0 +1,8 @@
+package com.frankenergie.smartasset.model
+
+import java.time.LocalDateTime
+
+data class DeliveryPeriod(
+    val startTime: LocalDateTime,
+    val endTime: LocalDateTime
+)

src/main/kotlin/com/frankenergie/smartasset/model/DeliveryQuarter.kt

@@ -0,0 +1,28 @@
+package com.frankenergie.smartasset.model
+
+import java.time.LocalDateTime
+import java.time.temporal.ChronoUnit
+
+data class DeliveryQuarter(
+    val startTime: LocalDateTime
+) {
+    val endTime: LocalDateTime = startTime.plusMinutes(15)
+
+    companion object {
+        fun from(dateTime: LocalDateTime): DeliveryQuarter {
+            val minute = (dateTime.minute / 15) * 15
+            val truncated = dateTime.truncatedTo(ChronoUnit.HOURS).plusMinutes(minute.toLong())
+            return DeliveryQuarter(truncated)
+        }
+
+        fun fromRange(start: LocalDateTime, end: LocalDateTime): List<DeliveryQuarter> {
+            val quarters = mutableListOf<DeliveryQuarter>()
+            var current = from(start)
+            while (current.startTime < end) {
+                quarters.add(current)
+                current = DeliveryQuarter(current.endTime)
+            }
+            return quarters
+        }
+    }
+}

src/main/kotlin/com/frankenergie/smartasset/model/Order.kt

@@ -0,0 +1,19 @@
+package com.frankenergie.smartasset.model
+
+import java.math.BigDecimal
+import java.time.Instant
+import java.time.LocalDateTime
+
+data class Order(
+    val orderId: String,
+    val deliveryStartTime: LocalDateTime,
+    val deliveryEndTime: LocalDateTime,
+    val orderSide: OrderSide,
+    val originalQuantity: BigDecimal,
+    var remainingQuantity: BigDecimal,
+    val price: BigDecimal,
+    val createdAt: Instant
+) {
+    val isFilled: Boolean
+        get() = remainingQuantity.compareTo(BigDecimal.ZERO) == 0
+}

src/main/kotlin/com/frankenergie/smartasset/model/Trade.kt

@@ -0,0 +1,14 @@
+package com.frankenergie.smartasset.model
+
+import java.math.BigDecimal
+import java.time.Instant
+import java.time.LocalDateTime
+
+data class Trade(
+    val tradeId: String,
+    val buyOrderId: String,
+    val sellOrderId: String,
+    val price: BigDecimal,
+    val quantity: BigDecimal,
+    val executedAt: Instant
+)

src/main/kotlin/com/frankenergie/smartasset/service/OrderBookService.kt

@@ -1,5 +1,7 @@
 package com.frankenergie.smartasset.service
 
+import com.frankenergie.smartasset.domain.OrderBook
+import com.frankenergie.smartasset.model.DeliveryPeriod
 import com.frankenergie.smartasset.model.OrderUpdateRequest
 import com.frankenergie.smartasset.model.OrderUpdateResponse
 import org.springframework.stereotype.Service
@@ -9,15 +11,24 @@ import java.util.UUID
 @Service
 class OrderBookService {
 
+    private val orderBook = OrderBook()
+
     fun processOrder(request: OrderUpdateRequest): OrderUpdateResponse {
         val orderId = UUID.randomUUID().toString()
 
-        // TODO: implement order book logic
+        val period = DeliveryPeriod(request.deliveryStartTime, request.deliveryEndTime)
+        val matchedQuantity = orderBook.processOrder(period, request.orderSide, request.quantity, request.price)
 
-        return OrderUpdateResponse(
-            orderId = orderId,
-            status = "ACCEPTED",
-            timestamp = Instant.now()
-        )
+        val status = when {
+            matchedQuantity == request.quantity -> "FILLED"
+            matchedQuantity > java.math.BigDecimal.ZERO -> "PARTIALLY_FILLED"
+            else -> "ACCEPTED"
+        }
+
+        // TODO: write this to a file
+
+        return OrderUpdateResponse(orderId = orderId, status = status, timestamp = Instant.now())
     }
+
+    fun getOrderBook(): OrderBook = orderBook
 }

src/test/kotlin/com/frankenergie/smartasset/domain/OrderBookTest.kt

@@ -0,0 +1,188 @@
+package com.frankenergie.smartasset.domain
+
+import com.frankenergie.smartasset.model.DeliveryPeriod
+import com.frankenergie.smartasset.model.OrderSide
+import org.junit.jupiter.api.Assertions.*
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import java.math.BigDecimal
+import java.time.LocalDateTime
+
+class OrderBookTest {
+
+    private lateinit var orderBook: OrderBook
+    private lateinit var period: DeliveryPeriod
+
+    @BeforeEach
+    fun setUp() {
+        orderBook = OrderBook()
+        period = DeliveryPeriod(
+            LocalDateTime.of(2024, 1, 15, 10, 0),
+            LocalDateTime.of(2024, 1, 15, 10, 15)
+        )
+    }
+
+    @Test
+    fun `buy order added to empty book`() {
+        val matched = orderBook.processOrder(period, OrderSide.BUY, BigDecimal("10"), BigDecimal("50.00"))
+
+        assertEquals(BigDecimal.ZERO, matched)
+        assertEquals(BigDecimal("10"), orderBook.getBids(period)[BigDecimal("50.00")])
+        assertTrue(orderBook.getAsks(period).isEmpty())
+    }
+
+    @Test
+    fun `sell order added to empty book`() {
+        val matched = orderBook.processOrder(period, OrderSide.SELL, BigDecimal("10"), BigDecimal("55.00"))
+
+        assertEquals(BigDecimal.ZERO, matched)
+        assertEquals(BigDecimal("10"), orderBook.getAsks(period)[BigDecimal("55.00")])
+        assertTrue(orderBook.getBids(period).isEmpty())
+    }
+
+    @Test
+    fun `buy order does not match higher priced sell order`() {
+        orderBook.processOrder(period, OrderSide.SELL, BigDecimal("10"), BigDecimal("55.00"))
+        val matched = orderBook.processOrder(period, OrderSide.BUY, BigDecimal("5"), BigDecimal("50.00"))
+
+        assertEquals(BigDecimal.ZERO, matched)
+        assertEquals(BigDecimal("10"), orderBook.getAsks(period)[BigDecimal("55.00")])
+        assertEquals(BigDecimal("5"), orderBook.getBids(period)[BigDecimal("50.00")])
+    }
+
+    @Test
+    fun `buy order fully matches equal priced sell order`() {
+        orderBook.processOrder(period, OrderSide.SELL, BigDecimal("10"), BigDecimal("50.00"))
+        val matched = orderBook.processOrder(period, OrderSide.BUY, BigDecimal("10"), BigDecimal("50.00"))
+
+        assertEquals(BigDecimal("10"), matched)
+        assertTrue(orderBook.getAsks(period).isEmpty())
+        assertTrue(orderBook.getBids(period).isEmpty())
+    }
+
+    @Test
+    fun `buy order fully matches lower priced sell order`() {
+        orderBook.processOrder(period, OrderSide.SELL, BigDecimal("10"), BigDecimal("48.00"))
+        val matched = orderBook.processOrder(period, OrderSide.BUY, BigDecimal("10"), BigDecimal("50.00"))
+
+        assertEquals(BigDecimal("10"), matched)
+        assertTrue(orderBook.getAsks(period).isEmpty())
+        assertTrue(orderBook.getBids(period).isEmpty())
+    }
+
+    @Test
+    fun `buy order partially matches sell order - remaining added to bids`() {
+        orderBook.processOrder(period, OrderSide.SELL, BigDecimal("10"), BigDecimal("50.00"))
+        val matched = orderBook.processOrder(period, OrderSide.BUY, BigDecimal("15"), BigDecimal("50.00"))
+
+        assertEquals(BigDecimal("10"), matched)
+        assertTrue(orderBook.getAsks(period).isEmpty())
+        assertEquals(BigDecimal("5"), orderBook.getBids(period)[BigDecimal("50.00")])
+    }
+
+    @Test
+    fun `buy order partially fills sell order - remaining stays in asks`() {
+        orderBook.processOrder(period, OrderSide.SELL, BigDecimal("15"), BigDecimal("50.00"))
+        val matched = orderBook.processOrder(period, OrderSide.BUY, BigDecimal("10"), BigDecimal("50.00"))
+
+        assertEquals(BigDecimal("10"), matched)
+        assertEquals(BigDecimal("5"), orderBook.getAsks(period)[BigDecimal("50.00")])
+        assertTrue(orderBook.getBids(period).isEmpty())
+    }
+
+    @Test
+    fun `sell order fully matches higher priced buy order`() {
+        orderBook.processOrder(period, OrderSide.BUY, BigDecimal("10"), BigDecimal("55.00"))
+        val matched = orderBook.processOrder(period, OrderSide.SELL, BigDecimal("10"), BigDecimal("50.00"))
+
+        assertEquals(BigDecimal("10"), matched)
+        assertTrue(orderBook.getBids(period).isEmpty())
+        assertTrue(orderBook.getAsks(period).isEmpty())
+    }
+
+    @Test
+    fun `sell order does not match lower priced buy order`() {
+        orderBook.processOrder(period, OrderSide.BUY, BigDecimal("10"), BigDecimal("50.00"))
+        val matched = orderBook.processOrder(period, OrderSide.SELL, BigDecimal("5"), BigDecimal("55.00"))
+
+        assertEquals(BigDecimal.ZERO, matched)
+        assertEquals(BigDecimal("10"), orderBook.getBids(period)[BigDecimal("50.00")])
+        assertEquals(BigDecimal("5"), orderBook.getAsks(period)[BigDecimal("55.00")])
+    }
+
+    @Test
+    fun `buy order matches multiple price levels`() {
+        orderBook.processOrder(period, OrderSide.SELL, BigDecimal("5"), BigDecimal("48.00"))
+        orderBook.processOrder(period, OrderSide.SELL, BigDecimal("5"), BigDecimal("49.00"))
+        orderBook.processOrder(period, OrderSide.SELL, BigDecimal("5"), BigDecimal("52.00"))
+
+        val matched = orderBook.processOrder(period, OrderSide.BUY, BigDecimal("12"), BigDecimal("50.00"))
+
+        assertEquals(BigDecimal("10"), matched)
+        assertEquals(BigDecimal("2"), orderBook.getBids(period)[BigDecimal("50.00")])
+        assertEquals(BigDecimal("5"), orderBook.getAsks(period)[BigDecimal("52.00")])
+    }
+
+    @Test
+    fun `sell order matches multiple price levels`() {
+        orderBook.processOrder(period, OrderSide.BUY, BigDecimal("5"), BigDecimal("52.00"))
+        orderBook.processOrder(period, OrderSide.BUY, BigDecimal("5"), BigDecimal("51.00"))
+        orderBook.processOrder(period, OrderSide.BUY, BigDecimal("5"), BigDecimal("48.00"))
+
+        val matched = orderBook.processOrder(period, OrderSide.SELL, BigDecimal("12"), BigDecimal("50.00"))
+
+        assertEquals(BigDecimal("10"), matched)
+        assertEquals(BigDecimal("2"), orderBook.getAsks(period)[BigDecimal("50.00")])
+        assertEquals(BigDecimal("5"), orderBook.getBids(period)[BigDecimal("48.00")])
+    }
+
+    @Test
+    fun `orders aggregate at same price level`() {
+        orderBook.processOrder(period, OrderSide.BUY, BigDecimal("5"), BigDecimal("50.00"))
+        orderBook.processOrder(period, OrderSide.BUY, BigDecimal("3"), BigDecimal("50.00"))
+
+        assertEquals(BigDecimal("8"), orderBook.getBids(period)[BigDecimal("50.00")])
+    }
+
+    @Test
+    fun `separate order books per delivery period`() {
+        val period1 = DeliveryPeriod(LocalDateTime.of(2024, 1, 15, 10, 0), LocalDateTime.of(2024, 1, 15, 10, 15))
+        val period2 = DeliveryPeriod(LocalDateTime.of(2024, 1, 15, 10, 15), LocalDateTime.of(2024, 1, 15, 10, 30))
+
+        orderBook.processOrder(period1, OrderSide.BUY, BigDecimal("10"), BigDecimal("50.00"))
+        orderBook.processOrder(period2, OrderSide.BUY, BigDecimal("20"), BigDecimal("55.00"))
+
+        assertEquals(BigDecimal("10"), orderBook.getBids(period1)[BigDecimal("50.00")])
+        assertEquals(BigDecimal("20"), orderBook.getBids(period2)[BigDecimal("55.00")])
+    }
+
+    @Test
+    fun `getBestBid returns highest bid`() {
+        orderBook.processOrder(period, OrderSide.BUY, BigDecimal("5"), BigDecimal("50.00"))
+        orderBook.processOrder(period, OrderSide.BUY, BigDecimal("3"), BigDecimal("52.00"))
+
+        val best = orderBook.getBestBid(period)!!
+        assertEquals(BigDecimal("52.00"), best.price)
+        assertEquals(BigDecimal("3"), best.quantity)
+    }
+
+    @Test
+    fun `getBestAsk returns lowest ask`() {
+        orderBook.processOrder(period, OrderSide.SELL, BigDecimal("5"), BigDecimal("55.00"))
+        orderBook.processOrder(period, OrderSide.SELL, BigDecimal("3"), BigDecimal("53.00"))
+
+        val best = orderBook.getBestAsk(period)!!
+        assertEquals(BigDecimal("53.00"), best.price)
+        assertEquals(BigDecimal("3"), best.quantity)
+    }
+
+    @Test
+    fun `getBestBid returns null for empty book`() {
+        assertNull(orderBook.getBestBid(period))
+    }
+
+    @Test
+    fun `getBestAsk returns null for empty book`() {
+        assertNull(orderBook.getBestAsk(period))
+    }
+}

src/test/kotlin/com/frankenergie/smartasset/service/OrderBookServiceTest.kt

@@ -0,0 +1,70 @@
+package com.frankenergie.smartasset.service
+
+import com.frankenergie.smartasset.model.OrderSide
+import com.frankenergie.smartasset.model.OrderUpdateRequest
+import org.junit.jupiter.api.Assertions.*
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import java.math.BigDecimal
+import java.time.LocalDateTime
+
+class OrderBookServiceTest {
+
+    private lateinit var service: OrderBookService
+
+    @BeforeEach
+    fun setUp() {
+        service = OrderBookService()
+    }
+
+    @Test
+    fun `processOrder returns ACCEPTED when no match`() {
+        val request = OrderUpdateRequest(
+            deliveryStartTime = LocalDateTime.of(2024, 1, 15, 10, 0),
+            deliveryEndTime = LocalDateTime.of(2024, 1, 15, 10, 15),
+            orderSide = OrderSide.BUY,
+            quantity = BigDecimal("10"),
+            price = BigDecimal("50.00")
+        )
+
+        val response = service.processOrder(request)
+
+        assertNotNull(response.orderId)
+        assertEquals("ACCEPTED", response.status)
+        assertNotNull(response.timestamp)
+    }
+
+    @Test
+    fun `processOrder returns FILLED when fully matched`() {
+        val sellRequest = OrderUpdateRequest(
+            deliveryStartTime = LocalDateTime.of(2024, 1, 15, 10, 0),
+            deliveryEndTime = LocalDateTime.of(2024, 1, 15, 10, 15),
+            orderSide = OrderSide.SELL,
+            quantity = BigDecimal("10"),
+            price = BigDecimal("50.00")
+        )
+        service.processOrder(sellRequest)
+
+        val buyRequest = sellRequest.copy(orderSide = OrderSide.BUY)
+        val response = service.processOrder(buyRequest)
+
+        assertEquals("FILLED", response.status)
+    }
+
+    @Test
+    fun `processOrder returns PARTIALLY_FILLED when partially matched`() {
+        val sellRequest = OrderUpdateRequest(
+            deliveryStartTime = LocalDateTime.of(2024, 1, 15, 10, 0),
+            deliveryEndTime = LocalDateTime.of(2024, 1, 15, 10, 15),
+            orderSide = OrderSide.SELL,
+            quantity = BigDecimal("5"),
+            price = BigDecimal("50.00")
+        )
+        service.processOrder(sellRequest)
+
+        val buyRequest = sellRequest.copy(orderSide = OrderSide.BUY, quantity = BigDecimal("10"))
+        val response = service.processOrder(buyRequest)
+
+        assertEquals("PARTIALLY_FILLED", response.status)
+    }
+}