kotlin-fork/libraries/stdlib/test/OrderingTest.kt

package test.compare

import java.util.*
import kotlin.test.*
import org.junit.Test

data class Item(val name: String, val rating: Int) : Comparable<Item> {
    public override fun compareTo(other: Item): Int {
        return compareValuesBy(this, other, { it.rating }, { it.name })
    }
}

class OrderingTest {
    val v1 = Item("wine", 9)
    val v2 = Item("beer", 10)

    @Test
    fun compareByCompareTo() {
        val diff = v1.compareTo(v2)
        assertTrue(diff < 0)
    }

    @Test
    fun compareByNameFirst() {
        val diff = compareValuesBy(v1, v2, { it.name }, { it.rating })
        assertTrue(diff > 0)
    }

    @Test
    fun compareByRatingFirst() {
        val diff = compareValuesBy(v1, v2, { it.rating }, { it.name })
        assertTrue(diff < 0)
    }

    @Test
    fun compareSameObjectsByRatingFirst() {
        val diff = compareValuesBy(v1, v1, { it.rating }, { it.name })
        assertTrue(diff == 0)
    }

    @Test
    fun compareNullables() {
        val v1: Item? = this.v1
        val v2: Item? = null
        val diff = compareValuesBy(v1, v2) { it?.rating }
        assertTrue(diff > 0)
        val diff2 = nullsLast(compareBy<Item> { it.rating }.thenBy { it.name }).compare(v1, v2)
        assertTrue(diff2 < 0)
    }

    @Test
    fun sortComparatorThenComparator() {
        val comparator = comparator<Item> { a, b -> a.name.compareTo(b.name) }.thenComparator { a, b -> a.rating.compareTo(b.rating) }

        val diff = comparator.compare(v1, v2)
        assertTrue(diff > 0)
        val items = arrayListOf(v1, v2).sortedWith(comparator)
        assertEquals(v2, items[0])
        assertEquals(v1, items[1])
    }

    @Test
    fun combineComparators() {
        val byName = compareBy<Item> { it.name }
        val byRating = compareBy<Item> { it.rating }
        val v3 = Item(v1.name, v1.rating + 1)
        val v4 = Item(v2.name + "_", v2.rating)
        assertTrue( (byName then byRating).compare(v1, v2) > 0 )
        assertTrue( (byName then byRating).compare(v1, v3) < 0 )
        assertTrue( (byName thenDescending byRating).compare(v1, v3) > 0 )

        assertTrue( (byRating then byName).compare(v1, v2) < 0 )
        assertTrue( (byRating then byName).compare(v4, v2) > 0 )
        assertTrue( (byRating thenDescending byName).compare(v4, v2) < 0 )
    }

    @Test
    fun reversedComparator() {
        val comparator = compareBy<Item> { it.name }
        val reversed = comparator.reversed()
        assertEquals(comparator.compare(v2, v1), reversed.compare(v1, v2))
        assertEquals(comparator, reversed.reversed())
    }

    @Test
    fun naturalOrderComparator() {
        val v1 = "a"
        val v2 = "beta"

        assertTrue(naturalOrder<String>().compare(v1, v2) < 0)
        assertTrue(reverseOrder<String>().compare(v1, v2) > 0)
        assertTrue(reverseOrder<Int>() === naturalOrder<Int>().reversed())
        assertTrue(naturalOrder<Int>() === reverseOrder<Int>().reversed())
    }

    @Test
    fun sortByThenBy() {
        val comparator = compareBy<Item> { it.rating }.thenBy { it.name }

        val diff = comparator.compare(v1, v2)
        assertTrue(diff < 0)
        val items = arrayListOf(v1, v2).sortedWith(comparator)
        assertEquals(v1, items[0])
        assertEquals(v2, items[1])
    }

    @Test
    fun sortByThenByDescending() {
        val comparator = compareBy<Item> { it.rating }.thenByDescending { it.name }

        val diff = comparator.compare(v1, v2)
        assertTrue(diff < 0)
        val items = arrayListOf(v1, v2).sortedWith(comparator)
        assertEquals(v1, items[0])
        assertEquals(v2, items[1])
    }

    @Test
    fun sortUsingFunctionalComparator() {
        val comparator = compareBy<Item>({ it.name }, { it.rating })
        val diff = comparator.compare(v1, v2)
        assertTrue(diff > 0)
        val items = arrayListOf(v1, v2).sortedWith(comparator)
        assertEquals(v2, items[0])
        assertEquals(v1, items[1])
    }

    @Test
    fun sortUsingCustomComparator() {
        val comparator = object : Comparator<Item> {
            override fun compare(o1: Item, o2: Item): Int {
                return compareValuesBy(o1, o2, { it.name }, { it.rating })
            }

            override fun equals(other: Any?): Boolean {
                return this == other
            }
        }
        val diff = comparator.compare(v1, v2)
        assertTrue(diff > 0)
        val items = arrayListOf(v1, v2).sortedWith(comparator)
        assertEquals(v2, items[0])
        assertEquals(v1, items[1])
    }

}