package moe.kageru.sekwences

import io.kotlintest.shouldBe
import io.kotlintest.specs.ShouldSpec

class CoalesceTest : ShouldSpec({
    "should merge numbers" {
        val input = sequenceOf(1, 2, 3, 4, 5, 6, 4)
        val output = input.coalesce { first, second ->
            val sum = first + second
            if (sum <= 10) sum else null
        }.toList()
        output shouldBe listOf(10, 5, 10)
    }

    "should merge collections" {
        val input = sequenceOf("apple", "apricot", "banana", "peach", "pear", "plum")
        val output = input.map { listOf(it) }.coalesce { first, second ->
            if (first.first()[0] == second.first()[0]) {
                first + second
            } else {
                null
            }
        }.toList()
        output shouldBe listOf(listOf("apple", "apricot"), listOf("banana"), listOf("peach", "pear", "plum"))
    }

    "should handle empty sequences" {
        val input = emptySequence<Int>()
        val output = input.coalesce { _, _ -> 0 }
        output shouldBe emptySequence()
    }

    "should handle single elements" {
        val input = sequenceOf(1)
        val output = input.coalesce { a, b -> if (a > 5) a else b }.toList()
        output shouldBe listOf(1)
    }

    "should not modify sequences that can’t be merged" {
        val input = listOf(6, 7, 34, 8)
        val output = input.asSequence().coalesce { first, second ->
            val sum = first + second
            if (sum <= 10) sum else null
        }.toList()
        output shouldBe input
    }
})