Kotlin Flow Dedup Extension Functions

FlowDedup.kt

package io.redigital.rebased.ext.flow

import arrow.core.None
import arrow.core.Option
import arrow.core.some
import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.flow.transform

fun <T> Flow<T>.dedup(): Flow<T> = dedupBy { it }

inline fun <T, U> Flow<T>.dedupBy(crossinline mapper: suspend (T) -> U): Flow<T> =
    dedupWith { prev, current -> mapper(prev) == mapper(current) }

inline fun <T> Flow<T>.dedupWith(crossinline equal: suspend (T, T) -> Boolean): Flow<T> = let {
    var prev: Option<T> = None

    transform { value ->
        if (prev.isNone() || prev.isSome { !equal(it, value) }) {
            emit(value)
            prev = value.some()
        }
    }
}