add selector

ratings/selector/src/commonMain/kotlin/models/RatingConfig.kt

@@ -0,0 +1,104 @@
+package dev.inmo.plaguposter.ratings.selector.models
+
+import dev.inmo.micro_utils.pagination.FirstPagePagination
+import dev.inmo.micro_utils.pagination.Pagination
+import dev.inmo.plaguposter.posts.models.PostId
+import dev.inmo.plaguposter.ratings.models.Rating
+import dev.inmo.plaguposter.ratings.repo.RatingsRepo
+import kotlinx.serialization.KSerializer
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.builtins.serializer
+import kotlinx.serialization.descriptors.SerialDescriptor
+import kotlinx.serialization.encoding.Decoder
+import kotlinx.serialization.encoding.Encoder
+import kotlin.random.Random
+
+@Serializable
+data class RatingConfig(
+    val min: Rating?,
+    val max: Rating?,
+    val prefer: Prefer
+) {
+    suspend fun select(repo: RatingsRepo, exclude: List<PostId>): PostId? {
+        var reversed: Boolean = false
+        var count: Int? = null
+
+        when (prefer) {
+            Prefer.Max -> {
+                reversed = true
+                count = 1
+            }
+            Prefer.Min -> {
+                reversed = false
+                count = 1
+            }
+            Prefer.Random -> {
+                reversed = false
+                count = null
+            }
+        }
+
+        val posts = when(min) {
+            null -> {
+                when (max) {
+                    null -> {
+                        repo.keys(
+                            count ?.let { Pagination(0, it) } ?: FirstPagePagination(repo.count().toInt()),
+                            reversed
+                        ).results.filterNot {
+                            it in exclude
+                        }
+                    }
+                    else -> {
+                        repo.getPostsWithRatingLessEq(max, exclude = exclude).keys
+                    }
+                }
+            }
+            else -> {
+                when (max) {
+                    null -> {
+                        repo.getPostsWithRatingGreaterEq(min, exclude = exclude).keys
+                    }
+                    else -> {
+                        repo.getPosts(min .. max, reversed, count, exclude = exclude).keys
+                    }
+                }
+            }
+        }
+
+        return when (prefer) {
+            Prefer.Max,
+            Prefer.Min -> posts.firstOrNull()
+            Prefer.Random -> posts.randomOrNull()
+        }
+    }
+
+    @Serializable(Prefer.Serializer::class)
+    sealed interface Prefer {
+        val type: String
+        @Serializable(Serializer::class)
+        object Max : Prefer { override val type: String = "max" }
+        @Serializable(Serializer::class)
+        object Min : Prefer { override val type: String = "min" }
+        @Serializable(Serializer::class)
+        object Random : Prefer { override val type: String = "random" }
+
+        object Serializer : KSerializer<Prefer> {
+            override val descriptor: SerialDescriptor = String.serializer().descriptor
+
+            override fun deserialize(decoder: Decoder): Prefer {
+                val identifier = decoder.decodeString().lowercase()
+                return values.first { it.type.lowercase() == identifier }
+            }
+
+            override fun serialize(encoder: Encoder, value: Prefer) {
+                encoder.encodeString(value.type.lowercase())
+            }
+
+        }
+
+        companion object {
+            val values = arrayOf(Max, Min, Random)
+        }
+    }
+}