package com.estateunified.panel

import com.google.gson.Gson
import com.google.gson.reflect.TypeToken
import java.nio.charset.StandardCharsets
import java.nio.file.Files
import java.nio.file.Path

internal data class FavoriteEntry(
    val userId: String,
    val listingId: String,
    val createdAtIso: String =
        java.time.format.DateTimeFormatter.ISO_LOCAL_DATE_TIME.format(java.time.LocalDateTime.now()),
)

internal class FavoritesStore(
    private val gson: Gson,
    private val file: Path,
) {
    private val lock = Any()

    fun listForUser(userId: String): List<FavoriteEntry> =
        synchronized(lock) { load().filter { it.userId == userId } }

    fun has(userId: String, listingId: String): Boolean =
        synchronized(lock) {
            load().any { it.userId == userId && it.listingId == listingId }
        }

    fun toggle(userId: String, listingId: String): Boolean =
        synchronized(lock) {
            val list = load().toMutableList()
            val idx = list.indexOfFirst { it.userId == userId && it.listingId == listingId }
            val added: Boolean
            if (idx >= 0) {
                list.removeAt(idx)
                added = false
            } else {
                list.add(0, FavoriteEntry(userId, listingId))
                added = true
            }
            persist(list)
            added
        }

    private fun load(): MutableList<FavoriteEntry> {
        if (!Files.isRegularFile(file)) return mutableListOf()
        val text = Files.readString(file, StandardCharsets.UTF_8)
        if (text.isBlank()) return mutableListOf()
        return runCatching {
            gson.fromJson<MutableList<FavoriteEntry>>(text, listType) ?: mutableListOf()
        }.getOrElse { mutableListOf() }
    }

    private fun persist(list: List<FavoriteEntry>) {
        Files.createDirectories(file.toAbsolutePath().parent)
        Files.writeString(file, gson.toJson(list), StandardCharsets.UTF_8)
    }

    companion object {
        private val listType = object : TypeToken<MutableList<FavoriteEntry>>() {}.type
    }
}