book-reader/desktopApp/src/desktopMain/kotlin/com/aryan/reader/desktop/DesktopLibraryDatabase.kt

package com.aryan.reader.desktop

import com.aryan.reader.shared.BookItem
import com.aryan.reader.shared.BookShelfRef
import com.aryan.reader.shared.FileType
import com.aryan.reader.shared.ShelfRecord
import com.aryan.reader.shared.Tag
import kotlinx.serialization.json.Json
import kotlinx.serialization.json.JsonArray
import kotlinx.serialization.json.JsonElement
import kotlinx.serialization.json.JsonNull
import kotlinx.serialization.json.JsonObject
import kotlinx.serialization.json.JsonPrimitive
import kotlinx.serialization.json.booleanOrNull
import kotlinx.serialization.json.doubleOrNull
import kotlinx.serialization.json.floatOrNull
import kotlinx.serialization.json.jsonArray
import kotlinx.serialization.json.jsonObject
import kotlinx.serialization.json.jsonPrimitive
import kotlinx.serialization.json.longOrNull
import java.io.File

data class DesktopLibrarySnapshot(
    val books: List<BookItem> = emptyList(),
    val shelfRecords: List<ShelfRecord> = emptyList(),
    val shelfRefs: List<BookShelfRef> = emptyList(),
    val tags: List<Tag> = emptyList()
)

class DesktopLibraryDatabase(
    private val databaseFile: File = defaultDatabaseFile()
) {
    private val json = Json {
        prettyPrint = true
        ignoreUnknownKeys = true
    }

    fun load(): DesktopLibrarySnapshot {
        if (!databaseFile.exists()) return DesktopLibrarySnapshot()
        val root = runCatching {
            json.parseToJsonElement(databaseFile.readText()).jsonObject
        }.getOrNull() ?: return DesktopLibrarySnapshot()

        return DesktopLibrarySnapshot(
            books = root.array("books").mapNotNull { it.asBookItemOrNull() },
            shelfRecords = root.array("shelves").mapNotNull { it.asShelfRecordOrNull() },
            shelfRefs = root.array("bookShelfRefs").mapNotNull { it.asBookShelfRefOrNull() },
            tags = root.array("tags").mapNotNull { it.asTagOrNull() }
        )
    }

    fun save(snapshot: DesktopLibrarySnapshot) {
        databaseFile.parentFile?.mkdirs()
        val root = JsonObject(
            mapOf(
                "schemaVersion" to JsonPrimitive(1),
                "books" to JsonArray(snapshot.books.map { it.toJsonObject() }),
                "shelves" to JsonArray(snapshot.shelfRecords.map { it.toJsonObject() }),
                "bookShelfRefs" to JsonArray(snapshot.shelfRefs.map { it.toJsonObject() }),
                "tags" to JsonArray(snapshot.tags.map { it.toJsonObject() })
            )
        )
        databaseFile.writeText(root.toString())
    }

    companion object {
        fun defaultDatabaseFile(): File {
            val baseDir = System.getenv("APPDATA")?.takeIf { it.isNotBlank() }
                ?: File(System.getProperty("user.home"), "AppData/Roaming").absolutePath
            return File(baseDir, "Episteme/library.json")
        }
    }
}

private fun JsonObject.array(name: String): List<JsonElement> {
    return runCatching { this[name]?.jsonArray?.toList().orEmpty() }.getOrDefault(emptyList())
}

private fun JsonObject.string(name: String): String? {
    return this[name]?.takeUnless { it is JsonNull }?.jsonPrimitive?.content
}

private fun JsonObject.long(name: String, fallback: Long = 0L): Long {
    return this[name]?.jsonPrimitive?.longOrNull ?: fallback
}

private fun JsonObject.float(name: String): Float? {
    return this[name]?.jsonPrimitive?.floatOrNull
}

private fun JsonObject.double(name: String): Double? {
    return this[name]?.jsonPrimitive?.doubleOrNull
}

private fun JsonObject.boolean(name: String, fallback: Boolean): Boolean {
    return this[name]?.jsonPrimitive?.booleanOrNull ?: fallback
}

private fun JsonElement.asBookItemOrNull(): BookItem? {
    val obj = runCatching { jsonObject }.getOrNull() ?: return null
    val id = obj.string("id") ?: return null
    val displayName = obj.string("displayName") ?: return null
    val type = obj.string("type")?.let { runCatching { FileType.valueOf(it) }.getOrNull() } ?: FileType.UNKNOWN
    return BookItem(
        id = id,
        path = obj.string("path"),
        type = type,
        displayName = displayName,
        timestamp = obj.long("timestamp"),
        title = obj.string("title"),
        author = obj.string("author"),
        progressPercentage = obj.float("progressPercentage"),
        isRecent = obj.boolean("isRecent", true),
        fileSize = obj.long("fileSize"),
        sourceFolder = obj.string("sourceFolder"),
        seriesName = obj.string("seriesName"),
        seriesIndex = obj.double("seriesIndex"),
        tags = obj.array("tags").mapNotNull { it.asTagOrNull() }
    )
}

private fun JsonElement.asShelfRecordOrNull(): ShelfRecord? {
    val obj = runCatching { jsonObject }.getOrNull() ?: return null
    return ShelfRecord(
        id = obj.string("id") ?: return null,
        name = obj.string("name") ?: return null,
        isSmart = obj.boolean("isSmart", false),
        smartRulesJson = obj.string("smartRulesJson")
    )
}

private fun JsonElement.asBookShelfRefOrNull(): BookShelfRef? {
    val obj = runCatching { jsonObject }.getOrNull() ?: return null
    return BookShelfRef(
        bookId = obj.string("bookId") ?: return null,
        shelfId = obj.string("shelfId") ?: return null,
        addedAt = obj.long("addedAt")
    )
}

private fun JsonElement.asTagOrNull(): Tag? {
    val obj = runCatching { jsonObject }.getOrNull() ?: return null
    return Tag(
        id = obj.string("id") ?: return null,
        name = obj.string("name") ?: return null,
        color = obj["color"]?.takeUnless { it is JsonNull }?.jsonPrimitive?.content?.toIntOrNull()
    )
}

private fun BookItem.toJsonObject(): JsonObject {
    return JsonObject(
        mapOf(
            "id" to JsonPrimitive(id),
            "path" to path.asJson(),
            "type" to JsonPrimitive(type.name),
            "displayName" to JsonPrimitive(displayName),
            "timestamp" to JsonPrimitive(timestamp),
            "title" to title.asJson(),
            "author" to author.asJson(),
            "progressPercentage" to progressPercentage.asJson(),
            "isRecent" to JsonPrimitive(isRecent),
            "fileSize" to JsonPrimitive(fileSize),
            "sourceFolder" to sourceFolder.asJson(),
            "seriesName" to seriesName.asJson(),
            "seriesIndex" to seriesIndex.asJson(),
            "tags" to JsonArray(tags.map { it.toJsonObject() })
        )
    )
}

private fun ShelfRecord.toJsonObject(): JsonObject {
    return JsonObject(
        mapOf(
            "id" to JsonPrimitive(id),
            "name" to JsonPrimitive(name),
            "isSmart" to JsonPrimitive(isSmart),
            "smartRulesJson" to smartRulesJson.asJson()
        )
    )
}

private fun BookShelfRef.toJsonObject(): JsonObject {
    return JsonObject(
        mapOf(
            "bookId" to JsonPrimitive(bookId),
            "shelfId" to JsonPrimitive(shelfId),
            "addedAt" to JsonPrimitive(addedAt)
        )
    )
}

private fun Tag.toJsonObject(): JsonObject {
    return JsonObject(
        mapOf(
            "id" to JsonPrimitive(id),
            "name" to JsonPrimitive(name),
            "color" to color.asJson()
        )
    )
}

private fun String?.asJson(): JsonElement = this?.let { JsonPrimitive(it) } ?: JsonNull
private fun Float?.asJson(): JsonElement = this?.let { JsonPrimitive(it) } ?: JsonNull
private fun Double?.asJson(): JsonElement = this?.let { JsonPrimitive(it) } ?: JsonNull
private fun Int?.asJson(): JsonElement = this?.let { JsonPrimitive(it) } ?: JsonNull