package com.peachpasswords.vault

import kotlinx.serialization.KSerializer
import kotlinx.serialization.descriptors.PrimitiveKind
import kotlinx.serialization.descriptors.PrimitiveSerialDescriptor
import kotlinx.serialization.descriptors.SerialDescriptor
import kotlinx.serialization.encoding.Decoder
import kotlinx.serialization.encoding.Encoder
import kotlinx.serialization.json.Json
import kotlinx.serialization.json.JsonDecoder
import kotlinx.serialization.json.JsonEncoder
import kotlinx.serialization.json.JsonObject
import kotlinx.serialization.json.JsonPrimitive

/**
 * Reads a passkey's `privateKeyJwk` whether it arrives as a JSON object or a
 * string, and writes it back as an object.
 *
 * The browser types this field as `JsonWebKey` (`shared/types.ts`) — a real JSON
 * object. Android modelled it as a `String`, so kotlinx hit `{` where it wanted
 * a quote and threw "Expected beginning of the string, but got …" partway
 * through the payload. Any browser vault holding a passkey with a private key
 * was unreadable on Android — a Codex restore or a sync of that vault failed
 * with a raw parser error naming a byte offset, which looks like corruption and
 * is nothing of the sort.
 *
 * Kept as a compact string in memory because that is what the rest of the app
 * and PeachScript already pass around; only the wire form changes.
 */
object JwkStringSerializer : KSerializer<String> {
    override val descriptor: SerialDescriptor =
        PrimitiveSerialDescriptor("com.peachpasswords.vault.JwkString", PrimitiveKind.STRING)

    private val json = Json { encodeDefaults = true }

    override fun deserialize(decoder: Decoder): String {
        val input = decoder as? JsonDecoder ?: return decoder.decodeString()
        return when (val element = input.decodeJsonElement()) {
            is JsonPrimitive -> if (element.isString) element.content else element.toString()
            else -> element.toString()
        }
    }

    override fun serialize(encoder: Encoder, value: String) {
        val output = encoder as? JsonEncoder ?: return encoder.encodeString(value)
        // Write the browser's shape back, so a vault that round-trips through
        // Android stays readable there.
        val element = runCatching { json.parseToJsonElement(value) }.getOrNull()
        if (element is JsonObject) output.encodeJsonElement(element) else output.encodeString(value)
    }
}