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/*
* SPDX-FileCopyrightText: 2023 Linnea Gräf <nea@nea.moe>
*
* SPDX-License-Identifier: GPL-3.0-or-later
*/
package moe.nea.firmament.util
import java.util.*
import kotlinx.serialization.DeserializationStrategy
import kotlinx.serialization.SerializationStrategy
import kotlinx.serialization.serializer
import moe.nea.firmament.Firmament
object TemplateUtil {
@JvmStatic
fun getTemplatePrefix(data: String): String? {
val decoded = maybeFromBase64Encoded(data) ?: return null
return decoded.replaceAfter("/", "", "").ifBlank { null }
}
@JvmStatic
fun intoBase64Encoded(raw: String): String {
return Base64.getEncoder().encodeToString(raw.encodeToByteArray())
}
private val base64Alphabet = charArrayOf(
'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/', '='
)
@JvmStatic
fun maybeFromBase64Encoded(raw: String): String? {
val raw = raw.trim()
if (raw.any { it !in base64Alphabet }) {
return null
}
return try {
Base64.getDecoder().decode(raw).decodeToString()
} catch (ex: Exception) {
null
}
}
/**
* Returns a base64 encoded string, truncated such that for all `x`, `x.startsWith(prefix)` implies
* `base64Encoded(x).startsWith(getPrefixComparisonSafeBase64Encoding(prefix))`
* (however, the inverse may not always be true).
*/
@JvmStatic
fun getPrefixComparisonSafeBase64Encoding(prefix: String): String {
val rawEncoded =
Base64.getEncoder().encodeToString(prefix.encodeToByteArray())
.replace("=", "")
return rawEncoded.substring(0, rawEncoded.length - rawEncoded.length % 4)
}
inline fun <reified T> encodeTemplate(sharePrefix: String, data: T): String =
encodeTemplate(sharePrefix, data, serializer())
fun <T> encodeTemplate(sharePrefix: String, data: T, serializer: SerializationStrategy<T>): String {
require(sharePrefix.endsWith("/"))
return intoBase64Encoded(sharePrefix + Firmament.json.encodeToString(serializer, data))
}
inline fun <reified T : Any> maybeDecodeTemplate(sharePrefix: String, data: String): T? =
maybeDecodeTemplate(sharePrefix, data, serializer())
fun <T : Any> maybeDecodeTemplate(sharePrefix: String, data: String, serializer: DeserializationStrategy<T>): T? {
require(sharePrefix.endsWith("/"))
val data = data.trim()
if (!data.startsWith(getPrefixComparisonSafeBase64Encoding(sharePrefix)))
return null
val decoded = maybeFromBase64Encoded(data) ?: return null
if (!decoded.startsWith(sharePrefix))
return null
return try {
Firmament.json.decodeFromString<T>(serializer, decoded.substring(sharePrefix.length))
} catch (e: Exception) {
null
}
}
}
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