feat(backup): add BackupCodec (JSON codec for backup chunks, checksum, reactions)
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package app.closer.data.remote
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import app.closer.domain.model.BackupMessageRecord
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import org.json.JSONArray
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import org.json.JSONObject
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import java.security.MessageDigest
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/**
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* Pure (no-Android) JSON codec for backup chunks/snapshots. The output string is what gets wrapped in
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* a couple-key `enc:v1:` envelope by the datasource, so the codec itself handles no crypto and stays
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* unit-testable. Round-trip must be stable (see `BackupCodecTest`).
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*/
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object BackupCodec {
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/** Encode a batch of message records into a canonical JSON payload string. */
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fun encode(records: List<BackupMessageRecord>): String {
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val arr = JSONArray()
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for (r in records) {
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val o = JSONObject()
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o.put("messageId", r.messageId)
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o.put("conversationId", r.conversationId)
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o.put("conversationType", r.conversationType)
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o.put("authorUserId", r.authorUserId)
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o.put("type", r.type)
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o.put("encText", r.encText ?: JSONObject.NULL)
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o.put("mediaUrl", r.mediaUrl ?: JSONObject.NULL)
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o.put("durationMs", r.durationMs ?: JSONObject.NULL)
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o.put("createdAt", r.createdAt)
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o.put("deleted", r.deleted)
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val reactions = JSONObject()
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for ((k, v) in r.reactions) reactions.put(k, v)
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o.put("reactions", reactions)
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arr.put(o)
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}
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return JSONObject().put("records", arr).toString()
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}
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/** Decode a payload string back into records. Unknown/extra fields are ignored (forward-compat). */
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fun decode(payload: String): List<BackupMessageRecord> {
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val arr = JSONObject(payload).optJSONArray("records") ?: return emptyList()
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val out = ArrayList<BackupMessageRecord>(arr.length())
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for (i in 0 until arr.length()) {
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val o = arr.getJSONObject(i)
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val reactions = LinkedHashMap<String, String>()
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o.optJSONObject("reactions")?.let { rj ->
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val keys = rj.keys()
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while (keys.hasNext()) {
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val k = keys.next()
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reactions[k] = rj.getString(k)
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}
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}
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out.add(
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BackupMessageRecord(
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messageId = o.optString("messageId"),
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conversationId = o.optString("conversationId"),
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conversationType = o.optString("conversationType", "main"),
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authorUserId = o.optString("authorUserId"),
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type = o.optString("type", "text"),
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encText = if (o.isNull("encText")) null else o.optString("encText"),
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mediaUrl = if (o.isNull("mediaUrl")) null else o.optString("mediaUrl"),
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durationMs = if (o.isNull("durationMs")) null else o.optLong("durationMs"),
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createdAt = o.optLong("createdAt"),
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deleted = o.optBoolean("deleted", false),
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reactions = reactions
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)
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)
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}
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return out
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}
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/** Serialize a uid→emoji reactions map to a compact JSON object (for the Room cache column). */
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fun reactionsToJson(reactions: Map<String, String>): String {
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val o = JSONObject()
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for ((k, v) in reactions) o.put(k, v)
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return o.toString()
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}
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fun reactionsFromJson(json: String?): Map<String, String> {
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if (json.isNullOrBlank()) return emptyMap()
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val o = runCatching { JSONObject(json) }.getOrNull() ?: return emptyMap()
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val out = LinkedHashMap<String, String>()
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val keys = o.keys()
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while (keys.hasNext()) {
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val k = keys.next()
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out[k] = o.getString(k)
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}
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return out
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}
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/** Integrity checksum of a plaintext payload (before encryption) — stored in the manifest. */
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fun checksum(payload: String): String {
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val digest = MessageDigest.getInstance("SHA-256").digest(payload.toByteArray(Charsets.UTF_8))
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return "sha256:" + digest.joinToString("") { "%02x".format(it) }
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}
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}
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@ -0,0 +1,65 @@
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package app.closer.data.remote
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import app.closer.domain.model.BackupCursor
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import app.closer.domain.model.BackupMessageRecord
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import org.junit.Assert.assertEquals
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import org.junit.Assert.assertNotEquals
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import org.junit.Assert.assertTrue
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import org.junit.Test
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class BackupCodecTest {
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private val records = listOf(
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BackupMessageRecord(
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messageId = "m1", conversationId = "main", conversationType = "main",
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authorUserId = "a", type = "text", encText = "enc:v1:abc", createdAt = 100L,
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reactions = mapOf("b" to "❤️")
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),
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BackupMessageRecord(
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messageId = "m2", conversationId = "main", conversationType = "main",
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authorUserId = "b", type = "image", mediaUrl = "https://x/y?token=1", createdAt = 200L, deleted = true
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)
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)
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@Test
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fun `encode then decode round-trips records including reactions and tombstones`() {
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val decoded = BackupCodec.decode(BackupCodec.encode(records))
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assertEquals(records.size, decoded.size)
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assertEquals("enc:v1:abc", decoded[0].encText)
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assertEquals(mapOf("b" to "❤️"), decoded[0].reactions)
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assertEquals("image", decoded[1].type)
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assertTrue(decoded[1].deleted)
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assertEquals("https://x/y?token=1", decoded[1].mediaUrl)
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assertEquals(records, decoded)
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}
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@Test
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fun `checksum is stable for identical payloads and differs otherwise`() {
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val a = BackupCodec.encode(records)
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assertEquals(BackupCodec.checksum(a), BackupCodec.checksum(a))
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assertNotEquals(BackupCodec.checksum(a), BackupCodec.checksum(BackupCodec.encode(records.take(1))))
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assertTrue(BackupCodec.checksum(a).startsWith("sha256:"))
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}
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@Test
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fun `reactions json round-trips`() {
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val map = mapOf("u1" to "😍", "u2" to "👍")
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assertEquals(map, BackupCodec.reactionsFromJson(BackupCodec.reactionsToJson(map)))
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assertEquals(emptyMap<String, String>(), BackupCodec.reactionsFromJson(null))
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}
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@Test
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fun `decode ignores unknown fields (forward-compat)`() {
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val payload = """{"records":[{"messageId":"x","conversationId":"main","createdAt":5,"futureField":"ignored"}],"extra":true}"""
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val decoded = BackupCodec.decode(payload)
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assertEquals(1, decoded.size)
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assertEquals("x", decoded[0].messageId)
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}
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@Test
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fun `cursor ordering is by createdAt then messageId`() {
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assertTrue(BackupCursor(200L, "a").isAfter(BackupCursor(100L, "z")))
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assertTrue(BackupCursor(100L, "b").isAfter(BackupCursor(100L, "a")))
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assertTrue(!BackupCursor(100L, "a").isAfter(BackupCursor(100L, "a")))
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}
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}
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