package com.sptmobile.link

import android.content.Context
import android.os.Build
import androidx.datastore.preferences.core.edit
import androidx.datastore.preferences.core.stringPreferencesKey
import androidx.datastore.preferences.preferencesDataStore
import java.util.UUID
import kotlinx.coroutines.flow.first

private val Context.deviceNameStore by preferencesDataStore(name = "device_name")

/**
 * The device string this phone is known by on every paired host. `pair`
 * registers the host-side spool under it and `spoolDrain` reads back by it —
 * the two MUST use the same value, which is why it lives here and not inline
 * in either caller.
 *
 * `MODEL-<uuid8>`: [Build.MODEL] alone collides — two phones of the same
 * model pairing with one host would share a spool (each drain-committing the
 * other's messages away). The per-install random suffix is minted once and
 * persisted, so the name is stable across restarts and re-pairs for the life
 * of the install.
 */
// [impl->REQ-INBOUND-NOTIFS]
object DeviceName {
    private val suffixKey = stringPreferencesKey("suffix")

    @Volatile
    private var cached: String? = null

    suspend fun value(context: Context): String {
        cached?.let { return it }
        val store = context.applicationContext.deviceNameStore
        var suffix = store.data.first()[suffixKey]
        if (suffix == null) {
            // Mint inside edit so a racing first-read can't double-mint.
            store.edit { prefs ->
                if (prefs[suffixKey] == null) {
                    prefs[suffixKey] = UUID.randomUUID().toString().take(8)
                }
            }
            suffix = store.data.first()[suffixKey]
        }
        return compose(Build.MODEL, suffix.orEmpty()).also { cached = it }
    }

    /** Pure name shape, JVM-testable: blank/absent model falls back. */
    fun compose(model: String?, suffix: String): String {
        val base = model?.takeIf { it.isNotBlank() } ?: "spt-mobile"
        return if (suffix.isBlank()) base else "$base-$suffix"
    }
}