package database

import io.github.oshai.kotlinlogging.KotlinLogging
import org.postgresql.PGConnection
import javax.sql.DataSource

private val logger = KotlinLogging.logger {}

class CacheInvalidator(
    private val dataSource: DataSource,
    private val onInvalidated: () -> Unit
) {
    @Volatile
    private var running = false
    private var thread: Thread? = null

    fun start() {
        running = true
        thread = Thread {
            while (running) {
                try {
                    dataSource.connection.use { conn ->
                        conn.autoCommit = true
                        val pgConn = conn.unwrap(PGConnection::class.java)

                        conn.createStatement().use { stmt ->
                            stmt.execute("LISTEN cache_changed")
                        }

                        logger.info { "Listening for cache changes via PG NOTIFY..." }

                        while (running && !conn.isClosed) {
                            val notifications = pgConn.notifications
                            if (notifications != null && notifications.isNotEmpty()) {
                                logger.debug { "Cache invalidation received" }
                                onInvalidated()
                            }
                            Thread.sleep(500)
                        }
                    }
                } catch (e: Exception) {
                    if (!running) break
                    logger.warn(e) { "Cache listener error, reconnecting in 5s..." }
                    Thread.sleep(5000)
                }
            }
        }.also { it.isDaemon = true }.apply {
            name = "pg-notify-listener"
            start()
        }
    }

    fun stop() {
        running = false
        thread?.interrupt()
    }
}