package com.gzzn.omms.msgexchange.processing

import com.gzzn.omms.msgexchange.config.MailboxProps
import com.gzzn.omms.msgexchange.config.PipelineProps
import com.gzzn.omms.msgexchange.domain.ErrorClass
import com.gzzn.omms.msgexchange.domain.ProcStatus
import com.gzzn.omms.msgexchange.infra.persistence.CminmsgInboxRepository
import com.gzzn.omms.msgexchange.infra.persistence.MailboxRow
import com.gzzn.omms.msgexchange.infra.stub.StubInbox
import com.gzzn.omms.msgexchange.infra.stub.StubProcState
import org.junit.jupiter.api.Assertions.assertEquals
import org.junit.jupiter.api.Assertions.assertFalse
import org.junit.jupiter.api.Assertions.assertNotNull
import org.junit.jupiter.api.Assertions.assertNull
import org.junit.jupiter.api.Assertions.assertTrue
import org.junit.jupiter.api.Test
import java.time.Clock
import java.time.Duration
import java.time.Instant
import java.time.ZoneOffset

/**
 * 回填环节的规矩：
 * - 处理完马上写标记，写不进去就按退避重试，重启后接着重试（状态都在数据库里）；
 * - 等得太久的消息无视退避强制补写，保证标记最终一定会写上；
 * - 只写还没有标记的行，已有的值不覆盖；
 * - 还没处理完的消息（PENDING / FAILED）不许写标记；
 * - 回填失败只是回填的事，不会把处理结果改回去。
 */
class BackfillServiceTest {

    private val t0: Instant = Instant.parse("2026-09-08T03:00:00Z")
    private val props = PipelineProps()

    /** 可以人为制造故障的信箱，用来验证回填失败时怎么处理。 */
    private class FakeMailbox(var fail: Boolean = false) : CminmsgInboxRepository {
        val marked = linkedSetOf<Long>()
        override fun insertRaw(rawXml: String): Long = 1L
        override fun rawOf(msgId: Long): String? = null
        override fun readRange(fromExclusive: Long, limit: Int): List<MailboxRow> = emptyList()
        override fun maxId(): Long? = null
        override fun markProcessedIfUnmarked(msgId: Long, value: String): Boolean {
            if (fail) throw IllegalStateException("mysql-down")
            return marked.add(msgId)
        }
    }

    private fun service(proc: StubProcState, mailbox: CminmsgInboxRepository, now: Instant = t0) =
        BackfillService(proc, mailbox, MailboxProps(), props, Clock.fixed(now, ZoneOffset.UTC))

    /** 终态 + 回填意图（固定时刻，避免依赖真实时钟）。 */
    private fun succeeded(proc: StubProcState, id: Long) {
        proc.insertIfAbsent(id, t0)
        proc.markTerminal(id, ProcStatus.SUCCEEDED, now = t0)
    }

    @Test
    fun `terminal message is marked immediately and the intent is cleared`() {
        val proc = StubProcState()
        val inbox = StubInbox().apply { clear() }
        val id = inbox.insertRaw("<MSG/>")
        succeeded(proc, id)

        service(proc, inbox).attempt(id)

        assertEquals("PROCESSED", inbox.markOf(id))
        val row = proc.find(id)!!
        assertNotNull(row.backfillAt)
        assertNull(row.backfillNextAt)
        assertNull(row.backfillError)
    }

    @Test
    fun `marking is monotonic - an existing value is never overwritten`() {
        val inbox = StubInbox().apply { clear() }
        val id = inbox.insertRaw("<MSG/>")

        assertTrue(inbox.markProcessedIfUnmarked(id, "PROCESSED"))
        assertFalse(inbox.markProcessedIfUnmarked(id, "OTHER"))   // 已经有标记了，不再写第二次
        assertEquals("PROCESSED", inbox.markOf(id))
    }

    @Test
    fun `already marked rows are idempotent and never recorded as failures`() {
        val proc = StubProcState()
        val inbox = StubInbox().apply { clear() }
        val id = inbox.insertRaw("<MSG/>")
        succeeded(proc, id)

        val backfill = service(proc, inbox)
        backfill.attempt(id)
        backfill.attempt(id)   // 重复补写没有副作用

        assertNull(proc.find(id)!!.backfillError)
        assertEquals(0, proc.find(id)!!.backfillAttempts)
    }

    @Test
    fun `failed attempt records backoff and never touches the terminal state`() {
        val proc = StubProcState()
        val mailbox = FakeMailbox(fail = true)
        succeeded(proc, 901L)

        service(proc, mailbox).attempt(901L)

        val row = proc.find(901L)!!
        assertEquals(ProcStatus.SUCCEEDED, row.state)            // 回填失败不会把处理结果改回去
        assertEquals(1, row.backfillAttempts)
        assertEquals("mysql-down", row.backfillError)
        assertEquals(t0.plus(Duration.ofSeconds(30)), row.backfillNextAt)
        assertNull(row.backfillAt)
    }

    @Test
    fun `sweep retries due rows and completes once the mailbox recovers`() {
        val proc = StubProcState()
        val mailbox = FakeMailbox(fail = true)
        succeeded(proc, 901L)
        val backfill = service(proc, mailbox)

        assertEquals(1, backfill.sweep(t0))                      // 到期 → 失败 → 退避
        assertEquals(0, backfill.sweep(t0.plusSeconds(29)))      // 未到期
        assertEquals(1, backfill.sweep(t0.plusSeconds(30)))      // 到期再试 → 仍失败（重启后同样收敛）

        mailbox.fail = false
        assertEquals(1, backfill.sweep(t0.plusSeconds(90)))

        assertTrue(901L in mailbox.marked)
        assertNotNull(proc.find(901L)!!.backfillAt)
    }

    /** 等得太久的消息不再等退避、直接补写：保证标记最终一定会写上。 */
    @Test
    fun `overdue rows bypass the retry backoff`() {
        val proc = StubProcState()
        val inbox = StubInbox().apply { clear() }
        val id = inbox.insertRaw("<MSG/>")
        val old = t0.minus(props.pipeline.overdueBackfill).minusSeconds(60)
        proc.insertIfAbsent(id, old)                             // 接收时间早于 R
        proc.markTerminal(id, ProcStatus.SUCCEEDED, now = t0)
        proc.recordBackfillFailure(id, "mysql-down", 5, t0.plus(Duration.ofMinutes(15)), t0)   // 退避推到很远之后

        assertEquals(1, service(proc, inbox).sweep(t0))

        assertNotNull(proc.find(id)!!.backfillAt)
    }

    /** 还没处理完的消息（PENDING / FAILED）永远不打标，等再久也不行。 */
    @Test
    fun `mid states are never marked even when far past the deadline`() {
        val proc = StubProcState()
        val inbox = StubInbox().apply { clear() }
        val pending = inbox.insertRaw("<MSG/>")
        val failed = inbox.insertRaw("<MSG/>")
        val old = t0.minus(props.pipeline.overdueBackfill).minusSeconds(60)
        proc.insertIfAbsent(pending, old)
        proc.insertIfAbsent(failed, old)
        proc.update(failed, ProcStatus.FAILED, errorClass = ErrorClass.INFRA)

        assertEquals(0, service(proc, inbox).sweep(t0))

        assertFalse(inbox.isMarked(pending))
        assertFalse(inbox.isMarked(failed))
    }

    @Test
    fun `backoff delay doubles per attempt and caps at fifteen minutes`() {
        assertEquals(Duration.ofSeconds(30), BackfillService.backoffDelayFor(1))
        assertEquals(Duration.ofMinutes(2), BackfillService.backoffDelayFor(3))
        assertEquals(Duration.ofMinutes(15), BackfillService.backoffDelayFor(10))
        assertEquals(Duration.ofMinutes(15), BackfillService.backoffDelayFor(50))
    }
}