package com.gzzn.omms.msgexchange.processing

import com.gzzn.omms.msgexchange.codec.FlopPayload
import com.gzzn.omms.msgexchange.codec.ScheduleBody
import com.gzzn.omms.msgexchange.codec.XmlCodec
import com.gzzn.omms.msgexchange.codec.unpersistedCollectionHits
import com.gzzn.omms.msgexchange.config.OperationDayProps
import com.gzzn.omms.msgexchange.config.PipelineProps
import com.gzzn.omms.msgexchange.domain.DecodedMessage
import com.gzzn.omms.msgexchange.domain.ErrorClass
import com.gzzn.omms.msgexchange.domain.MsgKind
import com.gzzn.omms.msgexchange.domain.ProcState
import com.gzzn.omms.msgexchange.domain.ProcStatus
import com.gzzn.omms.msgexchange.infra.log.TraceLog
import com.gzzn.omms.msgexchange.infra.metrics.PipelineCounters
import com.gzzn.omms.msgexchange.infra.persistence.CminmsgInboxRepository
import com.gzzn.omms.msgexchange.infra.persistence.InboxCursorRepository
import com.gzzn.omms.msgexchange.infra.persistence.ProcStateRepository
import com.gzzn.omms.msgexchange.infra.retry.ProcFailure
import jakarta.inject.Singleton
import java.time.Clock
import java.time.Duration
import java.time.Instant
import java.time.LocalDate
import java.util.concurrent.atomic.AtomicLong

/**
 * 处理主泵：一个线程按消息 ID 从小到大一条条处理，保证先来的先处理。
 *
 * 每次 tick 只看当前最小的未完成消息（"队头"）：
 * - 没有待处理消息就睡一个轮询间隔；
 * - 队头失败了还在退避期，就等到能重试的时刻；重试次数用尽才转死信，不放任它一直堵着；
 * - 其余情况交给 [MessageProcessor] 处理。
 *
 * 一次只处理一条是刻意的。后面的消息不能越过卡住的队头，否则同一条航班的报文
 * 可能被乱序应用，几十秒后才到的旧报文会把新状态覆盖回去。
 */
@Singleton
class Pump(
    private val procState: ProcStateRepository,
    private val cursor: InboxCursorRepository,
    private val processor: MessageProcessor,
    private val props: PipelineProps,
    private val clock: Clock,
) {
    private val log = org.slf4j.LoggerFactory.getLogger(Pump::class.java)

    /** 连续失败计数：仅用于日志/排障，不代表业务状态。 */
    private val tickFailures = AtomicLong(0)

    @Volatile
    private var running = true

    /** 请求停机：当前 tick 跑完就退出。线程中断由 PipelineLifecycle 负责。 */
    fun stop() {
        running = false
    }

    fun loop() {
        while (running) {
            try {
                tick()
                tickFailures.set(0)
            } catch (e: InterruptedException) {
                Thread.currentThread().interrupt()
                return
            } catch (e: Exception) {
                // 兜底：单条消息的失败状态已在 processOne 内记录；但 tick 整体失败（DB 断连、
                // 锁超时）在别处没有痕迹，必须留日志，否则排障无据可查。
                val failures = tickFailures.incrementAndGet()
                log.error("pump tick failed (failure #{})", failures, e)
                sleepQuietly(props.pipeline.pollInterval)
            }
        }
    }

    internal fun tick() {
        val head = procState.headUnfinished()
        if (head == null) {
            sleepQuietly(props.pipeline.pollInterval)
            return
        }
        // 只领取"已被水位覆盖"的队头（`msgId <= W`）。
        //
        // 水位以内的行都是收报按 ID 顺序发现并登记的；水位之外的行只可能来自兼容入口
        // 直接写 PROC_STATE（它不参与水位）。若允许领取，它就会越过那些尚未入队的较小 ID，
         // 破坏 FIFO（不变量"只领取已发现的行"，`invariants.md` INV-4）。这种行在空洞补齐、`W` 追平之后自然可领取。
        val watermark = cursor.load().committedUpTo
        if (head.msgId > watermark) {
            warnBeyondWatermark(head.msgId, watermark)
            sleepQuietly(props.pipeline.pollInterval)
            return
        }
        val now = clock.instant()
        when {
            head.state == ProcStatus.FAILED && head.attempts >= props.pipeline.maxAttempts -> {
                log.error("poison -> DEAD msgId={} attempts={} lastError={}", head.msgId, head.attempts, head.lastError)
                // markTerminal 在同一条 UPDATE 里登记回填意图；回填由扫描补写，不在这里做跨库写。
                procState.markTerminal(
                    head.msgId, ProcStatus.DEAD,
                    errorClass = ErrorClass.EXHAUSTED,
                    lastError = head.lastError ?: "attempts-exhausted",
                    attempts = head.attempts,
                    now = now,
                )
            }
            head.state == ProcStatus.FAILED && (head.nextAttemptAt ?: Instant.EPOCH) > now ->
                sleepQuietly(Duration.between(now, head.nextAttemptAt))
            // 其余情况（新消息，或退避到期的重试）交给处理入口
            else -> processor.processOne(head)
        }
    }

    /** 上一次"队头在水位之外"告警时的水位值：只在它变化时告警，避免每秒刷屏。 */
    private val warnedWatermark = AtomicLong(Long.MIN_VALUE)

    private fun warnBeyondWatermark(msgId: Long, watermark: Long) {
        if (warnedWatermark.getAndSet(watermark) != watermark) {
            log.warn(
                "head msgId={} is beyond watermark W={}; waiting for discovery " +
                    "(row injected by the compat entry point?)",
                msgId, watermark,
            )
        }
    }

    private fun sleepQuietly(d: Duration) {
        if (!d.isNegative && !d.isZero) Thread.sleep(d.toMillis().coerceAtLeast(1))
    }
}

/**
 * 处理一条消息：读原文 → 解码 → 绑定业务身份 → 分派给对应处理器。
 *
 * 业务数据、终态与回填意图都由各处理器在自己的事务里写入（终态与回填意图是同一条 UPDATE）。
 * **这里不做信箱回填**：主泵是 FIFO 关键路径，跨库写会把它绑在共享 MySQL 的可用性上。
 * 回填由 `JobRunner` 定时的 `BackfillService.sweep` 驱动（调度周期不等于完成时限）。
 *
 * 任何意外异常都算在当前这条消息头上（记 FAILED(INFRA) 后重试），不会把主泵线程带崩。
 * 报文非法和整包协议拒绝不重试，直接进死信等人工处置。
 */
@Singleton
class MessageProcessor(
    private val inbox: CminmsgInboxRepository,
    private val procState: ProcStateRepository,
    private val codec: XmlCodec,
    private val scheduleProcessor: ScheduleProcessor,
    private val flopProcessor: FlopProcessor,
    private val fdelProcessor: FdelProcessor,
    private val adftProcessor: AdftProcessor,
    private val procFailure: ProcFailure,
    private val props: PipelineProps,
    private val clock: Clock,
    private val operationDayProps: OperationDayProps,
    private val counters: PipelineCounters,
) {
    private val log = org.slf4j.LoggerFactory.getLogger(MessageProcessor::class.java)

    fun processOne(head: ProcState) {
        TraceLog.withTrace(head.msgId) {
            try {
                processInternal(head)
            } catch (e: InterruptedException) {
                Thread.currentThread().interrupt()
                throw e
            } catch (e: Exception) {
                // 边界化：异常归于本条 head，写 FAILED(INFRA)/DEAD，而不是穿出杀 pump
                log.warn("processOne unexpected failure msgId={} ec=INFRA msg={}", head.msgId, e.message ?: e.javaClass.simpleName)
                procFailure.fail(head, ErrorClass.INFRA, e.message ?: e.javaClass.simpleName)
            }
        }
    }

    private fun processInternal(head: ProcState) {
        val raw = inbox.rawOf(head.msgId)
        if (raw == null) {
            log.error("raw missing -> DEAD(MALFORMED) msgId={}", head.msgId)
            return deadMalformed(head, "raw-missing")
        }
        val decoded = when (val r = codec.decode(raw)) {
            is com.gzzn.omms.msgexchange.codec.DecodeResult.Ok -> r.message
            is com.gzzn.omms.msgexchange.codec.DecodeResult.Err -> {
                // MALFORMED（报文非法）→ DEAD 不重试；CODEC_ERROR（可随 codec 修复重放）→ FAILED 退避
                if (r.failure.errorClass == ErrorClass.MALFORMED) {
                    log.error("decode MALFORMED -> DEAD msgId={} detail={}", head.msgId, r.failure.detail)
                    return deadMalformed(head, r.failure.detail)
                }
                log.warn("decode {} -> FAILED msgId={} detail={}", r.failure.errorClass, head.msgId, r.failure.detail)
                return procFailure.fail(head, r.failure.errorClass, r.failure.detail)
            }
        }

        // [G-SRVT-VIPF]：SRVT/VIPF 段只保留在解码载荷里，尚未落明细表（清空语义待 Q13）。
        // 计数 + 告警替代此前的静默丢弃；出现即证明真实报文携带该段，可作为定案依据。
        val unpersisted = unpersistedCollectionHits(decoded.body)
        if (unpersisted.isNotEmpty()) {
            counters.unpersistedCollectionSeenAdd(unpersisted)
            log.warn("unpersisted collection(s) {} present msgId={} [G-SRVT-VIPF]", unpersisted, head.msgId)
        }

        // I3：identity 仅首次绑定（head.identityKey == null）；FAILED 重试不重绑
        if (head.identityKey == null) {
            val identity = Identity.of(
                decoded, props.identity, LocalDate.now(clock.withZone(operationDayProps.zoneId())),
            )
            if (!procState.tryBindIdentity(head.msgId, identity)) {
                val owner = procState.ownerOfIdentity(identity) ?: -1L
                log.info("duplicate-of:{} -> SKIPPED msgId={}", owner, head.msgId)
                procState.markTerminal(head.msgId, ProcStatus.SKIPPED, lastError = "duplicate-of:$owner", now = clock.instant())
                return
            }
        }

        // US-04：忽略清单命中 → SKIPPED + 回填意图，不取 PIPELINE_LOCK、不写航班表、不创建 MSG_EVENT
        val ignoreRule = IgnoreRules.match(decoded.meta.type)
        if (ignoreRule != null) {
            log.info("ignored:{} -> SKIPPED msgId={}", ignoreRule, head.msgId)
            counters.ignoredAdd()
            procState.markTerminal(head.msgId, ProcStatus.SKIPPED, lastError = "ignored:$ignoreRule", now = clock.instant())
            return
        }

        // 按报文类型分派：日计划走 SCHD，其余走 FLOP / FDEL / ADFT；报文缺载荷直接判为非法报文的死信
        val result: ApplyResult = when (val kind = decoded.kind) {
            is MsgKind.Schd -> {
                val body = decoded.body as? ScheduleBody
                if (body == null) return deadMalformed(head, "missing-schd-body")
                when (kind.subtype) {
                    MsgKind.SchdSubtype.DNLD, MsgKind.SchdSubtype.RESP ->
                        scheduleProcessor.applyScheduleRecords(head, decoded)
                    MsgKind.SchdSubtype.ADFT -> {
                        val record = body.records.singleOrNull()
                        if (record == null) return deadMalformed(head, "adft-needs-single-fltr")
                        adftProcessor.apply(head, decoded, record)
                    }
                }
            }
            MsgKind.Fdel -> {
                val payload = decoded.body as? FlopPayload
                if (payload == null) return deadMalformed(head, "missing-fdel-flid")
                fdelProcessor.apply(head, decoded, payload)
            }
            is MsgKind.Flop -> {
                val payload = decoded.body as? FlopPayload
                if (payload == null) return deadMalformed(head, "missing-flop-body")
                flopProcessor.apply(head, decoded, payload)
            }
            is MsgKind.Unsupported -> {
                // 还没有对应处理器的报文类型：先按可重试的失败处理，等能力补齐，不直接判死
                log.warn("unsupported type -> FAILED(UNSUPPORTED) msgId={} tag={}", head.msgId, kind.tag)
                return procFailure.fail(head, ErrorClass.UNSUPPORTED, "no-handler:${kind.tag}")
            }
        }

        if (result is ApplyResult.DeadProtocol) {
            // 整包被拒绝：不重试、立刻放掉队头，等人工确认
            log.error("DEAD(PROTOCOL) msgId={} reason={} flags={}", head.msgId, result.reason, result.flags)
            procState.markTerminal(
                head.msgId, ProcStatus.DEAD,
                errorClass = ErrorClass.PROTOCOL,
                lastError = result.reason.take(1000),
                now = clock.instant(),
            )
            return
        }

        // Succeeded / ReplaySkipped：SUCCEEDED 终态与回填意图已由处理器在自己的事务内落库
        log.info("SUCCEEDED msgId={} kind={}", head.msgId, decoded.typeTag)
    }

    private fun deadMalformed(head: ProcState, detail: String) {
        procState.markTerminal(head.msgId, ProcStatus.DEAD, errorClass = ErrorClass.MALFORMED, lastError = detail, now = clock.instant())
    }
}