import { createLogger } from '@sim/logger'
import { toError } from '@sim/utils/errors'
import { sleep } from '@sim/utils/helpers'
import { AbortBackend } from '@/lib/copilot/generated/trace-attribute-values-v1'
import { TraceAttr } from '@/lib/copilot/generated/trace-attributes-v1'
import { TraceSpan } from '@/lib/copilot/generated/trace-spans-v1'
import { withCopilotSpan } from '@/lib/copilot/request/otel'
import { acquireLock, extendLock, getRedisClient, releaseLock } from '@/lib/core/config/redis'
import { AbortReason } from './abort-reason'
import { clearAbortMarker, hasAbortMarker, writeAbortMarker } from './buffer'

const logger = createLogger('SessionAbort')

const activeStreams = new Map<string, AbortController>()
const pendingChatStreams = new Map<
  string,
  { promise: Promise<void>; resolve: () => void; streamId: string }
>()

const DEFAULT_ABORT_POLL_MS = 250

/**
 * TTL for the per-chat stream lock. Kept short so that if the Sim pod
 * holding the lock dies (SIGKILL, OOM, a SIGTERM drain that doesn't
 * reach the release path), the lock self-heals inside a minute rather
 * than stranding the chat for hours. A live stream keeps the lock alive
 * via `CHAT_STREAM_LOCK_HEARTBEAT_INTERVAL_MS` heartbeats.
 */
const CHAT_STREAM_LOCK_TTL_SECONDS = 60

/**
 * Heartbeat cadence for extending the per-chat stream lock. Set to a
 * third of the TTL so one missed beat still leaves room for recovery
 * before the lock expires under a still-live stream.
 */
const CHAT_STREAM_LOCK_HEARTBEAT_INTERVAL_MS = 20_000

export interface ChatStreamLockOwnersResult {
  status: 'verified' | 'unknown'
  ownersByChatId: Map<string, string>
}

function registerPendingChatStream(chatId: string, streamId: string): void {
  let resolve!: () => void
  const promise = new Promise<void>((r) => {
    resolve = r
  })
  pendingChatStreams.set(chatId, { promise, resolve, streamId })
}

function resolvePendingChatStream(chatId: string, streamId: string): void {
  const entry = pendingChatStreams.get(chatId)
  if (entry && entry.streamId === streamId) {
    entry.resolve()
    pendingChatStreams.delete(chatId)
  }
}

function getChatStreamLockKey(chatId: string): string {
  return `copilot:chat-stream-lock:${chatId}`
}

export function registerActiveStream(streamId: string, controller: AbortController): void {
  activeStreams.set(streamId, controller)
}

export function unregisterActiveStream(streamId: string): void {
  activeStreams.delete(streamId)
}

export async function waitForPendingChatStream(
  chatId: string,
  timeoutMs = 5_000,
  expectedStreamId?: string
): Promise<boolean> {
  const redis = getRedisClient()
  const deadline = Date.now() + timeoutMs

  for (;;) {
    const entry = pendingChatStreams.get(chatId)
    const localPending = !!entry && (!expectedStreamId || entry.streamId === expectedStreamId)

    if (redis) {
      try {
        const ownerStreamId = await redis.get(getChatStreamLockKey(chatId))
        const lockReleased =
          !ownerStreamId || (expectedStreamId !== undefined && ownerStreamId !== expectedStreamId)
        if (!localPending && lockReleased) {
          return true
        }
      } catch (error) {
        logger.warn('Failed to inspect chat stream lock while waiting', {
          chatId,
          expectedStreamId,
          error: toError(error).message,
        })
      }
    } else if (!localPending) {
      return true
    }

    if (Date.now() >= deadline) {
      return false
    }
    await sleep(200)
  }
}

export async function getPendingChatStreamId(chatId: string): Promise<string | null> {
  const localEntry = pendingChatStreams.get(chatId)
  if (localEntry?.streamId) {
    return localEntry.streamId
  }

  const redis = getRedisClient()
  if (!redis) {
    return null
  }

  try {
    return (await redis.get(getChatStreamLockKey(chatId))) || null
  } catch (error) {
    logger.warn('Failed to load chat stream lock owner', {
      chatId,
      error: toError(error).message,
    })
    return null
  }
}

/**
 * Loads canonical stream lock owners for chat IDs.
 *
 * `status: 'verified'` means Redis was queried successfully, so a missing
 * owner is authoritative. `status: 'unknown'` means only the process-local
 * pending map is known, which is not enough to declare remote streams inactive
 * in a multi-pod deployment.
 */
export async function getChatStreamLockOwners(
  chatIds: string[]
): Promise<ChatStreamLockOwnersResult> {
  const localOwnersByChatId = new Map<string, string>()
  if (chatIds.length === 0) {
    return { status: 'verified', ownersByChatId: localOwnersByChatId }
  }

  for (const chatId of chatIds) {
    const entry = pendingChatStreams.get(chatId)
    if (entry?.streamId) localOwnersByChatId.set(chatId, entry.streamId)
  }

  const redis = getRedisClient()
  if (!redis) {
    return { status: 'unknown', ownersByChatId: localOwnersByChatId }
  }

  try {
    const keys = chatIds.map(getChatStreamLockKey)
    const values = await redis.mget(keys)
    const redisOwnersByChatId = new Map<string, string>()
    for (let i = 0; i < chatIds.length; i++) {
      const owner = values[i]
      if (owner) redisOwnersByChatId.set(chatIds[i], owner)
    }
    return { status: 'verified', ownersByChatId: redisOwnersByChatId }
  } catch (error) {
    logger.warn('Failed to load chat stream lock owners (batch)', {
      count: chatIds.length,
      error: toError(error).message,
    })
    return { status: 'unknown', ownersByChatId: localOwnersByChatId }
  }
}

export async function releasePendingChatStream(chatId: string, streamId: string): Promise<void> {
  try {
    await releaseLock(getChatStreamLockKey(chatId), streamId)
  } catch (error) {
    logger.warn('Failed to release chat stream lock', {
      chatId,
      streamId,
      error: toError(error).message,
    })
  } finally {
    resolvePendingChatStream(chatId, streamId)
  }
}

export async function acquirePendingChatStream(
  chatId: string,
  streamId: string,
  timeoutMs = 5_000
): Promise<boolean> {
  // Span records wall time spent waiting for the per-chat stream lock.
  // Typical case: sub-10ms uncontested acquire. Worst case: up to
  // `timeoutMs` spent polling while a prior stream finishes. Previously
  // this time looked like "unexplained gap before llm.stream".
  return withCopilotSpan(
    TraceSpan.CopilotChatAcquirePendingStreamLock,
    {
      [TraceAttr.ChatId]: chatId,
      [TraceAttr.StreamId]: streamId,
      [TraceAttr.LockTimeoutMs]: timeoutMs,
    },
    async (span) => {
      const redis = getRedisClient()
      span.setAttribute(TraceAttr.LockBackend, redis ? AbortBackend.Redis : AbortBackend.InProcess)
      if (redis) {
        const deadline = Date.now() + timeoutMs
        for (;;) {
          try {
            const acquired = await acquireLock(
              getChatStreamLockKey(chatId),
              streamId,
              CHAT_STREAM_LOCK_TTL_SECONDS
            )
            if (acquired) {
              registerPendingChatStream(chatId, streamId)
              span.setAttribute(TraceAttr.LockAcquired, true)
              return true
            }
            if (!pendingChatStreams.has(chatId)) {
              const ownerStreamId = await redis.get(getChatStreamLockKey(chatId))
              if (ownerStreamId) {
                const settled = await waitForPendingChatStream(chatId, 0, ownerStreamId)
                if (settled) {
                  continue
                }
              }
            }
          } catch (error) {
            logger.warn('Failed to acquire chat stream lock', {
              chatId,
              streamId,
              error: toError(error).message,
            })
          }

          if (Date.now() >= deadline) {
            span.setAttribute(TraceAttr.LockAcquired, false)
            span.setAttribute(TraceAttr.LockTimedOut, true)
            return false
          }
          await sleep(200)
        }
      }

      for (;;) {
        const existing = pendingChatStreams.get(chatId)
        if (!existing) {
          registerPendingChatStream(chatId, streamId)
          span.setAttribute(TraceAttr.LockAcquired, true)
          return true
        }

        const settled = await Promise.race([
          existing.promise.then(() => true),
          new Promise<boolean>((resolve) => setTimeout(() => resolve(false), timeoutMs)),
        ])
        if (!settled) {
          span.setAttribute(TraceAttr.LockAcquired, false)
          span.setAttribute(TraceAttr.LockTimedOut, true)
          return false
        }
      }
    }
  )
}

/**
 * Returns `true` if it aborted an in-process controller,
 * `false` if it only wrote the marker (no local controller found).
 *
 * Spanned because the two operations inside can stall independently
 * — Redis latency on `writeAbortMarker` was previously invisible, and
 * the "no local controller" branch (happens when the stream handler
 * is on a different Sim box than the one receiving /chat/abort) is
 * a subtle but important outcome to distinguish from "aborted a live
 * controller" in dashboards.
 */
export async function abortActiveStream(streamId: string): Promise<boolean> {
  return withCopilotSpan(
    TraceSpan.CopilotChatAbortActiveStream,
    { [TraceAttr.StreamId]: streamId },
    async (span) => {
      await writeAbortMarker(streamId)
      span.setAttribute(TraceAttr.CopilotAbortMarkerWritten, true)
      const controller = activeStreams.get(streamId)
      if (!controller) {
        span.setAttribute(TraceAttr.CopilotAbortControllerFired, false)
        return false
      }
      controller.abort(AbortReason.UserStop)
      activeStreams.delete(streamId)
      span.setAttribute(TraceAttr.CopilotAbortControllerFired, true)
      return true
    }
  )
}

export type { AbortReasonValue } from './abort-reason'
/**
 * `AbortReason` vocabulary and the `isExplicitStopReason` classifier
 * live in a sibling zero-dependency module so the telemetry layer
 * (`request/otel.ts`) can import them without creating a circular
 * import back through `session/abort.ts`'s OTel-wrapped helpers.
 *
 * Context on why the distinction matters: when the user clicks Stop,
 * we fire `abortController.abort(AbortReason.UserStop)` from
 * `abortActiveStream()`. That causes Sim's SSE writer to close,
 * which in turn makes the BROWSER's SSE reader see the stream end
 * — which fires the browser-side fetch AbortController and
 * propagates back to Sim as `publisher.markDisconnected()`. So on
 * an explicit Stop you observe BOTH "explicit reason" AND
 * "client disconnected" — the discriminator is the reason string,
 * not the client flag.
 *
 * For any NEW abort path, add its reason in `./abort-reason.ts` and
 * update `isExplicitStopReason` if it should be classified as a user
 * stop.
 */
export { AbortReason, isExplicitStopReason } from './abort-reason'

const pollingStreams = new Set<string>()

export function startAbortPoller(
  streamId: string,
  abortController: AbortController,
  options?: { pollMs?: number; requestId?: string; chatId?: string }
): ReturnType<typeof setInterval> {
  const pollMs = options?.pollMs ?? DEFAULT_ABORT_POLL_MS
  const requestId = options?.requestId
  const chatId = options?.chatId

  let lastHeartbeatAt = Date.now()
  let heartbeatOwnershipLost = false

  return setInterval(() => {
    if (pollingStreams.has(streamId)) return
    pollingStreams.add(streamId)

    void (async () => {
      try {
        const shouldAbort = await hasAbortMarker(streamId)
        if (shouldAbort && !abortController.signal.aborted) {
          abortController.abort(AbortReason.RedisPoller)
          await clearAbortMarker(streamId)
        }
      } catch (error) {
        logger.warn('Failed to poll stream abort marker', {
          streamId,
          ...(requestId ? { requestId } : {}),
          error: toError(error).message,
        })
      } finally {
        pollingStreams.delete(streamId)
      }

      if (!chatId || heartbeatOwnershipLost) return
      if (Date.now() - lastHeartbeatAt < CHAT_STREAM_LOCK_HEARTBEAT_INTERVAL_MS) return

      try {
        const owned = await extendLock(
          getChatStreamLockKey(chatId),
          streamId,
          CHAT_STREAM_LOCK_TTL_SECONDS
        )
        lastHeartbeatAt = Date.now()
        if (!owned) {
          heartbeatOwnershipLost = true
          logger.warn('Lost ownership of chat stream lock — stopping heartbeat', {
            chatId,
            streamId,
            ...(requestId ? { requestId } : {}),
          })
        }
      } catch (error) {
        logger.warn('Failed to extend chat stream lock TTL', {
          chatId,
          streamId,
          ...(requestId ? { requestId } : {}),
          error: toError(error).message,
        })
      }
    })()
  }, pollMs)
}

export async function cleanupAbortMarker(streamId: string): Promise<void> {
  try {
    await clearAbortMarker(streamId)
  } catch (error) {
    logger.warn('Failed to clear stream abort marker during cleanup', {
      streamId,
      error: toError(error).message,
    })
  }
}