import type { ToolContextWithMetadata, OpencodeClient } from "./types"
import type { SessionMessage } from "./executor-types"
import { getDefaultSyncPollTimeoutMs, getTimingConfig } from "./timing"
import { log } from "../../shared/logger"
import { normalizeSDKResponse } from "../../shared"
import { extractErrorMessage } from "../../features/background-agent/error-classifier"

const NON_TERMINAL_FINISH_REASONS = new Set(["tool-calls", "unknown"])
const PENDING_TOOL_PART_TYPES = new Set(["tool", "tool_use", "tool-call"])
const ACTIVE_SESSION_STATUSES = new Set(["busy", "retry", "running"])

function wait(milliseconds: number): Promise<void> {
  const sharedBuffer = new SharedArrayBuffer(Int32Array.BYTES_PER_ELEMENT)
  const typedArray = new Int32Array(sharedBuffer)
  const result = Atomics.waitAsync(typedArray, 0, 0, milliseconds)
  return result.async ? result.value.then(() => undefined) : Promise.resolve()
}

function abortSyncSession(client: OpencodeClient, sessionID: string, reason: string): void {
  log("[task] Aborting sync session", { sessionID, reason })
  void client.session.abort({
    path: { id: sessionID },
  }).catch((error: unknown) => {
    log("[task] Failed to abort sync session", { sessionID, reason, error: String(error) })
  })
}

function isActiveSessionStatus(status: { type: string } | undefined): boolean {
  return status !== undefined && ACTIVE_SESSION_STATUSES.has(status.type)
}

async function fetchSessionMessages(
  client: OpencodeClient,
  sessionID: string
): Promise<SessionMessage[]> {
  const messagesResult = await client.session.messages({ path: { id: sessionID } })
  const rawData = (messagesResult as { data?: unknown })?.data ?? messagesResult
  return Array.isArray(rawData) ? (rawData as SessionMessage[]) : []
}

function getTerminalSessionError(messages: SessionMessage[]): string | null {
  const lastAssistant = [...messages].reverse().find((msg) => msg.info?.role === "assistant")
  const lastUser = [...messages].reverse().find((msg) => msg.info?.role === "user")
  if (lastUser?.info?.id && lastAssistant?.info?.id && lastAssistant.info.id <= lastUser.info.id) {
    return null
  }
  if (!lastAssistant?.info || !("error" in lastAssistant.info)) {
    return null
  }

  const errorMessage = extractErrorMessage((lastAssistant.info as { error?: unknown }).error)
  return errorMessage && errorMessage.length > 0 ? errorMessage : "Session error"
}

export function isSessionComplete(messages: SessionMessage[]): boolean {
  let lastUser: SessionMessage | undefined
  let lastAssistant: SessionMessage | undefined

  for (let i = messages.length - 1; i >= 0; i--) {
    const msg = messages[i]
    if (!lastAssistant && msg.info?.role === "assistant") lastAssistant = msg
    if (!lastUser && msg.info?.role === "user") lastUser = msg
    if (lastUser && lastAssistant) break
  }

  if (!lastAssistant?.info?.finish) return false
  if (NON_TERMINAL_FINISH_REASONS.has(lastAssistant.info.finish)) return false
  if (lastAssistant.parts?.some((part) => part.type && PENDING_TOOL_PART_TYPES.has(part.type))) return false
  if (!lastUser?.info?.id || !lastAssistant?.info?.id) return false
  return lastUser.info.id < lastAssistant.info.id
}

const DEFAULT_MAX_ASSISTANT_TURNS = 300

export async function pollSyncSession(
  ctx: ToolContextWithMetadata,
  client: OpencodeClient,
  input: {
    sessionID: string
    agentToUse: string
    toastManager: { removeTask: (id: string) => void } | null | undefined
    taskId: string | undefined
    anchorMessageCount?: number
    maxAssistantTurns?: number
  },
  timeoutMs?: number
): Promise<string | null> {
  const syncTiming = getTimingConfig()
  const maxPollTimeMs = Math.max(timeoutMs ?? getDefaultSyncPollTimeoutMs(), 50)
  const maxTurns = input.maxAssistantTurns ?? DEFAULT_MAX_ASSISTANT_TURNS
  const pollStart = Date.now()
  let inactiveStart = pollStart
  let pollCount = 0
  let timedOut = false
  let assistantTurnCount = 0
  let lastSeenAssistantId: string | undefined

  log("[task] Starting poll loop", { sessionID: input.sessionID, agentToUse: input.agentToUse, maxTurns })

  while (true) {
    const inactiveElapsedMs = Date.now() - inactiveStart
    if (inactiveElapsedMs >= maxPollTimeMs) {
      timedOut = true
      break
    }

    if (ctx.abort?.aborted) {
      try {
        const messages = await fetchSessionMessages(client, input.sessionID)
        const hasNewMessages =
          input.anchorMessageCount === undefined || messages.length > input.anchorMessageCount
        if (hasNewMessages && isSessionComplete(messages)) {
          log("[task] Abort detected after session already completed", { sessionID: input.sessionID })
          return null
        }
      } catch (error) {
        log("[task] Final messages fetch failed after abort, continuing with abort", {
          sessionID: input.sessionID,
          error: String(error),
        })
      }

      log("[task] Aborted by user", { sessionID: input.sessionID })
      abortSyncSession(client, input.sessionID, "parent_abort")
      if (input.toastManager && input.taskId) input.toastManager.removeTask(input.taskId)
      return `Task aborted.\n\nSession ID: ${input.sessionID}`
    }

    await wait(syncTiming.POLL_INTERVAL_MS)
    pollCount++

    let statusResult: { data?: Record<string, { type: string }> }
    try {
      statusResult = await client.session.status()
    } catch (error) {
      log("[task] Poll status fetch failed, retrying", { sessionID: input.sessionID, error: String(error) })
      continue
    }
    const allStatuses = normalizeSDKResponse(statusResult, {} as Record<string, { type: string }>)
    const sessionStatus = allStatuses[input.sessionID]

    if (pollCount % 10 === 0) {
      log("[task] Poll status", {
        sessionID: input.sessionID,
        pollCount,
        elapsed: Math.floor((Date.now() - pollStart) / 1000) + "s",
        inactiveElapsed: Math.floor(inactiveElapsedMs / 1000) + "s",
        sessionStatus: sessionStatus?.type ?? "not_in_status",
      })
    }

    if (isActiveSessionStatus(sessionStatus)) {
      inactiveStart = Date.now()
      continue
    }

    let messages: SessionMessage[]
    try {
      messages = await fetchSessionMessages(client, input.sessionID)
    } catch (error) {
      log("[task] Poll messages fetch failed, retrying", { sessionID: input.sessionID, error: String(error) })
      continue
    }

    if (input.anchorMessageCount !== undefined && messages.length <= input.anchorMessageCount) {
      continue
    }

    const sessionError = getTerminalSessionError(messages)
    if (sessionError) {
      log("[task] Poll detected terminal session error", { sessionID: input.sessionID, sessionError })
      return sessionError
    }

    if (isSessionComplete(messages)) {
      log("[task] Poll complete - terminal finish detected", { sessionID: input.sessionID, pollCount })
      break
    }

    // Count new assistant turns to circuit-break infinite loops
    const lastAssistant = [...messages].reverse().find((m) => m.info?.role === "assistant")
    if (lastAssistant?.info?.id && lastAssistant.info.id !== lastSeenAssistantId) {
      lastSeenAssistantId = lastAssistant.info.id
      assistantTurnCount++
      if (assistantTurnCount >= maxTurns) {
        log("[task] Max assistant turns reached, aborting to prevent infinite loop", {
          sessionID: input.sessionID,
          assistantTurnCount,
          maxTurns,
        })
        abortSyncSession(client, input.sessionID, "max_turns_exceeded")
        if (input.toastManager && input.taskId) input.toastManager.removeTask(input.taskId)
        return `Task aborted: subagent exceeded ${maxTurns} assistant turns without completing. This usually indicates an infinite tool-call loop. Session ID: ${input.sessionID}`
      }
    }

    const hasAssistantText = messages.some((m) => {
      if (m.info?.role !== "assistant") return false
      const parts = m.parts ?? []
      return parts.some((p) => {
        if (p.type !== "text" && p.type !== "reasoning") return false
        const text = (p.text ?? "").trim()
        return text.length > 0
      })
    })

    if (!lastAssistant?.info?.finish && hasAssistantText) {
      log("[task] Poll complete - assistant text detected (fallback)", {
        sessionID: input.sessionID,
        pollCount,
      })
      break
    }
  }

  if (timedOut) {
    log("[task] Poll inactivity timeout reached", { sessionID: input.sessionID, pollCount })
    abortSyncSession(client, input.sessionID, "poll_timeout")
  }

  return timedOut
    ? `Poll inactivity timeout reached after ${maxPollTimeMs}ms without active OpenCode status for session ${input.sessionID}`
    : null
}