import { log } from "./logger"
import {
  DEFAULT_SESSION_IDLE_SETTLE_MS,
  isSessionActive,
  settleAfterSessionIdle,
} from "./session-idle-settle"

export const DEFAULT_PROMPT_ASYNC_POST_DISPATCH_HOLD_MS = 250
export const DEFAULT_PROMPT_DISPATCH_TIMEOUT_MS = 30_000
export const DEFAULT_PROMPT_GATE_MESSAGES_FETCH_TIMEOUT_MS = 5_000

type PromptAsyncInput = {
  path?: { id?: string }
  body?: unknown
  query?: unknown
  signal?: unknown
  [key: string]: unknown
}

type PromptMessagesQuery = {
  directory: string
  limit?: number
}

type PromptAsyncClient<TInput> = {
  session?: {
    status?: () => Promise<unknown>
    messages?: (input: { path: { id: string }; query: PromptMessagesQuery }) => Promise<unknown>
    promptAsync?: (input: TInput) => Promise<unknown>
  }
}

type PromptClient<TInput> = {
  session?: {
    status?: () => Promise<unknown>
    messages?: (input: { path: { id: string }; query: PromptMessagesQuery }) => Promise<unknown>
    prompt?: (input: TInput) => Promise<unknown>
  }
}

type PromptAsyncReservation = {
  source: string
  reservedAt: number
  token: symbol
  expiresAt?: number
}

declare function setTimeout(callback: () => void, delay?: number): ReturnType<typeof globalThis.setTimeout>
declare function clearTimeout(timeout: ReturnType<typeof globalThis.setTimeout>): void

let promptGateMessagesFetchTimeoutMsForTesting: number | undefined

export type PromptAsyncGateResult =
  | { status: "dispatched"; response: unknown }
  | { status: "active" }
  | { status: "reserved"; reservedBy: string }
  | { status: "unavailable" }
  | { status: "failed"; error: unknown }

type PromptAsyncReservationReleaseOptions = {
  reservedBy?: string | readonly string[]
  reservedByPrefix?: string | readonly string[]
}

const promptAsyncReservations = new Map<string, PromptAsyncReservation>()

export function _setPromptGateMessagesFetchTimeoutMsForTesting(value: number | undefined): void {
  promptGateMessagesFetchTimeoutMsForTesting = value
}

function getPromptGateMessagesFetchTimeoutMs(): number {
  return promptGateMessagesFetchTimeoutMsForTesting ?? DEFAULT_PROMPT_GATE_MESSAGES_FETCH_TIMEOUT_MS
}

function pruneExpiredReservations(now = Date.now()): void {
  for (const [sessionID, reservation] of promptAsyncReservations) {
    if (typeof reservation.expiresAt === "number" && reservation.expiresAt <= now) {
      promptAsyncReservations.delete(sessionID)
      log("[prompt-async-gate] expired reservation released", {
        sessionID,
        source: reservation.source,
      })
    }
  }
}

function getActiveReservation(sessionID: string): PromptAsyncReservation | undefined {
  pruneExpiredReservations()
  return promptAsyncReservations.get(sessionID)
}

function reservationSourceMatches(
  reservationSource: string,
  expectedSource: string | readonly string[],
  expectedPrefix?: string | readonly string[],
): boolean {
  if (typeof expectedSource === "string") {
    if (reservationSource === expectedSource) {
      return true
    }
  } else if (expectedSource.includes(reservationSource)) {
    return true
  }

  if (expectedPrefix === undefined) {
    return false
  }

  const prefixes = typeof expectedPrefix === "string" ? [expectedPrefix] : expectedPrefix
  return prefixes
    .filter((prefix) => prefix.length > 0 && prefix.endsWith(":"))
    .some((prefix) => reservationSource.startsWith(prefix))
}

async function withDispatchTimeout<T>(
  operation: Promise<T>,
  dispatchTimeoutMs: number,
  operationName: string,
): Promise<T> {
  if (dispatchTimeoutMs <= 0) {
    return operation
  }

  let timeoutID: ReturnType<typeof globalThis.setTimeout> | undefined
  const timeoutPromise = new Promise<never>((_, reject) => {
    timeoutID = setTimeout(() => {
      reject(new Error(`${operationName} timed out after ${dispatchTimeoutMs}ms`))
    }, dispatchTimeoutMs)
  })

  try {
    return await Promise.race([operation, timeoutPromise])
  } finally {
    if (timeoutID !== undefined) {
      clearTimeout(timeoutID)
    }
  }
}

function isRecord(value: unknown): value is Record<string, unknown> {
  return typeof value === "object" && value !== null
}

function getPromptQuery(input: unknown): PromptMessagesQuery {
  if (!isRecord(input)) {
    return { directory: "" }
  }
  const query = input.query
  if (!isRecord(query)) {
    return { directory: "" }
  }

  const promptQuery: PromptMessagesQuery = { directory: "" }
  if (typeof query.directory === "string") {
    promptQuery.directory = query.directory
  }
  if (typeof query.limit === "number") {
    promptQuery.limit = query.limit
  }
  return promptQuery
}

function getMessagesData(response: unknown): unknown[] {
  if (isRecord(response) && Array.isArray(response.data)) {
    return response.data
  }
  return Array.isArray(response) ? response : []
}

function messageRole(message: unknown): string | undefined {
  if (!isRecord(message)) {
    return undefined
  }
  const info = message.info
  if (isRecord(info) && typeof info.role === "string") {
    return info.role
  }
  return typeof message.role === "string" ? message.role : undefined
}

function partIsWaitingOnTool(part: unknown): boolean {
  if (!isRecord(part)) {
    return false
  }
  if (part.type !== "tool" && part.type !== "tool_use") {
    return false
  }

  const state = part.state
  if (!isRecord(state)) {
    return false
  }
  return state.status === "pending" || state.status === "running"
}

function latestAssistantTurnIsWaitingOnTools(messages: unknown[]): boolean {
  for (let index = messages.length - 1; index >= 0; index--) {
    const message = messages[index]
    const role = messageRole(message)
    if (role === "assistant") {
      if (!isRecord(message) || !Array.isArray(message.parts)) {
        return false
      }
      return message.parts.some(partIsWaitingOnTool)
    }
    if (role === "user") {
      return false
    }
  }
  return false
}

async function sessionLatestAssistantIsWaitingOnTools<TInput>(args: {
  client: { session?: { messages?: (input: { path: { id: string }; query: PromptMessagesQuery }) => Promise<unknown> } }
  sessionID: string
  input: TInput
  sessionName: "promptAsync" | "prompt"
  source: string
  timeoutMs: number
}): Promise<boolean> {
  const messages = args.client.session?.messages
  if (typeof messages !== "function") {
    return false
  }

  try {
    const response = await withDispatchTimeout(
      messages({
        path: { id: args.sessionID },
        query: getPromptQuery(args.input),
      }),
      args.timeoutMs,
      `[prompt-async-gate] ${args.sessionName} session.messages`,
    )
    return latestAssistantTurnIsWaitingOnTools(getMessagesData(response))
  } catch (error) {
    log("[prompt-async-gate] latest assistant tool-state check failed", {
      sessionID: args.sessionID,
      source: args.source,
      error: String(error),
    })
    return false
  }
}

async function dispatchAfterSessionIdle<TInput>(args: {
  sessionName: "promptAsync" | "prompt"
  client: {
    session?: {
      status?: () => Promise<unknown>
      messages?: (input: { path: { id: string }; query: PromptMessagesQuery }) => Promise<unknown>
    }
  }
  sessionID: string
  input: TInput
  source: string
  settleMs: number
  postDispatchHoldMs: number
  dispatchTimeoutMs: number
  checkStatus: boolean
  checkToolState: boolean
  dispatch: (input: TInput) => Promise<unknown>
}): Promise<PromptAsyncGateResult> {
  const {
    sessionName,
    client,
    sessionID,
    input,
    source,
    settleMs,
    postDispatchHoldMs,
    dispatchTimeoutMs,
    checkStatus,
    checkToolState,
    dispatch,
  } = args

  const existing = getActiveReservation(sessionID)
  if (existing) {
    log(`[prompt-async-gate] ${sessionName} skipped because session is reserved`, {
      sessionID,
      source,
      reservedBy: existing.source,
      reservedAgeMs: Date.now() - existing.reservedAt,
    })
    return { status: "reserved", reservedBy: existing.source }
  }

  const reservation: PromptAsyncReservation = {
    source,
    reservedAt: Date.now(),
    token: Symbol(source),
  }
  promptAsyncReservations.set(sessionID, reservation)
  let dispatchAttempted = false

  try {
    const canReadStatus = checkStatus && typeof client.session?.status === "function"
    if (settleMs > 0) {
      await settleAfterSessionIdle(settleMs)
    }

    let sessionActive = false
    if (canReadStatus) {
      try {
        sessionActive = await withDispatchTimeout(
          isSessionActive(client, sessionID),
          Math.min(dispatchTimeoutMs, 5000),
          `[prompt-async-gate] ${sessionName} isSessionActive`,
        )
      } catch {
        sessionActive = false
      }
    }
    if (sessionActive) {
      log(`[prompt-async-gate] ${sessionName} skipped because session is active`, { sessionID, source })
      return { status: "active" }
    }

    if (
      checkToolState
      && typeof client.session?.messages === "function"
      && await sessionLatestAssistantIsWaitingOnTools({
        client,
        sessionID,
        input,
        sessionName,
        source,
        timeoutMs: Math.min(dispatchTimeoutMs, getPromptGateMessagesFetchTimeoutMs()),
      })
    ) {
      log(`[prompt-async-gate] ${sessionName} skipped because latest assistant is waiting on tools`, {
        sessionID,
        source,
      })
      return { status: "active" }
    }

    log(`[prompt-async-gate] ${sessionName} dispatching`, { sessionID, source })
    dispatchAttempted = true
    const response = await withDispatchTimeout(
      dispatch(input),
      dispatchTimeoutMs,
      `[prompt-async-gate] ${sessionName} dispatch`,
    )
    log(`[prompt-async-gate] ${sessionName} dispatched`, { sessionID, source })
    return { status: "dispatched", response }
  } catch (error) {
    log(`[prompt-async-gate] ${sessionName} failed`, { sessionID, source, error: String(error) })
    return { status: "failed", error }
  } finally {
    const current = promptAsyncReservations.get(sessionID)
    if (current?.token === reservation.token) {
      if (dispatchAttempted && postDispatchHoldMs > 0) {
        reservation.expiresAt = Date.now() + postDispatchHoldMs
      } else {
        promptAsyncReservations.delete(sessionID)
      }
    }
  }
}

export async function promptAsyncAfterSessionIdle<TInput = PromptAsyncInput>(args: {
  client: PromptAsyncClient<TInput>
  sessionID: string
  input: TInput
  source: string
  settleMs?: number
  postDispatchHoldMs?: number
  dispatchTimeoutMs?: number
  checkStatus?: boolean
  checkToolState?: boolean
}): Promise<PromptAsyncGateResult> {
  const {
    client,
    sessionID,
    input,
    source,
    settleMs = DEFAULT_SESSION_IDLE_SETTLE_MS,
  } = args
  const postDispatchHoldMs = args.postDispatchHoldMs ?? DEFAULT_PROMPT_ASYNC_POST_DISPATCH_HOLD_MS
  const dispatchTimeoutMs = args.dispatchTimeoutMs ?? DEFAULT_PROMPT_DISPATCH_TIMEOUT_MS
  const session = client.session

  if (typeof session?.promptAsync !== "function") {
    log("[prompt-async-gate] promptAsync unavailable", { sessionID, source })
    return { status: "unavailable" }
  }
  const dispatchPromptAsync = session.promptAsync.bind(session)

  return dispatchAfterSessionIdle({
    sessionName: "promptAsync",
    client,
    sessionID,
    input,
    source,
    settleMs,
    postDispatchHoldMs,
    dispatchTimeoutMs,
    checkStatus: args.checkStatus !== false,
    checkToolState: args.checkToolState !== false,
    dispatch: (dispatchInput) => dispatchPromptAsync(dispatchInput),
  })
}

export async function promptAfterSessionIdle<TInput = PromptAsyncInput>(args: {
  client: PromptClient<TInput>
  sessionID: string
  input: TInput
  source: string
  settleMs?: number
  postDispatchHoldMs?: number
  dispatchTimeoutMs?: number
  checkStatus?: boolean
  checkToolState?: boolean
}): Promise<PromptAsyncGateResult> {
  const {
    client,
    sessionID,
    input,
    source,
    settleMs = DEFAULT_SESSION_IDLE_SETTLE_MS,
  } = args
  const postDispatchHoldMs = args.postDispatchHoldMs ?? DEFAULT_PROMPT_ASYNC_POST_DISPATCH_HOLD_MS
  const dispatchTimeoutMs = args.dispatchTimeoutMs ?? DEFAULT_PROMPT_DISPATCH_TIMEOUT_MS
  const session = client.session

  if (typeof session?.prompt !== "function") {
    log("[prompt-async-gate] prompt unavailable", { sessionID, source })
    return { status: "unavailable" }
  }
  const dispatchPrompt = session.prompt.bind(session)

  return dispatchAfterSessionIdle({
    sessionName: "prompt",
    client,
    sessionID,
    input,
    source,
    settleMs,
    postDispatchHoldMs,
    dispatchTimeoutMs,
    checkStatus: args.checkStatus !== false,
    checkToolState: args.checkToolState !== false,
    dispatch: (dispatchInput) => dispatchPrompt(dispatchInput),
  })
}

export function releaseAllPromptAsyncReservationsForTesting(): void {
  promptAsyncReservations.clear()
  promptGateMessagesFetchTimeoutMsForTesting = undefined
}

export function releasePromptAsyncReservation(
  sessionID: string,
  source: string,
  options?: PromptAsyncReservationReleaseOptions,
): boolean {
  const existing = promptAsyncReservations.get(sessionID)
  if (!existing) {
    return false
  }

  const expectedSource = options?.reservedBy ?? source
  if (!reservationSourceMatches(existing.source, expectedSource, options?.reservedByPrefix)) {
    log("[prompt-async-gate] promptAsync reservation release skipped for different source", {
      sessionID,
      source,
      reservedBy: existing.source,
    })
    return false
  }

  promptAsyncReservations.delete(sessionID)
  log("[prompt-async-gate] promptAsync reservation released", {
    sessionID,
    source,
    reservedBy: existing.source,
  })
  return true
}