// Test-local programmable IApiClient fake (NOT the fixture: fixture is a demo
// data source on a real clock; behavior tests need per-case responses and
// deferred-controlled timing). Streams are hand pumps: pushMux/pushHost.
import type { CommandId } from '@deepseek-ai/dsh-commands/brand'
import type {
  CommandDescriptor, HostFrame, IApiClient, ModelTarget, MuxFrame,
  RpcRequest, RpcResponse, SessionId, SessionModels, SessionSearchItem, SkillEntry,
} from '../src/client/api.ts'
import { RpcId } from '../src/client/api.ts'

export interface Deferred<T> {
  promise: Promise<T>
  resolve(value: T): void
  reject(error: unknown): void
}

/** Test-held settlement: the case decides when an RPC lands (history-pending injections etc.). */
export function deferred<T>(): Deferred<T> {
  let resolve!: (value: T) => void
  let reject!: (error: unknown) => void
  const promise = new Promise<T>((res, rej) => {
    resolve = res
    reject = rej
  })
  return { promise, resolve, reject }
}

let nextRpc = 0

export function ok<T>(value: T): RpcResponse<T> {
  return { rpcId: RpcId(`fake-${nextRpc++}`), result: { ok: true, value } }
}


type StreamItem<F> = { kind: 'frame'; envelope: RpcRequest<F> } | { kind: 'end' } | { kind: 'fail'; error: unknown }

interface StreamConn<F> {
  feed(item: StreamItem<F>): void
}

export class FakeApiClient implements IApiClient {
  /** Chronological call record: [method, payload]. */
  readonly calls: { method: string; payload: unknown }[] = []

  // Programmable slots (defaults answer OK-empty); reassign per case.
  onList: (payload: unknown) => Promise<RpcResponse<{ items: never[] }>> = () => Promise.resolve(ok({ items: [] }))
  onSearch: (payload: unknown) => Promise<RpcResponse<{ items: SessionSearchItem[]; hasMore: boolean }>> =
    () => Promise.resolve(ok({ items: [], hasMore: false }))
  onCreate: (payload: unknown) => Promise<RpcResponse<{ sessionId: SessionId }>> = () => Promise.resolve(ok({ sessionId: 'fk-new' as SessionId }))
  onRename: (payload: unknown) => Promise<RpcResponse<{ title: string; seq: number }>> = () => Promise.resolve(ok({ title: 'fk-renamed', seq: 0 }))
  onFork: (payload: unknown) => Promise<RpcResponse<{ sessionId: SessionId }>> = () => Promise.resolve(ok({ sessionId: 'fk-fork' as SessionId }))
  onHistory: (payload: { sessionId: SessionId; beforeSeq?: number; maxMessages?: number })
  => Promise<RpcResponse<{ events: never[]; hasMore: boolean; modelTarget: ModelTarget }>> =
    () => Promise.resolve(ok({
      events: [],
      hasMore: false,
      modelTarget: { provider: 'deepseek-official', model: 'deepseek-chat' },
    }))

  onModels: (payload: unknown) => Promise<RpcResponse<SessionModels>> = () => Promise.resolve(ok({
    current: { provider: 'deepseek-official', model: 'deepseek-chat' },
    routable: true,
    groups: [],
    failures: [],
  }))
  onSelectModel: (payload: ModelTarget & { sessionId: SessionId })
  => Promise<RpcResponse<{ selected: ModelTarget }>> =
    payload => Promise.resolve(ok({ selected: { provider: payload.provider, model: payload.model } }))
  onPrompt: (payload: unknown) => Promise<RpcResponse<{ accepted: true }>> = () => Promise.resolve(ok({ accepted: true as const }))
  onUpdateQueue: (payload: unknown) => Promise<RpcResponse<{ accepted: true }>> = () => Promise.resolve(ok({ accepted: true as const }))
  onCancel: (payload: unknown) => Promise<RpcResponse<{ accepted: true }>> = () => Promise.resolve(ok({ accepted: true as const }))
  onDescribe: (payload: unknown) => Promise<RpcResponse<{ version: string; cwd: string; attachedSessions: number }>> =
    () => Promise.resolve(ok({ version: '0-fake', cwd: '/f', attachedSessions: 0 }))
  onPickDirectory: (payload: unknown) => Promise<RpcResponse<{ path: string | null }>> =
    () => Promise.resolve(ok({ path: null }))
  onOpenPath: (payload: unknown) => Promise<RpcResponse<{ opened: true }>> =
    () => Promise.resolve(ok({ opened: true as const }))

  onListDirectory: (payload: unknown) => Promise<RpcResponse<{
    path: string
    home: string
    crumbs: { name: string; path: string; hidden: boolean }[]
    entries: { name: string; path: string; hidden: boolean }[]
    truncated: boolean
  }>> =
    () => Promise.resolve(ok({ path: '/home/fake', home: '/home/fake', crumbs: [{ name: '/', path: '/', hidden: false }], entries: [], truncated: false }))

  onCreateDirectory: (payload: unknown) => Promise<RpcResponse<{ path: string }>> =
    () => Promise.resolve(ok({ path: '/home/fake/new' }))

  private readonly muxConns: StreamConn<MuxFrame>[] = []
  private readonly hostConns: StreamConn<HostFrame>[] = []
  lastSearchSignal: AbortSignal | undefined

  // Parameter annotations below are local structural types on purpose: the CI
  // lint lane runs without built artifacts, where IApiClient's wire types
  // (apiproxy subpath) resolve to any and inferred params trip no-unsafe-argument.
  readonly sessions: IApiClient['sessions'] = {
    list: (payload: unknown) => this.record('session.list', payload, this.onList(payload)),
    search: (payload: unknown, signal?: AbortSignal) => {
      this.lastSearchSignal = signal
      return this.record('session.search', payload, this.onSearch(payload))
    },
    create: (payload: unknown) => this.record('session.create', payload, this.onCreate(payload)),
    history: (payload: { sessionId: SessionId; beforeSeq?: number; maxMessages?: number }) =>
      this.record('session.history', payload, this.onHistory(payload)),
    models: (payload: unknown) => this.record('session.models', payload, this.onModels(payload)),
    selectModel: (payload: ModelTarget & { sessionId: SessionId }) =>
      this.record('session.selectModel', payload, this.onSelectModel(payload)),
    rename: (payload: unknown) => this.record('session.rename', payload, this.onRename(payload)),
    fork: (payload: unknown) => this.record('session.fork', payload, this.onFork(payload)),
    prompt: (payload: unknown) => this.record('session.prompt', payload, this.onPrompt(payload)),
    updateQueue: (payload: unknown) => this.record('session.updateQueue', payload, this.onUpdateQueue(payload)),
    cancel: (payload: unknown) => this.record('session.cancel', payload, this.onCancel(payload)),
  }

  readonly subagents: IApiClient['subagents'] = {
    list: (payload: unknown) => this.record('subagent.list', payload, Promise.resolve(ok({
      entries: [],
      parentAvailable: true,
    }))),
    history: (payload: unknown) => this.record('subagent.history', payload, Promise.resolve(ok({
      events: [],
      hasMore: false,
    }))),
    prompt: (payload: unknown) => this.record('subagent.prompt', payload, Promise.resolve(ok({
      messageId: 'fake-message' as never,
    }))),
  }

  readonly host: IApiClient['host'] = {
    describe: payload => this.record('host.describe', payload, this.onDescribe(payload)),
    pickDirectory: payload => this.record('host.pickDirectory', payload, this.onPickDirectory(payload)),
    listDirectory: payload => this.record('host.listDirectory', payload, this.onListDirectory(payload)),
    createDirectory: payload => this.record('host.createDirectory', payload, this.onCreateDirectory(payload)),
    openPath: payload => this.record('host.openPath', payload, this.onOpenPath(payload)),
  }

  readonly workspace: IApiClient['workspace'] = {
    list: (payload: unknown) => this.record('workspace.list', payload, Promise.resolve(ok({ items: [], archivedSessionIds: [] }))),
    create: (payload: unknown) => this.record('workspace.create', payload, Promise.resolve(ok({
      workspace: { workspaceId: 'fk-ws' as never, path: '/f/ws', title: 'ws', sessionIds: [], createdAt: '0', updatedAt: '0' },
      created: true,
    }))),
    rename: (payload: unknown) => this.record('workspace.rename', payload, Promise.resolve(ok({
      workspace: { workspaceId: 'fk-ws' as never, path: '/f/ws', title: 'ws', sessionIds: [], createdAt: '0', updatedAt: '0' },
    }))),
    delete: (payload: unknown) => this.record('workspace.delete', payload, Promise.resolve(ok({ deleted: true as const }))),
    insertSessionBefore: (payload: unknown) => this.record('workspace.insertSessionBefore', payload, Promise.resolve(ok({
      workspace: { workspaceId: 'fk-ws' as never, path: '/f/ws', title: 'ws', sessionIds: [], createdAt: '0', updatedAt: '0' },
    }))),
    archiveSession: (payload: unknown) => this.record('workspace.archiveSession', payload, Promise.resolve(ok({
      archivedSessionIds: [(payload as { sessionId: SessionId }).sessionId],
    }))),
  }

  // Payloads stay `unknown` (lint-lane note above); response rows are the real
  // wire shapes so cases can program catalogs and skill lists without casts.
  onCommandList: (payload: unknown) => Promise<RpcResponse<{ commands: CommandDescriptor[] }>>
    = () => Promise.resolve(ok({ commands: [] }))
  onCommandExecute: (payload: unknown) => Promise<RpcResponse<{ matched: boolean; commandId?: CommandId }>>
    = () => Promise.resolve(ok({ matched: false }))
  onSkillList: (payload: unknown) => Promise<RpcResponse<{ skills: SkillEntry[] }>>
    = () => Promise.resolve(ok({ skills: [] }))

  readonly commands: IApiClient['commands'] = {
    list: (payload: unknown) => this.record('command.list', payload, this.onCommandList(payload)),
    execute: (payload: unknown) => this.record('command.execute', payload, this.onCommandExecute(payload)),
  }

  readonly skills: IApiClient['skills'] = {
    list: (payload: unknown) => this.record('skill.list', payload, this.onSkillList(payload)),
  }

  readonly goals: IApiClient['goals'] = {
    create: payload => this.record('goal.create', payload, Promise.resolve(ok({ ref: { id: 'fake-goal' as never, revision: 1 } }))),
    edit: payload => this.record('goal.edit', payload, Promise.resolve(ok({ ref: { id: 'fake-goal' as never, revision: 1 } }))),
    pause: payload => this.record('goal.pause', payload, Promise.resolve(ok({ ref: { id: 'fake-goal' as never, revision: 1 } }))),
    resume: payload => this.record('goal.resume', payload, Promise.resolve(ok({ ref: { id: 'fake-goal' as never, revision: 1 } }))),
    complete: payload => this.record('goal.complete', payload, Promise.resolve(ok({ ref: { id: 'fake-goal' as never, revision: 1 } }))),
    clear: payload => this.record('goal.clear', payload, Promise.resolve(ok({ cleared: true as const }))),
  }

  readonly settings: IApiClient['settings'] = {
    describe: payload => this.record('settings.describe', payload, Promise.resolve(ok({ writable: true, hasDocument: false, namespaces: [] }))),
    openDocument: payload => this.record('settings.openDocument', payload, Promise.resolve(ok({ opened: true as const }))),
    update: payload => this.record('settings.update', payload, Promise.resolve(ok({ ns: 'fake', schema: {}, value: {}, applies: 'live' as const, secrets: [], revision: 0 }))),
    replace: payload => this.record('settings.replace', payload, Promise.resolve(ok({ ns: 'fake', schema: {}, value: {}, applies: 'live' as const, secrets: [], revision: 0 }))),
    mutate: payload => this.record('settings.mutate', payload, Promise.resolve(ok({ ns: 'fake', schema: {}, value: {}, applies: 'live' as const, secrets: [], revision: 0 }))),
  }

  readonly credentials: IApiClient['credentials'] = {
    describe: payload => this.record('credentials.describe', payload, Promise.resolve(ok({ credentials: {} }))),
    set: payload => this.record('credentials.set', payload, Promise.resolve(ok({}))),
    unset: payload => this.record('credentials.unset', payload, Promise.resolve(ok({}))),
  }

  readonly llm: IApiClient['llm'] = {
    providers: payload => this.record('llm.providers', payload, Promise.resolve(ok({ providers: [] }))),
    models: payload => this.record('llm.models', payload, Promise.resolve(ok({ groups: [], failures: [] }))),
    discoverModels: payload => this.record('llm.discoverModels', payload, Promise.resolve(ok({ models: [] }))),
  }

  /** When true, streams never fire onOpen (misbehaving-carrier material for the handshake timeout guard). */
  suppressStreamOpen = false

  /** When true, onOpen callbacks are parked instead of fired; releaseStreamOpens() fires them.
   *  Lets a case hold the readiness handshake open (describe done, streams not yet "established"). */
  holdStreamOpen = false
  private heldOpens: (() => void)[] = []

  releaseStreamOpens(): void {
    const held = this.heldOpens
    this.heldOpens = []
    for (const fire of held) fire()
  }

  readonly events: IApiClient['events'] = {
    mux: (_payload: unknown, signal: AbortSignal, onOpen?: () => void) =>
      this.openStream(this.muxConns, signal, onOpen),
    host: (_payload: unknown, signal: AbortSignal, onOpen?: () => void) =>
      this.openStream(this.hostConns, signal, onOpen),
  }

  respond(): Promise<{ accepted: false; reason: 'not-pending' }> {
    return Promise.resolve({ accepted: false, reason: 'not-pending' })
  }

  /** Push one mux frame to every open mux stream (rpcId minted unless pinned by the case). */
  pushMux(frame: MuxFrame, rpcId?: string): void {
    for (const conn of [...this.muxConns]) conn.feed({ kind: 'frame', envelope: { rpcId: RpcId(rpcId ?? `push-${nextRpc++}`), payload: frame } })
  }

  pushHost(frame: HostFrame, rpcId?: string): void {
    for (const conn of [...this.hostConns]) conn.feed({ kind: 'frame', envelope: { rpcId: RpcId(rpcId ?? `push-${nextRpc++}`), payload: frame } })
  }

  /** End (clean close) or fail (throw) every open stream — reconnect-path material. */
  endStreams(): void {
    for (const conn of [...this.muxConns, ...this.hostConns]) conn.feed({ kind: 'end' })
  }

  failStreams(error: unknown): void {
    for (const conn of [...this.muxConns, ...this.hostConns]) conn.feed({ kind: 'fail', error })
  }

  get openMuxCount(): number {
    return this.muxConns.length
  }

  callsOf(method: string): unknown[] {
    return this.calls.filter(c => c.method === method).map(c => c.payload)
  }

  private record<T>(method: string, payload: unknown, response: Promise<T>): Promise<T> {
    this.calls.push({ method, payload })
    return response
  }

  private async *openStream<F>(registry: StreamConn<F>[], signal: AbortSignal, onOpen?: () => void): AsyncGenerator<RpcRequest<F>> {
    const inbox: StreamItem<F>[] = []
    let wake: (() => void) | null = null
    const conn: StreamConn<F> = {
      feed: (item) => {
        inbox.push(item)
        wake?.()
      },
    }
    registry.push(conn)
    if (this.holdStreamOpen && onOpen !== undefined) this.heldOpens.push(onOpen)
    else if (!this.suppressStreamOpen) onOpen?.()
    try {
      while (!signal.aborted) {
        while (inbox.length > 0) {
          const item = inbox.shift() as StreamItem<F>
          if (item.kind === 'end') return
          if (item.kind === 'fail') throw item.error
          yield item.envelope
        }
        await new Promise<void>((resolve) => {
          wake = resolve
          signal.addEventListener('abort', () => { resolve() }, { once: true })
        })
        wake = null
      }
    } finally {
      registry.splice(registry.indexOf(conn), 1)
    }
  }
}
