utils/suggestions/slackChannelSuggestions.ts

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import { z } from 'zod'
import type { SuggestionItem } from '../../components/PromptInput/PromptInputFooterSuggestions.js'
import type { MCPServerConnection } from '../../services/mcp/types.js'
import { logForDebugging } from '../debug.js'
import { lazySchema } from '../lazySchema.js'
import { createSignal } from '../signal.js'
import { jsonParse } from '../slowOperations.js'

const SLACK_SEARCH_TOOL = 'slack_search_channels'

// Plain Map (not LRUCache) — findReusableCacheEntry needs to iterate all
// entries for prefix matching, which LRUCache doesn't expose cleanly.
const cache = new Map<string, string[]>()
// Flat set of every channel name ever returned by MCP — used to gate
// highlighting so only confirmed-real channels turn blue in the prompt.
const knownChannels = new Set<string>()
let knownChannelsVersion = 0
const knownChannelsChanged = createSignal()
export const subscribeKnownChannels = knownChannelsChanged.subscribe
let inflightQuery: string | null = null
let inflightPromise: Promise<string[]> | null = null

function findSlackClient(
  clients: MCPServerConnection[],
): MCPServerConnection | undefined {
  return clients.find(c => c.type === 'connected' && c.name.includes('slack'))
}

async function fetchChannels(
  clients: MCPServerConnection[],
  query: string,
): Promise<string[]> {
  const slackClient = findSlackClient(clients)
  if (!slackClient || slackClient.type !== 'connected') {
    return []
  }

  try {
    const result = await slackClient.client.callTool(
      {
        name: SLACK_SEARCH_TOOL,
        arguments: {
          query,
          limit: 20,
          channel_types: 'public_channel,private_channel',
        },
      },
      undefined,
      { timeout: 5000 },
    )

    const content = result.content
    if (!Array.isArray(content)) return []

    const rawText = content
      .filter((c): c is { type: 'text'; text: string } => c.type === 'text')
      .map(c => c.text)
      .join('\n')

    return parseChannels(unwrapResults(rawText))
  } catch (error) {
    logForDebugging(`Failed to fetch Slack channels: ${error}`)
    return []
  }
}

// The Slack MCP server wraps its markdown in a JSON envelope:
// {"results":"# Search Results...\nName: #chan\n..."}
const resultsEnvelopeSchema = lazySchema(() =>
  z.object({ results: z.string() }),
)

function unwrapResults(text: string): string {
  const trimmed = text.trim()
  if (!trimmed.startsWith('{')) return text
  try {
    const parsed = resultsEnvelopeSchema().safeParse(jsonParse(trimmed))
    if (parsed.success) return parsed.data.results
  } catch {
    // jsonParse threw — fall through
  }
  return text
}

// Parse channel names from slack_search_channels text output.
// The Slack MCP server returns markdown with "Name: #channel-name" lines.
function parseChannels(text: string): string[] {
  const channels: string[] = []
  const seen = new Set<string>()

  for (const line of text.split('\n')) {
    const m = line.match(/^Name:\s*#?([a-z0-9][a-z0-9_-]{0,79})\s*$/)
    if (m && !seen.has(m[1]!)) {
      seen.add(m[1]!)
      channels.push(m[1]!)
    }
  }

  return channels
}

export function hasSlackMcpServer(clients: MCPServerConnection[]): boolean {
  return findSlackClient(clients) !== undefined
}

export function getKnownChannelsVersion(): number {
  return knownChannelsVersion
}

export function findSlackChannelPositions(
  text: string,
): Array<{ start: number; end: number }> {
  const positions: Array<{ start: number; end: number }> = []
  const re = /(^|\s)#([a-z0-9][a-z0-9_-]{0,79})(?=\s|$)/g
  let m: RegExpExecArray | null
  while ((m = re.exec(text)) !== null) {
    if (!knownChannels.has(m[2]!)) continue
    const start = m.index + m[1]!.length
    positions.push({ start, end: start + 1 + m[2]!.length })
  }
  return positions
}

// Slack's search tokenizes on hyphens and requires whole-word matches, so
// "claude-code-team-en" returns 0 results. Strip the trailing partial segment
// so the MCP query is "claude-code-team" (complete words only), then filter
// locally. This keeps the query maximally specific (avoiding the 20-result
// cap) while never sending a partial word that kills the search.
function mcpQueryFor(searchToken: string): string {
  const lastSep = Math.max(
    searchToken.lastIndexOf('-'),
    searchToken.lastIndexOf('_'),
  )
  return lastSep > 0 ? searchToken.slice(0, lastSep) : searchToken
}

// Find a cached entry whose key is a prefix of mcpQuery and still has
// matches for searchToken. Lets typing "c"→"cl"→"cla" reuse the "c" cache
// instead of issuing a new MCP call per keystroke.
function findReusableCacheEntry(
  mcpQuery: string,
  searchToken: string,
): string[] | undefined {
  let best: string[] | undefined
  let bestLen = 0
  for (const [key, channels] of cache) {
    if (
      mcpQuery.startsWith(key) &&
      key.length > bestLen &&
      channels.some(c => c.startsWith(searchToken))
    ) {
      best = channels
      bestLen = key.length
    }
  }
  return best
}

export async function getSlackChannelSuggestions(
  clients: MCPServerConnection[],
  searchToken: string,
): Promise<SuggestionItem[]> {
  if (!searchToken) return []

  const mcpQuery = mcpQueryFor(searchToken)
  const lower = searchToken.toLowerCase()

  let channels = cache.get(mcpQuery) ?? findReusableCacheEntry(mcpQuery, lower)
  if (!channels) {
    if (inflightQuery === mcpQuery && inflightPromise) {
      channels = await inflightPromise
    } else {
      inflightQuery = mcpQuery
      inflightPromise = fetchChannels(clients, mcpQuery)
      channels = await inflightPromise
      cache.set(mcpQuery, channels)
      const before = knownChannels.size
      for (const c of channels) knownChannels.add(c)
      if (knownChannels.size !== before) {
        knownChannelsVersion++
        knownChannelsChanged.emit()
      }
      if (cache.size > 50) {
        cache.delete(cache.keys().next().value!)
      }
      if (inflightQuery === mcpQuery) {
        inflightQuery = null
        inflightPromise = null
      }
    }
  }

  return channels
    .filter(c => c.startsWith(lower))
    .sort()
    .slice(0, 10)
    .map(c => ({
      id: `slack-channel-${c}`,
      displayText: `#${c}`,
    }))
}

export function clearSlackChannelCache(): void {
  cache.clear()
  knownChannels.clear()
  knownChannelsVersion = 0
  inflightQuery = null
  inflightPromise = null
}