/**
 * Tool operation orchestration over session-query service capabilities.
 *
 * @module @deepseek-ai/dsh-tool-session-query/operations
 */

import type { Context } from 'cordis'
import { HarnessError } from '@deepseek-ai/dsh-llm'
import type { SessionId } from '@deepseek-ai/dsh-session'
import {
  SessionQueryError,
  type SessionEventSearchPage,
  type SessionEventSurface,
  type SessionRecord,
  type SessionSearchCursor,
} from '@deepseek-ai/dsh-session-query'
import type { ToolRunContext } from '@deepseek-ai/dsh-tools'
import { toolInput } from './input.ts'
import { presentation } from './presentation.ts'
import { serviceBoundary } from './service-boundary.ts'
import { workspaceAccess } from './workspace-access.ts'

type SessionSearchArgs = Parameters<typeof toolInput.buildSessionFilters>[0]

interface EventSearchArgs {
  session_id?: string
  query: string
  seq_from?: number
  seq_to?: number
  time_from?: string
  time_to?: string
  event_types?: string[]
  surfaces?: SessionEventSurface[]
}

interface SessionTargetArgs {
  session_id?: string
}

interface EventTargetArgs extends SessionTargetArgs {
  seq: number
}

interface EventReadArgs extends EventTargetArgs {
  before?: number
  after?: number
}

interface SearchCollection<T> {
  readonly items: T[]
  readonly capped: boolean
}

async function executeSessionSearch(
  ctx: Context,
  args: SessionSearchArgs,
  exec: ToolRunContext,
  maxResults: number,
): Promise<string> {
  const caller = workspaceAccess.callerOf(exec)
  const cwd = caller.header.cwd
  if (cwd === undefined) {
    throw new HarnessError(
      'cross-session search is unavailable because the caller session has no workspace',
      'SESSION_QUERY_TOOL_UNAUTHORIZED',
    )
  }
  const query = toolInput.normalizeQuery(args.query)
  const sessionFilters = toolInput.buildSessionFilters(args)
  const eventFilters = toolInput.buildEventFilters({
    seqFrom: args.event_seq_from,
    seqTo: args.event_seq_to,
    timeFrom: args.event_time_from,
    timeTo: args.event_time_to,
    eventTypes: args.event_types,
    surfaces: args.event_surfaces,
  })
  const requestedParentIds = toolInput.materializeParentSessionIds(args.parent_session_ids)
  if (requestedParentIds !== undefined || args.include_root_sessions === true) {
    const authorizedParentIds = requestedParentIds === undefined
      ? new Set<SessionId>()
      : await workspaceAccess.authorizeSessionIds(ctx, caller, requestedParentIds, exec.signal)
    const parentValues: Array<SessionId | null> = requestedParentIds
      ?.filter(id => authorizedParentIds.has(id)) ?? []
    if (args.include_root_sessions === true) parentValues.push(null)
    if (parentValues.length === 0) return presentation.formatEmptySessionSearch()
    sessionFilters.push({ kind: 'parent', values: parentValues })
  }
  sessionFilters.push({ kind: 'cwd', values: [cwd] })
  const collected = await collectPages(
    maxResults,
    exec.signal,
    cursor => serviceBoundary.call(ctx, exec.signal, 'session search', () =>
      ctx.sessionQuery.searchSessions({
        query,
        sessionFilters,
        eventFilters,
        ...cursor === undefined ? {} : { cursor },
      }, { signal: exec.signal })),
    hit => hit.header.id !== caller.id && workspaceAccess.recordAuthorized(hit, caller),
  )

  const parentIds = collected.items
    .map(hit => hit.header.parentSession)
    .filter((id): id is SessionId => id !== undefined)
  const authorizedParents = await workspaceAccess.authorizeSessionIds(ctx, caller, parentIds, exec.signal)
  const titles = await workspaceAccess.readTitles(
    ctx,
    caller,
    collected.items.map(hit => hit.header.id),
    exec.signal,
  )
  return presentation.formatSessionSearch(collected, titles, authorizedParents)
}

async function executeEventSearch(
  ctx: Context,
  args: EventSearchArgs,
  exec: ToolRunContext,
  maxResults: number,
): Promise<string> {
  const caller = workspaceAccess.callerOf(exec)
  const sessionId = workspaceAccess.targetId(args, caller)
  await workspaceAccess.authorizeTarget(ctx, caller, sessionId, exec.signal)
  const query = toolInput.normalizeQuery(args.query)
  const range = toolInput.sequenceRange(args.seq_from, args.seq_to)
  if (sessionId === caller.id) {
    const stepStart = caller.events.findLast(event => event.type === 'step/start')
    if (stepStart === undefined) {
      throw new HarnessError(
        'current-session search requires an active step boundary',
        'SESSION_QUERY_TOOL_NO_CURRENT_STEP',
      )
    }
    range.to = Math.min(range.to ?? Number.MAX_SAFE_INTEGER, stepStart.seq - 1)
  }
  const title = await workspaceAccess.readTitle(ctx, caller, sessionId, exec.signal)
  if (range.from !== undefined && range.to !== undefined && range.from > range.to) {
    return presentation.formatEventSearch(sessionId, title, { items: [], capped: false })
  }
  const filters = toolInput.buildEventFilters({
    seqFrom: range.from,
    seqTo: range.to,
    timeFrom: args.time_from,
    timeTo: args.time_to,
    eventTypes: args.event_types,
    surfaces: args.surfaces,
  })
  const collected = await collectPages(
    maxResults,
    exec.signal,
    async (cursor): Promise<SessionEventSearchPage> => {
      const page = await serviceBoundary.call(ctx, exec.signal, 'event search', () =>
        ctx.sessionQuery.searchEvents({
          sessionId,
          query,
          filters,
          ...cursor === undefined ? {} : { cursor },
        }, { signal: exec.signal }))
      workspaceAccess.assertObservedTargetAuthorized(caller, sessionId, page.session)
      return page
    },
    () => true,
  )
  return presentation.formatEventSearch(sessionId, title, collected)
}

async function executeSessionTrace(
  ctx: Context,
  args: SessionTargetArgs,
  exec: ToolRunContext,
): Promise<string> {
  const caller = workspaceAccess.callerOf(exec)
  const sessionId = workspaceAccess.targetId(args, caller)
  await workspaceAccess.authorizeTarget(ctx, caller, sessionId, exec.signal)
  const trace = await serviceBoundary.call(ctx, exec.signal, 'session lineage trace', () =>
    ctx.sessionQuery.traceSession(sessionId, exec.signal))
  workspaceAccess.assertObservedTargetAuthorized(caller, sessionId, trace.target.header)

  const ancestors: SessionRecord[] = []
  let ancestorBoundary = false
  for (const ancestor of trace.ancestors) {
    if (!workspaceAccess.recordAuthorized(ancestor, caller)) {
      ancestorBoundary = true
      break
    }
    ancestors.push(ancestor)
  }
  if (ancestors.length === trace.ancestors.length && !trace.complete) ancestorBoundary = true
  const descendants = workspaceAccess.authorizeDescendants(trace.descendants, caller)
  const visibleIds = [
    trace.target.header.id,
    ...ancestors.map(record => record.header.id),
    ...workspaceAccess.descendantIds(descendants),
  ]
  const titles = await workspaceAccess.readTitles(ctx, caller, visibleIds, exec.signal)
  return presentation.formatSessionTrace(trace, ancestors, ancestorBoundary, descendants, titles)
}

async function executeEventTrace(
  ctx: Context,
  args: EventTargetArgs,
  exec: ToolRunContext,
): Promise<string> {
  toolInput.assertNonNegativeSafeInteger('seq', args.seq)
  const caller = workspaceAccess.callerOf(exec)
  const sessionId = workspaceAccess.targetId(args, caller)
  await workspaceAccess.authorizeTarget(ctx, caller, sessionId, exec.signal)
  const trace = await serviceBoundary.call(ctx, exec.signal, 'event trace', () =>
    ctx.sessionQuery.traceEvent({ sessionId, seq: args.seq }, exec.signal))
  workspaceAccess.assertObservedTargetAuthorized(caller, sessionId, trace.session)
  const title = await workspaceAccess.readTitle(ctx, caller, sessionId, exec.signal)
  return presentation.formatEventTrace(sessionId, title, trace)
}

async function executeEventRead(
  ctx: Context,
  args: EventReadArgs,
  exec: ToolRunContext,
): Promise<string> {
  toolInput.assertNonNegativeSafeInteger('seq', args.seq)
  if (args.before !== undefined) toolInput.assertNonNegativeSafeInteger('before', args.before)
  if (args.after !== undefined) toolInput.assertNonNegativeSafeInteger('after', args.after)
  const caller = workspaceAccess.callerOf(exec)
  const sessionId = workspaceAccess.targetId(args, caller)
  await workspaceAccess.authorizeTarget(ctx, caller, sessionId, exec.signal)
  const window = await serviceBoundary.call(ctx, exec.signal, 'event read', () =>
    ctx.sessionQuery.readEvent({
      sessionId,
      seq: args.seq,
      ...args.before === undefined ? {} : { before: args.before },
      ...args.after === undefined ? {} : { after: args.after },
    }, exec.signal))
  workspaceAccess.assertObservedTargetAuthorized(caller, sessionId, window.session)
  const title = await workspaceAccess.readTitle(ctx, caller, sessionId, exec.signal)
  return presentation.formatEventRead(sessionId, title, window)
}

async function collectPages<T>(
  maxResults: number,
  signal: AbortSignal,
  request: (cursor?: SessionSearchCursor) => Promise<{
    readonly items: readonly T[]
    readonly nextCursor?: SessionSearchCursor
  }>,
  accept: (item: T) => boolean,
): Promise<SearchCollection<T>> {
  const items: T[] = []
  const seen = new Set<SessionSearchCursor>()
  let cursor: SessionSearchCursor | undefined
  while (true) {
    signal.throwIfAborted()
    const page = await request(cursor)
    signal.throwIfAborted()
    for (const item of page.items) {
      if (!accept(item)) continue
      if (items.length === maxResults) {
        return { items, capped: true }
      }
      items.push(item)
    }
    if (page.nextCursor === undefined) return { items, capped: false }
    if (seen.has(page.nextCursor)) {
      throw new SessionQueryError(
        'session-search provider repeated a continuation cursor',
        'SESSION_QUERY_INVALID_CURSOR',
      )
    }
    seen.add(page.nextCursor)
    cursor = page.nextCursor
  }
}

/** Five model-facing session-query operation implementations. */
export const operations = {
  executeSessionSearch,
  executeEventSearch,
  executeSessionTrace,
  executeEventTrace,
  executeEventRead,
}
