import type { RealtimeChannel } from '@supabase/supabase-js'
import type {
  D3roSupabaseClient,
  KnowledgeDocument,
  KnowledgeFileType,
} from '@d3ro/api-client'
import { SUPABASE_URL } from '@d3ro/core/supabase-config'
import { supabase } from '../../lib/supabase'
import { createUuidV4 } from '../../lib/random-id'
import {
  type ForegroundReconciliationDeps,
  knowledgeRealtimeBindings,
  startForegroundReconciliation,
} from './knowledge-realtime'

export type MobileKnowledgeFileType = Extract<KnowledgeFileType, 'txt' | 'md'>

export type KnowledgeServiceErrorCode =
  | 'auth'
  | 'cancelled'
  | 'conflict'
  | 'forbidden'
  | 'index-failed'
  | 'index-unavailable'
  | 'invalid-response'
  | 'network'
  | 'not-found'
  | 'server'
  | 'timeout'
  | 'validation'

export class KnowledgeServiceError extends Error {
  constructor(
    public readonly code: KnowledgeServiceErrorCode,
    public readonly retryable: boolean,
    public readonly status: number | null = null,
    message: string = code,
  ) {
    super(message)
    this.name = 'KnowledgeServiceError'
  }
}

export interface KnowledgeListOptions {
  userId: string
  search?: string
  page?: number
  pageSize?: number
}

export interface KnowledgeListResult {
  documents: KnowledgeDocument[]
  total: number
  page: number
  pageSize: number
  hasMore: boolean
}

export interface CreateKnowledgeDocumentInput {
  userId: string
  title: string
  fileName: string
  fileType: MobileKnowledgeFileType
  content: string
}

export interface KnowledgeSearchResult {
  id: string
  documentId: string
  chunkIndex: number
  content: string
  similarity: number
}

export interface KnowledgeDocumentSubscription {
  unsubscribe: () => Promise<void>
}

interface KnowledgeSearchOptions {
  accessToken: string
  query: string
  count?: number
  signal?: AbortSignal
  timeoutMs?: number
}

interface KnowledgeIndexOptions {
  accessToken: string
  userId: string
  document: KnowledgeDocument
  signal?: AbortSignal
  timeoutMs?: number
}

const UUID_PATTERN = /^[0-9a-f]{8}-[0-9a-f]{4}-[1-5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i
const DEFAULT_PAGE_SIZE = 30
const MAX_PAGE_SIZE = 50
const MAX_TITLE_LENGTH = 160
export const KNOWLEDGE_MAX_CONTENT_CHARS = 250_000
export const KNOWLEDGE_CHUNK_SIZE = 800
const MAX_SEARCH_LENGTH = 500
const MAX_SEARCH_RESULTS = 12

function client(): D3roSupabaseClient {
  return supabase as unknown as D3roSupabaseClient
}

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

function requireUuid(value: string, label: string): void {
  if (!UUID_PATTERN.test(value)) {
    throw new KnowledgeServiceError('auth', false, null, `A valid ${label} is required`)
  }
}

export function normalizeKnowledgeTitle(value: string): string {
  const title = value.trim().replace(/\s+/g, ' ')
  if (title.length === 0 || title.length > MAX_TITLE_LENGTH) {
    throw new KnowledgeServiceError(
      'validation',
      false,
      null,
      `Knowledge titles must contain 1-${MAX_TITLE_LENGTH} characters`,
    )
  }
  return title
}

export function sanitizeKnowledgeSearch(value: string): string {
  return value
    .trim()
    .slice(0, MAX_SEARCH_LENGTH)
    .replace(/[\\%_,()]/g, ' ')
    .replace(/\s+/g, ' ')
    .trim()
}

export function normalizeKnowledgeContent(value: string): string {
  const withoutBom = value.charCodeAt(0) === 0xfeff ? value.slice(1) : value
  const content = withoutBom.trim()
  if (
    content.length === 0
    || content.length > KNOWLEDGE_MAX_CONTENT_CHARS
    || content.includes('\u0000')
  ) {
    throw new KnowledgeServiceError(
      'validation',
      false,
      null,
      `Knowledge content must contain 1-${KNOWLEDGE_MAX_CONTENT_CHARS} text characters`,
    )
  }
  return content
}

export function chunkKnowledgeText(value: string): string[] {
  const content = normalizeKnowledgeContent(value)
  const chunks: string[] = []
  let offset = 0

  while (offset < content.length) {
    const hardEnd = Math.min(offset + KNOWLEDGE_CHUNK_SIZE, content.length)
    let end = hardEnd
    if (hardEnd < content.length) {
      const candidate = content.lastIndexOf('\n', hardEnd)
      if (candidate > offset + Math.floor(KNOWLEDGE_CHUNK_SIZE * 0.6)) end = candidate
    }
    const chunk = content.slice(offset, end).trim()
    if (chunk.length > 0) chunks.push(chunk)
    offset = end
    while (offset < content.length && /\s/.test(content[offset])) offset += 1
  }

  if (chunks.length === 0) {
    throw new KnowledgeServiceError('validation', false, null, 'Knowledge content is empty')
  }
  return chunks
}

function assertDocument(row: KnowledgeDocument | null, expectedId?: string): KnowledgeDocument {
  if (row === null) {
    throw new KnowledgeServiceError('not-found', false, 404, 'Knowledge document was not found')
  }
  requireUuid(row.id, 'knowledge document id')
  requireUuid(row.user_id, 'knowledge owner id')
  if (expectedId !== undefined && row.id !== expectedId) {
    throw new KnowledgeServiceError('invalid-response', true, null, 'Server returned a different document')
  }
  if (
    typeof row.title !== 'string'
    || row.title.trim().length === 0
    || row.title.length > 500
    || (row.file_name !== null && (typeof row.file_name !== 'string' || row.file_name.length > 255))
    || typeof row.indexed !== 'boolean'
    || !Number.isSafeInteger(row.chunk_count)
    || row.chunk_count < 0
    || !Number.isFinite(Date.parse(row.created_at))
    || !Number.isFinite(Date.parse(row.updated_at))
  ) {
    throw new KnowledgeServiceError('invalid-response', true, null, 'Server returned an invalid document')
  }
  return row
}

function toKnowledgeError(error: unknown): KnowledgeServiceError {
  if (error instanceof KnowledgeServiceError) return error

  const candidate = error as { code?: unknown; message?: unknown }
  const code = typeof candidate?.code === 'string' ? candidate.code : ''
  const message = typeof candidate?.message === 'string'
    ? candidate.message
    : 'Knowledge request failed'
  const lower = message.toLowerCase()

  if (
    error instanceof TypeError
    || lower.includes('network request failed')
    || lower.includes('failed to fetch')
    || lower.includes('networkerror')
  ) {
    return new KnowledgeServiceError('network', true, null, message)
  }
  if (code === '42501' || lower.includes('permission denied') || lower.includes('row-level security')) {
    return new KnowledgeServiceError('forbidden', false, 403, message)
  }
  if (code === 'PGRST301' || lower.includes('jwt')) {
    return new KnowledgeServiceError('auth', false, 401, message)
  }
  if (code.startsWith('22')) {
    return new KnowledgeServiceError('validation', false, 400, message)
  }
  return new KnowledgeServiceError('server', true, null, message)
}

function createRequestDeadline(
  externalSignal: AbortSignal | undefined,
  timeoutMs: number,
): { signal: AbortSignal; dispose: () => void; didTimeout: () => boolean } {
  const controller = new AbortController()
  let timedOut = false
  const abortFromCaller = (): void => controller.abort()
  if (externalSignal?.aborted === true) controller.abort()
  else externalSignal?.addEventListener('abort', abortFromCaller, { once: true })
  const timer = setTimeout(() => {
    timedOut = true
    controller.abort()
  }, timeoutMs)
  return {
    signal: controller.signal,
    didTimeout: () => timedOut,
    dispose: () => {
      clearTimeout(timer)
      externalSignal?.removeEventListener('abort', abortFromCaller)
    },
  }
}

async function responseJson(response: Response): Promise<unknown> {
  return response.json().catch(() => null)
}

function edgeErrorCode(status: number, body: unknown): KnowledgeServiceErrorCode {
  const serverCode = isRecord(body) && typeof body.error === 'string' ? body.error : ''
  if (status === 401) return 'auth'
  if (status === 400) return 'validation'
  if (status === 403) return 'forbidden'
  if (status === 404) return 'not-found'
  if (
    status === 503
    && (serverCode === 'embedding_provider_unavailable'
      || serverCode === 'knowledge_storage_unavailable')
  ) return 'index-unavailable'
  if (
    status === 502
    && (serverCode === 'embedding_failed'
      || serverCode === 'embedding_upstream_failed'
      || serverCode === 'embedding_response_invalid')
  ) return 'index-failed'
  if (status === 504) return 'timeout'
  return 'server'
}

export async function listKnowledgeDocuments(
  options: KnowledgeListOptions,
): Promise<KnowledgeListResult> {
  requireUuid(options.userId, 'authenticated user')
  const page = Math.max(0, Math.floor(options.page ?? 0))
  const pageSize = Math.max(1, Math.min(Math.floor(options.pageSize ?? DEFAULT_PAGE_SIZE), MAX_PAGE_SIZE))
  const search = sanitizeKnowledgeSearch(options.search ?? '')

  try {
    let query = client()
      .from('knowledge_documents')
      .select('*', { count: 'exact' })
      .order('created_at', { ascending: false })
      .order('id', { ascending: false })
      .range(page * pageSize, (page + 1) * pageSize - 1)

    if (search.length > 0) query = query.ilike('title', `%${search}%`)
    const { data, error, count } = await query
    if (error !== null) throw error
    const documents = (data ?? []).map((row) => assertDocument(row))
    const total = count ?? documents.length
    return {
      documents,
      total,
      page,
      pageSize,
      hasMore: (page + 1) * pageSize < total,
    }
  } catch (error) {
    throw toKnowledgeError(error)
  }
}

export function mergeKnowledgeDocuments(
  current: KnowledgeDocument[],
  incoming: KnowledgeDocument[],
): KnowledgeDocument[] {
  const merged = new Map(current.map((document) => [document.id, document]))
  for (const document of incoming) {
    const existing = merged.get(document.id)
    if (existing === undefined || document.updated_at >= existing.updated_at) {
      merged.set(document.id, document)
    }
  }
  return [...merged.values()].sort((left, right) => {
    const byCreated = right.created_at.localeCompare(left.created_at)
    return byCreated !== 0 ? byCreated : right.id.localeCompare(left.id)
  })
}

export async function createKnowledgeDocument(
  input: CreateKnowledgeDocumentInput,
): Promise<KnowledgeDocument> {
  requireUuid(input.userId, 'authenticated user')
  const title = normalizeKnowledgeTitle(input.title)
  const fileName = input.fileName.trim()
  if (fileName.length === 0 || fileName.length > 255 || !['txt', 'md'].includes(input.fileType)) {
    throw new KnowledgeServiceError('validation', false, null, 'Knowledge file metadata is invalid')
  }
  const chunks = chunkKnowledgeText(input.content)
  let created: KnowledgeDocument | null = null

  try {
    const documentResult = await client()
      .from('knowledge_documents')
      .insert({
        user_id: input.userId,
        title,
        file_name: fileName,
        file_type: input.fileType,
        storage_key: null,
        chunk_count: chunks.length,
        indexed: false,
        indexed_at: null,
      })
      .select('*')
      .single()
    if (documentResult.error !== null) throw documentResult.error
    created = assertDocument(documentResult.data)

    const chunkResult = await client()
      .from('knowledge_chunks')
      .insert(chunks.map((content, chunkIndex) => ({
        document_id: created?.id ?? '',
        chunk_index: chunkIndex,
        content,
      })))
      .select('id')
    if (chunkResult.error !== null) throw chunkResult.error
    if ((chunkResult.data ?? []).length !== chunks.length) {
      throw new KnowledgeServiceError(
        'invalid-response',
        true,
        null,
        'Server did not confirm every knowledge chunk',
      )
    }
    return created
  } catch (error) {
    if (created !== null) {
      const cleanup = await client()
        .from('knowledge_documents')
        .delete()
        .eq('id', created.id)
        .eq('user_id', input.userId)
      if (cleanup.error !== null) {
        throw new KnowledgeServiceError(
          'server',
          true,
          null,
          'Knowledge import failed and its incomplete document could not be removed',
        )
      }
    }
    throw toKnowledgeError(error)
  }
}

async function forcePendingIndexState(
  userId: string,
  documentId: string,
): Promise<void> {
  await client()
    .from('knowledge_documents')
    .update({ indexed: false, indexed_at: null })
    .eq('id', documentId)
    .eq('user_id', userId)
}

export async function indexKnowledgeDocument(
  options: KnowledgeIndexOptions,
): Promise<KnowledgeDocument> {
  requireUuid(options.userId, 'authenticated user')
  const document = assertDocument(options.document)
  if (document.user_id !== options.userId) {
    throw new KnowledgeServiceError('forbidden', false, 403, 'Only the document owner can index it')
  }
  const token = options.accessToken.trim()
  if (token.length === 0) throw new KnowledgeServiceError('auth', false, 401)
  const deadline = createRequestDeadline(options.signal, options.timeoutMs ?? 90_000)

  try {
    const response = await fetch(`${SUPABASE_URL}/functions/v1/embed-chunks`, {
      method: 'POST',
      headers: {
        Authorization: `Bearer ${token}`,
        'Content-Type': 'application/json',
      },
      body: JSON.stringify({ document_id: document.id }),
      signal: deadline.signal,
    })
    const body = await responseJson(response)
    if (!response.ok) {
      const code = edgeErrorCode(response.status, body)
      throw new KnowledgeServiceError(
        code,
        code === 'index-unavailable' || code === 'timeout' || code === 'server',
        response.status,
      )
    }
    if (
      !isRecord(body)
      || !Number.isSafeInteger(body.embedded)
      || Number(body.embedded) < 0
      || !Number.isSafeInteger(body.total)
      || Number(body.total) !== document.chunk_count
      || body.indexed !== true
    ) {
      throw new KnowledgeServiceError(
        'invalid-response',
        true,
        response.status,
        'Embedding service did not confirm a complete index',
      )
    }

    const [documentResult, embeddedCountResult] = await Promise.all([
      client()
        .from('knowledge_documents')
        .select('*')
        .eq('id', document.id)
        .maybeSingle(),
      client()
        .from('knowledge_chunks')
        .select('id', { count: 'exact', head: true })
        .eq('document_id', document.id)
        .not('embedding', 'is', null),
    ])
    if (documentResult.error !== null) throw documentResult.error
    if (embeddedCountResult.error !== null) throw embeddedCountResult.error
    const updated = assertDocument(documentResult.data, document.id)
    if (updated.indexed !== true || embeddedCountResult.count !== updated.chunk_count) {
      throw new KnowledgeServiceError(
        'invalid-response',
        true,
        response.status,
        'Server marked an incomplete knowledge index as ready',
      )
    }
    return updated
  } catch (error) {
    await forcePendingIndexState(options.userId, document.id).catch(() => undefined)
    if (error instanceof KnowledgeServiceError) throw error
    if (deadline.signal.aborted) {
      const callerCancelled = options.signal?.aborted === true && !deadline.didTimeout()
      throw new KnowledgeServiceError(
        callerCancelled ? 'cancelled' : 'timeout',
        !callerCancelled,
        callerCancelled ? null : 504,
      )
    }
    throw toKnowledgeError(error)
  } finally {
    deadline.dispose()
  }
}

export async function deleteKnowledgeDocument(
  userId: string,
  document: KnowledgeDocument,
): Promise<void> {
  requireUuid(userId, 'authenticated user')
  assertDocument(document)
  if (document.user_id !== userId) {
    throw new KnowledgeServiceError('forbidden', false, 403, 'Only the owner can delete this document')
  }
  try {
    const { data, error } = await client()
      .from('knowledge_documents')
      .delete()
      .eq('id', document.id)
      .eq('user_id', userId)
      .eq('updated_at', document.updated_at)
      .select('id')
      .maybeSingle()
    if (error !== null) throw error
    if (data === null) {
      throw new KnowledgeServiceError(
        'conflict',
        true,
        409,
        'Knowledge document changed or was removed on another device',
      )
    }
  } catch (error) {
    throw toKnowledgeError(error)
  }
}

function parseSearchResult(value: unknown): KnowledgeSearchResult {
  if (!isRecord(value)) throw new KnowledgeServiceError('invalid-response', true)
  const id = typeof value.id === 'string' ? value.id : ''
  const documentId = typeof value.document_id === 'string' ? value.document_id : ''
  const content = typeof value.content === 'string' ? value.content.trim() : ''
  const chunkIndex = value.chunk_index
  const similarity = value.similarity
  if (
    !UUID_PATTERN.test(id)
    || !UUID_PATTERN.test(documentId)
    || content.length === 0
    || content.length > 8_000
    || !Number.isSafeInteger(chunkIndex)
    || Number(chunkIndex) < 0
    || typeof similarity !== 'number'
    || !Number.isFinite(similarity)
    || similarity < 0
    || similarity > 1
  ) {
    throw new KnowledgeServiceError('invalid-response', true)
  }
  return {
    id,
    documentId,
    chunkIndex: Number(chunkIndex),
    content,
    similarity,
  }
}

export async function searchKnowledge(
  options: KnowledgeSearchOptions,
): Promise<KnowledgeSearchResult[]> {
  const token = options.accessToken.trim()
  if (token.length === 0) throw new KnowledgeServiceError('auth', false, 401)
  const query = options.query.trim()
  if (query.length === 0 || query.length > MAX_SEARCH_LENGTH) {
    throw new KnowledgeServiceError('validation', false, 400)
  }
  const count = Math.max(1, Math.min(Math.floor(options.count ?? 8), MAX_SEARCH_RESULTS))
  const deadline = createRequestDeadline(options.signal, options.timeoutMs ?? 45_000)

  try {
    const response = await fetch(`${SUPABASE_URL}/functions/v1/search-knowledge`, {
      method: 'POST',
      headers: {
        Authorization: `Bearer ${token}`,
        'Content-Type': 'application/json',
      },
      body: JSON.stringify({ query, count }),
      signal: deadline.signal,
    })
    const body = await responseJson(response)
    if (!response.ok) {
      const code = edgeErrorCode(response.status, body)
      throw new KnowledgeServiceError(
        code,
        code === 'index-unavailable' || code === 'timeout' || code === 'server',
        response.status,
      )
    }
    if (!isRecord(body) || !Array.isArray(body.results) || body.results.length > count) {
      throw new KnowledgeServiceError('invalid-response', true, response.status)
    }
    return body.results.map(parseSearchResult)
  } catch (error) {
    if (error instanceof KnowledgeServiceError) throw error
    if (deadline.signal.aborted) {
      const callerCancelled = options.signal?.aborted === true && !deadline.didTimeout()
      throw new KnowledgeServiceError(
        callerCancelled ? 'cancelled' : 'timeout',
        !callerCancelled,
        callerCancelled ? null : 504,
      )
    }
    throw toKnowledgeError(error)
  } finally {
    deadline.dispose()
  }
}

export interface KnowledgeDocumentSubscriptionOptions {
  /**
   * Owner whose documents the list shows. When given, INSERT/UPDATE events are
   * narrowed to that owner so teammates' shared-document writes do not trigger
   * list refetches for a list that only shows owned documents.
   */
  userId?: string
  /** Injectable foreground/interval ports for deletion reconciliation. */
  reconciliation?: ForegroundReconciliationDeps
}

/**
 * Live updates for the Knowledge list. Only INSERT/UPDATE are subscribed:
 * Postgres Changes cannot filter DELETE events and does not apply RLS to them,
 * so a DELETE subscription would leak other accounts' document ids and fan out
 * a refetch to every client on every deletion. Deletions are reconciled by
 * foreground polling instead (same policy as use-history-sync.ts).
 */
export function subscribeToKnowledgeDocuments(
  onChanged: () => void,
  onStatus: (connected: boolean) => void,
  options: KnowledgeDocumentSubscriptionOptions = {},
): KnowledgeDocumentSubscription {
  if (options.userId !== undefined) requireUuid(options.userId, 'knowledge owner id')
  let channel: RealtimeChannel = supabase.channel(`mobile-knowledge-${createUuidV4()}`)
  for (const binding of knowledgeRealtimeBindings(options.userId)) {
    channel = channel.on('postgres_changes', binding, onChanged)
  }
  channel = channel.subscribe((status) => onStatus(status === 'SUBSCRIBED'))
  const reconciliation = startForegroundReconciliation(onChanged, options.reconciliation)

  return {
    unsubscribe: async () => {
      reconciliation.stop()
      await supabase.removeChannel(channel)
    },
  }
}