import {
  afterUnloadDocumentPayload,
  Extension,
  onChangePayload,
  onDisconnectPayload,
  onLoadDocumentPayload,
  onStoreDocumentPayload,
} from '@hocuspocus/server';
import * as Y from 'yjs';
import { Injectable, Logger } from '@nestjs/common';
import { TiptapTransformer } from '@hocuspocus/transformer';
import {
  getPageId,
  isEmptyParagraphDoc,
  jsonToText,
  tiptapExtensions,
} from '../collaboration.util';
import { PageRepo } from '@docmost/db/repos/page/page.repo';
import { PageHistoryRepo } from '@docmost/db/repos/page/page-history.repo';
import { InjectKysely } from 'nestjs-kysely';
import { KyselyDB } from '@docmost/db/types/kysely.types';
import { executeTx } from '@docmost/db/utils';
import { InjectQueue } from '@nestjs/bullmq';
import { QueueJob, QueueName } from '../../integrations/queue/constants';
import { ProvenanceSource } from '../../core/auth/dto/jwt-payload';
import { Queue } from 'bullmq';
import {
  extractMentions,
  extractUserMentions,
} from '../../common/helpers/prosemirror/utils';
import { isDeepStrictEqual } from 'node:util';
import {
  IPageHistoryJob,
  IPageMentionNotificationJob,
} from '../../integrations/queue/constants/queue.interface';
import { Page } from '@docmost/db/types/entity.types';
import { CollabHistoryService } from '../services/collab-history.service';
import {
  HISTORY_FAST_INTERVAL,
  HISTORY_FAST_THRESHOLD,
  HISTORY_INTERVAL,
} from '../constants';
import { TransclusionService } from '../../core/page/transclusion/transclusion.service';

/**
 * Resolve the provenance source for a coalesced snapshot.
 *
 * The snapshot is tagged 'agent' if any agent edit landed in the coalescing
 * window (sticky marker) OR if the current writer is the agent; otherwise
 * 'user'. Pure so the §15 H2 marker logic is unit-testable in isolation.
 */
export function resolveSource(
  stickyTouched: boolean,
  contextActor?: string,
): ProvenanceSource {
  // An EXPLICIT current-write actor is authoritative for THIS write and wins
  // over the sticky-agent fallback. Order: explicit 'agent' > explicit
  // 'git-sync' > sticky agent marker > plain human 'user'. The git-sync case
  // must NOT be masked by the sticky marker, or the PageChangeListener
  // loop-guard (which keys on lastUpdatedSource === 'git-sync') would re-export
  // git-sync's own writes (#14). Explicit agent still wins so a window that
  // mixed an agent edit stays tagged 'agent'.
  if (contextActor === 'agent') return 'agent';
  if (contextActor === 'git-sync') return 'git-sync';
  if (stickyTouched) return 'agent';
  return 'user';
}

/**
 * Compute the BullMQ job id + delay for a page-history snapshot job. Pure so
 * the data-loss-sensitive timing arithmetic is unit-testable; `now` is injected
 * (caller passes `Date.now()`) for determinism.
 *
 * - Agent edits: delay 0 and a source-keyed job id `${page.id}-agent`. The
 *   delay MUST stay 0 — the worker re-reads the page row at run time, so any
 *   delay risks reading content a later human edit has already overwritten
 *   (mis-tagged snapshot). 0 minimizes that window. The `-agent` suffix keeps
 *   the job from coalescing with the bare-page.id human job.
 * - Human edits: age-based debounce so rapid human edits coalesce into one
 *   snapshot; job id is the bare `page.id`.
 *
 * BullMQ forbids ':' in custom job ids (Redis key separator), so '-' is used;
 * page.id is a UUID, so `${page.id}-agent` cannot collide with a human job.
 */
export function computeHistoryJob(
  page: Pick<Page, 'id' | 'createdAt'>,
  source: string,
  now: number,
): { jobId: string; delay: number } {
  const isAgent = source === 'agent';
  const pageAge = now - new Date(page.createdAt).getTime();
  const delay = isAgent
    ? 0
    : pageAge < HISTORY_FAST_THRESHOLD
      ? HISTORY_FAST_INTERVAL
      : HISTORY_INTERVAL;
  const jobId = isAgent ? `${page.id}-agent` : page.id;
  return { jobId, delay };
}

@Injectable()
export class PersistenceExtension implements Extension {
  private readonly logger = new Logger(PersistenceExtension.name);
  private contributors: Map<string, Set<string>> = new Map();
  // Sticky agent-edit marker (§15 H2): a coalesced snapshot may mix human and
  // agent edits. We accumulate "an agent touched this document during the
  // coalescing window" per document and OR it across all edits in the window,
  // so the snapshot is marked 'agent' regardless of who wrote last.
  private agentTouched: Map<string, boolean> = new Map();

  constructor(
    private readonly pageRepo: PageRepo,
    private readonly pageHistoryRepo: PageHistoryRepo,
    @InjectKysely() private readonly db: KyselyDB,
    @InjectQueue(QueueName.AI_QUEUE) private aiQueue: Queue,
    @InjectQueue(QueueName.HISTORY_QUEUE) private historyQueue: Queue,
    @InjectQueue(QueueName.NOTIFICATION_QUEUE) private notificationQueue: Queue,
    private readonly collabHistory: CollabHistoryService,
    private readonly transclusionService: TransclusionService,
  ) {}

  async onLoadDocument(data: onLoadDocumentPayload) {
    const { documentName, document } = data;
    const pageId = getPageId(documentName);

    if (!document.isEmpty('default')) {
      return;
    }

    const page = await this.pageRepo.findById(pageId, {
      includeContent: true,
      includeYdoc: true,
    });

    if (!page) {
      this.logger.warn('page not found');
      return;
    }

    if (page.ydoc) {
      this.logger.debug(`ydoc loaded from db: ${pageId}`);

      const doc = new Y.Doc();
      const dbState = new Uint8Array(page.ydoc);

      Y.applyUpdate(doc, dbState);
      return doc;
    }

    // if no ydoc state in db convert json in page.content to Ydoc.
    if (page.content) {
      this.logger.debug(`converting json to ydoc: ${pageId}`);

      const ydoc = TiptapTransformer.toYdoc(
        page.content,
        'default',
        tiptapExtensions,
      );

      Y.encodeStateAsUpdate(ydoc);
      return ydoc;
    }

    this.logger.debug(`creating fresh ydoc: ${pageId}`);
    return new Y.Doc();
  }

  /**
   * LOSS-ON-FAST-CLOSE FIX (QA #119). When the LAST editor disconnects, FLUSH any
   * pending (debounced) store to the DB IMMEDIATELY instead of waiting out the
   * up-to-10s `debounce` window.
   *
   * The collab server runs with `unloadImmediately: false` (collaboration.gateway),
   * so on a last-client disconnect Hocuspocus does NOT flush the debounced
   * onStoreDocument — it relies on the timer firing later. A quick edit-then-close
   * (closing the tab within the debounce window, ~3-18s) therefore left the edit
   * only in the soon-to-be-unloaded in-memory Y.Doc; meanwhile git-sync mirrored
   * the STALE/empty DB body to the vault (the reported "59-byte frontmatter-only"
   * data loss). Running the already-scheduled store now closes that window.
   *
   * Gated tightly so it never adds a redundant write: only on the LAST disconnect
   * (`clientsCount === 0`), only for a fully-loaded doc, and only when a store is
   * actually pending (`isDebounced`). `executeNow` runs the SAME payload Hocuspocus
   * scheduled (preserving the edit's context/actor) and clears the timer.
   */
  async onDisconnect(data: onDisconnectPayload) {
    const { instance, document, documentName, clientsCount } = data;
    if (clientsCount > 0) return;
    if (!document || document.isLoading) return;
    const debounceId = `onStoreDocument-${documentName}`;
    if (!instance?.debouncer?.isDebounced(debounceId)) return;
    try {
      await instance.debouncer.executeNow(debounceId);
    } catch (err) {
      this.logger.error(
        `onDisconnect flush failed for ${documentName}: ` +
          (err instanceof Error ? err.message : String(err)),
      );
    }
  }

  async onStoreDocument(data: onStoreDocumentPayload) {
    const { documentName, document, context } = data;

    const pageId = getPageId(documentName);

    const tiptapJson = TiptapTransformer.fromYdoc(document, 'default');

    const ydocState = Buffer.from(Y.encodeStateAsUpdate(document));

    let textContent = null;

    try {
      textContent = jsonToText(tiptapJson);
    } catch (err) {
      this.logger.warn('jsonToText' + err?.['message']);
    }

    let page: Page = null;
    const editingUserIds = this.consumeContributors(documentName);
    // Sticky agent marker: 'agent' if any agent edit landed in this window, OR
    // if the current writer is the agent (covers a store with no prior onChange
    // agent event in the same window). §15 H2.
    // Provenance precedence: agent > git-sync > user (see resolveSource). A
    // 'git-sync' store is NOT given an immediate history snapshot — it is
    // debounced like a human edit (a git-sync write is a block-level merge into
    // the live doc, so it reads like an incremental human edit, not a bulk
    // import that would warrant its own immediate snapshot).
    const lastUpdatedSource = resolveSource(
      this.consumeAgentTouched(documentName),
      context?.actor,
    );

    // Persist with a small bounded retry. The in-memory Y.Doc is the ONLY copy
    // of the latest edit until this hook returns: hocuspocus destroys/unloads the
    // doc right after onStoreDocument resolves (see storeDocumentHooks' finally
    // -> unloadDocument). If a transient DB error (deadlock, serialization
    // failure, dropped connection) is merely logged and swallowed, the function
    // resolves "successfully", the doc is unloaded, and the edit is lost silently
    // (#206 persist-1). Retrying here re-attempts the write while we still hold
    // the doc; on total failure we clear `page` so the post-store side effects
    // (badge broadcast, history snapshot) never report a save that didn't happen.
    const MAX_STORE_ATTEMPTS = 3;
    for (let attempt = 1; attempt <= MAX_STORE_ATTEMPTS; attempt++) {
      try {
        await executeTx(this.db, async (trx) => {
          page = await this.pageRepo.findById(pageId, {
            withLock: true,
            includeContent: true,
            trx,
          });

          if (!page) {
            this.logger.error(`Page with id ${pageId} not found`);
            return;
          }

          if (isDeepStrictEqual(tiptapJson, page.content)) {
            page = null;
            return;
          }

          let contributorIds = undefined;
          try {
            const existingContributors = page.contributorIds || [];
            contributorIds = Array.from(
              new Set([
                ...existingContributors,
                ...editingUserIds,
                page.creatorId,
              ]),
            );
          } catch (err) {
            //this.logger.debug('Contributors error:' + err?.['message']);
          }

          // Approach A — boundary snapshot before a MACHINE write overwrites a
          // human (or other-source) baseline. When this store is from a machine
          // source — the AGENT or GIT-SYNC — and the page's currently persisted
          // state was authored by a DIFFERENT source, pin that prior state as its
          // own history version BEFORE the machine write overwrites it. `page`
          // still holds the OLD content/provenance here, so saveHistory(page)
          // captures the pre-write state. The machine's new content is snapshotted
          // later by the debounced PAGE_HISTORY job.
          //
          // For GIT-SYNC this is the OBSERVABLE-LOSS guard (SPEC §9 conflict
          // contract): a git-sync body write is a block-level 3-way merge whose
          // same-block rule is "git wins". Without this pin, a concurrent human
          // edit to a block git also changed would be overwritten with NO trace.
          // Pinning the pre-merge state here means the human's content is always
          // RECOVERABLE via page history rather than silently lost — git still
          // wins the live doc deterministically, but nothing is destroyed.
          //
          // Skip if the prior state was already authored by THIS machine source
          // (boundary already pinned on the transition into it), if the page is
          // effectively empty, or if the latest existing snapshot already equals
          // the prior state (avoid duplicates).
          const isMachineWrite =
            lastUpdatedSource === 'agent' || lastUpdatedSource === 'git-sync';
          if (isMachineWrite && page.lastUpdatedSource !== lastUpdatedSource) {
            const lastHistory = await this.pageHistoryRepo.findPageLastHistory(
              pageId,
              { includeContent: true, trx },
            );
            const humanBaselineMissing =
              !lastHistory ||
              !isDeepStrictEqual(lastHistory.content, page.content);
            if (
              !isEmptyParagraphDoc(page.content as any) &&
              humanBaselineMissing
            ) {
              await this.pageHistoryRepo.saveHistory(page, {
                contributorIds: page.contributorIds ?? undefined,
                trx,
              });
            }
          }

          await this.pageRepo.updatePage(
            {
              content: tiptapJson,
              textContent: textContent,
              ydoc: ydocState,
              lastUpdatedById: context.user.id,
              // Human stays the responsible author; these annotate the source.
              lastUpdatedSource,
              lastUpdatedAiChatId: context?.aiChatId ?? null,
              contributorIds: contributorIds,
            },
            pageId,
            trx,
          );

          this.logger.debug(`Page updated: ${pageId} - SlugId: ${page.slugId}`);
        });
        break;
      } catch (err) {
        this.logger.error(
          `Failed to update page ${pageId} (attempt ${attempt}/${MAX_STORE_ATTEMPTS})`,
          err,
        );
        // The write failed and rolled back; clear the partially-assigned `page`
        // so the post-store success branch below is skipped (no false "saved"
        // broadcast / history snapshot for content that was never persisted).
        page = null;
        if (attempt < MAX_STORE_ATTEMPTS) {
          await new Promise((resolve) => setTimeout(resolve, attempt * 50));
        }
      }
    }

    if (page) {
      document.broadcastStateless(
        JSON.stringify({
          type: 'page.updated',
          updatedAt: new Date().toISOString(),
          // Provenance for a future live badge; 'user' for human edits.
          source: lastUpdatedSource,
          lastUpdatedById: context?.user?.id,
          lastUpdatedBy: context?.user
            ? {
                id: context.user?.id,
                name: context.user?.name,
                avatarUrl: context.user?.avatarUrl,
              }
            : undefined,
        }),
      );

      await this.syncTransclusion(pageId, page.workspaceId, tiptapJson);
    }

    if (page) {
      await this.collabHistory.addContributors(pageId, editingUserIds);

      const mentions = extractMentions(tiptapJson);

      const userMentions = extractUserMentions(mentions);
      const oldMentions = page.content ? extractMentions(page.content) : [];
      const oldMentionedUserIds = extractUserMentions(oldMentions).map(
        (m) => m.entityId,
      );

      if (userMentions.length > 0) {
        await this.notificationQueue.add(QueueJob.PAGE_MENTION_NOTIFICATION, {
          userMentions: userMentions.map((m) => ({
            userId: m.entityId,
            mentionId: m.id,
            creatorId: m.creatorId,
          })),
          oldMentionedUserIds,
          pageId,
          spaceId: page.spaceId,
          workspaceId: page.workspaceId,
        } as IPageMentionNotificationJob);
      }

      await this.aiQueue.add(QueueJob.PAGE_CONTENT_UPDATED, {
        pageIds: [pageId],
        workspaceId: page.workspaceId,
      });

      await this.enqueuePageHistory(page, lastUpdatedSource);
    }
  }

  async onChange(data: onChangePayload) {
    const documentName = data.documentName;
    const userId = data.context?.user?.id;

    if (!userId) return;

    if (!this.contributors.has(documentName)) {
      this.contributors.set(documentName, new Set());
    }

    this.contributors.get(documentName).add(userId);

    // Sticky agent marker: once an agent connection touches the document in the
    // coalescing window, keep it marked until the next snapshot consumes it.
    if (data.context?.actor === 'agent') {
      this.agentTouched.set(documentName, true);
    }
  }

  async afterUnloadDocument(data: afterUnloadDocumentPayload) {
    const documentName = data.documentName;
    this.contributors.delete(documentName);
    this.agentTouched.delete(documentName);
  }

  private consumeContributors(documentName: string): string[] {
    const contributorSet = this.contributors.get(documentName);
    if (!contributorSet) return [];
    const userIds = [...contributorSet];
    this.contributors.delete(documentName);
    return userIds;
  }

  /** Read and clear the sticky agent-touched flag for this coalescing window. */
  private consumeAgentTouched(documentName: string): boolean {
    const touched = this.agentTouched.get(documentName) ?? false;
    this.agentTouched.delete(documentName);
    return touched;
  }

  private async enqueuePageHistory(
    page: Page,
    lastUpdatedSource: string,
  ): Promise<void> {
    // Job id + delay arithmetic lives in the pure `computeHistoryJob` (see its
    // doc comment for the agent-delay-0 / age-based-debounce invariants).
    const { jobId, delay } = computeHistoryJob(
      page,
      lastUpdatedSource,
      Date.now(),
    );

    await this.historyQueue.add(
      QueueJob.PAGE_HISTORY,
      { pageId: page.id } as IPageHistoryJob,
      { jobId, delay },
    );
  }

  /**
   * Refresh `page_transclusions` and `page_transclusion_references` to match
   * the page's current content. Runs outside the page-write transaction and
   * isolates each call so a failure here cannot affect the page save itself.
   * The diff is idempotent — the next save converges if a round drops anything.
   */
  private async syncTransclusion(
    pageId: string,
    workspaceId: string,
    tiptapJson: unknown,
  ): Promise<void> {
    try {
      await this.transclusionService.syncPageTransclusions(
        pageId,
        workspaceId,
        tiptapJson,
      );
    } catch (err) {
      this.logger.error(
        { err, pageId },
        'Failed to sync transclusions for page',
      );
    }
    try {
      await this.transclusionService.syncPageReferences(
        pageId,
        workspaceId,
        tiptapJson,
      );
    } catch (err) {
      this.logger.error(
        { err, pageId },
        'Failed to sync transclusion references for page',
      );
    }
    try {
      await this.transclusionService.syncPageTemplateReferences(
        pageId,
        workspaceId,
        tiptapJson,
      );
    } catch (err) {
      this.logger.error(
        { err, pageId },
        'Failed to sync page template references for page',
      );
    }
  }
}