import { Injectable, NotFoundException } from '@nestjs/common';
import { PageView } from '@dorfteich/shared';
import { User } from '@prisma/client';
import { PinoLogger } from 'nestjs-pino';

import { AuditService } from '../audit/audit.service';
import { ClockService } from '../common/clock.service';
import { PagesService } from '../pages/pages.service';
import { PermissionService } from '../permissions/permission.service';
import { PrismaService } from '../prisma/prisma.service';
import { WatchesService } from '../watches/watches.service';
import { QuotaService } from '../quotas/quota.service';
import { InstanceSettingsService } from '../settings/instance-settings.service';
import { FileStorageService } from '../files/file-storage.service';

const MS_PER_DAY = 24 * 60 * 60 * 1000;

/**
 * Page trash: soft delete (already done by `PagesService.softDelete`,
 * issue #23), list/restore/purge-single, and the scheduled purge job
 * (issue #31, ADR 0013). Deleting a page never touches its content or
 * files — only `purgePage` does, so restore is always intact by
 * construction as long as purge hasn't run yet.
 */
@Injectable()
export class TrashService {
  constructor(
    private readonly prisma: PrismaService,
    private readonly permissions: PermissionService,
    private readonly pages: PagesService,
    private readonly settings: InstanceSettingsService,
    private readonly quotas: QuotaService,
    private readonly storage: FileStorageService,
    private readonly clock: ClockService,
    private readonly watches: WatchesService,
    private readonly audit: AuditService,
    private readonly logger: PinoLogger,
  ) {
    this.logger.setContext(TrashService.name);
  }

  /** A pond's trash: the trashed pages the user could edit — trash access is
   * write capability (ADR 0013), resolved per page (issue #52). */
  async list(user: User, pondId: string): Promise<PageView[]> {
    const pond = await this.prisma.pond.findFirst({ where: { id: pondId, deletedAt: null } });
    if (!pond) throw new NotFoundException();
    const pages = await this.prisma.page.findMany({
      where: { pondId, deletedAt: { not: null } },
      orderBy: { deletedAt: 'desc' },
    });
    const editable = await this.permissions.filterPages(
      user,
      pondId,
      pages.map((page) => ({ id: page.id })),
      'write',
    );
    return pages.filter((page) => editable.has(page.id)).map((page) => this.pages.viewOf(page));
  }

  /**
   * Restore a trashed page. Trashed pages keep their `parentId` (issue #107),
   * so the original spot may itself be in the trash by now — the page
   * re-attaches to its nearest **live** ancestor, or to the root when the
   * whole chain is gone. That makes restore order-independent: restoring the
   * parent afterwards does not re-claim an already-restored child.
   */
  async restore(user: User, id: string): Promise<PageView> {
    const page = await this.prisma.page.findFirst({ where: { id } });
    if (!page || !page.deletedAt) throw new NotFoundException();

    const pondPages = await this.prisma.page.findMany({
      where: { pondId: page.pondId },
      select: { id: true, parentId: true, deletedAt: true },
    });
    const byId = new Map(pondPages.map((p) => [p.id, p]));
    let parentId: string | null = null;
    const seen = new Set<string>([page.id]);
    for (let current = page.parentId; current && !seen.has(current);) {
      seen.add(current);
      const ancestor = byId.get(current);
      if (!ancestor) break;
      if (ancestor.deletedAt === null) {
        parentId = ancestor.id;
        break;
      }
      current = ancestor.parentId;
    }

    const restored = await this.prisma.page.update({
      where: { id },
      data: { deletedAt: null, deletedBy: null, parentId },
    });
    this.logger.info({ pageId: id, userId: user.id, parentId }, 'audit: page restored from trash');
    return this.pages.viewOf(restored);
  }

  /** Manual "purge single" (scope's third trash endpoint) — bypasses retention. */
  async purgeNow(user: User, id: string): Promise<void> {
    const page = await this.prisma.page.findFirst({ where: { id } });
    if (!page || !page.deletedAt) throw new NotFoundException();
    await this.purgePage(id);
    this.logger.info({ pageId: id, userId: user.id }, 'audit: page purged from trash');
  }

  /** Scheduled job entry point (registered with SchedulerService, trash.module.ts). */
  async purgeDuePages(): Promise<void> {
    const retentionDays = await this.settings.get('trash.retentionDays');
    const cutoff = new Date(this.clock.now().getTime() - retentionDays * MS_PER_DAY);
    const due = await this.prisma.page.findMany({
      where: { deletedAt: { lte: cutoff } },
      select: { id: true },
    });
    for (const { id } of due) {
      await this.purgePage(id);
    }
  }

  /** Manual pond purge (issue #193) — Site-Admin-only, guarded at the controller. */
  async purgePondNow(actor: User, pondId: string): Promise<void> {
    const pond = await this.prisma.pond.findFirst({
      where: { id: pondId, deletedAt: { not: null } },
    });
    if (!pond) throw new NotFoundException();
    const counts = await this.purgePond(pondId);
    if (!counts) throw new NotFoundException(); // restored or raced away meanwhile
    await this.audit.record({
      action: 'pond.purged',
      actorId: actor.id,
      targetType: 'pond',
      targetId: pondId,
      details: { trigger: 'manual', ...counts },
    });
  }

  /** Scheduled half of the pond purge (issue #193) — same retention as pages. */
  async purgeDuePonds(): Promise<void> {
    const retentionDays = await this.settings.get('trash.retentionDays');
    const cutoff = new Date(this.clock.now().getTime() - retentionDays * MS_PER_DAY);
    const due = await this.prisma.pond.findMany({
      where: { deletedAt: { lte: cutoff } },
      select: { id: true },
    });
    for (const { id } of due) {
      const counts = await this.purgePond(id);
      if (counts) {
        await this.audit.record({
          action: 'pond.purged',
          targetType: 'pond',
          targetId: id,
          details: { trigger: 'retention', ...counts },
        });
      }
    }
  }

  /**
   * Deletes a trashed pond with everything it holds (issue #193). Files go
   * first — `rm(force)` is idempotent, so a crash between files and rows
   * leaves a resumable state (rows intact, next run retries). The rows go
   * in ONE transaction, ordered around the FK actions: attachments and
   * labels are `Restrict` against the pond and must precede it; the page
   * delete cascades versions, comments, content cache (incl. the search
   * vector), update log, mentions, pending contributors, label
   * assignments, favorites, outgoing links, and open collab sessions; the
   * pond delete cascades grants, usage counters (that IS the quota
   * correction — pond capacity derives from live pond rows), pond-plugin
   * opt-ins, and conversion jobs. Watches and quota overrides are
   * polymorphic (no FK) and are deleted explicitly. A purge racing a
   * restore or another purge is a no-op (`null`).
   */
  private async purgePond(pondId: string): Promise<{ pages: number; attachments: number } | null> {
    const pond = await this.prisma.pond.findUnique({ where: { id: pondId } });
    if (!pond || !pond.deletedAt) return null;

    const attachments = await this.prisma.attachment.findMany({
      where: { pondId },
      select: { id: true },
    });
    for (const attachment of attachments) {
      await this.storage.delete(pondId, attachment.id);
    }
    const pageIds = (
      await this.prisma.page.findMany({ where: { pondId }, select: { id: true } })
    ).map((page) => page.id);

    await this.prisma.$transaction([
      this.prisma.attachment.deleteMany({ where: { pondId } }),
      this.prisma.watch.deleteMany({
        where: {
          OR: [
            { targetType: 'POND', targetId: pondId },
            { targetType: 'PAGE', targetId: { in: pageIds } },
          ],
        },
      }),
      this.prisma.quotaOverride.deleteMany({
        where: { subjectType: 'POND', subjectId: pondId },
      }),
      this.prisma.page.deleteMany({ where: { pondId } }),
      this.prisma.label.deleteMany({ where: { pondId } }),
      this.prisma.pond.delete({ where: { id: pondId } }),
    ]);
    this.logger.info(
      { pondId, pages: pageIds.length, attachments: attachments.length },
      'audit: pond purged',
    );
    return { pages: pageIds.length, attachments: attachments.length };
  }

  /**
   * Deletes state, content cache, files, and (once M3 exists) versions for
   * one page — the fixed set of things `#31`'s scope names. Version rows
   * are a placeholder: `page_versions` doesn't exist until M3 (#33–#42).
   */
  private async purgePage(pageId: string): Promise<void> {
    const page = await this.prisma.page.findUnique({ where: { id: pageId } });
    if (!page) return; // already gone — e.g. a manual purge raced the job

    const attachments = await this.prisma.attachment.findMany({ where: { pageId } });
    for (const attachment of attachments) {
      await this.storage.delete(attachment.pondId, attachment.id);
      await this.quotas.release(attachment.pondId, attachment.sizeBytes);
    }
    await this.prisma.attachment.deleteMany({ where: { pageId } });
    await this.prisma.pageContentCache.deleteMany({ where: { pageId } });
    await this.prisma.pageUpdate.deleteMany({ where: { pageId } });
    await this.watches.removeForPage(pageId);
    // Children (live or trashed) move up to the purged page's parent (issue
    // #107) — the FK's SetNull is only the backstop for rows created outside
    // this path.
    await this.prisma.page.updateMany({
      where: { parentId: pageId },
      data: { parentId: page.parentId },
    });
    await this.prisma.page.delete({ where: { id: pageId } });
    this.logger.info({ pageId }, 'audit: page purged (retention)');
  }
}