import {
  BadRequestException,
  ConflictException,
  Injectable,
  NotFoundException,
} from '@nestjs/common';
import { AccessRuleView, Grant, GrantView, grantValidationError } from '@dorfteich/shared';
import { Pond, RoleGrant, User } from '@prisma/client';
import { PinoLogger } from 'nestjs-pino';

import { AuditService } from '../audit/audit.service';
import { PondPermissionCache } from '../permissions/pond-permission-cache';
import { PondAccessNotifier } from '../ponds/pond-access-notifier.service';
import { PrismaService } from '../prisma/prisma.service';
import { toGrant, toGrantColumns } from './grant-mappers';

/**
 * Writes and reads over the permission table (`role_grants`, issues #51/#52).
 * Who may manage grants is the guard's job (Pond Admin); this service
 * validates the grant itself — the shared structural rules, plus that the
 * scope and subject actually exist in this pond. Every mutation invalidates
 * the pond's permission context and notifies the collab server so live
 * sessions revalidate (issue #39; full revocation UX is #53), and leaves an
 * audit log line.
 */
@Injectable()
export class GrantsService {
  constructor(
    private readonly prisma: PrismaService,
    private readonly permissionCache: PondPermissionCache,
    private readonly accessNotifier: PondAccessNotifier,
    private readonly audit: AuditService,
    private readonly logger: PinoLogger,
  ) {
    this.logger.setContext(GrantsService.name);
  }

  /** All grants in a pond, as the shared resolver model (kept for callers
   * that resolve rather than manage; PermissionService reads its own copy). */
  async grantsForPond(pondId: string): Promise<Grant[]> {
    const rows = await this.prisma.roleGrant.findMany({ where: { pondId } });
    return rows.map(toGrant);
  }

  private static viewOf(row: RoleGrant): GrantView {
    return {
      ...toGrant(row),
      id: row.id,
      pondId: row.pondId,
      createdBy: row.createdBy,
      createdAt: row.createdAt.toISOString(),
    };
  }

  private async requireLivePond(pondId: string): Promise<Pond> {
    const pond = await this.prisma.pond.findFirst({ where: { id: pondId, deletedAt: null } });
    if (!pond) throw new NotFoundException();
    return pond;
  }

  /** A pond's grants for the management UI, newest last. */
  async listGrants(pondId: string): Promise<GrantView[]> {
    await this.requireLivePond(pondId);
    const rows = await this.prisma.roleGrant.findMany({
      where: { pondId },
      orderBy: { createdAt: 'asc' },
    });
    return rows.map((row) => GrantsService.viewOf(row));
  }

  /**
   * A pond's grants enriched with the display names the access-rules UI renders
   * as sentences (issue #55): each user subject's display name and each
   * label/page scope's name, resolved in one batched query per kind so the
   * client needs no id lookups.
   */
  async listAccessRules(pondId: string): Promise<AccessRuleView[]> {
    await this.requireLivePond(pondId);
    const rows = await this.prisma.roleGrant.findMany({
      where: { pondId },
      orderBy: { createdAt: 'asc' },
    });

    const userIds = rows.filter((r) => r.subjectId).map((r) => r.subjectId!);
    const labelIds = rows
      .filter((r) => r.scopeType === 'LABEL' && r.scopeId)
      .map((r) => r.scopeId!);
    const pageIds = rows.filter((r) => r.scopeType === 'PAGE' && r.scopeId).map((r) => r.scopeId!);

    const [users, labels, pages] = await Promise.all([
      this.prisma.user.findMany({
        where: { id: { in: userIds } },
        select: { id: true, displayName: true },
      }),
      this.prisma.label.findMany({
        where: { id: { in: labelIds } },
        select: { id: true, name: true },
      }),
      this.prisma.page.findMany({
        where: { id: { in: pageIds } },
        select: { id: true, title: true },
      }),
    ]);
    const userName = new Map(users.map((u) => [u.id, u.displayName]));
    const labelName = new Map(labels.map((l) => [l.id, l.name]));
    const pageTitle = new Map(pages.map((p) => [p.id, p.title]));

    return rows.map((row) => {
      const base = GrantsService.viewOf(row);
      const scopeName =
        row.scopeType === 'LABEL'
          ? (labelName.get(row.scopeId ?? '') ?? null)
          : row.scopeType === 'PAGE'
            ? (pageTitle.get(row.scopeId ?? '') ?? null)
            : null;
      return {
        ...base,
        subjectName: row.subjectId ? (userName.get(row.subjectId) ?? null) : null,
        scopeName,
      };
    });
  }

  /** The grant must point at things that exist in this pond — a label/page
   * from elsewhere would silently never match during resolution. */
  private async assertScopeAndSubjectExist(pondId: string, grant: Grant): Promise<void> {
    if (grant.scopeType === 'label' && grant.scopeId) {
      const label = await this.prisma.label.findFirst({
        where: { id: grant.scopeId, pondId },
        select: { id: true },
      });
      if (!label) throw new BadRequestException({ code: 'grant_scope_not_found' });
    }
    if (grant.scopeType === 'page' && grant.scopeId) {
      const page = await this.prisma.page.findFirst({
        where: { id: grant.scopeId, pondId },
        select: { id: true },
      });
      if (!page) throw new BadRequestException({ code: 'grant_scope_not_found' });
    }
    if (grant.subjectType === 'user' && grant.subjectId) {
      const user = await this.prisma.user.findUnique({
        where: { id: grant.subjectId },
        select: { id: true },
      });
      if (!user) throw new BadRequestException({ code: 'grant_subject_not_found' });
    }
  }

  /**
   * Create a grant after validating its structural constraints (issue #51):
   * pond_admin only at pond scope for a user subject, no extra admins on a
   * personal pond, and scope/subject must exist here. Rejects duplicates.
   */
  async createGrant(user: User, pondId: string, grant: Grant): Promise<GrantView> {
    const pond = await this.requireLivePond(pondId);

    const invalid = grantValidationError(grant, {
      pondType: pond.type === 'PERSONAL' ? 'personal' : 'shared',
    });
    if (invalid) throw new BadRequestException({ code: invalid });
    await this.assertScopeAndSubjectExist(pondId, grant);

    const columns = toGrantColumns(grant);
    const existing = await this.prisma.roleGrant.findFirst({
      where: { pondId, ...columns },
      select: { id: true },
    });
    if (existing) throw new ConflictException({ code: 'grant_exists' });

    const created = await this.prisma.roleGrant.create({
      data: { pondId, createdBy: user.id, ...columns },
    });
    await this.accessChanged(pondId);
    await this.audit.record({
      action: 'grant.created',
      actorId: user.id,
      targetType: 'pond',
      targetId: pondId,
      details: {
        grantId: created.id,
        subject: grant.subjectType,
        subjectId: grant.subjectId,
        role: grant.role,
        scope: grant.scopeType,
        scopeId: grant.scopeId,
        effect: grant.effect,
      },
    });
    return GrantsService.viewOf(created);
  }

  /**
   * Remove a grant by id within its pond. The last remaining Pond Admin
   * grant is protected — deleting it would leave the pond unmanageable
   * (only a Site Admin could recover it).
   */
  async deleteGrant(user: User, pondId: string, grantId: string): Promise<void> {
    const grant = await this.prisma.roleGrant.findFirst({ where: { id: grantId, pondId } });
    if (!grant) throw new NotFoundException();

    if (grant.role === 'POND_ADMIN') {
      const admins = await this.prisma.roleGrant.count({
        where: { pondId, role: 'POND_ADMIN', effect: 'ALLOW' },
      });
      if (admins <= 1) throw new ConflictException({ code: 'grant_last_admin' });
    }

    await this.prisma.roleGrant.delete({ where: { id: grantId } });
    await this.accessChanged(pondId);
    await this.audit.record({
      action: 'grant.deleted',
      actorId: user.id,
      targetType: 'pond',
      targetId: pondId,
      details: { grantId, subjectId: grant.subjectId, role: grant.role },
    });
  }

  /** Revoked/added permission takes effect immediately: drop the cached pond
   * context and tell the collab server to revalidate its sessions. */
  private async accessChanged(pondId: string): Promise<void> {
    this.permissionCache.invalidate(pondId);
    await this.accessNotifier.notifyAccessChanged(pondId);
  }
}