import {
  BadRequestException,
  ConflictException,
  Injectable,
  NotFoundException,
} from '@nestjs/common';
import {
  AddMemberInput,
  ChangeMemberRoleInput,
  Grant,
  MemberRole,
  MemberView,
  PondMembersView,
  grantValidationError,
} from '@dorfteich/shared';
import { Pond, Prisma, User } from '@prisma/client';
import { PinoLogger } from 'nestjs-pino';

import { toGrant, toGrantColumns } from '../grants/grant-mappers';
import { PermissionService } from '../permissions/permission.service';
import { PondPermissionCache } from '../permissions/pond-permission-cache';
import { PondAccessNotifier } from '../ponds/pond-access-notifier.service';
import { AuditService } from '../audit/audit.service';
import { PrismaService } from '../prisma/prisma.service';
import { QuotaService, quotaExceeded } from '../quotas/quota.service';
import { UsersService } from '../users/users.service';

/** Highest capability wins when a user somehow holds several pond-scope grants. */
const ROLE_RANK: Record<MemberRole, number> = { reader: 0, editor: 1, pond_admin: 2 };

/**
 * Pond membership management (issue #54): a member-centric view over the
 * pond-scope user grants (#51/#52). Adding by exact username/e-mail keeps the
 * user directory private; editor/reader seats are enforced against the
 * per-pond quotas (#22). Personal-pond and last-admin rules come from the
 * shared grant model and the grant table, respectively. Every change
 * invalidates the pond's permission cache and notifies the collab server so
 * live sessions re-validate at once (#39/#53).
 */
@Injectable()
export class MembersService {
  constructor(
    private readonly prisma: PrismaService,
    private readonly users: UsersService,
    private readonly quotas: QuotaService,
    private readonly permissions: PermissionService,
    private readonly permissionCache: PondPermissionCache,
    private readonly accessNotifier: PondAccessNotifier,
    private readonly audit: AuditService,
    private readonly logger: PinoLogger,
  ) {
    this.logger.setContext(MembersService.name);
  }

  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;
  }

  private static pondScopeUserGrant(pondId: string, userId: string) {
    return {
      pondId,
      subjectType: 'USER' as const,
      subjectId: userId,
      scopeType: 'POND' as const,
      effect: 'ALLOW' as const,
    };
  }

  private grantOf(role: MemberRole, userId: string): Grant {
    return {
      subjectType: 'user',
      subjectId: userId,
      role,
      scopeType: 'pond',
      scopeId: null,
      effect: 'allow',
    };
  }

  private static seatKey(role: 'editor' | 'reader'): 'editors_per_pond' | 'readers_per_pond' {
    return role === 'editor' ? 'editors_per_pond' : 'readers_per_pond';
  }

  /** The member list, seat usage, and whether the caller may manage (issue #54). */
  async list(user: User | null, pondId: string): Promise<PondMembersView> {
    const pond = await this.requireLivePond(pondId);

    const grants = await this.prisma.roleGrant.findMany({
      where: { pondId, subjectType: 'USER', scopeType: 'POND', effect: 'ALLOW' },
    });
    // A user's effective role is the strongest grant they hold at pond scope.
    const roleByUser = new Map<string, MemberRole>();
    for (const row of grants) {
      const userId = row.subjectId;
      if (!userId) continue;
      const role = toGrant(row).role;
      const current = roleByUser.get(userId);
      if (!current || ROLE_RANK[role] > ROLE_RANK[current]) roleByUser.set(userId, role);
    }

    const users = await this.prisma.user.findMany({
      where: { id: { in: [...roleByUser.keys()] } },
      select: { id: true, username: true, displayName: true },
    });
    const members: MemberView[] = users
      .map((u) => ({
        userId: u.id,
        username: u.username,
        displayName: u.displayName,
        role: roleByUser.get(u.id)!,
        isOwner: u.id === pond.ownerId,
      }))
      .sort(
        (a, b) =>
          ROLE_RANK[b.role] - ROLE_RANK[a.role] || a.displayName.localeCompare(b.displayName),
      );

    const editorLimit = await this.quotas.getEffective('editors_per_pond', {
      pondId,
      userId: pond.ownerId,
    });
    const readerLimit = await this.quotas.getEffective('readers_per_pond', {
      pondId,
      userId: pond.ownerId,
    });
    const canManage = await this.permissions.hasPondRole(user, pondId, 'pond_admin');

    return {
      members,
      seats: {
        editor: { used: members.filter((m) => m.role === 'editor').length, limit: editorLimit },
        reader: { used: members.filter((m) => m.role === 'reader').length, limit: readerLimit },
      },
      pondType: pond.type === 'PERSONAL' ? 'personal' : 'shared',
      canManage,
    };
  }

  /** Add a user (by exact username or e-mail) as a member with a role. */
  async add(actor: User, pondId: string, input: AddMemberInput): Promise<MemberView> {
    const pond = await this.requireLivePond(pondId);
    const target = await this.users.findByUsernameOrEmail(input.usernameOrEmail);
    if (!target) throw new BadRequestException({ code: 'member_not_found' });

    const grant = this.grantOf(input.role, target.id);
    this.assertGrantValid(grant, pond);

    await this.prisma.$transaction(async (tx) => {
      await this.lockMembership(tx, pondId);
      const existing = await tx.roleGrant.count({
        where: MembersService.pondScopeUserGrant(pondId, target.id),
      });
      if (existing > 0) throw new ConflictException({ code: 'member_exists' });
      await this.assertSeatAvailable(tx, pond, input.role, null);
      await tx.roleGrant.create({
        data: { pondId, createdBy: actor.id, ...toGrantColumns(grant) },
      });
    });

    await this.accessChanged(pondId);
    await this.audit.record({
      action: 'member.added',
      actorId: actor.id,
      targetType: 'pond',
      targetId: pondId,
      details: { member: target.id, role: input.role },
    });
    return this.viewOf(target, input.role, pond);
  }

  /** Change a member's role, replacing their pond-scope grant. */
  async changeRole(
    actor: User,
    pondId: string,
    memberUserId: string,
    input: ChangeMemberRoleInput,
  ): Promise<MemberView> {
    const pond = await this.requireLivePond(pondId);
    if (memberUserId === pond.ownerId) throw new ConflictException({ code: 'member_is_owner' });
    const target = await this.prisma.user.findUnique({
      where: { id: memberUserId },
      select: { id: true, username: true, displayName: true },
    });
    if (!target) throw new NotFoundException({ code: 'member_not_a_member' });

    const grant = this.grantOf(input.role, memberUserId);
    this.assertGrantValid(grant, pond);

    const changed = await this.prisma.$transaction(async (tx) => {
      await this.lockMembership(tx, pondId);
      const current = await tx.roleGrant.findMany({
        where: MembersService.pondScopeUserGrant(pondId, memberUserId),
      });
      if (current.length === 0) throw new NotFoundException({ code: 'member_not_a_member' });
      // Already exactly this role: nothing to do.
      if (current.length === 1 && toGrant(current[0]!).role === input.role) return false;
      // Demoting away from admin must leave at least one Pond Admin behind.
      if (current.some((g) => g.role === 'POND_ADMIN') && input.role !== 'pond_admin') {
        await this.assertNotLastAdmin(tx, pondId);
      }
      // The replaced grants free their own seat, so exclude this user from the count.
      await this.assertSeatAvailable(tx, pond, input.role, memberUserId);
      await tx.roleGrant.deleteMany({
        where: MembersService.pondScopeUserGrant(pondId, memberUserId),
      });
      await tx.roleGrant.create({
        data: { pondId, createdBy: actor.id, ...toGrantColumns(grant) },
      });
      return true;
    });

    if (changed) {
      await this.accessChanged(pondId);
      await this.audit.record({
        action: 'member.role_changed',
        actorId: actor.id,
        targetType: 'pond',
        targetId: pondId,
        details: { member: memberUserId, role: input.role },
      });
    }
    return this.viewOf(target, input.role, pond);
  }

  /** Remove a member (drops their pond-scope grant). */
  async remove(actor: User, pondId: string, memberUserId: string): Promise<void> {
    const pond = await this.requireLivePond(pondId);
    if (memberUserId === pond.ownerId) throw new ConflictException({ code: 'member_is_owner' });

    await this.prisma.$transaction(async (tx) => {
      await this.lockMembership(tx, pondId);
      const current = await tx.roleGrant.findMany({
        where: MembersService.pondScopeUserGrant(pondId, memberUserId),
      });
      if (current.length === 0) throw new NotFoundException({ code: 'member_not_a_member' });
      if (current.some((g) => g.role === 'POND_ADMIN')) await this.assertNotLastAdmin(tx, pondId);
      await tx.roleGrant.deleteMany({
        where: MembersService.pondScopeUserGrant(pondId, memberUserId),
      });
    });

    await this.accessChanged(pondId);
    await this.audit.record({
      action: 'member.removed',
      actorId: actor.id,
      targetType: 'pond',
      targetId: pondId,
      details: { member: memberUserId },
    });
  }

  private assertGrantValid(grant: Grant, pond: Pond): void {
    const invalid = grantValidationError(grant, {
      pondType: pond.type === 'PERSONAL' ? 'personal' : 'shared',
    });
    if (invalid) throw new BadRequestException({ code: invalid });
  }

  /** Serialize concurrent membership changes on one pond (seat counts can't race). */
  private async lockMembership(tx: Prisma.TransactionClient, pondId: string): Promise<void> {
    // ::text because Prisma cannot deserialize the function's void result.
    await tx.$queryRaw`SELECT pg_advisory_xact_lock(hashtext(${`members:${pondId}`}))::text`;
  }

  private async assertNotLastAdmin(tx: Prisma.TransactionClient, pondId: string): Promise<void> {
    const admins = await tx.roleGrant.count({
      where: { pondId, role: 'POND_ADMIN', effect: 'ALLOW' },
    });
    if (admins <= 1) throw new ConflictException({ code: 'grant_last_admin' });
  }

  /** Enforce editor/reader seat quotas; admins are unlimited. */
  private async assertSeatAvailable(
    tx: Prisma.TransactionClient,
    pond: Pond,
    role: MemberRole,
    excludeUserId: string | null,
  ): Promise<void> {
    if (role === 'pond_admin') return;
    const key = MembersService.seatKey(role);
    const limit = await this.quotas.getEffective(key, { pondId: pond.id, userId: pond.ownerId });
    const used = await tx.roleGrant.count({
      where: {
        pondId: pond.id,
        role: role === 'editor' ? 'EDITOR' : 'READER',
        scopeType: 'POND',
        subjectType: 'USER',
        effect: 'ALLOW',
        ...(excludeUserId ? { subjectId: { not: excludeUserId } } : {}),
      },
    });
    if (used >= limit) throw quotaExceeded(key, limit);
  }

  private viewOf(
    user: { id: string; username: string; displayName: string },
    role: MemberRole,
    pond: Pond,
  ): MemberView {
    return {
      userId: user.id,
      username: user.username,
      displayName: user.displayName,
      role,
      isOwner: user.id === pond.ownerId,
    };
  }

  private async accessChanged(pondId: string): Promise<void> {
    this.permissionCache.invalidate(pondId);
    await this.accessNotifier.notifyAccessChanged(pondId);
  }
}