import {
  BadRequestException,
  ConflictException,
  Injectable,
  NotFoundException,
} from '@nestjs/common';
import {
  AuthorityNotice,
  AuthorityNoticeKind,
  Prisma,
} from '../../generated/prisma';
import { AuditLogService } from '../audit/audit-log.service';
import { berlinToday, dayToDate } from '../common/dates';
import { optionalDate } from '../common/patch-values';
import { PrismaService } from '../prisma/prisma.service';
import { lockRowForUpdate } from '../prisma/row-lock';
import { CreateAuthorityNoticeDto } from './dto/create-authority-notice.dto';
import { MarkSentDto } from './dto/mark-sent.dto';
import { UpdateAuthorityNoticeDto } from './dto/update-authority-notice.dto';
import { buildHerdSnapshot, loadHerdApiaryRows } from './herd-snapshot';
import {
  COMPLIANCE_SETTINGS_ID,
  complianceSettingsIn,
  findBaselineIn,
} from './herd-status';
import { buildNoticePdfModel } from './pdf/authority-notice-model';
import { renderAuthorityNoticePdf } from './pdf/authority-notice-pdf';

const AUDIT_ENTITY = 'AuthorityNotice';
const LIST_LIMIT = 200;
const UNIQUE_VIOLATION = 'P2002';

type NoticeUpdate = Prisma.AuthorityNoticeUncheckedUpdateInput;

interface DraftInput {
  kind: AuthorityNoticeKind;
  year?: number;
  referenceDate: Date;
}

interface TransitionOptions {
  /** Takes the ComplianceSettings mutex first (the open key is involved). */
  mutex?: boolean;
}

/** "REGISTRATION" | "HERD_CHANGE" | "TSK_REPORT:<year>": at most one draft each. */
function openKeyOf(kind: AuthorityNoticeKind, year: number | null): string {
  return kind === 'TSK_REPORT' ? `TSK_REPORT:${year}` : kind;
}

function trimmedOrNull(
  value: string | null | undefined,
): string | null | undefined {
  if (value === undefined) {
    return undefined;
  }
  return value?.trim() || null;
}

function notAllowed(message: string): ConflictException {
  return new ConflictException({ statusCode: 409, message });
}

function draftExists(existingId: string): ConflictException {
  return new ConflictException({
    statusCode: 409,
    code: 'DRAFT_EXISTS',
    message: 'Es gibt schon einen offenen Entwurf dieser Anzeige.',
    existingId,
  });
}

function isUniqueViolation(error: unknown): boolean {
  return (
    error instanceof Prisma.PrismaClientKnownRequestError &&
    error.code === UNIQUE_VIOLATION
  );
}

function assertYearFits(kind: AuthorityNoticeKind, year?: number): void {
  if (kind === 'TSK_REPORT' && year === undefined) {
    throw new BadRequestException('Die TSK-Zählung braucht ein Jahr');
  }
  if (kind !== 'TSK_REPORT' && year !== undefined) {
    throw new BadRequestException('Ein Jahr gibt es nur bei der TSK-Zählung');
  }
}

/** A notice cannot have been sent tomorrow: sentOn must not lie after the Berlin day. */
function futureSentOnError(
  sentOn: string | null | undefined,
): BadRequestException | undefined {
  return sentOn && sentOn > berlinToday()
    ? new BadRequestException(
        'Das Sendedatum darf nicht in der Zukunft liegen.',
      )
    : undefined;
}

@Injectable()
export class AuthorityNoticesService {
  constructor(
    private readonly prisma: PrismaService,
    private readonly auditLog: AuditLogService,
  ) {}

  findAll(q: {
    kind?: AuthorityNoticeKind;
    year?: number;
  }): Promise<AuthorityNotice[]> {
    return this.prisma.authorityNotice.findMany({
      where: { kind: q.kind, year: q.year },
      orderBy: [{ createdAt: 'desc' }, { id: 'desc' }],
      take: LIST_LIMIT,
    });
  }

  async findOne(id: string): Promise<AuthorityNotice> {
    const notice = await this.prisma.authorityNotice.findUnique({
      where: { id },
    });
    if (!notice) {
      throw new NotFoundException('Anzeige nicht gefunden');
    }
    return notice;
  }

  /**
   * The PDF of a notice. A change notice compares with the notice that was
   * the baseline when it was (or would be) sent. The file name carries the
   * id only, never user input.
   */
  async pdf(id: string): Promise<{ buffer: Buffer; fileName: string }> {
    const notice = await this.findOne(id);
    const [site, settings, baseline] = await Promise.all([
      this.prisma.siteSettings.findUnique({ where: { id: 'singleton' } }),
      complianceSettingsIn(this.prisma),
      notice.kind === 'HERD_CHANGE'
        ? this.baselineFor(notice)
        : Promise.resolve(null),
    ]);
    const model = buildNoticePdfModel({
      notice,
      baseline,
      site: {
        holderName: site?.holderName ?? null,
        holderAddress: site?.holderAddress ?? null,
      },
      settings,
      now: new Date(),
    });
    return {
      buffer: await renderAuthorityNoticePdf(model),
      fileName: `anzeige-${notice.id}.pdf`,
    };
  }

  /** A sent notice compares with the one sent before it, a draft with the newest. */
  private baselineFor(
    notice: AuthorityNotice,
  ): Promise<AuthorityNotice | null> {
    if (notice.status !== 'SENT' || !notice.sentOn) {
      return findBaselineIn(this.prisma);
    }
    return this.prisma.authorityNotice.findFirst({
      where: {
        status: 'SENT',
        kind: { in: ['REGISTRATION', 'HERD_CHANGE'] },
        id: { not: notice.id },
        OR: [
          { sentOn: { lt: notice.sentOn } },
          {
            sentOn: notice.sentOn,
            createdAt: { lt: notice.createdAt },
          },
        ],
      },
      orderBy: [{ sentOn: 'desc' }, { createdAt: 'desc' }, { id: 'desc' }],
    });
  }

  /**
   * Creates a draft, or a SENT notice at once when `sentOn` is given (the
   * way to record what was already reported). A second open draft of the
   * same kind and year answers 409 DRAFT_EXISTS with the id of the first.
   */
  async create(
    dto: CreateAuthorityNoticeDto,
    actingUserId: string,
  ): Promise<AuthorityNotice> {
    assertYearFits(dto.kind, dto.year);
    const futureError = futureSentOnError(dto.sentOn);
    if (futureError) {
      throw futureError;
    }
    const input = {
      kind: dto.kind,
      year: dto.year,
      referenceDate: dayToDate(dto.referenceDate ?? berlinToday()),
      sentOn: dto.sentOn ? dayToDate(dto.sentOn) : undefined,
    };
    try {
      return await this.prisma.$transaction((tx) =>
        this.insertIn(tx, input, actingUserId),
      );
    } catch (error) {
      if (!isUniqueViolation(error)) {
        throw error;
      }
      const winner = await this.prisma.authorityNotice.findFirst({
        where: { openKey: openKeyOf(dto.kind, dto.year ?? null) },
        select: { id: true },
      });
      if (winner) {
        throw draftExists(winner.id);
      }
      throw error;
    }
  }

  /** The shared core of create: the daily TSK job calls it in its own transaction. */
  createDraftIn(
    tx: Prisma.TransactionClient,
    input: DraftInput,
    userId: string | null,
  ): Promise<AuthorityNotice> {
    assertYearFits(input.kind, input.year);
    return this.insertIn(tx, input, userId);
  }

  /** Replaces the herd picture and the total; only a draft can be recounted. */
  recount(id: string, actingUserId: string): Promise<AuthorityNotice> {
    return this.transition(id, actingUserId, {}, async (tx, before) => {
      if (before.status !== 'DRAFT') {
        throw notAllowed('Nur ein Entwurf kann neu gezählt werden.');
      }
      const countedAt = new Date();
      const snapshot = await this.countIn(tx, before.kind, countedAt);
      return {
        snapshot: snapshot as unknown as Prisma.InputJsonValue,
        totalColonies: snapshot.totalLiving,
        countedAt,
      };
    });
  }

  markSent(
    id: string,
    dto: MarkSentDto,
    actingUserId: string,
  ): Promise<AuthorityNotice> {
    const futureError = futureSentOnError(dto.sentOn);
    if (futureError) {
      return Promise.reject(futureError);
    }
    return this.transition(id, actingUserId, { mutex: true }, (_tx, before) => {
      if (before.status !== 'DRAFT') {
        return Promise.reject(
          notAllowed('Nur ein Entwurf kann als gesendet markiert werden.'),
        );
      }
      return Promise.resolve({
        status: 'SENT',
        sentOn: dayToDate(dto.sentOn ?? berlinToday()),
        sentVia: trimmedOrNull(dto.sentVia),
        reference: trimmedOrNull(dto.reference),
        openKey: null,
      });
    });
  }

  reopen(id: string, actingUserId: string): Promise<AuthorityNotice> {
    return this.transition(
      id,
      actingUserId,
      { mutex: true },
      async (tx, before) => {
        if (before.status !== 'SENT') {
          throw notAllowed('Nur eine gesendete Anzeige kann geöffnet werden.');
        }
        const openKey = openKeyOf(before.kind, before.year);
        const other = await tx.authorityNotice.findFirst({
          where: { openKey },
          select: { id: true },
        });
        if (other) {
          throw draftExists(other.id);
        }
        return { status: 'DRAFT', openKey, sentOn: null };
      },
    );
  }

  cancel(id: string, actingUserId: string): Promise<AuthorityNotice> {
    return this.transition(id, actingUserId, {}, (_tx, before) => {
      if (before.status !== 'DRAFT') {
        return Promise.reject(
          notAllowed('Nur ein Entwurf kann verworfen werden.'),
        );
      }
      return Promise.resolve({ status: 'CANCELLED', openKey: null });
    });
  }

  update(
    id: string,
    dto: UpdateAuthorityNoticeDto,
    actingUserId: string,
  ): Promise<AuthorityNotice> {
    // A new sent day can change which notice is the baseline: the mutex
    // comes first, in lock order, whenever the sent day is touched.
    const futureError = futureSentOnError(dto.sentOn);
    if (futureError) {
      return Promise.reject(futureError);
    }
    const mutex = dto.sentOn !== undefined;
    return this.transition(id, actingUserId, { mutex }, (_tx, before) => {
      if (before.status === 'CANCELLED') {
        return Promise.reject(
          notAllowed('Eine verworfene Anzeige kann nicht geändert werden.'),
        );
      }
      if (before.status === 'DRAFT' && dto.sentOn != null) {
        return Promise.reject(
          new BadRequestException('Ein Entwurf hat kein Sendedatum.'),
        );
      }
      if (before.status === 'SENT' && dto.sentOn === null) {
        return Promise.reject(
          new BadRequestException(
            'Eine gesendete Anzeige braucht ihr Sendedatum',
          ),
        );
      }
      return Promise.resolve({
        totalColonies: dto.totalColonies,
        referenceDate: dto.referenceDate
          ? dayToDate(dto.referenceDate)
          : undefined,
        sentOn: optionalDate(dto.sentOn),
        sentVia: trimmedOrNull(dto.sentVia),
        reference: trimmedOrNull(dto.reference),
        notes: trimmedOrNull(dto.notes),
      });
    });
  }

  private async countIn(
    tx: Prisma.TransactionClient,
    kind: AuthorityNoticeKind,
    countedAt: Date,
  ) {
    const settings = await tx.complianceSettings.findUniqueOrThrow({
      where: { id: COMPLIANCE_SETTINGS_ID },
    });
    return buildHerdSnapshot(
      await loadHerdApiaryRows(tx),
      countedAt,
      kind === 'TSK_REPORT' ? settings.tskExcludedColonyTypes : [],
    );
  }

  private async insertIn(
    tx: Prisma.TransactionClient,
    input: DraftInput & { sentOn?: Date },
    userId: string | null,
  ): Promise<AuthorityNotice> {
    await this.lockSettingsIn(tx);
    const baseline = await findBaselineIn(tx);
    if (input.kind === 'REGISTRATION' && baseline) {
      throw notAllowed('Die Erstanzeige ist schon erfasst.');
    }
    if (input.kind === 'HERD_CHANGE' && !baseline) {
      throw notAllowed('Erst die Erstanzeige erfassen.');
    }
    const openKey = openKeyOf(input.kind, input.year ?? null);
    // A notice recorded as already sent has no open key and cannot collide.
    const draft = input.sentOn
      ? null
      : await tx.authorityNotice.findFirst({
          where: { openKey },
          select: { id: true },
        });
    if (draft) {
      throw draftExists(draft.id);
    }
    const countedAt = new Date();
    const snapshot = await this.countIn(tx, input.kind, countedAt);
    const created = await tx.authorityNotice.create({
      data: {
        kind: input.kind,
        status: input.sentOn ? 'SENT' : 'DRAFT',
        year: input.year ?? null,
        referenceDate: input.referenceDate,
        countedAt,
        snapshot: snapshot as unknown as Prisma.InputJsonValue,
        totalColonies: snapshot.totalLiving,
        sentOn: input.sentOn ?? null,
        openKey: input.sentOn ? null : openKey,
        createdByUserId: userId,
      },
    });
    await this.auditLog.record(
      {
        entityType: AUDIT_ENTITY,
        entityId: created.id,
        action: 'CREATE',
        userId: userId ?? undefined,
        afterData: created,
      },
      tx,
    );
    return created;
  }

  /** The ComplianceSettings row is the mutex of everything around the open key. */
  private async lockSettingsIn(tx: Prisma.TransactionClient): Promise<void> {
    await tx.complianceSettings.upsert({
      where: { id: COMPLIANCE_SETTINGS_ID },
      update: {},
      create: { id: COMPLIANCE_SETTINGS_ID },
    });
    await lockRowForUpdate(tx, 'ComplianceSettings', COMPLIANCE_SETTINGS_ID);
  }

  /**
   * One state change: lock (settings mutex first when asked, then the notice
   * row), read "before" under the lock, check the transition, write, audit.
   */
  private async transition(
    id: string,
    actingUserId: string,
    options: TransitionOptions,
    change: (
      tx: Prisma.TransactionClient,
      before: AuthorityNotice,
    ) => Promise<NoticeUpdate>,
  ): Promise<AuthorityNotice> {
    return this.prisma.$transaction(async (tx) => {
      if (options.mutex) {
        await this.lockSettingsIn(tx);
      }
      if (!(await lockRowForUpdate(tx, 'AuthorityNotice', id))) {
        throw new NotFoundException('Anzeige nicht gefunden');
      }
      const before = await tx.authorityNotice.findUnique({ where: { id } });
      if (!before) {
        throw new NotFoundException('Anzeige nicht gefunden');
      }
      const after = await tx.authorityNotice.update({
        where: { id },
        data: await change(tx, before),
      });
      await this.auditLog.record(
        {
          entityType: AUDIT_ENTITY,
          entityId: id,
          action: 'UPDATE',
          userId: actingUserId,
          beforeData: before,
          afterData: after,
        },
        tx,
      );
      return after;
    });
  }
}