import {
  BadRequestException,
  ConflictException,
  Injectable,
  NotFoundException,
} from '@nestjs/common';
import {
  CreateCustomFontInput,
  CustomFontView,
  FONT_CATALOG,
  FontCategory,
  FontUploadFormat,
  MAX_FONT_FILE_BYTES,
  MAX_FONT_WEIGHTS,
  fontSlug,
  hasFontMagic,
} from '@dorfteich/shared';
import { User } from '@prisma/client';
import { PinoLogger } from 'nestjs-pino';

import { AuditService } from '../audit/audit.service';
import { PrismaService } from '../prisma/prisma.service';
import { CustomFontStorageService } from './custom-font-storage.service';

/** One weight's bytes as they arrive from the controller. */
export interface WeightUpload {
  weight: number;
  woff2: Buffer;
  woff?: Buffer;
}

/**
 * Operator-uploaded font families (issue #303, ADR 0016 §#303).
 *
 * Site-Admin-only, additive to the compile-time catalog, and deliberately
 * incurious about the files: the api validates the magic number and the size
 * and then stores the bytes. Family, category and licence come from the form.
 */
@Injectable()
export class CustomFontsService {
  constructor(
    private readonly prisma: PrismaService,
    private readonly storage: CustomFontStorageService,
    private readonly audit: AuditService,
    private readonly logger: PinoLogger,
  ) {
    this.logger.setContext(CustomFontsService.name);
  }

  /**
   * Rejects bytes that are not what they claim to be, before anything is
   * written. Deliberately the ONLY inspection: parsing the font would gain
   * metadata the form already carries, at the price of a known
   * memory-safety surface (ADR 0016 §#303).
   */
  private assertUsableFont(bytes: Buffer, format: FontUploadFormat): void {
    if (bytes.length === 0) throw new BadRequestException({ code: 'font_file_empty' });
    if (bytes.length > MAX_FONT_FILE_BYTES) {
      throw new BadRequestException({ code: 'font_file_too_large' });
    }
    if (!hasFontMagic(bytes, format)) {
      throw new BadRequestException({ code: 'font_file_not_a_font' });
    }
  }

  /**
   * A custom family must not collide with a catalog one, by name or by slug:
   * a pond stores `fonts.<slot>.family` as a plain string, so two families
   * answering to the same name would make the PDF path embed whichever file
   * it happened to find.
   */
  private async assertNameIsFree(family: string, slug: string): Promise<void> {
    const catalogHit = FONT_CATALOG.some(
      (entry) => entry.family === family || fontSlug(entry.family) === slug,
    );
    if (catalogHit) throw new ConflictException({ code: 'font_family_reserved' });
    const existing = await this.prisma.customFont.findFirst({
      where: { OR: [{ family }, { slug }] },
      select: { id: true },
    });
    if (existing) throw new ConflictException({ code: 'font_family_exists' });
  }

  private viewOf(font: {
    id: string;
    family: string;
    slug: string;
    category: string;
    licence: string;
    licenceUrl: string | null;
    createdAt: Date;
    weights: { weight: number }[];
  }): CustomFontView {
    return {
      id: font.id,
      family: font.family,
      slug: font.slug,
      category: font.category as FontCategory,
      licence: font.licence,
      licenceUrl: font.licenceUrl,
      weights: font.weights.map((row) => row.weight).sort((a, b) => a - b),
      createdAt: font.createdAt.toISOString(),
    };
  }

  async list(): Promise<CustomFontView[]> {
    const fonts = await this.prisma.customFont.findMany({
      orderBy: { family: 'asc' },
      include: { weights: { select: { weight: true } } },
    });
    return fonts.map((font) => this.viewOf(font));
  }

  async create(
    admin: User,
    input: CreateCustomFontInput,
    uploads: WeightUpload[],
  ): Promise<CustomFontView> {
    if (uploads.length === 0) throw new BadRequestException({ code: 'font_no_weights' });
    if (uploads.length > MAX_FONT_WEIGHTS) {
      throw new BadRequestException({ code: 'font_too_many_weights' });
    }
    for (const upload of uploads) {
      this.assertUsableFont(upload.woff2, 'woff2');
      if (upload.woff) this.assertUsableFont(upload.woff, 'woff');
    }

    const slug = fontSlug(input.family);
    if (!slug) throw new BadRequestException({ code: 'font_family_unusable' });
    await this.assertNameIsFree(input.family, slug);

    // Row first, then bytes: a row without files is repairable (re-upload the
    // weight), while files without a row would be invisible litter.
    const font = await this.prisma.customFont.create({
      data: {
        family: input.family,
        slug,
        category: input.category,
        licence: input.licence,
        licenceUrl: input.licenceUrl,
        uploadedBy: admin.id,
        weights: {
          create: uploads.map((upload) => ({
            weight: upload.weight,
            hasWoff: Boolean(upload.woff),
            byteSize: upload.woff2.length,
          })),
        },
      },
      include: { weights: { select: { weight: true } } },
    });

    for (const upload of uploads) {
      await this.storage.save(slug, upload.weight, 'woff2', upload.woff2);
      if (upload.woff) await this.storage.save(slug, upload.weight, 'woff', upload.woff);
    }

    await this.audit.record({
      action: 'font.uploaded',
      actorId: admin.id,
      targetType: 'font',
      targetId: font.id,
      details: { family: font.family },
    });
    return this.viewOf(font);
  }

  async addWeight(admin: User, fontId: string, upload: WeightUpload): Promise<CustomFontView> {
    this.assertUsableFont(upload.woff2, 'woff2');
    if (upload.woff) this.assertUsableFont(upload.woff, 'woff');

    const font = await this.prisma.customFont.findUnique({
      where: { id: fontId },
      include: { weights: { select: { weight: true } } },
    });
    if (!font) throw new NotFoundException();
    if (font.weights.length >= MAX_FONT_WEIGHTS) {
      throw new BadRequestException({ code: 'font_too_many_weights' });
    }
    if (font.weights.some((row) => row.weight === upload.weight)) {
      throw new ConflictException({ code: 'font_weight_exists' });
    }

    await this.prisma.customFontWeight.create({
      data: {
        fontId,
        weight: upload.weight,
        hasWoff: Boolean(upload.woff),
        byteSize: upload.woff2.length,
      },
    });
    await this.storage.save(font.slug, upload.weight, 'woff2', upload.woff2);
    if (upload.woff) await this.storage.save(font.slug, upload.weight, 'woff', upload.woff);

    await this.audit.record({
      action: 'font.uploaded',
      actorId: admin.id,
      targetType: 'font',
      targetId: fontId,
      details: { family: font.family, weight: upload.weight },
    });
    const updated = await this.prisma.customFont.findUniqueOrThrow({
      where: { id: fontId },
      include: { weights: { select: { weight: true } } },
    });
    return this.viewOf(updated);
  }

  /**
   * How many live ponds still name this family in any of their three font
   * slots. Shown before deletion — those ponds keep working (an unknown
   * family falls back to the system stack) but they visibly change.
   */
  async pondsUsing(family: string): Promise<number> {
    const rows = await this.prisma.$queryRaw<{ count: bigint }[]>`
      SELECT count(*)::bigint AS count
        FROM ponds
       WHERE deleted_at IS NULL
         AND (settings #>> '{fonts,heading,family}' = ${family}
           OR settings #>> '{fonts,body,family}' = ${family}
           OR settings #>> '{fonts,mono,family}' = ${family})
    `;
    return Number(rows[0]?.count ?? 0);
  }

  /**
   * Deletion is never blocked by usage. `fontStack` already yields the system
   * fallback for an unknown family, so affected ponds degrade rather than
   * break, and re-uploading the family restores them — but the count travels
   * into the audit entry so the change is not silent.
   */
  async remove(admin: User, fontId: string): Promise<void> {
    const font = await this.prisma.customFont.findUnique({ where: { id: fontId } });
    if (!font) throw new NotFoundException();
    const pondsAffected = await this.pondsUsing(font.family);

    await this.prisma.customFont.delete({ where: { id: fontId } });
    await this.storage.deleteFamily(font.slug);

    await this.audit.record({
      action: 'font.deleted',
      actorId: admin.id,
      targetType: 'font',
      targetId: fontId,
      details: { family: font.family, pondsAffected },
    });
    this.logger.info({ fontId, family: font.family, pondsAffected }, 'custom font deleted');
  }
}