import { Injectable, Logger, OnApplicationBootstrap } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository } from 'typeorm';
import * as fs from 'fs/promises';
import sharp = require('sharp');
import { PdfService } from '../preprocessing/pdf.service';
import { QrCodeService } from '../preprocessing/qr-code.service';
import {
  BarcodeTemplate,
  type BarcodeActionType,
} from '../database/entities/barcode-template.entity';
import {
  InboxDocument,
  type StoredQrCode,
} from '../database/entities/inbox-document.entity';
import { PageCacheService } from './page-cache.service';
import {
  applyTemplate,
  buildVariables,
} from '../inbox-postprocessor/variable-resolver';

export interface MatchedBarcode {
  page: number;
  value: string;
  templateId: number | null;
  templateName: string | null;
  dateinameTemplate: string | null;
  splitBefore: boolean;
  actions: BarcodeActionType[];
}

@Injectable()
export class BarcodeScannerService implements OnApplicationBootstrap {
  private readonly logger = new Logger(BarcodeScannerService.name);
  private templatesCache: BarcodeTemplate[] | null = null;

  constructor(
    private readonly pdfService: PdfService,
    private readonly qrCodeService: QrCodeService,
    private readonly pageCache: PageCacheService,
    @InjectRepository(BarcodeTemplate)
    private readonly templateRepo: Repository<BarcodeTemplate>,
    @InjectRepository(InboxDocument)
    private readonly documentRepo: Repository<InboxDocument>,
  ) {}

  async onApplicationBootstrap(): Promise<void> {
    await this.migrateLegacySplitBefore();
  }

  invalidateTemplates(): void {
    this.templatesCache = null;
  }

  private async migrateLegacySplitBefore(): Promise<void> {
    let rows: BarcodeTemplate[];
    try {
      rows = await this.templateRepo.find();
    } catch (err: any) {
      this.logger.warn(
        `Template-Migration: Query fehlgeschlagen: ${err.message}`,
      );
      return;
    }
    let migrated = 0;
    for (const tpl of rows) {
      const actions = (tpl.Actions ?? []) as string[];
      if (actions.includes('SPLIT_BEFORE')) {
        tpl.SplitBefore = true;
        tpl.Actions = actions.filter(
          (a) => a !== 'SPLIT_BEFORE',
        ) as BarcodeActionType[];
        await this.templateRepo.save(tpl);
        migrated += 1;
      }
    }
    if (migrated > 0) {
      this.logger.log(
        `Template-Migration: ${migrated} Vorlage(n) auf SplitBefore-Flag umgestellt`,
      );
    }
  }

  /**
   * Rendert alle Seiten, extrahiert QR-Codes, persistiert Page-Cache + DB-Row.
   * Wird nach dem Move aus dem Watcher und beim Backfill aufgerufen.
   */
  async scanAndMatch(doc: InboxDocument): Promise<MatchedBarcode[]> {
    const pdfPath = this.pageCache.documentPdfPath(doc.Id);
    const { qrCodes, pageCount } = await this.performScan(doc.Id, pdfPath);

    doc.QrCodes = qrCodes;
    doc.PageCount = pageCount;
    doc.IsScanned = true;
    try {
      await this.documentRepo.save(doc);
    } catch (err: any) {
      this.logger.warn(
        `Scan-Ergebnis konnte nicht gespeichert werden (${doc.Id}): ${err.message}`,
      );
    }

    return this.matchTemplates(qrCodes);
  }

  /**
   * Scannt nur, wenn die Row noch keine Seitenanzahl hat (= noch nie gescannt).
   */
  async ensureScanned(doc: InboxDocument): Promise<boolean> {
    if (doc.PageCount > 0) return false;
    await this.scanAndMatch(doc);
    return true;
  }

  /**
   * Read-only: mapped die persistierten QR-Codes auf MatchedBarcodes.
   */
  async getMatched(doc: InboxDocument): Promise<MatchedBarcode[]> {
    return this.matchTemplates(doc.QrCodes ?? []);
  }

  private async matchTemplates(
    qrCodes: StoredQrCode[],
  ): Promise<MatchedBarcode[]> {
    if (qrCodes.length === 0) return [];
    const templates = await this.getTemplates();
    return qrCodes.map((qr) => {
      const tpl = this.firstMatch(qr.value, templates);
      return {
        page: qr.page,
        value: qr.value,
        templateId: tpl?.Id ?? null,
        templateName: tpl?.Name ?? null,
        dateinameTemplate: tpl?.DateinameTemplate
          ? applyTemplate(
              tpl.DateinameTemplate,
              buildVariables({
                doc: {} as InboxDocument,
                template: tpl,
                matchingQrValue: qr.value,
              }),
            )
          : null,
        splitBefore: tpl?.SplitBefore ?? false,
        actions: tpl?.Actions ?? [],
      };
    });
  }

  private firstMatch(
    value: string,
    templates: BarcodeTemplate[],
  ): BarcodeTemplate | null {
    for (const tpl of templates) {
      try {
        const re = new RegExp(tpl.Regex);
        if (re.test(value)) return tpl;
      } catch {
        // ignore invalid regex
      }
    }
    return null;
  }

  private async getTemplates(): Promise<BarcodeTemplate[]> {
    if (!this.templatesCache) {
      this.templatesCache = await this.templateRepo.find({
        order: { Id: 'ASC' },
      });
    }
    return this.templatesCache;
  }

  private async performScan(
    documentId: string,
    pdfPath: string,
  ): Promise<{ qrCodes: StoredQrCode[]; pageCount: number }> {
    let images: string[] = [];
    try {
      images = await this.pdfService.pdfToImages(pdfPath, 400);
      const qrCodes: StoredQrCode[] = [];
      const templates = await this.getTemplates();

      for (let i = 0; i < images.length; i++) {
        try {
          const buffer = await fs.readFile(images[i]);
          const qrs = await this.qrCodeService.extractFromImage(buffer);
          // Nur QR-Codes speichern, die zu einer Eingangsdokumentart passen.
          // Mehrere passende QRs pro Seite werden alle übernommen.
          for (const qr of qrs) {
            if (this.firstMatch(qr.data, templates)) {
              qrCodes.push({ page: i + 1, value: qr.data });
            }
          }
        } catch (err: any) {
          this.logger.warn(
            `QR-Scan fehlgeschlagen (${pdfPath}, Seite ${i + 1}): ${err.message}`,
          );
        }
      }

      await this.pageCache.clear(documentId);
      await this.pageCache.generate(documentId, images);

      return { qrCodes, pageCount: images.length };
    } catch (err: any) {
      this.logger.warn(`Kein QR-Scan möglich für ${pdfPath}: ${err.message}`);
      return { qrCodes: [], pageCount: 0 };
    } finally {
      await this.pdfService.cleanup(images);
    }
  }

  /**
   * Rendert eine einzelne Seite bei hoher DPI, beschneidet den angegebenen
   * Bereich (normalisierte Koordinaten 0..1) und scannt ihn nach QR-Codes.
   * Neu gefundene QR-Codes werden in der DB persistiert.
   */
  async scanRegion(
    doc: InboxDocument,
    pdfPath: string,
    page: number,
    x: number,
    y: number,
    w: number,
    h: number,
  ): Promise<{ found: string[] }> {
    let imagePath: string | null = null;
    try {
      imagePath = await this.pdfService.pdfPageToImage(pdfPath, page, 400);

      const image = sharp(imagePath);
      const { width: imgW, height: imgH } = await image.metadata();
      if (!imgW || !imgH) return { found: [] };

      const left = Math.round(Math.max(0, x * imgW));
      const top = Math.round(Math.max(0, y * imgH));
      const width = Math.round(Math.min(imgW - left, w * imgW));
      const height = Math.round(Math.min(imgH - top, h * imgH));
      if (width <= 0 || height <= 0) return { found: [] };

      const cropped = await image
        .extract({ left, top, width, height })
        .png()
        .toBuffer();
      const qrResults = await this.qrCodeService.extractFromImage(cropped);
      if (qrResults.length === 0) return { found: [] };

      const existingKeys = new Set(
        (doc.QrCodes ?? []).map((qr) => `${qr.page}:${qr.value}`),
      );
      const found: string[] = [];
      let changed = false;

      for (const qr of qrResults) {
        found.push(qr.data);
        const key = `${page}:${qr.data}`;
        if (!existingKeys.has(key)) {
          doc.QrCodes = [...(doc.QrCodes ?? []), { page, value: qr.data }];
          changed = true;
        }
      }

      if (changed) {
        await this.documentRepo.save(doc);
      }

      return { found };
    } finally {
      if (imagePath) await this.pdfService.cleanup([imagePath]);
    }
  }

  /**
   * Rescannt alle Inbox-Dokumente — wird nach Änderungen an Eingangsdokumentarten aufgerufen.
   * Läuft sequenziell, um PDF-Rendering nicht zu überlasten. Fire-and-forget vom Caller.
   */
  async rescanAll(): Promise<{ scanned: number; failed: number }> {
    this.invalidateTemplates();
    let docs: InboxDocument[];
    try {
      docs = await this.documentRepo.find();
    } catch (err: any) {
      this.logger.warn(`Rescan: DB-Query fehlgeschlagen: ${err.message}`);
      return { scanned: 0, failed: 0 };
    }
    if (docs.length === 0) return { scanned: 0, failed: 0 };

    this.logger.log(
      `Rescan: starte Neuerfassung für ${docs.length} Inbox-Dokument(e)`,
    );
    let scanned = 0;
    let failed = 0;
    for (const doc of docs) {
      try {
        const pdfPath = this.pageCache.documentPdfPath(doc.Id);
        try {
          await fs.access(pdfPath);
        } catch {
          this.logger.warn(`Rescan: PDF fehlt für ${doc.Id} (${pdfPath})`);
          failed++;
          continue;
        }
        const { qrCodes, pageCount } = await this.performScan(doc.Id, pdfPath);
        doc.QrCodes = qrCodes;
        doc.PageCount = pageCount;
        await this.documentRepo.save(doc);
        scanned++;
      } catch (err: any) {
        this.logger.warn(`Rescan fehlgeschlagen für ${doc.Id}: ${err.message}`);
        failed++;
      }
    }
    this.logger.log(
      `Rescan abgeschlossen: ${scanned} ok, ${failed} fehlgeschlagen`,
    );
    return { scanned, failed };
  }
}