import { Injectable, NotFoundException } from "@nestjs/common";
import { existsSync, readdirSync, statSync } from "node:fs";
import { basename, extname, join } from "node:path";
import { eq, inArray } from "drizzle-orm";
import { DatabaseService } from "../database/database.service.js";
import { automationSettings, books, libraries, series } from "../database/schema.js";
import { JobsService } from "../jobs/jobs.service.js";
import { MetadataService } from "../metadata/metadata.service.js";
import { extractSeriesVolume } from "../metadata/use-cases/extract-series-volume.js";
import { normalizePublishedDate } from "../metadata/use-cases/normalize-published-date.js";
import { extractMetadata } from "./metadata.js";

@Injectable()
export class ScannerService {
  constructor(
    private readonly database: DatabaseService,
    private readonly jobs: JobsService,
    private readonly metadata: MetadataService
  ) {}

  enqueueLibraryScan(libraryId: number) {
    const library = this.database.db.select().from(libraries).where(eq(libraries.id, libraryId)).get();
    if (!library) {
      throw new NotFoundException("Library not found");
    }
    const job = this.jobs.create("library-scan", `Scanning ${library.path}`);
    setImmediate(() => {
      void this.scanLibrary(job.id, library).catch((error) => this.jobs.markFailed(job.id, error));
    });
    return job;
  }

  enqueueAllLibrariesScan(detail = "Scanning all enabled libraries") {
    const job = this.jobs.create("library-scan-all", detail);
    setImmediate(() => {
      void this.scanAllLibraries(job.id).catch((error) => this.jobs.markFailed(job.id, error));
    });
    return job;
  }

  enqueueMetadataEnrichment(detail = "Enriching existing books") {
    const job = this.jobs.create("metadata-enrich", detail);
    setImmediate(() => {
      void this.enrichExistingBooks(job.id).catch((error) => this.jobs.markFailed(job.id, error));
    });
    return job;
  }

  private async scanLibrary(jobId: number, library: typeof libraries.$inferSelect): Promise<void> {
    this.jobs.markRunning(jobId, `Scanning ${library.path}`);
    let count = 0;
    const failures: ScanFailure[] = [];
    const seen = new Set<string>();
    for (const filePath of walkBooks(library.path)) {
      seen.add(filePath);
      try {
        await this.ingestFile(library.id, filePath);
        count += 1;
      } catch (error) {
        failures.push({ filePath, error: errorMessage(error) });
        this.ingestIncompleteFile(library.id, filePath);
      }
    }
    const removed = this.removeMissingBooks(library.id, seen);
    this.jobs.markSucceeded(jobId, scanDigest(count, removed, failures));
  }

  private async scanAllLibraries(jobId: number): Promise<void> {
    this.jobs.markRunning(jobId, "Scanning all enabled libraries");
    const enabledLibraries = this.database.db.select().from(libraries).where(eq(libraries.enabled, true)).all();
    let scanned = 0;
    const failures: ScanFailure[] = [];
    for (const library of enabledLibraries) {
      for (const filePath of walkBooks(library.path)) {
        try {
          await this.ingestFile(library.id, filePath);
          scanned += 1;
        } catch (error) {
          failures.push({ filePath, error: errorMessage(error) });
          this.ingestIncompleteFile(library.id, filePath);
        }
      }
    }
    this.jobs.markSucceeded(jobId, scanDigest(scanned, 0, failures, `across ${enabledLibraries.length} library/libraries`));
  }

  private async enrichExistingBooks(jobId: number): Promise<void> {
    this.jobs.markRunning(jobId, "Enriching existing books");
    const rows = this.database.db.select({ id: books.id }).from(books).all();
    let count = 0;
    const failures: ScanFailure[] = [];
    for (const row of rows) {
      this.markBookEnrichmentStatus(row.id, "running");
      try {
        await this.metadata.enrichBook(row.id);
        this.markBookEnrichmentStatus(row.id, "succeeded");
        count += 1;
      } catch (error) {
        this.markBookEnrichmentStatus(row.id, "failed");
        failures.push({ filePath: `book #${row.id}`, error: errorMessage(error) });
      }
    }
    this.jobs.markSucceeded(jobId, enrichmentDigest(count, failures));
  }

  private async ingestFile(libraryId: number, filePath: string): Promise<void> {
    const stats = statSync(filePath);
    const existing = this.database.db.select().from(books).where(eq(books.filePath, filePath)).get();
    if (existing) {
      this.database.db
        .update(books)
        .set({ scanStatus: "running", enrichmentStatus: "running", updatedAt: this.database.now() })
        .where(eq(books.id, existing.id))
        .run();
    }
    const localMetadata = await extractMetadata(filePath, this.database.config.storageDir);
    const now = this.database.now();
    const format = bookFormatFromPath(filePath);
    const shouldRemoteEnrich = !existing ? this.shouldAutoEnrichNewBooks() : true;
    const metadata = await this.metadata.enrichMetadata(localMetadata, filePath, { remote: shouldRemoteEnrich });
    const seriesInfo = this.resolveSeries(metadata.title, filePath);
    const values = {
      libraryId,
      seriesId: seriesInfo.seriesId,
      title: metadata.title,
      author: metadata.author,
      description: metadata.description,
      isbn: metadata.isbn,
      isbn13: metadata.isbn13,
      identifiersJson: metadata.identifiersJson,
      localMetadataJson: metadata.localMetadataJson,
      language: metadata.language,
      publisher: metadata.publisher,
      publishedDate: metadata.publishedDate,
      volumeNumber: seriesInfo.volumeNumber,
      volumeLabel: seriesInfo.volumeLabel,
      format,
      filePath,
      coverPath: metadata.coverPath,
      metadataStatus: metadata.metadataStatus,
      metadataProvenanceJson: metadata.metadataProvenanceJson,
      scanStatus: "succeeded" as const,
      enrichmentStatus: shouldRemoteEnrich ? ("succeeded" as const) : ("idle" as const),
      fileSize: stats.size,
      fileMtime: stats.mtime.toISOString(),
      updatedAt: now
    };

    this.upsertBookByFilePath(values, existing, now);
  }

  private ingestIncompleteFile(libraryId: number, filePath: string): void {
    const stats = statSync(filePath);
    const now = this.database.now();
    const existing = this.database.db.select().from(books).where(eq(books.filePath, filePath)).get();
    const seriesInfo = this.resolveSeries(basename(filePath, extname(filePath)), filePath);
    const values = {
      libraryId,
      seriesId: seriesInfo.seriesId,
      title: basename(filePath, extname(filePath)),
      author: null,
      description: null,
      isbn: null,
      isbn13: null,
      identifiersJson: JSON.stringify({ candidates: [], isbn10: null, isbn13: null }),
      localMetadataJson: JSON.stringify({
        title: basename(filePath, extname(filePath)),
        author: null,
        year: null,
        isbn: null,
        fileTitle: basename(filePath, extname(filePath)),
        raw: {
          title: basename(filePath, extname(filePath)),
          author: null,
          publishedDate: null,
          fileName: basename(filePath, extname(filePath))
        }
      }),
      language: null,
      publisher: null,
      publishedDate: null,
      volumeNumber: seriesInfo.volumeNumber,
      volumeLabel: seriesInfo.volumeLabel,
      format: bookFormatFromPath(filePath),
      filePath,
      coverPath: null,
      metadataStatus: "none" as const,
      metadataProvenanceJson: JSON.stringify({ title: "local" }),
      scanStatus: "failed" as const,
      enrichmentStatus: "failed" as const,
      fileSize: stats.size,
      fileMtime: stats.mtime.toISOString(),
      updatedAt: now
    };

    this.upsertBookByFilePath(values, existing, now);
  }

  private upsertBookByFilePath(
    values: Omit<typeof books.$inferInsert, "createdAt">,
    existing: typeof books.$inferSelect | undefined,
    createdAt: string
  ): void {
    if (existing) {
      this.database.db.update(books).set(preserveExistingBookValues(values, existing)).where(eq(books.id, existing.id)).run();
      return;
    }
    try {
      this.database.db.insert(books).values({ ...values, createdAt }).run();
      return;
    } catch (error) {
      if (!isUniqueFilePathError(error)) throw error;
      const current = this.database.db.select().from(books).where(eq(books.filePath, values.filePath)).get();
      if (!current) throw error;
      this.database.db.update(books).set(preserveExistingBookValues(values, current)).where(eq(books.id, current.id)).run();
    }
  }

  private removeMissingBooks(libraryId: number, seen: Set<string>): number {
    const existing = this.database.db.select({ id: books.id, filePath: books.filePath }).from(books).where(eq(books.libraryId, libraryId)).all();
    const missing = existing.filter((book) => !seen.has(book.filePath) && !existsSync(book.filePath));
    if (!missing.length) return 0;
    this.database.db.delete(books).where(inArray(books.id, missing.map((book) => book.id))).run();
    return missing.length;
  }

  private shouldAutoEnrichNewBooks(): boolean {
    return Boolean(
      this.database.db
        .select({ autoEnrichNewBooks: automationSettings.autoEnrichNewBooks })
        .from(automationSettings)
        .where(eq(automationSettings.id, 1))
        .get()?.autoEnrichNewBooks
    );
  }

  private markBookEnrichmentStatus(id: number, enrichmentStatus: "running" | "succeeded" | "failed"): void {
    this.database.db.update(books).set({ enrichmentStatus, updatedAt: this.database.now() }).where(eq(books.id, id)).run();
  }

  private resolveSeries(title: string, filePath: string): { seriesId: number; volumeNumber: number | null; volumeLabel: string | null } {
    const parsed = extractSeriesVolume(title, filePath);
    const now = this.database.now();
    const row = this.database.db
      .insert(series)
      .values({
        title: parsed.seriesTitle,
        normalizedTitle: parsed.normalizedSeriesTitle,
        description: null,
        publisher: null,
        createdAt: now,
        updatedAt: now
      })
      .onConflictDoUpdate({
        target: series.normalizedTitle,
        set: { title: parsed.seriesTitle, updatedAt: now }
      })
      .returning({ id: series.id })
      .get();
    return { seriesId: row.id, volumeNumber: parsed.volumeNumber, volumeLabel: parsed.volumeLabel };
  }
}

type ScanFailure = {
  filePath: string;
  error: string;
};

export function scanDigest(scanned: number, removed: number, failures: ScanFailure[], suffix?: string): string {
  const base = suffix ? `Scanned ${scanned} file(s) ${suffix}` : `Scanned ${scanned} file(s), removed ${removed} missing book(s)`;
  if (!failures.length) return base;
  const examples = failures
    .slice(0, 3)
    .map((failure) => `${basename(failure.filePath)}: ${truncate(failure.error)}`)
    .join("; ");
  const extra = failures.length > 3 ? `; ${failures.length - 3} more` : "";
  return `${base}, ${failures.length} incomplete file(s): ${examples}${extra}`;
}

export function enrichmentDigest(enriched: number, failures: ScanFailure[]): string {
  const base = `Enriched ${enriched} book(s)`;
  if (!failures.length) return base;
  const examples = failures
    .slice(0, 3)
    .map((failure) => `${basename(failure.filePath)}: ${truncate(failure.error)}`)
    .join("; ");
  const extra = failures.length > 3 ? `; ${failures.length - 3} more` : "";
  return `${base}, ${failures.length} incomplete book(s): ${examples}${extra}`;
}

function errorMessage(error: unknown): string {
  if (error instanceof Error && error.message) return truncate(error.message);
  return truncate(String(error));
}

function truncate(value: string): string {
  return value.length > 120 ? `${value.slice(0, 117)}...` : value;
}

function* walkBooks(root: string): Generator<string> {
  for (const entry of readdirSync(root, { withFileTypes: true })) {
    const path = join(root, entry.name);
    if (entry.isDirectory()) {
      yield* walkBooks(path);
      continue;
    }
    if (!entry.isFile()) continue;
    const extension = extname(entry.name).toLowerCase();
    if (extension === ".epub" || extension === ".pdf" || extension === ".cbz" || extension === ".cbr") {
      yield path;
    }
  }
}

function bookFormatFromPath(filePath: string): "epub" | "pdf" | "cbz" | "cbr" {
  const extension = extname(filePath).toLowerCase();
  if (extension === ".epub") return "epub";
  if (extension === ".cbz") return "cbz";
  if (extension === ".cbr") return "cbr";
  return "pdf";
}

export function preserveExistingBookValues<T extends Partial<typeof books.$inferInsert>>(values: T, existing: typeof books.$inferSelect): T {
  const next = { ...values };
  if (next.scanStatus === "failed" && existing.title) {
    next.title = existing.title as never;
  }
  for (const field of ["author", "description", "isbn", "isbn13", "language", "publisher", "publishedDate", "coverPath", "seriesId", "volumeNumber", "volumeLabel"] as const) {
    if (field === "publishedDate") {
      next.publishedDate = (normalizePublishedDate(next.publishedDate) ?? normalizePublishedDate(existing.publishedDate)) as never;
      continue;
    }
    if (next[field] == null && existing[field] != null) {
      next[field] = existing[field] as never;
    }
  }
  next.metadataStatus = computeMetadataStatus(next, existing.metadataStatus) as never;
  next.metadataProvenanceJson = mergeProvenanceJson(String(next.metadataProvenanceJson ?? "{}"), existing.metadataProvenanceJson) as never;
  return next;
}

function computeMetadataStatus(values: Partial<typeof books.$inferInsert>, existingStatus: string): "enriched" | "partial" | "none" {
  const hasCover = Boolean(values.coverPath);
  const filled = [values.author, values.description, values.isbn, values.language, values.publisher, values.publishedDate].filter(Boolean).length;
  const computed = hasCover && filled >= 2 ? "enriched" : hasCover || filled > 0 ? "partial" : "none";
  const rank = { none: 0, partial: 1, enriched: 2 } as const;
  const safeExisting = existingStatus === "enriched" || existingStatus === "partial" || existingStatus === "none" ? existingStatus : "none";
  return rank[computed] >= rank[safeExisting] ? computed : safeExisting;
}

function mergeProvenanceJson(nextJson: string, existingJson: string | null): string {
  return JSON.stringify({ ...parseJsonObject(existingJson), ...parseJsonObject(nextJson) });
}

function parseJsonObject(value: string | null): Record<string, unknown> {
  if (!value) return {};
  try {
    const parsed = JSON.parse(value) as unknown;
    return parsed && typeof parsed === "object" && !Array.isArray(parsed) ? (parsed as Record<string, unknown>) : {};
  } catch {
    return {};
  }
}

function isUniqueFilePathError(error: unknown): boolean {
  return error instanceof Error && error.message.includes("UNIQUE constraint failed: books.file_path");
}