import { Injectable, NotFoundException } from "@nestjs/common";
import { createReadStream, existsSync } from "node:fs";
import { and, eq, sql } from "drizzle-orm";
import { BookQueryDto } from "@readabook/shared";
import { DatabaseService } from "../database/database.service.js";
import { books } from "../database/schema.js";

@Injectable()
export class BooksService {
  constructor(private readonly database: DatabaseService) {}

  list(query: BookQueryDto) {
    const filters = [];
    if (query.format) filters.push(eq(books.format, query.format));
    if (query.libraryId) filters.push(eq(books.libraryId, query.libraryId));
    if (query.q) {
      return this.search(query.q, query.limit, query.offset);
    }
    return this.database.db
      .select()
      .from(books)
      .where(filters.length ? and(...filters) : undefined)
      .orderBy(books.title)
      .limit(query.limit)
      .offset(query.offset)
      .all();
  }

  search(q: string, limit = 50, offset = 0) {
    const rows = this.database.sqlite
      .prepare(
        `
        SELECT books.*
        FROM book_fts
        JOIN books ON books.id = book_fts.rowid
        WHERE book_fts MATCH ?
        ORDER BY bm25(book_fts)
        LIMIT ? OFFSET ?
      `
      )
      .all(`${q.replace(/"/g, '""')}*`, limit, offset);
    return (rows as Array<Record<string, unknown>>).map(mapBookRow);
  }

  get(id: number) {
    const book = this.database.db.select().from(books).where(eq(books.id, id)).get();
    if (!book) {
      throw new NotFoundException("Book not found");
    }
    return book;
  }

  streamFile(id: number) {
    const book = this.get(id);
    if (!existsSync(book.filePath)) {
      throw new NotFoundException("Book file not found on disk");
    }
    return { book, stream: createReadStream(book.filePath) };
  }

  streamCover(id: number) {
    const book = this.get(id);
    if (!book.coverPath || !existsSync(book.coverPath)) {
      throw new NotFoundException("Cover not found");
    }
    return { book, stream: createReadStream(book.coverPath), coverPath: book.coverPath };
  }

  count() {
    return this.database.db.select({ count: sql<number>`count(*)` }).from(books).get()?.count ?? 0;
  }
}

function mapBookRow(row: Record<string, unknown>) {
  return {
    id: Number(row.id),
    libraryId: Number(row.library_id),
    title: String(row.title),
    author: nullable(row.author),
    description: nullable(row.description),
    isbn: nullable(row.isbn),
    language: nullable(row.language),
    publisher: nullable(row.publisher),
    publishedDate: nullable(row.published_date),
    format: row.format,
    filePath: String(row.file_path),
    coverPath: nullable(row.cover_path),
    fileSize: Number(row.file_size),
    fileMtime: String(row.file_mtime),
    createdAt: String(row.created_at),
    updatedAt: String(row.updated_at)
  };
}

function nullable(value: unknown): string | null {
  return value === null || value === undefined ? null : String(value);
}