import { Injectable, NotFoundException } from "@nestjs/common";
import { eq, sql } from "drizzle-orm";
import { UpdateReaderPreferencesDto } from "@readabook/shared";
import { DatabaseService } from "../database/database.service.js";
import { books, readerPreferences } from "../database/schema.js";

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

  find(userId: number, bookId: number) {
    const row = this.database.db
      .select({
        mode: readerPreferences.mode,
        fit: readerPreferences.fit,
        updatedAt: readerPreferences.updatedAt
      })
      .from(readerPreferences)
      .where(sql`${readerPreferences.userId} = ${userId} AND ${readerPreferences.bookId} = ${bookId}`)
      .get();
    return row ?? { mode: "paged", fit: null };
  }

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

    const current = this.find(userId, bookId);
    const now = this.database.now();
    const mode = input.mode ?? current.mode;
    const fit = input.fit === undefined ? current.fit : input.fit;

    this.database.sqlite
      .prepare(
        `
        INSERT INTO reader_preferences(user_id, book_id, mode, fit, created_at, updated_at)
        VALUES (?, ?, ?, ?, ?, ?)
        ON CONFLICT(user_id, book_id) DO UPDATE SET
          mode = excluded.mode,
          fit = excluded.fit,
          updated_at = excluded.updated_at
      `
      )
      .run(userId, bookId, mode, fit, now, now);
    return this.find(userId, bookId);
  }
}