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

const READ_COMPLETION_THRESHOLD = 95;

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

  upsert(userId: number, bookId: number, input: UpdateProgressDto) {
    this.assertBookExists(bookId);
    const now = this.database.now();
    const percent = Math.round(input.percent);
    const current = this.find(userId, bookId);
    const readStatus = statusFromProgressPercent(percent);
    const completedAt = readStatus === "read" ? current?.completedAt ?? now : null;
    this.database.sqlite
      .prepare(
        `
        INSERT INTO progress(user_id, book_id, locator, percent, read_status, completed_at, read_status_source, created_at, updated_at)
        VALUES (?, ?, ?, ?, ?, ?, 'progress', ?, ?)
        ON CONFLICT(user_id, book_id) DO UPDATE SET
          locator = excluded.locator,
          percent = excluded.percent,
          read_status = excluded.read_status,
          completed_at = excluded.completed_at,
          read_status_source = excluded.read_status_source,
          updated_at = excluded.updated_at
      `
      )
      .run(userId, bookId, input.locator, percent, readStatus, completedAt, now, now);
    return this.get(userId, bookId);
  }

  markReadStatus(userId: number, bookId: number, input: UpdateReadStatusDto) {
    this.assertBookExists(bookId);
    const now = this.database.now();
    const current = this.find(userId, bookId);
    const status = input.status;
    const percent = status === "read" ? 100 : 0;
    const locator = status === "read" ? current?.locator ?? "manual:read" : "manual:unread";
    const completedAt = status === "read" ? current?.completedAt ?? now : null;
    this.database.sqlite
      .prepare(
        `
        INSERT INTO progress(user_id, book_id, locator, percent, read_status, completed_at, read_status_source, created_at, updated_at)
        VALUES (?, ?, ?, ?, ?, ?, 'manual', ?, ?)
        ON CONFLICT(user_id, book_id) DO UPDATE SET
          locator = excluded.locator,
          percent = excluded.percent,
          read_status = excluded.read_status,
          completed_at = excluded.completed_at,
          read_status_source = excluded.read_status_source,
          updated_at = excluded.updated_at
      `
      )
      .run(userId, bookId, locator, percent, status, completedAt, now, now);
    return this.get(userId, bookId);
  }

  get(userId: number, bookId: number) {
    const row = this.find(userId, bookId);
    if (!row) {
      throw new NotFoundException("Progress not found");
    }
    return row;
  }

  find(userId: number, bookId: number) {
    const row = this.database.db
      .select({
        bookId: progress.bookId,
        locator: progress.locator,
        percent: progress.percent,
        readStatus: progress.readStatus,
        completedAt: progress.completedAt,
        readStatusSource: progress.readStatusSource,
        updatedAt: progress.updatedAt
      })
      .from(progress)
      .where(sql`${progress.userId} = ${userId} AND ${progress.bookId} = ${bookId}`)
      .get();
    return row ?? null;
  }

  continueReading(userId: number) {
    return this.database.db
      .select({
        book: books,
        progress: {
          bookId: progress.bookId,
          locator: progress.locator,
          percent: progress.percent,
          readStatus: progress.readStatus,
          completedAt: progress.completedAt,
          readStatusSource: progress.readStatusSource,
          updatedAt: progress.updatedAt
        }
      })
      .from(progress)
      .innerJoin(books, eq(progress.bookId, books.id))
      .where(sql`${progress.userId} = ${userId} AND ${progress.readStatus} = 'reading'`)
      .orderBy(desc(progress.updatedAt))
      .limit(20)
      .all();
  }

  private assertBookExists(bookId: number): void {
    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");
    }
  }
}

function statusFromProgressPercent(percent: number): "unread" | "reading" | "read" {
  if (percent >= READ_COMPLETION_THRESHOLD) return "read";
  if (percent > 0) return "reading";
  return "unread";
}