package main

import (
	"encoding/json"
	"fmt"
	"os"
)

type Book struct {
	Title  string `json:"title"`
	Author string `json:"author"`
	Read   bool   `json:"read"`
	ID     int    `json:"id"`
}

func addBook(title string, author string) error {

	fmt.Println("add...")

	books, err := readJson()

	if err != nil {
		return err
	}

	var newID int
	if len(books) == 0 {
		newID = 1
	} else {
		last := books[len(books)-1]
		newID = last.ID + 1
	}

	newBook := Book{Title: title, Author: author, Read: false, ID: newID}

	books = append(books, newBook)

	erro := writeJson(books)

	if erro != nil {
		return erro
	}

	return nil

}

func listBooks() error {

	fmt.Println("list...")

	books, err := readJson()

	if err != nil {
		return err
	}

	fmt.Println("Hier ist Ihre aktuelle Buchübersicht:\n")

	for _, book := range books {
		fmt.Println("Titel:", book.Title)
		fmt.Println("Author:", book.Author)
		fmt.Println("Gelesen:", book.Read)
		fmt.Println("ID:", book.ID)
		fmt.Println("============================================")
	}

	return nil
}

func markBook(id int) error {

	books, err := readJson()

	if err != nil {
		return err
	}

	for i := 0; i < len(books); i++ {
		if books[i].ID == id {
			books[i].Read = true

			erro := writeJson(books)

			if erro != nil {
				return erro
			}

			return nil
		}
	}

	return fmt.Errorf("ID %d nicht gefunden!", id)
}

func readJson() ([]Book, error) {

	fmt.Println("read json...")

	data, err := os.ReadFile("books.json")

	if err != nil {
		return nil, err
	}

	var books []Book
	err = json.Unmarshal(data, &books)
	if err != nil {
		fmt.Println(err)
		return nil, err
	}

	return books, nil

}

func writeJson(books []Book) error {
	data, err := json.MarshalIndent(books, "", "	")
	if err != nil {
		return err
	}

	return os.WriteFile("books.json", data, 0644)
}

func ensureFileExists() error {
	_, err := os.Stat("books.json")

	if os.IsNotExist(err) {
		// Initialer Inhalt: leeres JSON-Array
		initialData := []byte("[]")

		return os.WriteFile("books.json", initialData, 0644)
	}

	return err
}