Library System in Go (ZTM Course)

library.go

//--Summary:
//  Create a program to manage lending of library books.
//
//--Requirements:
//* The library must have books and members, and must include:
//  - Which books have been checked out
//  - What time the books were checked out
//  - What time the books were returned
//* Perform the following:
//  - Add at least 4 books and at least 3 members to the library
//  - Check out a book
//  - Check in a book
//  - Print out initial library information, and after each change
//* There must only ever be one copy of the library in memory at any time
//
//--Notes:
//* Use the `time` package from the standard library for check in/out times
//* Liberal use of type aliases, structs, and maps will help organize this project

package main

import (
	"fmt"
	"time"
)

//--Requirements:
//* The library must have books and members, and must include:
//  - Which books have been checked out
//  - What time the books were checked out
//  - What time the books were returned

type Book struct {
	title string
}

type Member struct {
	name      string
	libraryId uint64
}

type LendingRecord struct {
	book       *Book
	issueTime  time.Time
	returnTime time.Time
}

type Library struct {
	books          map[*Book]uint64
	lendingRecords map[*Member]LendingRecord
}

func checkOutBook(book *Book, member *Member, library *Library) {
	noOfBooks, hasBook := library.books[book]
	_, hasIssued := library.lendingRecords[member]
	if !hasBook || noOfBooks == 0 {
		fmt.Println("Book is out of stock")
	} else if hasIssued {
		fmt.Println("You already have a book issued, please return it before issuing a new book")
	} else {
		library.books[book] -= 1
		lendToMember := LendingRecord{
			book:      book,
			issueTime: time.Now(),
		}
		library.lendingRecords[member] = lendToMember
		fmt.Println("Book ", library.lendingRecords[member].book.title, " has been issued to ",
			member.name)
	}
}

func checkInBook(book *Book, member *Member, library *Library) {
	_, hasIssued := library.lendingRecords[member]
	if !hasIssued {
		fmt.Println("Dear", member.name, ",you have no book to return")
	} else {
		library.books[book] += 1
		library.lendingRecords[member] = LendingRecord{
			book:       library.lendingRecords[member].book,
			issueTime:  library.lendingRecords[member].issueTime,
			returnTime: time.Now(),
		}
		fmt.Println("Book ", library.lendingRecords[member].book.title, " has been retruned")
	}
}

func printLendingRecord(lendingRecord *LendingRecord) {
	fmt.Println(lendingRecord.book.title, ":", lendingRecord.issueTime, ",", lendingRecord.returnTime)
}

func printLibrary(library *Library) {
	fmt.Println("============Library: Start=============")
	for book, count := range library.books {
		fmt.Println(book.title, ":", count)
	}
	for member, lendingRecord := range library.lendingRecords {
		fmt.Println(member.name, ":")
		printLendingRecord(&lendingRecord)
	}
	fmt.Println("============Library: End=============")
}

//* Perform the following:
//  - Add at least 4 books and at least 3 members to the library
//  - Check out a book
//  - Check in a book
//  - Print out initial library information, and after each change
//* There must only ever be one copy of the library in memory at any time
func main() {
	harryPotter1 := Book{
		title: "Harry Potter and the Philosopher's stone",
	}
	harryPotter2 := Book{
		title: "Harry Potter and the chamber of secrets",
	}
	harryPotter3 := Book{
		title: "Harry Potter and the prisoner of askaban",
	}
	harryPotter4 := Book{
		title: "Harry Potter and the goblet of fire",
	}
	memeber1 := Member{
		name:      "Yash Tibrewal",
		libraryId: 1,
	}
	memeber2 := Member{
		name:      "Kushagra Tibrewal",
		libraryId: 2,
	}
	memeber3 := Member{
		name:      "Nikhil Tibrewal",
		libraryId: 3,
	}
	library := Library{
		books:          make(map[*Book]uint64),
		lendingRecords: make(map[*Member]LendingRecord),
	}
	fmt.Println("===========Initializing =================================")
	printLibrary(&library)

	library.books[&harryPotter1] = 10
	library.books[&harryPotter2] = 4
	library.books[&harryPotter3] = 7
	library.books[&harryPotter4] = 0
	fmt.Println("===========Books Stocked=================================")
	printLibrary(&library)

	checkOutBook(&harryPotter4, &memeber1, &library)
	checkOutBook(&harryPotter1, &memeber2, &library)
	checkOutBook(&harryPotter1, &memeber3, &library)
	fmt.Println("===========After Books Issued=================================")
	printLibrary(&library)

	checkInBook(&harryPotter4, &memeber1, &library)
	checkInBook(&harryPotter1, &memeber3, &library)
	fmt.Println("===========After Books Returned=================================")
	printLibrary(&library)
}