justguestbook/guestbook.go

package justguestbook

import (
	"errors"
	"fmt"
	"time"
)

const (
	// DateFormat is a format of the date and time used in a guestbook.
	DateFormat = "2006-01-02 15:04:05"

	// entryWebsiteMaxLength is a maximum length for a Website field of an Entry.
	entryWebsiteMaxLength = 255
)

// Reply holds a reply for a guestbook's entry.
type Reply struct {
	// ID of a guestbook's entry is used when update of a reply is performed.
	//
	// Not present in JSON because a reply comes within its corresponding entry.
	ID int64 `json:"-"`

	// Created holds a date and time when a reply was created.
	Created time.Time `json:"created,omitempty"`

	// Message holds a reply's message.
	Message string `json:"message"`
}

// NewReply creates a new reply and, before that, verifies that a passed message
// is not empty.
func NewReply(entryID int64, message string) (*Reply, error) {
	if message == "" {
		return nil, errors.New("empty message field")
	}

	return &Reply{
		ID:      entryID,
		Created: time.Now().UTC(),
		Message: message}, nil
}

// Entry holds a guestbook entry.
type Entry struct {
	// ID of an entry.
	ID int64 `json:"entry_id"`

	// Created holds the date and time when an entry was created.
	Created time.Time `json:"created"`

	// Name holds a nick-/name of a guest who posted an entry.
	Name string `json:"name"`

	// Website of a guest. Can be empty.
	Website string `json:"website,omitempty"`

	// HideWebsite tells wether to hide or show guest's website.
	HideWebsite bool `json:"hide_website,omitempty"`

	// Message that a guest wrote.
	Message string `json:"message"`

	// Reply holds a reply for this entry.
	Reply *Reply `json:"reply,omitempty"`
}

// NewEntry creates a new Entry and, before that, verifies if the name and message
// aren't empty and the website field do not exceed the limit.
func NewEntry(name, message, website string, hideWebsite bool) (*Entry, error) {
	if name == "" || message == "" {
		return nil, errors.New("name and message field are required")
	}

	if len(website) > entryWebsiteMaxLength {
		return nil, errors.New(fmt.Sprint("website field's max length is",
			entryWebsiteMaxLength, "but", len(website), "was given"))
	}

	return &Entry{
		Created:     time.Now().UTC(),
		Name:        name,
		Website:     website,
		HideWebsite: hideWebsite,
		Message:     message}, nil
}

// Guestbook is an interface that should be implemented by a DB.
type Guestbook interface {
	// Entries returns a slice of guestbook entries.
	Entries(page, pageSize int64) ([]*Entry, error)
	// Count returns how much entries are in a DB.
	Count() (int64, error)
	// NewEntry inserts a given Entry into a DB.
	NewEntry(entry *Entry) error
	// EditEntry modifies the fields of an existing entry.
	EditEntry(entry *Entry) error
	// DeleteEntry removes an Entry with a given ID.
	DeleteEntry(entryID int64) error
	// NewReply inserts a given Reply into a DB.
	NewReply(reply *Reply) error
	// EditReply modifies a message field of a given Reply.
	EditReply(reply *Reply) error
	// DeleteReply removes a Reply with a given ID of an Entry.
	DeleteReply(entryID int64) error
	// Close closes a DB.
	Close() error
}