ozon-task/internal/storage/storage.go

package storage

import (
	"context"
	"fmt"
	"log"
	"os"

	"git.obamna.ru/erius/ozon-task/graph/model"
	"git.obamna.ru/erius/ozon-task/internal/storage/db"
)

type IDNotFoundError struct {
	objName string
	id      uint
}

func (e *IDNotFoundError) Error() string {
	return fmt.Sprintf("%s with id %d doesn't exist", e.objName, e.id)
}

// storage types enum
const (
	inMemory = "inmemory"
	postgres = "postgres"
)

var storage, storageSpecified = os.LookupEnv("APP_STORAGE")

type Storage interface {
	AddPost(input *model.PostInput) (*model.AddResult, error)

	// assumes that input.ParentCommentID is not nil
	AddReplyToComment(input *model.CommentInput) (*model.AddResult, error)

	// assumes that input.ParentPostID is not nil
	AddCommentToPost(input *model.CommentInput) (*model.AddResult, error)

	// passing query context to analyze requested fields and prevent overfetching
	GetPost(id uint, ctx context.Context) (*model.Post, error)
	GetComment(id uint, ctx context.Context) (*model.Comment, error)

	// returns paginated data in the form of model.*Connection (passing context to prevent overfetching)
	GetPosts(first uint, cursor *uint, ctx context.Context) (*model.PostsConnection, error)
	GetComments(post *model.Post, first uint, cursor *uint, ctx context.Context) (*model.CommentsConnection, error)
	GetReplies(comment *model.Comment, first uint, cursor *uint, ctx context.Context) (*model.CommentsConnection, error)
}

func InitStorage() (Storage, error) {
	if !storageSpecified {
		log.Println("APP_STORAGE isn't specified, falling back to default in-memory storage", storage)
		return InitInMemory(), nil
	}
	log.Printf("initializing storage of type %s...", storage)
	switch storage {
	case inMemory:
		return InitInMemory(), nil
	case postgres:
		return db.InitPostgres()
	default:
		return nil, fmt.Errorf("storage of type %s doesn't exists, change the value of APP_STORAGE env variable", storage)
	}
}