any-remark/backend/datastore/mapper.go

package datastore

import (
	"database/sql"
	"fmt"
	"git.sa.vin/any-remark/backend/types"
	"math/rand"
)

type Mapper interface {
	GetOpenGraphData(url string) (string, error)
	SaveOpenGraphData(url, opengraph string) error
	AddComment(req types.AddCommentRequest) error
	GetComments(url string) ([]types.Comment, error)
}

type mapper struct {
	db *sql.DB
}

func NewMapper(db *sql.DB) Mapper {
	// Empty function for NewMapper
	return &mapper{
		db: db,
	}
}

func (m *mapper) GetOpenGraphData(url string) (string, error) {
	// get the opengraph data from the db table named "webpages" using the url
	query := `SELECT opengraph FROM webpages WHERE url = ?`
	rows, err := m.db.Query(query, url)
	if err != nil {
		if err == sql.ErrNoRows {
			return "", fmt.Errorf("no data found in db for url: %s", url)
		}
		return "", fmt.Errorf("error getting webpage data from db: %s", err)
	}
	defer rows.Close()

	// get the opengraph data from the rows array
	var opengraph string
	for rows.Next() {
		err = rows.Scan(&opengraph)
		if err != nil {
			return "", fmt.Errorf("error scanning opengraph data: %s", err)
		}
		return opengraph, nil
	}
	return "", fmt.Errorf("no data found in db for url: %s", url)
}

// SaveOpenGraphData saves the opengraph data to the db
func (m *mapper) SaveOpenGraphData(url, opengraph string) error {
	// generate a unique id for the webpage make it 24 bytes long
	id := "wp_" + generateID(24)
	// insert the opengraph data to the db table named "webpages" using the url
	query := `INSERT INTO webpages (id, url, opengraph) VALUES (?, ?, ?)`
	_, err := m.db.Exec(query, id, url, opengraph)
	if err != nil {
		return fmt.Errorf("error inserting webpage data to db: %s", err)
	}
	return nil
}

func (m *mapper) GetWebpageID(url string) (string, error) {
	// get the id of the webpage from the db table named "webpages" using the url
	query := `SELECT id FROM webpages WHERE url = ?`
	rows, err := m.db.Query(query, url)
	if err != nil {
		if err == sql.ErrNoRows {
			return "", fmt.Errorf("no data found in db for url: %s", url)
		}
		return "", fmt.Errorf("error getting webpage data from db: %s", err)
	}
	defer rows.Close()

	// get the id from the rows array
	var id string
	for rows.Next() {
		err = rows.Scan(&id)
		if err != nil {
			return "", fmt.Errorf("error scanning webpage id: %s", err)
		}
		return id, nil
	}
	return "", fmt.Errorf("no data found in db for url: %s", url)
}

func (m *mapper) AddComment(req types.AddCommentRequest) error {
	webpageID, err := m.GetWebpageID(req.URL)
	if err != nil {
		return fmt.Errorf("error getting webpage id: %s", err)
	}

	// generate a unique id for the comment make it 24 bytes long
	id := "c_" + generateID(24)
	// insert the comment data to the db table named "comments" using the url
	query := `INSERT INTO comments (id, content, webpage_id, commenter) VALUES (?, ?, ?, ?)`
	_, err = m.db.Exec(query, id, req.Comment, webpageID, req.UserID)
	if err != nil {
		return fmt.Errorf("error inserting comment data to db: %s", err)
	}
	return nil
}

func (m *mapper) GetComments(url string) ([]types.Comment, error) {
	webpageID, err := m.GetWebpageID(url)
	if err != nil {
		return nil, fmt.Errorf("error getting webpage id: %s", err)
	}

	// TODO: add up vote and down vote counts
	// TODO: attach avatar url to commenter
	// TODO: provide order by recent or most upvoted
	// TODO: bubble up the current user's comments
	// get the comments from the db table named "comments" using the webpage_id
	query := `SELECT id, content, commenter FROM comments WHERE webpage_id = ?`
	rows, err := m.db.Query(query, webpageID)
	if err != nil {
		if err == sql.ErrNoRows {
			return nil, fmt.Errorf("no data found in db for url: %s", url)
		}
		return nil, fmt.Errorf("error getting comments from db: %s", err)
	}
	defer rows.Close()

	// get the comments from the rows array
	var comments []types.Comment
	for rows.Next() {
		var comment types.Comment
		err = rows.Scan(&comment.ID, &comment.Content, &comment.Commenter)
		if err != nil {
			return nil, fmt.Errorf("error scanning comments: %s", err)
		}
		comments = append(comments, comment)
	}
	return comments, nil
}

func generateID(n int) string {
	// generate a unique id for the webpage make it 24 bytes
	// long using the following character set
	charSet := "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
	charSetLen := len(charSet)
	id := make([]byte, n)
	for i := range id {
		// choose a random character from the character set
		id[i] = charSet[rand.Intn(charSetLen)]
	}
	return string(id)
}