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feed.go
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feed.go
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package feed
import (
"context"
"fmt"
"net/http"
"net/url"
"time"
"github.com/NoHomey/chaos-go-camp-proj/ctxerr"
"github.com/mmcdole/gofeed"
"go.uber.org/zap"
)
//ErrInvalURL is used to report invalid URLs.
type ErrInvalURL struct {
wrapped error
URL string
}
func (err ErrInvalURL) Error() string {
return fmt.Sprintf("Invalid URL: %s. Error: %s", err.URL, err.wrapped.Error())
}
func (err ErrInvalURL) Unwrap() error {
return err.wrapped
}
//Text returns human readable error text.
func (err ErrInvalURL) Text() string {
return fmt.Sprintf("Invalid URL: %s", err.URL)
}
//Context returns error Context.
func (err ErrInvalURL) Context() ctxerr.Context {
return ctxerr.Context{
Name: "invalid-url",
Data: err.URL,
}
}
//HttpStatusCode returns http status code for the error.
func (err ErrInvalURL) HttpStatusCode() int {
return 400
}
//ErrParseFeed is used to report errors from parsing feeds.
type ErrParseFeed struct {
wrapped error
URL string
}
func (err ErrParseFeed) Error() string {
return fmt.Sprintf("Could not parse feed for URL: %s. Error: %s", err.URL, err.wrapped.Error())
}
func (err ErrParseFeed) Unwrap() error {
return err.wrapped
}
//Text returns human readable error text.
func (err ErrParseFeed) Text() string {
return fmt.Sprintf("Could not parse feed for URL: %s", err.URL)
}
//Context returns error Context.
func (err ErrParseFeed) Context() ctxerr.Context {
return ctxerr.Context{
Name: "parse-feed",
Data: err.URL,
}
}
//HttpStatusCode returns http status code for the error.
func (err ErrParseFeed) HttpStatusCode() int {
return 400
}
//Details represents feed details extracted from given URL.
type Details struct {
FeedURL string `json:"feedUrl"`
Title string `json:"title"`
Author string `json:"author"`
Description string `json:"description"`
}
//Item represents feed entry/item.
type Item struct {
URL string `json:"url"`
Title string `json:"title"`
Description string `json:"description"`
PublishedAt time.Time `json:"publishedAt"`
}
//Service abstracts the feed service.
type Service interface {
Details(ctx context.Context, url string) (*Details, ctxerr.Error)
FeedBatches(ctx context.Context, url string, batchSize uint) ([][]*Item, ctxerr.Error)
}
//Use constructs Service wich uses the given logger.
func Use(logger *zap.Logger) Service {
return service{logger}
}
type service struct {
logger *zap.Logger
}
func (srvc service) Details(ctx context.Context, url string) (*Details, ctxerr.Error) {
feed, cerr := srvc.fetchFeed(ctx, url)
if cerr != nil {
return nil, cerr
}
author := ""
if feed.Author != nil {
author = feed.Author.Name
}
return &Details{
FeedURL: url,
Title: feed.Title,
Author: author,
Description: feed.Description,
}, nil
}
func (srvc service) FeedBatches(ctx context.Context, url string, batchSize uint) ([][]*Item, ctxerr.Error) {
feed, cerr := srvc.fetchFeed(ctx, url)
if cerr != nil {
return nil, cerr
}
batches := [][]*Item{
make([]*Item, batchSize),
}
batch := uint(0)
currSize := uint(0)
for _, item := range feed.Items {
if currSize == batchSize {
batches = append(batches, make([]*Item, batchSize))
batch++
currSize = 0
}
publishedAt := time.Now()
if item.PublishedParsed != nil {
publishedAt = *item.PublishedParsed
}
batches[batch][currSize] = &Item{
URL: item.Link,
Title: item.Title,
Description: item.Description,
PublishedAt: publishedAt,
}
currSize++
}
return batches, nil
}
func (srvc service) fetchFeed(ctx context.Context, urlStr string) (*gofeed.Feed, ctxerr.Error) {
url, err := url.Parse(urlStr)
if err != nil {
srvc.logger.Error(
"Failed to parse url",
zap.String("url", urlStr),
zap.Error(err),
)
return nil, ErrInvalURL{err, urlStr}
}
req, err := http.NewRequestWithContext(ctx, "GET", url.String(), nil)
if err != nil {
srvc.logger.Error(
"Failed to create new request",
zap.String("url", url.String()),
zap.Error(err),
)
return nil, ctxerr.NewInternal(err)
}
resp, err := http.DefaultClient.Do(req)
if err != nil {
srvc.logger.Error(
"Failed to fetch feed",
zap.String("url", url.String()),
zap.Error(err),
)
return nil, ctxerr.NewInternal(err)
}
defer resp.Body.Close()
feed, err := gofeed.NewParser().Parse(resp.Body)
if err != nil {
srvc.logger.Error(
"Failed to parse feed",
zap.String("url", url.String()),
zap.Error(err),
)
return nil, ErrParseFeed{err, url.String()}
}
srvc.logger.Info(
"Fetched and parsed feed",
zap.String("url", url.String()),
)
return feed, nil
}