fetch.go

/*
Copyright © 2023-2024 Thomas von Dein

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/

package main

import (
	"errors"
	"fmt"
	"io"
	"log/slog"
	"net/http"
	"net/http/cookiejar"
	"net/url"
)

// convenient wrapper to fetch some web content
type Fetcher struct {
	Config  *Config
	Client  *http.Client
	Cookies []*http.Cookie
}

func NewFetcher(conf *Config) (*Fetcher, error) {
	jar, err := cookiejar.New(nil)
	if err != nil {
		return nil, fmt.Errorf("failed to create a cookie jar obj: %w", err)
	}

	return &Fetcher{
			Client: &http.Client{
				Transport: &loggingTransport{}, // implemented in http.go
				Jar:       jar,
			},
			Config:  conf,
			Cookies: []*http.Cookie{},
		},
		nil
}

func (f *Fetcher) Get(uri string) (io.ReadCloser, error) {
	req, err := http.NewRequest(http.MethodGet, uri, http.NoBody)
	if err != nil {
		return nil, fmt.Errorf("failed to create a new HTTP request obj: %w", err)
	}

	req.Header.Set("User-Agent", f.Config.UserAgent)

	if len(f.Cookies) > 0 {
		uriobj, _ := url.Parse(Baseuri)

		slog.Debug("have cookies, sending them",
			"sample-cookie-name", f.Cookies[0].Name,
			"sample-cookie-expire", f.Cookies[0].Expires,
		)

		f.Client.Jar.SetCookies(uriobj, f.Cookies)
	}

	res, err := f.Client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("failed to initiate HTTP request to %s: %w", uri, err)
	}

	if res.StatusCode != http.StatusOK {
		return nil, errors.New("could not get page via HTTP")
	}

	slog.Debug("got cookies?", "cookies", res.Cookies())
	f.Cookies = res.Cookies()

	return res.Body, nil
}

// fetch an image
func (f *Fetcher) Getimage(uri string) (io.ReadCloser, error) {
	slog.Debug("fetching ad image", "uri", uri)

	body, err := f.Get(uri)
	if err != nil {
		if f.Config.IgnoreErrors {
			slog.Info("Failed to download image, error ignored", "error", err.Error())

			return nil, nil
		}

		return nil, err
	}

	return body, nil
}