disk_net.go

/*
Copyright 2023 Milan Suk

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this db except in compliance with the License.
You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package main

import (
	"fmt"
	"io"
	"net/http"
	"sync"
)

type DiskNetJob struct {
	url   string
	agent string

	progress float64 //...
	done     bool

	data []byte
	err  error
}

func (job *DiskNetJob) downloadWithAgent() {
	client := &http.Client{}

	req, err := http.NewRequest("GET", job.url, nil)
	if err != nil {
		job.err = err
		return
	}

	req.Header.Set("User-Agent", job.agent)

	res, err := client.Do(req)
	if err != nil {
		job.err = err
		return
	}

	job.data, err = io.ReadAll(res.Body)
	if err != nil {
		job.err = err
		return
	}
}

func (job *DiskNetJob) download() {

	resp, err := http.Get(job.url)
	if err != nil {
		job.err = err
		return
	}
	defer resp.Body.Close()

	job.data, err = io.ReadAll(resp.Body)
	if err != nil {
		job.err = err
		return
	}
}

type DiskNet struct {
	lock sync.Mutex
	ch   chan bool

	jobs   []*DiskNetJob
	online bool

	num_jobs_done   int
	num_jobs_errors int
}

func NewDiskNet() *DiskNet {
	net := &DiskNet{}
	net.online = true

	net.ch = make(chan bool, 65536) //buffered channels - so send is non-blocking

	go net.Loop()

	return net
}

func (net *DiskNet) Destroy() {
	net.add("", "")
	net.ch <- true //end loop
}

func (net *DiskNet) Loop() {

	for {

		ch := <-net.ch
		if ch {
			break
		}

		//get
		jb := net.getNext()

		//download
		if jb != nil {
			if jb.agent != "" {
				jb.downloadWithAgent()
			} else {
				jb.download()
			}
			jb.done = true

			net.num_jobs_done++
			if jb.err != nil {
				net.num_jobs_errors++
			}
		}
	}
}

func (net *DiskNet) getNext() *DiskNetJob {
	net.lock.Lock()
	defer net.lock.Unlock()

	for i := len(net.jobs) - 1; i >= 0; i-- { //latest has higher priority
		if !net.jobs[i].done {
			return net.jobs[i]
		}
	}
	return nil
}

func (net *DiskNet) add(url string, agent string) *DiskNetJob {
	net.lock.Lock()
	defer net.lock.Unlock()

	//find
	for i, jb := range net.jobs {
		if jb.url == url && jb.agent == agent {
			if jb.done {
				net.jobs = append(net.jobs[:i], net.jobs[i+1:]...) //remove
			}
			return jb
		}
	}

	//add
	jb := &DiskNetJob{url: url, agent: agent}
	net.jobs = append(net.jobs, jb) //add

	net.ch <- false

	return jb
}

func (net *DiskNet) GetFile(url string, agent string) ([]byte, bool, float64, error) {
	if net.online {
		jb := net.add(url, agent)
		return jb.data, jb.done, jb.progress, jb.err
	} else {
		return nil, true, 0, fmt.Errorf("internet is disabled(Menu:Settings:Internet Connection)")
	}
}