/*
DESCRIPTION
  request.go provides unexported functionality for creating and sending requests
  required to configure settings of the GeoVision camera.

AUTHORS
  Saxon A. Nelson-Milton <saxon@ausocean.org>

LICENSE
  Copyright (C) 2019 the Australian Ocean Lab (AusOcean)

  It is free software: you can redistribute it and/or modify them
  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.

  It 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
  in gpl.txt.  If not, see http://www.gnu.org/licenses.
*/

package config

import (
	"bytes"
	"fmt"
	"io/ioutil"
	"net/http"
	"net/url"
	"regexp"
	"strconv"
)

// Relevant sub directories.
const (
	loginSubDir    = "/ssi.cgi/login.htm" // Used to get log-in page.
	loggedInSubDir = "/LoginPC.cgi"       // Used to submit log-in.
	settingsSubDir = "/VideoSetting.cgi"  // Used to submit settings.
)

// TODO: make this configurable.
const (
	user = "admin"
	pass = "admin"
)

// getLogin gets the log-in page and extracts the randomly generated cc values
// from which (as well as username and password) two hashes are generated.
// The generated hex is encoded into a url encoded form and returned as a string.
func getLogin(c *http.Client, id, host string) (string, error) {
	req, err := http.NewRequest("GET", "http://"+host+loginSubDir, nil)
	if err != nil {
		return "", fmt.Errorf("can't create GET request for log-in page: %w", err)
	}

	req.Header.Set("Connection", "keep-alive")
	req.Header.Set("Cache-Control", "max-age=0")
	req.Header.Set("Upgrade-Insecure-Requests", "1")
	req.Header.Set("User-Agent", "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/77.0.3865.90 Safari/537.36")
	req.Header.Set("Accept", "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3")
	req.Header.Set("Accept-Encoding", "gzip, deflate")
	req.Header.Set("Accept-Language", "en-GB,en-US;q=0.9,en;q=0.8")
	req.Header.Set("Cookie", "CLIENT_ID="+id)

	resp, err := c.Do(req)
	if err != nil {
		return "", fmt.Errorf("could not do GET request for log-in page: %w", err)
	}

	defer resp.Body.Close()
	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		return "", fmt.Errorf("could not read response of GET request for log-in page: %w", err)
	}

	// Find the CC values in the source of the response.
	// These are used in calculation of the md5 hashes for the form submitted at
	// log-in.
	var cc [2]string
	for i := range cc {
		regStr := "cc" + strconv.Itoa(i+1) + "=\".{4}\""
		exp := regexp.MustCompile(regStr).FindString(string(body))
		cc[i] = exp[5 : len(exp)-1]
	}

	f := url.Values{}
	f.Set("grp", "-1")
	f.Set("username", "")
	f.Set("password", "")
	f.Set("Apply", "Apply")
	f.Set("umd5", md5Hex(cc[0]+user+cc[1]))
	f.Set("pmd5", md5Hex(cc[1]+pass+cc[0]))
	f.Set("browser", "1")
	f.Set("is_check_OCX_OK", "0")

	return f.Encode(), nil
}

// login will submit the form b generated by genLogin.
func login(c *http.Client, id, host, b string) error {
	req, err := http.NewRequest("POST", "http://"+host+loggedInSubDir, bytes.NewBuffer([]byte(b)))
	if err != nil {
		return fmt.Errorf("could not create log-in request: %w", err)
	}

	req.Header.Set("Connection", "keep-alive")
	req.Header.Set("Content-Length", "142")
	req.Header.Set("Cache-Control", "max-age=0")
	req.Header.Set("Origin", "http://"+host)
	req.Header.Set("Upgrade-Insecure-Requests", "1")
	req.Header.Set("User-Agent", "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/77.0.3865.90 Safari/537.36")
	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
	req.Header.Set("Accept", "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3")
	req.Header.Set("Referer", "http://"+host+"/ssi.cgi/Login.htm")
	req.Header.Set("Accept-Encoding", "gzip, deflate")
	req.Header.Set("Accept-Language", "en-GB,en-US;q=0.9,en;q=0.8")
	req.Header.Set("Cookie", "CLIENT_ID="+id+"; CLIENT_ID="+id)

	_, err = c.Do(req)
	if err != nil {
		return fmt.Errorf("could not do log-in request: %w", err)
	}

	return nil
}

// submitSettings will populate a url encoded form using s and submit the
// settings to the server.
func submitSettings(c *http.Client, id, host string, s settings) error {
	fBytes := []byte(populateForm(s).Encode())
	req, err := http.NewRequest("POST", "http://"+host+settingsSubDir, bytes.NewReader(fBytes))
	if err != nil {
		return fmt.Errorf("could not create settings submit request: %w", err)
	}

	req.Header.Set("Connection", "keep-alive")
	req.Header.Set("Content-Length", strconv.Itoa(len(fBytes)))
	req.Header.Set("Cache-Control", "max-age=0")
	req.Header.Set("Origin", "http://"+host)
	req.Header.Set("Upgrade-Insecure-Requests", "1")
	req.Header.Set("User-Agent", "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/77.0.3865.90 Safari/537.36")
	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
	req.Header.Set("Accept", "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3")
	req.Header.Set("Referer", "http://"+host+"/ssi.cgi/VideoSettingSub.htm?cam="+strconv.Itoa(int(s.ch)))
	req.Header.Set("Accept-Encoding", "gzip, deflate")
	req.Header.Set("Accept-Language", "en-GB,en-US;q=0.9,en;q=0.8")
	req.Header.Set("Cookie", "CLIENT_ID="+id)

	// NB: not capturing error, as we always get one here for some reason.
	// TODO: figure out why. Does not affect submission.
	c.Do(req)

	return nil
}