/*
DESCRIPTION
  utils.go provides general constants, structs and helper functions for use in
  this package.

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 gvctrl

import (
	"crypto/md5"
	"encoding/hex"
	"math"
	"net/url"
	"strconv"
	"strings"
)

// The strings used in encoding the settings form to indicate resultion.
const (
	res256  = "4480256"   // 480x256
	res360  = "6400360"   // 640x360
	res720  = "12800720"  // 1280x720
	res1080 = "192001080" // 1920x1080
)

// Default values for fields in the settings struct when the newSettings
// constructor is used.
const (
	defaultCodec      = CodecH264
	defaultRes        = "6400360" // 360p
	defaultFrameRate  = "25000"   // 25 fps
	defaultVBR        = "0"       // Variable bitrate off
	defaultQuality    = QualityGood
	defaultVBRBitrate = "250000" // 512 kbps (lowest with 360p)
	defaultCBRBitrate = "512000"
	defaultRefresh    = "2000" // 2 seconds
	defaultChan       = 2
)

// settings holds string representations required by the settings form for each
// of the parameters configurable through this API.
type settings struct {
	codec      Codec
	res        string
	frameRate  string
	vbr        string
	quality    Quality
	vbrBitrate string
	cbrBitrate string
	refresh    string
	ch         int
}

// newSetting will return a settings with default values.
func newSettings() settings {
	return settings{
		codec:      defaultCodec,
		res:        defaultRes,
		frameRate:  defaultFrameRate,
		vbr:        defaultVBR,
		quality:    defaultQuality,
		vbrBitrate: defaultVBRBitrate,
		cbrBitrate: defaultCBRBitrate,
		refresh:    defaultRefresh,
		ch:         defaultChan,
	}
}

// md5Hex returns the md5 hex string of s with alphanumerics as upper case.
func md5Hex(s string) string {
	h := md5.New()
	h.Write([]byte(s))
	return strings.ToUpper(hex.EncodeToString(h.Sum(nil)))
}

// closestValIdx will return the index of the value in l that is closest to the
// value v.
func closestValIdx(v int, l []int) int {
	var idx int
	for i := range l {
		if math.Abs(float64(l[i]-v)) < math.Abs(float64(l[idx]-v)) {
			idx = i
		}
	}
	return idx
}

// convRate is used to firstly find a value in l closest to the bitrate v (in
// kbps), convert from kbps to bps, and the convert to string.
func convRate(v int, l []int) string {
	return strconv.Itoa(l[closestValIdx(v, l)] * 1000)
}

// populateForm will populate the settings form using the passed settings struct
// s and return as a url.Values.
func populateForm(s settings) url.Values {
	f := url.Values{}
	f.Set("dwConnType", "5")
	f.Set("mpeg_type", string(s.codec))
	f.Set("dwflicker_hz", "0")
	f.Set("szResolution", s.res)
	f.Set("dwFrameRate", s.frameRate)
	f.Set("custom_qp_init", "25")

	if s.codec == CodecMJPEG {
		f.Set("vbr_enable", "1")
		f.Set("dwVbrQuality", string(s.quality))

		switch s.res {
		case res256:
			f.Set("vbrmaxbitrate", "250000")
		case res360:
			f.Set("vbrmaxbitrate", "500000")
		case res720:
			f.Set("vbrmaxbitrate", "750000")
		default:
			panic("invalid resolution")
		}
	} else {
		switch s.vbr {
		case "0":
			f.Set("vbr_enable", "0")
			f.Set("max_bit_rate", s.cbrBitrate)
		case "1":
			f.Set("vbr_enable", "1")
			f.Set("dwVbrQuality", string(s.quality))
			f.Set("vbrmaxbitrate", s.vbrBitrate)
		default:
			panic("invalid vbrEnable parameter")
		}

		f.Set("custom_rate_control_type", "0")
		f.Set("custom_bitrate", "0")
		f.Set("custom_qp_min", "10")
		f.Set("custom_qp_max", "40")
	}

	f.Set("gop_N", s.refresh)
	if s.codec == CodecMJPEG {
		f.Set("gop_N", "1500")
	}

	if s.codec == CodecH264 || s.codec == CodecH265 {
		f.Set("dwEncProfile", "1")
		f.Set("dwEncLevel", "31")
		f.Set("dwEntropy", "0")
	}

	f.Set("u8PreAlarmBuf", "1")
	f.Set("u32PostAlarmBuf2Disk", "1")
	f.Set("u8SplitInterval", "5")
	f.Set("bEnableIO", "1")
	f.Set("bEbIoIn", "1")
	f.Set("bEbIoIn1", "1")
	f.Set("bOSDFontSize", "0")
	f.Set("bEnableOSDCameraName", "1")
	f.Set("bCamNamePos", "2")
	f.Set("bEnableOSDDate", "1")
	f.Set("bDatePos", "2")
	f.Set("bEnableOSDTime", "1")
	f.Set("bTimePos", "2")
	f.Set("szOsdCamName", "Camera")
	f.Set("u16PostAlarmBuf", "1")
	f.Set("dwCameraId", "1") // Channel=1 => cameraID=0 and chanel=2 => cameraID=1
	f.Set("LangCode", "undefined")
	f.Set("Recflag", "0")
	f.Set("submit", "Apply")
	return f
}