/*
DESCRIPTION
  gvctrl.go provides a programmatic interface for controlling the HTTP based
  server hosted by GeoVision cameras for settings control.

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 (
	"fmt"
	"math/rand"
	"net/http"
	"net/http/cookiejar"
	"strconv"
	"time"
)

type codec string

const (
	codecH265  codec = "28"
	codecH264  codec = "10"
	codecMJPEG codec = "4"
)

type quality string

const (
	qualityStandard  quality = "0"
	qualityFair      quality = "1"
	qualityGood      quality = "2"
	qualityGreat     quality = "3"
	qualityExcellent quality = "4"
)

const (
	res256 = "4480256"
	res360 = "6400360"
	res720 = "12800720"
)

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
)

type settings struct {
	codec      codec
	res        string
	frameRate  string
	vbr        string
	quality    quality
	vbrBitRate string
	cbrBitRate string
	refresh    string
}

func newSettings() settings {
	return settings{
		codec:      defaultCodec,
		res:        defaultRes,
		frameRate:  defaultFrameRate,
		vbr:        defaultVBR,
		quality:    defaultQuality,
		vbrBitRate: defaultVBRBitRate,
		cbrBitRate: defaultCBRBitRate,
		refresh:    defaultRefresh,
	}
}

type option func(s settings) (settings, error)

func Set(host string, options ...option) error {
	// Randomly generate an ID our client will use.
	const (
		minID = 10000
		maxID = 99999
	)
	rand.Seed(time.Now().UTC().UnixNano())
	id := strconv.Itoa(maxID + rand.Intn(maxID-minID))

	// Create a client with a cookie jar.
	jar, err := cookiejar.New(nil)
	if err != nil {
		return fmt.Errorf("could not create cookie jar, failed with error: %v", err)
	}

	client := &http.Client{
		Timeout: time.Duration(5 * time.Second),
		Jar:     jar,
	}

	// Get the request body required for log in.
	body, err := genLogIn(client, id, host)
	if err != nil {
		return fmt.Errorf("could not generate log in request data: %v", err)
	}

	// Log in using generated log in request body.
	err = logIn(client, id, host, body)
	if err != nil {
		return fmt.Errorf("could not logIn: %v", err)
	}

	// Apply the options to the settings specified by the user.
	s := newSettings()
	for _, op := range options {
		s, err = op(s)
		if err != nil {
			return fmt.Errorf("could not action option: %v", err)
		}
	}

	// Submit the settings to the server.
	err = submitSettings(client, id, host, s)
	if err != nil {
		return fmt.Errorf("could not submit settings: %v", err)
	}
	return nil
}

func Codec(c codec) option {
	return func(s settings) (settings, error) {
		switch c {
		case codecH265, codecH264, codecMJPEG:
			s.codec = c
			return s, nil
		default:
			return s, fmt.Errorf("unknown codec: %v", c)
		}
	}
}

func Height(h int) option {
	return func(s settings) (settings, error) {
		v, ok := map[int]string{256: res256, 360: res360, 720: res720}[h]
		if !ok {
			return s, fmt.Errorf("invalid display height: %d", h)
		}
		s.res = v
		return s, nil
	}
}

func FrameRate(f int) option {
	return func(s settings) (settings, error) {
		if 1 > f || f > 30 {
			return s, fmt.Errorf("invalid frame rate: %d", f)
		}
		s.frameRate = strconv.Itoa(f * 1000)
		return s, nil
	}
}

func VariableBitRate(b bool) option {
	return func(s settings) (settings, error) {
		s.vbr = "0"
		if b {
			s.vbr = "1"
		}
		return s, nil
	}
}

func VBRQuality(q quality) option {
	return func(s settings) (settings, error) {
		switch q {
		case qualityStandard, qualityFair, qualityGood, qualityGreat, qualityExcellent:
			s.quality = q
			return s, nil
		default:
			return s, fmt.Errorf("invalid quality: %v", q)
		}
	}
}

func VBRBitRate(r int) option {
	return func(s settings) (settings, error) {
		var vbrRates = []int{250, 500, 750, 1000, 1250, 1500, 1750, 2000, 2250, 2500}
		if s.vbr == "1" {
			s.vbrBitRate = convRate(r, vbrRates)
			return s, nil
		}
		return s, nil
	}
}

func CBRBitRate(r int) option {
	return func(s settings) (settings, error) {
		var (
			cbrRates256 = []int{128, 256, 512, 1024}
			cbrRates360 = []int{512, 1024, 2048, 3072}
			cbrRates720 = []int{1024, 2048, 4096, 6144}
		)

		switch s.res {
		case res720:
			s.cbrBitRate = convRate(r, cbrRates720)
		case res360:
			s.cbrBitRate = convRate(r, cbrRates360)
		case res256:
			s.cbrBitRate = convRate(r, cbrRates256)
		default:
			panic("bad resolution")
		}
		return s, nil
	}
}

func Refresh(r float64) option {
	return func(s settings) (settings, error) {
		const (
			maxRefreshPeriod = 5
			minRefreshPeriod = .25
		)

		if minRefreshPeriod > r || r > maxRefreshPeriod {
			return s, fmt.Errorf("invalid refresh period: %g", r)
		}

		refOptions := []int{250, 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000}
		s.refresh = strconv.Itoa(refOptions[closestValIdx(int(r*1000), refOptions)])
		return s, nil
	}
}