// MXL Flow Definition helper
package flowdef

import (
	"encoding/json"
	"errors"
)

const (
	TYPE_VIDEO = iota
	TYPE_VIDEO_ALPHA
	TYPE_AUDIO
)

var (
	ErrUnknownFlowType   = errors.New("Unknown flow type provided")
	ErrIncorrectFlowUUID = errors.New("Incorrect flow uuid")
)

type flowDef struct {
	Description   string              `json:"description"`
	Id            string              `json:"id"`
	Tags          map[string][]string `json:"tags"`
	Format        string              `json:"format"`
	Label         string              `json:"label"`
	Parents       []string            `json:"parents"`
	MediaType     string              `json:"media_type"`
	GrainRate     grainRate           `json:"grain_rate"`
	FrameWidth    uint                `json:"frame_width"`
	FrameHeight   uint                `json:"frame_height"`
	InterlaceMode string              `json:"interlace_mode"`
	ColorSpace    string              `json:"colorspace"`
	Components    [3]videoComponent   `json:"components"`
}

type grainRate struct {
	Numerator   uint `json:"numerator"`
	Denominator uint `json:"denominator"`
}

type videoComponent struct {
	Name     string `json:"name"`
	Width    uint   `json:"width"`
	Height   uint   `json:"height"`
	BitDepth uint   `json:"bit_depth"`
}

func NewFlowDefJSON(
	feedType int,
	uuid string,
	width uint,
	height uint,
	fpsNum uint,
	fpsDen uint,
) (string, error) {
	if feedType != TYPE_VIDEO &&
		feedType != TYPE_VIDEO_ALPHA &&
		feedType != TYPE_AUDIO {
		return "", ErrUnknownFlowType
	}
	if uuid == "" {
		return "", ErrIncorrectFlowUUID
	}
	tags := map[string][]string{
		"urn:x-nmos:tag:grouphint/v1.0": {
			"___one day I will follow NMOS specs___:Video",
		},
	}
	flowDef := flowDef{
		Description: "go-mxl-pattern-gen generated feed",
		Id:          uuid,
		Tags:        tags,
		Format:      "urn:x-nmos:format:video",
		Label:       "go-mxl-pattern-gen generated feed",
		Parents:     nil,
		MediaType:   "video/v210",
		GrainRate: grainRate{
			Numerator:   fpsNum,
			Denominator: fpsDen,
		},
		FrameWidth:    width,
		FrameHeight:   height,
		InterlaceMode: "progressive",
		ColorSpace:    "BT709",
		Components: [3]videoComponent{
			videoComponent{
				Name:     "Y",
				Width:    width,
				Height:   height,
				BitDepth: 10,
			},
			videoComponent{
				Name:     "Cb",
				Width:    width / 2,
				Height:   height,
				BitDepth: 10,
			},
			videoComponent{
				Name:     "Cr",
				Width:    width / 2,
				Height:   height,
				BitDepth: 10,
			},
		},
	}
	jsonBytes, err := json.Marshal(flowDef)
	if err != nil {
		return "", err
	}
	return string(jsonBytes), nil
}