package utilities

import (
	"fmt"
	"gopkg.in/yaml.v3"
	"math"
	"time"
)

type Ratio struct {
	Numerator   int
	Denominator int
}

func (r Ratio) Float64() float64 {
	return float64(r.Numerator) / float64(r.Denominator)
}

func (r Ratio) PTSToDuration(pts int64) time.Duration {
	return (time.Duration(pts) * time.Second * time.Duration(r.Numerator)) / time.Duration(r.Denominator)
}

func (r *Ratio) UnmarshalJSON(buf []byte) error {
	_, err := fmt.Sscanf(string(buf), "\"%d:%d\"", &r.Numerator, &r.Denominator)
	return err
}

func (r *Ratio) UnmarshalYAML(node *yaml.Node) error {
	_, err := fmt.Sscanf(node.Value, "%d:%d", &r.Numerator, &r.Denominator)
	return err
}

func (r Ratio) MarshalJSON() ([]byte, error) {
	return []byte("\"" + r.String() + "\""), nil
}

func (r Ratio) String() string {
	return fmt.Sprintf("%d:%d", r.Numerator, r.Denominator)
}

// Reciprocal get the reciprocal, for example, to convert frame rate into time base
func (r Ratio) Reciprocal() Ratio {
	return Ratio{Numerator: r.Denominator, Denominator: r.Numerator}
}

const NTSCRatio = float64(1001) / 1000

const ratioEpsilon = 1.0e-9

func NewRatio(n, d int) Ratio {
	return Ratio{
		Numerator:   n,
		Denominator: d,
	}
}

// FPSToRatio Attempt common FPS conversions to ratios
func FPSToRatio(fps float64) Ratio {
	// common NTSC
	ntscValue := fps * NTSCRatio

	// Number is whole NTSC
	if math.Abs(ntscValue-math.Round(ntscValue)) < ratioEpsilon {
		return NewRatio(int(math.Round(ntscValue))*1000, 1001)
	}

	// Number is whole other
	if math.Abs(fps-math.Round(fps)) < ratioEpsilon {
		return NewRatio(int(math.Round(fps)), 1)
	}

	// Get a few decimals of precision
	return Ratio{
		Numerator:   int(fps * 1000),
		Denominator: 1000,
	}
}