package pill

import (
	// Used for embedding pill.
	_ "embed"
	"fmt"
	"io"
	"math"
	"text/template"
)

var (
	//go:embed pill.svg
	pill string

	tmpl = template.New("svgTemplate")
)

const (
	modifier = 0.2
	max      = 190
	blue     = 55
)

// Pill is used to execute the pill.svg template.
// Width is dependent on whether the percentage is 2 digits or 3 digits.
type Pill struct {
	Percentage string
	Colour     string
	Width      string
}

// NewPill creates creates a Pill, automatically calculating the colour, width, and formatting the percentage.
// Note: %02.0f gives us a float with 0 decimals and 0 padding for 2 numbers less than 10.
func NewPill(percentDecimal float64) Pill {
	square := math.Pow(percentDecimal, 2)
	red := modifier + clamp(2-2*square, 0, 1)*(1-modifier)
	green := modifier + clamp(2*square, 0, 1)*(1-modifier)

	percentage := fmt.Sprintf("%.0f", percentDecimal*100)
	colour := fmt.Sprintf("rgb(%.0f, %.0f, %d)", red*max, green*max, blue)
	width := "250"
	if len(percentage) == 1 {
		percentage = " " + percentage
		width = "220"
	}
	if len(percentage) == 3 {
		width = "300"
	}

	return Pill{
		Percentage: percentage,
		Colour:     colour,
		Width:      width,
	}
}

// Execute runs the pill template with the data and writes the result to the writer given.
func (p Pill) Execute(w io.Writer) error {
	var err error
	tmpl, err = tmpl.Parse(pill)
	if err != nil {
		return err
	}

	err = tmpl.Execute(w, p)
	return err
}

func clamp(n, min, max float64) float64 {
	switch {
	case n > max:
		return max
	case n < min:
		return min
	default:
		return n
	}
}