package sprite

import (
	"fmt"
	"image/color"
	"strconv"
	"strings"
)

// Transparent is the color used for pixels that should not be drawn.
var Transparent = color.NRGBA{0, 0, 0, 0}

// ParseColor accepts:
//
//	none | transparent | -           -> fully transparent
//	#RGB #RGBA #RRGGBB #RRGGBBAA     -> hex
//	rgb(r,g,b) rgba(r,g,b,a)         -> 0-255 channels, alpha 0-255 or 0.0-1.0
//	CSS named colors                 -> "red", "rebeccapurple", ...
func ParseColor(s string) (color.NRGBA, error) {
	t := strings.ToLower(strings.TrimSpace(s))
	if t == "" {
		return Transparent, fmt.Errorf("empty color value")
	}
	switch t {
	case "none", "transparent", "-":
		return Transparent, nil
	}
	if strings.HasPrefix(t, "#") {
		return parseHex(t)
	}
	if strings.HasPrefix(t, "rgb(") || strings.HasPrefix(t, "rgba(") {
		return parseRGBFunc(t)
	}
	if c, ok := cssColors[t]; ok {
		return c, nil
	}
	return Transparent, fmt.Errorf("unknown color %q (use #RRGGBB, rgb(r,g,b), a CSS color name, or 'none')", s)
}

func parseHex(t string) (color.NRGBA, error) {
	h := t[1:]
	var r, g, b, a uint64
	var err error
	dup := func(s string) (uint64, error) {
		v, err := strconv.ParseUint(s, 16, 8)
		return v*16 + v, err
	}
	a = 255
	switch len(h) {
	case 3, 4:
		if r, err = dup(h[0:1]); err == nil {
			if g, err = dup(h[1:2]); err == nil {
				b, err = dup(h[2:3])
			}
		}
		if err == nil && len(h) == 4 {
			a, err = dup(h[3:4])
		}
	case 6, 8:
		if r, err = strconv.ParseUint(h[0:2], 16, 8); err == nil {
			if g, err = strconv.ParseUint(h[2:4], 16, 8); err == nil {
				b, err = strconv.ParseUint(h[4:6], 16, 8)
			}
		}
		if err == nil && len(h) == 8 {
			a, err = strconv.ParseUint(h[6:8], 16, 8)
		}
	default:
		return Transparent, fmt.Errorf("hex color %q must be #RGB, #RGBA, #RRGGBB or #RRGGBBAA", t)
	}
	if err != nil {
		return Transparent, fmt.Errorf("invalid hex color %q", t)
	}
	return color.NRGBA{uint8(r), uint8(g), uint8(b), uint8(a)}, nil
}

func parseRGBFunc(t string) (color.NRGBA, error) {
	open := strings.Index(t, "(")
	close := strings.Index(t, ")")
	if close < open {
		return Transparent, fmt.Errorf("invalid color %q: missing ')'", t)
	}
	parts := strings.Split(t[open+1:close], ",")
	if len(parts) != 3 && len(parts) != 4 {
		return Transparent, fmt.Errorf("invalid color %q: want rgb(r,g,b) or rgba(r,g,b,a)", t)
	}
	var ch [4]uint8
	ch[3] = 255
	for i, p := range parts {
		p = strings.TrimSpace(p)
		if i == 3 && strings.Contains(p, ".") {
			// CSS-style fractional alpha 0.0 - 1.0
			f, err := strconv.ParseFloat(p, 64)
			if err != nil || f < 0 || f > 1 {
				return Transparent, fmt.Errorf("invalid alpha %q in %q (want 0.0-1.0 or 0-255)", p, t)
			}
			ch[3] = uint8(f*255 + 0.5)
			continue
		}
		v, err := strconv.ParseUint(p, 10, 8)
		if err != nil {
			return Transparent, fmt.Errorf("invalid channel %q in %q (want 0-255)", p, t)
		}
		ch[i] = uint8(v)
	}
	return color.NRGBA{ch[0], ch[1], ch[2], ch[3]}, nil
}

// FormatColor renders a color the way it should appear in a .sprite file.
func FormatColor(c color.NRGBA) string {
	if c.A == 0 {
		return "none"
	}
	if c.A == 255 {
		return fmt.Sprintf("#%02X%02X%02X", c.R, c.G, c.B)
	}
	return fmt.Sprintf("#%02X%02X%02X%02X", c.R, c.G, c.B, c.A)
}

// cssColors is the full CSS Color Module Level 4 named-color list.
var cssColors = map[string]color.NRGBA{
	"aliceblue":            {240, 248, 255, 255},
	"antiquewhite":         {250, 235, 215, 255},
	"aqua":                 {0, 255, 255, 255},
	"aquamarine":           {127, 255, 212, 255},
	"azure":                {240, 255, 255, 255},
	"beige":                {245, 245, 220, 255},
	"bisque":               {255, 228, 196, 255},
	"black":                {0, 0, 0, 255},
	"blanchedalmond":       {255, 235, 205, 255},
	"blue":                 {0, 0, 255, 255},
	"blueviolet":           {138, 43, 226, 255},
	"brown":                {165, 42, 42, 255},
	"burlywood":            {222, 184, 135, 255},
	"cadetblue":            {95, 158, 160, 255},
	"chartreuse":           {127, 255, 0, 255},
	"chocolate":            {210, 105, 30, 255},
	"coral":                {255, 127, 80, 255},
	"cornflowerblue":       {100, 149, 237, 255},
	"cornsilk":             {255, 248, 220, 255},
	"crimson":              {220, 20, 60, 255},
	"cyan":                 {0, 255, 255, 255},
	"darkblue":             {0, 0, 139, 255},
	"darkcyan":             {0, 139, 139, 255},
	"darkgoldenrod":        {184, 134, 11, 255},
	"darkgray":             {169, 169, 169, 255},
	"darkgreen":            {0, 100, 0, 255},
	"darkgrey":             {169, 169, 169, 255},
	"darkkhaki":            {189, 183, 107, 255},
	"darkmagenta":          {139, 0, 139, 255},
	"darkolivegreen":       {85, 107, 47, 255},
	"darkorange":           {255, 140, 0, 255},
	"darkorchid":           {153, 50, 204, 255},
	"darkred":              {139, 0, 0, 255},
	"darksalmon":           {233, 150, 122, 255},
	"darkseagreen":         {143, 188, 143, 255},
	"darkslateblue":        {72, 61, 139, 255},
	"darkslategray":        {47, 79, 79, 255},
	"darkslategrey":        {47, 79, 79, 255},
	"darkturquoise":        {0, 206, 209, 255},
	"darkviolet":           {148, 0, 211, 255},
	"deeppink":             {255, 20, 147, 255},
	"deepskyblue":          {0, 191, 255, 255},
	"dimgray":              {105, 105, 105, 255},
	"dimgrey":              {105, 105, 105, 255},
	"dodgerblue":           {30, 144, 255, 255},
	"firebrick":            {178, 34, 34, 255},
	"floralwhite":          {255, 250, 240, 255},
	"forestgreen":          {34, 139, 34, 255},
	"fuchsia":              {255, 0, 255, 255},
	"gainsboro":            {220, 220, 220, 255},
	"ghostwhite":           {248, 248, 255, 255},
	"gold":                 {255, 215, 0, 255},
	"goldenrod":            {218, 165, 32, 255},
	"gray":                 {128, 128, 128, 255},
	"green":                {0, 128, 0, 255},
	"greenyellow":          {173, 255, 47, 255},
	"grey":                 {128, 128, 128, 255},
	"honeydew":             {240, 255, 240, 255},
	"hotpink":              {255, 105, 180, 255},
	"indianred":            {205, 92, 92, 255},
	"indigo":               {75, 0, 130, 255},
	"ivory":                {255, 255, 240, 255},
	"khaki":                {240, 230, 140, 255},
	"lavender":             {230, 230, 250, 255},
	"lavenderblush":        {255, 240, 245, 255},
	"lawngreen":            {124, 252, 0, 255},
	"lemonchiffon":         {255, 250, 205, 255},
	"lightblue":            {173, 216, 230, 255},
	"lightcoral":           {240, 128, 128, 255},
	"lightcyan":            {224, 255, 255, 255},
	"lightgoldenrodyellow": {250, 250, 210, 255},
	"lightgray":            {211, 211, 211, 255},
	"lightgreen":           {144, 238, 144, 255},
	"lightgrey":            {211, 211, 211, 255},
	"lightpink":            {255, 182, 193, 255},
	"lightsalmon":          {255, 160, 122, 255},
	"lightseagreen":        {32, 178, 170, 255},
	"lightskyblue":         {135, 206, 250, 255},
	"lightslategray":       {119, 136, 153, 255},
	"lightslategrey":       {119, 136, 153, 255},
	"lightsteelblue":       {176, 196, 222, 255},
	"lightyellow":          {255, 255, 224, 255},
	"lime":                 {0, 255, 0, 255},
	"limegreen":            {50, 205, 50, 255},
	"linen":                {250, 240, 230, 255},
	"magenta":              {255, 0, 255, 255},
	"maroon":               {128, 0, 0, 255},
	"mediumaquamarine":     {102, 205, 170, 255},
	"mediumblue":           {0, 0, 205, 255},
	"mediumorchid":         {186, 85, 211, 255},
	"mediumpurple":         {147, 112, 219, 255},
	"mediumseagreen":       {60, 179, 113, 255},
	"mediumslateblue":      {123, 104, 238, 255},
	"mediumspringgreen":    {0, 250, 154, 255},
	"mediumturquoise":      {72, 209, 204, 255},
	"mediumvioletred":      {199, 21, 133, 255},
	"midnightblue":         {25, 25, 112, 255},
	"mintcream":            {245, 255, 250, 255},
	"mistyrose":            {255, 228, 225, 255},
	"moccasin":             {255, 228, 181, 255},
	"navajowhite":          {255, 222, 173, 255},
	"navy":                 {0, 0, 128, 255},
	"oldlace":              {253, 245, 230, 255},
	"olive":                {128, 128, 0, 255},
	"olivedrab":            {107, 142, 35, 255},
	"orange":               {255, 165, 0, 255},
	"orangered":            {255, 69, 0, 255},
	"orchid":               {218, 112, 214, 255},
	"palegoldenrod":        {238, 232, 170, 255},
	"palegreen":            {152, 251, 152, 255},
	"paleturquoise":        {175, 238, 238, 255},
	"palevioletred":        {219, 112, 147, 255},
	"papayawhip":           {255, 239, 213, 255},
	"peachpuff":            {255, 218, 185, 255},
	"peru":                 {205, 133, 63, 255},
	"pink":                 {255, 192, 203, 255},
	"plum":                 {221, 160, 221, 255},
	"powderblue":           {176, 224, 230, 255},
	"purple":               {128, 0, 128, 255},
	"rebeccapurple":        {102, 51, 153, 255},
	"red":                  {255, 0, 0, 255},
	"rosybrown":            {188, 143, 143, 255},
	"royalblue":            {65, 105, 225, 255},
	"saddlebrown":          {139, 69, 19, 255},
	"salmon":               {250, 128, 114, 255},
	"sandybrown":           {244, 164, 96, 255},
	"seagreen":             {46, 139, 87, 255},
	"seashell":             {255, 245, 238, 255},
	"sienna":               {160, 82, 45, 255},
	"silver":               {192, 192, 192, 255},
	"skyblue":              {135, 206, 235, 255},
	"slateblue":            {106, 90, 205, 255},
	"slategray":            {112, 128, 144, 255},
	"slategrey":            {112, 128, 144, 255},
	"snow":                 {255, 250, 250, 255},
	"springgreen":          {0, 255, 127, 255},
	"steelblue":            {70, 130, 180, 255},
	"tan":                  {210, 180, 140, 255},
	"teal":                 {0, 128, 128, 255},
	"thistle":              {216, 191, 216, 255},
	"tomato":               {255, 99, 71, 255},
	"turquoise":            {64, 224, 208, 255},
	"violet":               {238, 130, 238, 255},
	"wheat":                {245, 222, 179, 255},
	"white":                {255, 255, 255, 255},
	"whitesmoke":           {245, 245, 245, 255},
	"yellow":               {255, 255, 0, 255},
	"yellowgreen":          {154, 205, 50, 255},
}