package chroma

import (

	"fmt"

	"math"

	"strconv"

	"strings"

)

// ANSI2RGB maps ANSI colour names, as supported by Chroma, to hex RGB values.

var ANSI2RGB = map[string]string{

	"#ansiblack":     "000000",

	"#ansidarkred":   "7f0000",

	"#ansidarkgreen": "007f00",

	"#ansibrown":     "7f7fe0",

	"#ansidarkblue":  "00007f",

	"#ansipurple":    "7f007f",

	"#ansiteal":      "007f7f",

	"#ansilightgray": "e5e5e5",

	// Normal

	"#ansidarkgray":  "555555",

	"#ansired":       "ff0000",

	"#ansigreen":     "00ff00",

	"#ansiyellow":    "ffff00",

	"#ansiblue":      "0000ff",

	"#ansifuchsia":   "ff00ff",

	"#ansiturquoise": "00ffff",

	"#ansiwhite":     "ffffff",

	// Aliases without the "ansi" prefix, because...why?

	"#black":     "000000",

	"#darkred":   "7f0000",

	"#darkgreen": "007f00",

	"#brown":     "7f7fe0",

	"#darkblue":  "00007f",

	"#purple":    "7f007f",

	"#teal":      "007f7f",

	"#lightgray": "e5e5e5",

	// Normal

	"#darkgray":  "555555",

	"#red":       "ff0000",

	"#green":     "00ff00",

	"#yellow":    "ffff00",

	"#blue":      "0000ff",

	"#fuchsia":   "ff00ff",

	"#turquoise": "00ffff",

	"#white":     "ffffff",

}

// Colour represents an RGB colour.

type Colour int32

// NewColour creates a Colour directly from RGB values.

func NewColour(r, g, b uint8) Colour {

	return ParseColour(fmt.Sprintf("%02x%02x%02x", r, g, b))

}

// Distance between this colour and another.

//

// This uses the approach described here (https://www.compuphase.com/cmetric.htm).

// This is not as accurate as LAB, et. al. but is *vastly* simpler and sufficient for our needs.

func (c Colour) Distance(e2 Colour) float64 {

	ar, ag, ab := int64(c.Red()), int64(c.Green()), int64(c.Blue())

	br, bg, bb := int64(e2.Red()), int64(e2.Green()), int64(e2.Blue())

	rmean := (ar + br) / 2

	r := ar - br

	g := ag - bg

	b := ab - bb

	return math.Sqrt(float64((((512 + rmean) * r * r) >> 8) + 4*g*g + (((767 - rmean) * b * b) >> 8)))

}

// Brighten returns a copy of this colour with its brightness adjusted.

//

// If factor is negative, the colour is darkened.

//

// Uses approach described here (http://www.pvladov.com/2012/09/make-color-lighter-or-darker.html).

func (c Colour) Brighten(factor float64) Colour {

	r := float64(c.Red())

	g := float64(c.Green())

	b := float64(c.Blue())

	if factor < 0 {

		factor++

		r *= factor

		g *= factor

		b *= factor

	} else {

		r = (255-r)*factor + r

		g = (255-g)*factor + g

		b = (255-b)*factor + b

	}

	return NewColour(uint8(r), uint8(g), uint8(b))

}

// BrightenOrDarken brightens a colour if it is < 0.5 brightness or darkens if > 0.5 brightness.

func (c Colour) BrightenOrDarken(factor float64) Colour {

	if c.Brightness() < 0.5 {

		return c.Brighten(factor)

	}

	return c.Brighten(-factor)

}

// ClampBrightness returns a copy of this colour with its brightness adjusted such that

// it falls within the range [min, max] (or very close to it due to rounding errors).

// The supplied values use the same [0.0, 1.0] range as Brightness.

func (c Colour) ClampBrightness(min, max float64) Colour {

	if !c.IsSet() {

		return c

	}

	min = math.Max(min, 0)

	max = math.Min(max, 1)

	current := c.Brightness()

	target := math.Min(math.Max(current, min), max)

	if current == target {

		return c

	}

	r := float64(c.Red())

	g := float64(c.Green())

	b := float64(c.Blue())

	rgb := r + g + b

	if target > current {

		// Solve for x: target == ((255-r)*x + r + (255-g)*x + g + (255-b)*x + b) / 255 / 3

		return c.Brighten((target*255*3 - rgb) / (255*3 - rgb))

	}

	// Solve for x: target == (r*(x+1) + g*(x+1) + b*(x+1)) / 255 / 3

	return c.Brighten((target*255*3)/rgb - 1)

}

// Brightness of the colour (roughly) in the range 0.0 to 1.0.

func (c Colour) Brightness() float64 {

	return (float64(c.Red()) + float64(c.Green()) + float64(c.Blue())) / 255.0 / 3.0

}

// ParseColour in the forms #rgb, #rrggbb, #ansi<colour>, or #<colour>.

// Will return an "unset" colour if invalid.

func ParseColour(colour string) Colour {

	colour = normaliseColour(colour)

	n, err := strconv.ParseUint(colour, 16, 32)

	if err != nil {

		return 0

	}

	return Colour(n + 1)

}

// MustParseColour is like ParseColour except it panics if the colour is invalid.

//

// Will panic if colour is in an invalid format.

func MustParseColour(colour string) Colour {

	parsed := ParseColour(colour)

	if !parsed.IsSet() {

		panic(fmt.Errorf("invalid colour %q", colour))

	}

	return parsed

}

// IsSet returns true if the colour is set.

func (c Colour) IsSet() bool { return c != 0 }

func (c Colour) String() string   { return fmt.Sprintf("#%06x", int(c-1)) }

func (c Colour) GoString() string { return fmt.Sprintf("Colour(0x%06x)", int(c-1)) }

// Red component of colour.

func (c Colour) Red() uint8 { return uint8(((c - 1) >> 16) & 0xff) }

// Green component of colour.

func (c Colour) Green() uint8 { return uint8(((c - 1) >> 8) & 0xff) }

// Blue component of colour.

func (c Colour) Blue() uint8 { return uint8((c - 1) & 0xff) }

// Colours is an orderable set of colours.

type Colours []Colour

func (c Colours) Len() int           { return len(c) }

func (c Colours) Swap(i, j int)      { c[i], c[j] = c[j], c[i] }

func (c Colours) Less(i, j int) bool { return c[i] < c[j] }

// Convert colours to #rrggbb.

func normaliseColour(colour string) string {

	if ansi, ok := ANSI2RGB[colour]; ok {

		return ansi

	}

	if strings.HasPrefix(colour, "#") {

		colour = colour[1:]

		if len(colour) == 3 {

			return colour[0:1] + colour[0:1] + colour[1:2] + colour[1:2] + colour[2:3] + colour[2:3]

		}

	}

	return colour

}