// forked from https://github.com/sindresorhus/rgb-hex
import {ColorRGB} from './common'

type RGBColorValue = number | string

export function rgbToHex(rgba: string): string
export function rgbToHex(red: number, green: number, blue: number, alpha?: RGBColorValue): string
export function rgbToHex(red: RGBColorValue, green?: RGBColorValue, blue?: RGBColorValue, alpha?: RGBColorValue) {
    const isPercent = ((red as string) + (alpha || '')).toString().includes('%')

    if (typeof red === 'string') {
        [red, green, blue, alpha] = red.match(/(0?\.?\d{1,3})%?\b/g)!.map(Number)
    } else if (alpha !== undefined && typeof alpha === 'string') {
        alpha = parseFloat(alpha)
    }

    if (typeof red !== 'number'
        || typeof green !== 'number'
        || typeof blue !== 'number'
        || red > 255
        || green > 255
        || blue > 255
    ) {
        throw new TypeError('Expected three numbers below 256')
    }

    if (typeof alpha === 'number') {
        if (!isPercent && alpha >= 0 && alpha <= 1) {
            alpha = Math.round(255 * alpha)
        } else if (isPercent && alpha >= 0 && alpha <= 100) {
            alpha = Math.round(255 * alpha / 100)
        } else {
            throw new TypeError(`Expected alpha value (${alpha}) as a fraction or percentage`)
        }

        alpha = (alpha | 1 << 8).toString(16).slice(1)
    } else {
        alpha = ''
    }

    return ((blue | green << 8 | red << 16) | 1 << 24).toString(16).slice(1) + alpha
}

// forked from https://github.com/sindresorhus/hex-rgb
const hexCharacters = 'a-f\\d'
const match3or4Hex = `#?[${hexCharacters}]{3}[${hexCharacters}]?`
const match6or8Hex = `#?[${hexCharacters}]{6}([${hexCharacters}]{2})?`
const nonHexChars = new RegExp(`[^#${hexCharacters}]`, 'gi')
const validHexSize = new RegExp(`^${match3or4Hex}$|^${match6or8Hex}$`, 'i')

export function hexToRgb(hex: string): ColorRGB {
    if (typeof hex !== 'string' || nonHexChars.test(hex) || !validHexSize.test(hex)) {
        throw new TypeError('Expected a valid hex string')
    }

    hex = hex.replace(/^#/, '')
    let alpha = 1

    if (hex.length === 8) {
        alpha = parseInt(hex.slice(6, 8), 16) / 255
        hex = hex.slice(0, 6)
    }

    if (hex.length === 4) {
        alpha = parseInt(hex.slice(3, 4).repeat(2), 16) / 255
        hex = hex.slice(0, 3)
    }

    if (hex.length === 3) {
        hex = hex[0] + hex[0] + hex[1] + hex[1] + hex[2] + hex[2]
    }

    const num = parseInt(hex, 16)
    const red = num >> 16
    const green = (num >> 8) & 255
    const blue = num & 255

    return {r: red, g: green, b: blue, a: alpha}
}