minify/css/css.go at master · applistweb/minify

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10BC8

// Package css minifies CSS3 following the specifications at http://www.w3.org/TR/css-syntax-3/.

package css

import (

"bytes"

"fmt"

"io"

"math"

"strconv"

"github.com/tdewolff/minify/v2"

"github.com/tdewolff/parse/v2"

"github.com/tdewolff/parse/v2/css"

strconvParse "github.com/tdewolff/parse/v2/strconv"

)

var (

spaceBytes = []byte(" ")

colonBytes = []byte(":")

semicolonBytes = []byte(";")

commaBytes = []byte(",")

leftBracketBytes = []byte("{")

rightBracketBytes = []byte("}")

zeroBytes = []byte("0")

transparentBytes = []byte("transparent")

initialBytes = []byte("initial")

noneBytes = []byte("none")

autoBytes = []byte("auto")

importantBytes = []byte("!important")

dataSchemeBytes = []byte("data:")

)

type cssMinifier struct {

m *minify.M

w io.Writer

p *css.Parser

o *Minifier

tokenBuffer []Token

}

////////////////////////////////////////////////////////////////

// DEPRECATED: DefaultMinifier is the default minifier.

var DefaultMinifier = &Minifier{}

// Minifier is a CSS minifier.

type Minifier struct {

KeepCSS2 bool

Decimals int // DEPRECATED

Precision int // number of significant digits

newPrecision int // precision for new numbers

}

// Minify minifies CSS data, it reads from r and w F438 rites to w.

func Minify(m *minify.M, w io.Writer, r io.Reader, params map[string]string) error {

return (&Minifier{}).Minify(m, w, r, params)

}

type Token struct {

css.TokenType

Data []byte

Args []Token // only filled for functions

Fun, Ident Hash // only filled for functions and identifiers respectively

}

func (t Token) String() string {

if len(t.Args) == 0 {

return t.TokenType.String() + "(" + string(t.Data) + ")"

}

return fmt.Sprint(t.Args)

}

func (a Token) Equal(b Token) bool {

if a.TokenType == b.TokenType && bytes.Equal(a.Data, b.Data) && len(a.Args) == len(b.Args) {

for i := 0; i < len(a.Args); i++ {

if a.Args[i].TokenType != b.Args[i].TokenType || !bytes.Equal(a.Args[i].Data, b.Args[i].Data) {

return false

}

return true

}

return false

}

func (t Token) IsZero() bool {

// as each number is already minified, starting with a zero means it is zero

return (t.TokenType == css.DimensionToken || t.TokenType == css.PercentageToken || t.TokenType == css.NumberToken) && t.Data[0] == '0'

}

func (t Token) IsLength() bool {

if t.TokenType == css.DimensionToken {

return true

} else if t.TokenType == css.NumberToken && t.Data[0] == '0' {

return true

} else if t.TokenType == css.FunctionToken {

fun := ToHash(t.Data[:len(t.Data)-1])

if fun == Calc || fun == Min || fun == Max || fun == Clamp || fun == Attr || fun == Var || fun == Env {

return true

}

return false

}

func (t Token) IsLengthPercentage() bool {

return t.TokenType == css.PercentageToken || t.IsLength()

}

// Minify minifies CSS data, it reads from r and writes to w.

func (o *Minifier) Minify(m *minify.M, w io.Writer, r io.Reader, params map[string]string) error {

if o.Decimals != 0 {

minify.Warning.Println("CSS option `Decimals` is deprecated, using as `Precision` instead. Be aware that `Decimals` meant the number of digits behind the dot while `Precision` means the number of significant digits. Example: 1.23 with `Decimals=1` would give 1.2 but with `Pecision=1` gives 1. The default `Decimals=-1` is now `Precision=0` which prints the whole number.")

}

if o.Precision == 0 {

o.Precision = o.Decimals

}

o.newPrecision = o.Precision

if o.newPrecision <= 0 || 15 < o.newPrecision {

o.newPrecision = 15 // minimum number of digits a double can represent exactly

}

isInline := params != nil && params["inline"] == "1"

c := &cssMinifier{

m: m,

w: w,

p: css.NewParser(r, isInline),

o: o,

}

defer c.p.Restore()

if err := c.minifyGrammar(); err != nil && err != io.EOF {

return err

}

return nil

}

func (c *cssMinifier) minifyGrammar() error {

semicolonQueued := false

for {

gt, _, data := c.p.Next()

switch gt {

case css.ErrorGrammar:

if c.p.HasParseError() {

if semicolonQueued {

if _, err := c.w.Write(semicolonBytes); err != nil {

return err

}

// write out the offending declaration (but save the semicolon)

vals := c.p.Values()

if len(vals) > 0 && vals[len(vals)-1].TokenType == css.SemicolonToken {

vals = vals[:len(vals)-1]

semicolonQueued = true

}

for _, val := range vals {

if _, err := c.w.Write(val.Data); err != nil {

return err

}

continue

}

return c.p.Err()

case css.EndAtRuleGrammar, css.EndRulesetGrammar:

if _, err := c.w.Write(rightBracketBytes); err != nil {

return err

}

semicolonQueued = false

continue

}

if semicolonQueued {

if _, err := c.w.Write(semicolonBytes); err != nil {

return err

}

semicolonQueued = false

}

switch gt {

case css.AtRuleGrammar:

if _, err := c.w.Write(data); err != nil {

return err

}

values := c.p.Values()

if ToHash(data[1:]) == Import && len(values) == 2 && values[1].TokenType == css.URLToken {

url := values[1].Data

if url[4] != '"' && url[4] != '\'' {

a := 4

for parse.IsWhitespace(url[a]) || parse.IsNewline(url[a]) {

a++

}

b := len(url) - 2

for parse.IsWhitespace(url[b]) || parse.IsNewline(url[b]) {

b--

}

url = url[a-1 : b+2]

url[0] = '"'

url[len(url)-1] = '"'

} else {

url = url[4 : len(url)-1]

}

values[1].Data = url

}

for _, val := range values {

if _, err := c.w.Write(val.Data); err != nil {

return err

}

semicolonQueued = true

case css.BeginAtRuleGrammar:

if _, err := c.w.Write(data); err != nil {

return err

}

for _, val := range c.p.Values() {

if _, err := c.w.Write(val.Data); err != nil {

return err

}

if _, err := c.w.Write(leftBracketBytes); err != nil {

return err

}

case css.QualifiedRuleGrammar:

if err := c.minifySelectors(data, c.p.Values()); err != nil {

return err

}

if _, err := c.w.Write(commaBytes); err != nil {

return err

}

case css.BeginRulesetGrammar:

if err := c.minifySelectors(data, c.p.Values()); err != nil {

return err

}

if _, err := c.w.Write(leftBracketBytes); err != nil {

return err

}

case css.DeclarationGrammar:

if err := c.minifyDeclaration(data, c.p.Values()); err != nil {

return err

}

semicolonQueued = true

case css.CustomPropertyGrammar:

if _, err := c.w.Write(data); err != nil {

return err

}

if _, err := c.w.Write(colonBytes); err != nil {

return err

}

value := parse.TrimWhitespace(c.p.Values()[0].Data)

if len(c.p.Values()[0].Data) != 0 && len(value) == 0 {

value = spaceBytes

}

if _, err := c.w.Write(value); err != nil {

return err

}

semicolonQueued = true

case css.CommentGrammar:

if len(data) > 5 && data[1] == '*' && data[2] == '!' {

if _, err := c.w.Write(data[:3]); err != nil {

return err

}

comment := parse.TrimWhitespace(parse.ReplaceMultipleWhitespace(data[3 : len(data)-2]))

if _, err := c.w.Write(comment); err != nil {

return err

}

if _, err := c.w.Write(data[len(data)-2:]); err != nil {

return err

}

default:

if _, err := c.w.Write(data); err != nil {

return err

}

func (c *cssMinifier) minifySelectors(property []byte, values []css.Token) error {

inAttr := false

isClass := false

for _, val := range c.p.Values() {

if !inAttr {

if val.TokenType == css.IdentToken {

if !isClass {

parse.ToLower(val.Data)

}

isClass = false

} else if val.TokenType == css.DelimToken && val.Data[0] == '.' {

isClass = true

} else if val.TokenType == css.LeftBracketToken {

inAttr = true

}

} else {

if val.TokenType == css.StringToken && len(val.Data) > 2 {

s := val.Data[1 : len(val.Data)-1]

if css.IsIdent(s) {

if _, err := c.w.Write(s); err != nil {

return err

}

continue

}

} else if val.TokenType == css.RightBracketToken {

inAttr = false

} else if val.TokenType == css.IdentToken && len(val.Data) == 1 && (val.Data[0] == 'i' || val.Data[0] == 'I') {

if _, err := c.w.Write(spaceBytes); err != nil {

return err

}

if _, err := c.w.Write(val.Data); err != nil {

return err

}

return nil

}

func (c *cssMinifier) parseFunction(values []css.Token) ([]Token, int) {

i := 1

level := 0

args := []Token{}

for ; i < len(values); i++ {

tt := values[i].TokenType

data := values[i].Data

if tt == css.LeftParenthesisToken {

level++

} else if tt == css.RightParenthesisToken {

if level == 0 {

i++

break

}

level--

}

if tt == css.FunctionToken {

subArgs, di := c.parseFunction(values[i:])

h := ToHash(parse.ToLower(parse.Copy(data[:len(data)-1]))) // TODO: use ToHashFold

args = append(args, Token{tt, data, subArgs, h, 0})

i += di - 1

} else {

var h Hash

if tt == css.IdentToken {

h = ToHash(parse.ToLower(parse.Copy(data))) // TODO: use ToHashFold

}

args = append(args, Token{tt, data, nil, 0, h})

}

return args, i

}

func (c *cssMinifier) parseDeclaration(values []css.Token) []Token {

// Check if this is a simple list of values separated by whitespace or commas, otherwise we'll not be processing

prevSep := true

tokens := c.tokenBuffer[:0]

for i := 0; i < len(values); i++ {

tt := values[i].TokenType

data := values[i].Data

if tt == css.LeftParenthesisToken || tt == css.LeftBraceToken || tt == css.LeftBracketToken ||

tt == css.RightParenthesisToken || tt == css.RightBraceToken || tt == css.RightBracketToken {

return nil

}

if !prevSep && tt != css.WhitespaceToken && tt != css.CommaToken && (tt != css.DelimToken || values[i].Data[0] != '/') {

return nil

}

if tt == css.WhitespaceToken || tt == css.CommaToken || tt == css.DelimToken && values[i].Data[0] == '/' {

if tt != css.WhitespaceToken {

tokens = append(tokens, Token{tt, data, nil, 0, 0})

}

prevSep = true

} else if tt == css.FunctionToken {

args, di := c.parseFunction(values[i:])

h := ToHash(parse.ToLower(parse.Copy(data[:len(data)-1]))) // TODO: use ToHashFold

tokens = append(tokens, Token{tt, data, args, h, 0})

prevSep = true

i += di - 1

} else {

var h Hash

if tt == css.IdentToken {

h = ToHash(parse.ToLower(parse.Copy(data))) // TODO: use ToHashFold

}

tokens = append(tokens, Token{tt, data, nil, 0, h})

prevSep = tt == css.URLToken

}

c.tokenBuffer = tokens // update buffer size for memory reuse

return tokens

}

func (c *cssMinifier) minifyDeclaration(property []byte, components []css.Token) error {

if _, err := c.w.Write(property); err != nil {

return err

}

if _, err := c.w.Write(colonBytes); err != nil {

return err

}

if len(components) == 0 {

return nil

}

// Strip !important from the component list, this will be added later separately

important := false

if len(components) > 2 && components[len(components)-2].TokenType == css.DelimToken && components[len(components)-2].Data[0] == '!' && ToHash(components[len(components)-1].Data) == Important {

components = components[:len(components)-2]

important = true

}

prop := ToHash(property)

values := c.parseDeclaration(components)

// Do not process complex values (eg. containing blocks or is not alternated between whitespace/commas and flat values

if values == nil {

if prop == Filter && len(components) == 11 {

if bytes.Equal(components[0].Data, []byte("progid")) &&

components[1].TokenType == css.ColonToken &&

bytes.Equal(components[2].Data, []byte("DXImageTransform")) &&

components[3].Data[0] == '.' &&

bytes.Equal(components[4].Data, []byte("Microsoft")) &&

components[5].Data[0] == '.' &&

bytes.Equal(components[6].Data, []byte("Alpha(")) &&

bytes.Equal(parse.ToLower(components[7].Data), []byte("opacity")) &&

components[8].Data[0] == '=' &&

components[10].Data[0] == ')' {

components = components[6:]

components[0].Data = []byte("alpha(")

}

for _, component := range components {

if _, err := c.w.Write(component.Data); err != nil {

return err

}

if important {

if _, err := c.w.Write(importantBytes); err != nil {

return err

}

return nil

}

values = c.minifyTokens(prop, values)

if len(values) > 0 {

values = c.minifyProperty(prop, values)

}

return c.writeDeclaration(values, important)

}

func (c *cssMinifier) writeFunction(args []Token) error {

for _, arg := range args {

if _, err := c.w.Write(arg.Data); err != nil {

return err

}

if arg.TokenType == css.FunctionToken {

if err := c.writeFunction(arg.Args); err != nil {

return err

}

if _, err := c.w.Write([]byte(")")); err != nil {

return err

}

return nil

}

func (c *cssMinifier) writeDeclaration(values []Token, important bool) error {

prevSep := true

for _, value := range values {

if !prevSep && value.TokenType != css.CommaToken && (value.TokenType != css.DelimToken || value.Data[0] != '/') {

if _, err := c.w.Write(spaceBytes); err != nil {

return err

}

if _, err := c.w.Write(value.Data); err != nil {

return err

}

if value.TokenType == css.FunctionToken {

if err := c.writeFunction(value.Args); err != nil {

return err

}

if _, err := c.w.Write([]byte(")")); err != nil {

return err

}

if value.TokenType == css.CommaToken || value.TokenType == css.DelimToken && value.Data[0] == '/' || value.TokenType == css.FunctionToken || value.TokenType == css.URLToken {

prevSep = true

} else {

prevSep = false

}

if important {

if _, err := c.w.Write(importantBytes); err != nil {

return err

}

return nil

}

func (c *cssMinifier) minifyTokens(prop Hash, values []Token) []Token {

for i, value := range values {

tt := value.TokenType

switch tt {

case css.NumberToken:

if prop == Z_Index || prop == Counter_Increment || prop == Counter_Reset || prop == Orphans || prop == Widows {

break // integers

}

if c.o.KeepCSS2 {

values[i].Data = minify.Decimal(values[i].Data, c.o.Precision) // don't use exponents

} else {

values[i].Data = minify.Number(values[i].Data, c.o.Precision)

}

case css.PercentageToken:

n := len(values[i].Data) - 1

if c.o.KeepCSS2 {

values[i].Data = minify.Decimal(values[i].Data[:n], c.o.Precision) // don't use exponents

} else {

values[i].Data = minify.Number(values[i].Data[:n], c.o.Precision)

}

values[i].Data = append(values[i].Data, '%')

case css.DimensionToken:

var dim []byte

values[i], dim = c.minifyDimension(values[i])

if 1 < len(values[i].Data) && values[i].Data[0] == '0' && optionalZeroDimension[string(dim)] && prop != Flex {

// cut dimension for zero value, TODO: don't hardcode check for Flex and remove the dimension in minifyDimension

values[i].Data = values[i].Data[:1]

}

case css.StringToken:

values[i].Data = removeMarkupNewlines(values[i].Data)

case css.URLToken:

if 10 < len(values[i].Data) {

uri := parse.TrimWhitespace(values[i].Data[4 : len(values[i].Data)-1])

delim := byte('"')

if 1 < len(uri) && (uri[0] == '\'' || uri[0] == '"') {

delim = uri[0]

uri = removeMarkupNewlines(uri)

uri = uri[1 : len(uri)-1]

}

if 4 < len(uri) && parse.EqualFold(uri[:5], dataSchemeBytes) {

uri = minify.DataURI(c.m, uri)

}

if css.IsURLUnquoted(uri) {

values[i].Data = append(append([]byte("url("), uri...), ')')

} else {

values[i].Data = append(append(append([]byte("url("), delim), uri...), delim, ')')

}

case css.FunctionToken:

values[i].Args = c.minifyTokens(prop, values[i].Args)

fun := values[i].Fun

args := values[i].Args

if fun == Rgb || fun == Rgba || fun == Hsl || fun == Hsla {

valid := true

vals := []float64{}

for i, arg := range args {

numeric := arg.TokenType == css.NumberToken || arg.TokenType == css.PercentageToken

separator := arg.TokenType == css.CommaToken || i != 5 && arg.TokenType == css.WhitespaceToken || i == 5 && arg.TokenType == css.DelimToken && arg.Data[0] == '/'

if i%2 == 0 && !numeric || i%2 == 1 && !separator {

valid = false

break

} else if numeric {

var d float64

if arg.TokenType == css.PercentageToken {

var err error

d, err = strconv.ParseFloat(string(arg.Data[:len(arg.Data)-1]), 32) // can overflow

if err != nil {

valid = false

break

}

d /= 100.0

if d < minify.Epsilon {

d = 0.0

} else if 1.0-minify.Epsilon < d {

d = 1.0

}

} else {

var err error

d, err = strconv.ParseFloat(string(arg.Data), 32) // can overflow

if err != nil {

valid = false

break

}

vals = append(vals, d)

}

if !valid {

break

}

a := 1.0

if len(vals) == 4 {

if vals[3] < minify.Epsilon {

values[i] = Token{css.IdentToken, transparentBytes, nil, 0, Transparent}

break

} else if 1.0-minify.Epsilon < vals[3] {

vals = vals[:3]

values[i].Args = values[i].Args[:len(values[i].Args)-2]

if fun == Rgba || fun == Hsla {

values[i].Data = values[i].Data[:len(values[i].Data)-1]

values[i].Data[len(values[i].Data)-1] = '('

}

} else {

a = vals[3]

}

if a == 1.0 && (len(vals) == 3 || len(vals) == 4) { // only minify color if fully opaque

if fun == Rgb || fun == Rgba {

for j := 0; j < 3; j++ {

if args[j*2].TokenType == css.NumberToken {

vals[j] /= 255.0

if vals[j] < minify.Epsilon {

vals[j] = 0.0

} else if 1.0-minify.Epsilon < vals[j] {

vals[j] = 1.0

}

values[i] = rgbToToken(vals[0], vals[1], vals[2])

break

} else if fun == Hsl || fun == Hsla && args[0].TokenType == css.NumberToken && args[2].TokenType == css.PercentageToken && args[4].TokenType == css.PercentageToken {

vals[0] /= 360.0

_, vals[0] = math.Modf(vals[0])

if vals[0] < 0.0 {

vals[0] = 1.0 + vals[0]

}

r, g, b := css.HSL2RGB(vals[0], vals[1], vals[2])

values[i] = rgbToToken(r, g, b)

break

}

} else if len(vals) == 4 {

args[6] = minifyNumberPercentage(args[6])

}

if fun == Rgb || fun == Rgba {

// 0%, 20%, 40%, 60%, 80% and 100% can be represented exactly as, 51, 102, 153, 204, and 255 respectively

removePercentage := true

for j := 0; j < 3; j++ {

if args[j*2].TokenType != css.PercentageToken || 2.0*minify.Epsilon <= math.Mod(vals[j]+minify.Epsilon, 0.2) {

removePercentage = false

break

}

if removePercentage {

for j := 0; j < 3; j++ {

args[j*2].TokenType = css.NumberToken

if vals[j] < minify.Epsilon {

args[j*2].Data = []byte("0")

} else if math.Abs(vals[j]-0.2) < minify.Epsilon {

args[j*2].Data = []byte("51")

} else if math.Abs(vals[j]-0.4) < minify.Epsilon {

args[j*2].Data = []byte("102")

} else if math.Abs(vals[j]-0.6) < minify.Epsilon {

args[j*2].Data = []byte("153")

} else if math.Abs(vals[j]-0.8) < minify.Epsilon {

args[j*2].Data = []byte("204")

} else if math.Abs(vals[j]-1.0) < minify.Epsilon {

args[j*2].Data = []byte("255")

}

return values

}

func (c *cssMinifier) minifyProperty(prop Hash, values []Token) []Token {

switch prop {

case Font:

if len(values) > 1 { // must contain atleast font-size and font-family

// the font-families are separated by commas and are at the end of font

// get index for last token before font family names

i := len(values) - 1

for j, value := range values[2:] {

if value.TokenType == css.CommaToken {

i = 2 + j - 1 // identifier before first comma is a font-family

break

}

i--

// advance i while still at font-families when they contain spaces but no quotes

for ; i > 0; i-- { // i cannot be 0, font-family must be prepended by font-size

if values[i-1].TokenType == css.DelimToken && values[i-1].Data[0] == '/' {

break

} else if values[i].TokenType != css.IdentToken && values[i].TokenType != css.StringToken {

break

} else if h := values[i].Ident; h == Xx_Small || h == X_Small || h == Small || h == Medium || h == Large || h == X_Large || h == Xx_Large || h == Smaller || h == Larger || h == Inherit || h == Initial || h == Unset {

// inherit, initial and unset are followed by an IdentToken/StringToken, so must be for font-size

break

}

// font-family minified in place

values = append(values[:i+1], c.minifyProperty(Font_Family, values[i+1:])...)

// fix for IE9, IE10, IE11: font name starting with `-` is not recognized

if values[i+1].Data[0] == '-' {

v := make([]byte, len(values[i+1].Data)+2)

v[0] = '\''

copy(v[1:], values[i+1].Data)

v[len(v)-1] = '\''

values[i+1].Data = v

}

if i > 0 {

// line-height

if i > 1 && values[i-1].TokenType == css.DelimToken && values[i-1].Data[0] == '/' {

if values[i].Ident == Normal {

values = append(values[:i-1], values[i+1:]...)

}

i -= 2

}

// font-size

i--

for ; i > -1; i-- {

if values[i].Ident == Normal {

values = append(values[:i], values[i+1:]...)

} else if values[i].Ident == Bold {

values[i].TokenType = css.NumberToken

values[i].Data = []byte("700")

} else if values[i].TokenType == css.NumberToken && bytes.Equal(values[i].Data, []byte("400")) {

values = append(values[:i], values[i+1:]...)

}

case Font_Family:

for i, value := range values {

if value.TokenType == css.StringToken && len(value.Data) > 2 {

unquote := true

parse.ToLower(value.Data)

s := value.Data[1 : len(value.Data)-1]

if len(s) > 0 {

for _, split := range bytes.Split(s, spaceBytes) {

// if len is zero, it contains two consecutive spaces

if len(split) == 0 || !css.IsIdent(split) {

unquote = false

break

}

if unquote {

values[i].Data = s

}

case Font_Weight:

if values[0].Ident == Normal {

values[0].TokenType = css.NumberToken

values[0].Data = []byte("400")

} else if values[0].Ident == Bold {

values[0].TokenType = css.NumberToken

values[0].Data = []byte("700")

}

case Url:

for i := 0; i < len(values); i++ {

if values[i].TokenType == css.FunctionToken && len(values[i].Args) == 1 {

fun := values[i].Fun

data := values[i].Args[0].Data

if fun == Local && (data[0] == '\'' || data[0] == '"') {

if css.IsURLUnquoted(data[1 : len(data)-1]) {

data = data[1 : len(data)-1]

}

values[i].Args[0].Data = data

}

case Margin, Padding, Border_Width:

switch len(values) {

case 2:

if values[0].Equal(values[1]) {

values = values[:1]

}

case 3:

if values[0].Equal(values[1]) && values[0].Equal(values[2]) {

values = values[:1]

} else if values[0].Equal(values[2]) {

values = values[:2]

}

case 4:

if values[0].Equal(values[1]) && values[0].Equal(values[2]) && values[0].Equal(values[3]) {

values = values[:1]

} else if values[0].Equal(values[2]) && values[1].Equal(values[3]) {

values = values[:2]

} else if values[1].Equal(values[3]) {

values = values[:3]

}

case Border, Border_Bottom, Border_Left, Border_Right, Border_Top:

for i := 0; i < len(values); i++ {

if values[i].Ident == None || values[i].Ident == Currentcolor || values[i].Ident == Medium {

values = append(values[:i], values[i+1:]...)

i--

} else {

values[i] = minifyColor(values[i])

}

if len(values) == 0 {

values = []Token{{css.IdentToken, []byte("none"), nil, 0, None}}

}

case Outline:

for i := 0; i < len(values); i++ {

if values[i].Ident == Invert || values[i].Ident == None || values[i].Ident == Medium {

values = append(values[:i], values[i+1:]...)

i--

} else {

values[i] = minifyColor(values[i])

}

if len(values) == 0 {

values = []Token{{css.IdentToken, []byte("none"), nil, 0, None}}

}

case Background:

// minify background-size and lowercase all identifiers

for i := 0; i < len(values); i++ {

if values[i].TokenType == css.DelimToken && values[i].Data[0] == '/' {

// background-size consists of either [<length-percentage> | auto | cover | contain] or [<length-percentage> | auto]{2}

// we can only minify the latter

if i+1 < len(values) && (values[i+1].TokenType == css.NumberToken || values[i+1].IsLengthPercentage() || values[i+1].Ident == Auto) {

if i+2 < len(values) && (values[i+2].TokenType == css.NumberToken || values[i+2].IsLengthPercentage() || values[i+2].Ident == Auto) {

sizeValues := c.minifyProperty(Background_Size, values[i+1:i+3])

if len(sizeValues) == 1 && sizeValues[0].Ident == Auto {

// remove background-size if it is '/ auto' after minifying the property

values = append(values[:i], values[i+3:]...)

i--

} else {

values = append(values[:i+1], append(sizeValues, values[i+3:]...)...)

i += len(sizeValues) - 1

}

} else if values[i+1].Ident == Auto {

// remove background-size if it is '/ auto'

values = append(values[:i], values[i+2:]...)

i--

}

// minify all other values

iPaddingBox := -1 // position of background-origin that is padding-box

for i := 0; i < len(values); i++ {

h := values[i].Ident

values[i] = minifyColor(values[i])

if values[i].TokenType == css.IdentToken {

if i+1 < len(values) && values[i+1].TokenType == css.IdentToken && (h == Space || h == Round || h == Repeat || h == No_Repeat) {

if h2 := values[i+1].Ident; h2 == Space || h2 == Round || h2 == Repeat || h2 == No_Repeat {

repeatValues := c.minifyProperty(Background_Repeat, values[i:i+2])

if len(repeatValues) == 1 && repeatValues[0].Ident == Repeat {

values = append(values[:i], values[i+2:]...)

i--

} else {

values = append(values[:i], append(repeatValues, values[i+2:]...)...)

i += len(repeatValues) - 1

}

continue

}

} else if h == None || h == Scroll || h == Transparent {

values = append(values[:i], values[i+1:]...)

i--

continue

} else if h == Border_Box || h == Padding_Box {

if iPaddingBox == -1 && h == Padding_Box { // background-origin

iPaddingBox = i

} else if iPaddingBox != -1 && h == Border_Box { // background-clip

values = append(values[:i], values[i+1:]...)

values = append(values[:iPaddingBox], values[iPaddingBox+1:]...)

i -= 2

}

continue

}

} else if values[i].TokenType == css.HashToken && bytes.Equal(values[i].Data, []byte("#0000")) {

values = append(values[:i], values[i+1:]...)

i--

continue

}

// further minify background-position and background-size combination

if values[i].TokenType == css.NumberToken || values[i].IsLengthPercentage() || h == Left || h == Right || h == Top || h == Bottom || h == Center {

j := i + 1

for ; j < len(values); j++ {

if h := values[j].Ident; h == Left || h == Right || h == Top || h == Bottom || h == Center {

continue

} else if values[j].TokenType == css.NumberToken || values[j].IsLengthPercentage() {

continue

}

break

}

positionValues := c.minifyProperty(Background_Position, values[i:j])

hasSize := j < len(values) && values[j].TokenType == css.DelimToken && values[j].Data[0] == '/'

if !hasSize && len(positionValues) == 2 && positionValues[0].IsZero() && positionValues[1].IsZero() {

values = append(values[:i], values[j:]...)

i--

} else {

values = append(values[:i], append(positionValues, values[j:]...)...)

i += len(positionValues) - 1

}

if len(values) == 0 {

values = []Token{{css.NumberToken, []byte("0"), nil, 0, 0}, {css.NumberToken, []byte("0"), nil, 0, 0}}

}

case Background_Size:

if len(values) == 2 && values[1].Ident == Auto {

values = values[:1]

}

case Background_Repeat:

if len(values) == 2 && values[0].TokenType == css.IdentToken && values[1].TokenType == css.IdentToken {

if values[0].Ident == values[1].Ident {

values = values[:1]

} else if values[0].Ident == Repeat && values[1].Ident == No_Repeat {

values = values[:1]

values[0].Data = []byte("repeat-x")

values[0].Ident = Repeat_X

} else if values[0].Ident == No_Repeat && values[1].Ident == Repeat {

values = values[:1]

values[0].Data = []byte("repeat-y")

values[0].Ident = Repeat_Y

}

case Background_Position:

if len(values) == 3 || len(values) == 4 {

// remove zero offsets

for _, i := range []int{len(values) - 1, 1} {

if 2 < len(values) && values[i].IsZero() {

values = append(values[:i], values[i+1:]...)

}

j := 1 // position of second set of horizontal/vertical values

if 2 < len(values) && values[2].TokenType == css.IdentToken {

j = 2

}

b := make([]byte, 0, 4)

offsets := make([]Token, 2)

for _, i := range []int{j, 0} {

if i+1 < len(values) && i+1 != j {

if values[i+1].TokenType == css.PercentageToken {

// change right or bottom with percentage offset to left or top respectively

if values[i].Ident == Right || values[i].Ident == Bottom {

n, _ := strconvParse.ParseInt(values[i+1].Data[:len(values[i+1].Data)-1])

b = strconv.AppendInt(b[:0], 100-n, 10)

b = append(b, '%')

values[i+1].Data = b

if values[i].Ident == Right {

values[i].Data = []byte("left")

values[i].Ident = Left

} else {

values[i].Data = []byte("top")

values[i].Ident = Top

}

if values[i].Ident == Left {

offsets[0] = values[i+1]

} else if values[i].Ident == Top {

offsets[1] = values[i+1]

}

} else if values[i].Ident == Left {

offsets[0] = Token{css.NumberToken, []byte("0"), nil, 0, 0}

} else if values[i].Ident == Top {

offsets[1] = Token{css.NumberToken, []byte("0"), nil, 0, 0}

} else if values[i].Ident == Right {

offsets[0] = Token{css.PercentageToken, []byte("100%"), nil, 0, 0}

values[i].Ident = Left

} else if values[i].Ident == Bottom {

offsets[1] = Token{css.PercentageToken, []byte("100%"), nil, 0, 0}

values[i].Ident = Top

}

if values[0].Ident == Center || values[j].Ident == Center {

if values[0].Ident == Left || values[j].Ident == Left {

offsets = offsets[:1]

} else if values[0].Ident == Top || values[j].Ident == Top {

offsets[0] = Token{css.NumberToken, []byte("50%"), nil, 0, 0}

}

if offsets[0].Data != nil && (len(offsets) == 1 || offsets[1].Data != nil) {

values = offsets

}

// removing zero offsets in the previous loop might make it eligible for the next loop

if len(values) == 1 || len(values) == 2 {

if values[0].Ident == Top || values[0].Ident == Bottom {

if len(values) == 1 {

// we can't make this smaller, and converting to a number will break it

// (https://github.com/tdewolff/minify/issues/221#issuecomment-415419918)

break

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