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var postcss = require('postcss');
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module.exports = postcss.plugin('postcss-media-minmax', function () {
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return function(css) {
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var feature_unit = {
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'width': 'px',
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'height': 'px',
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'device-width': 'px',
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'device-height': 'px',
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'aspect-ratio': '',
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'device-aspect-ratio': '',
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'color': '',
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'color-index': '',
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'monochrome': '',
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'resolution': 'dpi'
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};
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//支持 min-/max- 前缀的属性
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var feature_name = Object.keys(feature_unit);
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var step = .001; // smallest even number that won’t break complex queries (1in = 96px)
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var power = {
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'>': 1,
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'<': -1
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};
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var minmax = {
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'>': 'min',
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'<': 'max'
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};
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function create_query(name, gtlt, eq, value, params) {
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return value.replace(/([-\d\.]+)(.*)/, function (match, number, unit) {
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var initialNumber = parseFloat(number);
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if (parseFloat(number) || eq) {
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// if eq is true, then number remains same
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if (!eq) {
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// change integer pixels value only on integer pixel
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if (unit === 'px' && initialNumber === parseInt(number, 10)) {
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number = initialNumber + power[gtlt];
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} else {
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number = Number(Math.round(parseFloat(number) + step * power[gtlt] + 'e6')+'e-6');
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}
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}
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} else {
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number = power[gtlt] + feature_unit[name];
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}
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return '(' + minmax[gtlt] + '-' + name + ': ' + number + unit + ')';
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});
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}
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// 读取 media-feature
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css.walkAtRules(function(rule, i) {
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if (rule.name !== "media" && rule.name !== "custom-media") {
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return
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}
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/**
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* 转换 <mf-name> <|>= <mf-value>
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* $1 $2 $3
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* (width >= 300px) => (min-width: 300px)
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* (width <= 900px) => (max-width: 900px)
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*/
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//取值不支持负值
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//But -0 is always equivalent to 0 in CSS, and so is also accepted as a valid <mq-boolean> value.
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rule.params = rule.params.replace(/\(\s*([a-z-]+?)\s*([<>])(=?)\s*((?:-?\d*\.?(?:\s*\/?\s*)?\d+[a-z]*)?)\s*\)/gi, function($0, $1, $2, $3, $4) {
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var params = '';
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if (feature_name.indexOf($1) > -1) {
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return create_query($1, $2, $3, $4, rule.params);
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}
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//如果不是指定的属性，不做替换
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return $0;
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})
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/**
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* 转换 <mf-value> <|<= <mf-name> <|<= <mf-value>
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* 转换 <mf-value> >|>= <mf-name> >|>= <mf-value>
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* $1 $2$3 $4 $5$6 $7
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* (500px <= width <= 1200px) => (min-width: 500px) and (max-width: 1200px)
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* (500px < width <= 1200px) => (min-width: 501px) and (max-width: 1200px)
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* (900px >= width >= 300px) => (min-width: 300px) and (max-width: 900px)
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*/
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rule.params = rule.params.replace(/\(\s*((?:-?\d*\.?(?:\s*\/?\s*)?\d+[a-z]*)?)\s*(<|>)(=?)\s*([a-z-]+)\s*(<|>)(=?)\s*((?:-?\d*\.?(?:\s*\/?\s*)?\d+[a-z]*)?)\s*\)/gi, function($0, $1, $2, $3, $4, $5, $6, $7) {
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if (feature_name.indexOf($4) > -1) {
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if ($2 === '<' && $5 === '<' || $2 === '>' && $5 === '>') {
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var min = ($2 === '<') ? $1 : $7;
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var max = ($2 === '<') ? $7 : $1;
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// output differently depended on expression direction
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// <mf-value> <|<= <mf-name> <|<= <mf-value>
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// or
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// <mf-value> >|>= <mf-name> >|>= <mf-value>
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var equals_for_min = $3;
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var equals_for_max = $6;
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if ($2 === '>') {
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equals_for_min = $6;
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equals_for_max = $3;
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}
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return create_query($4, '>', equals_for_min, min) + ' and ' + create_query($4, '<', equals_for_max, max);
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}
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}
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//如果不是指定的属性，不做替换
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return $0;
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});
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});
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}
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});
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