postcss-alter-property-value.js

/* postcss alter property value (papv) */
/* ES5 code */

var postcss = require('postcss');

module.exports = postcss.plugin('postcss-alter-property-value', function (options) {
  var options = options || {},
      declarations = options.declarations || {},
      config = options.config || {};

  return function (root, result) {
    var props = Object.keys(declarations);

    props.map(function (prop, index) {
      root.walkDecls(prop, function (decl) {
          var value = declarations[prop],
              copyProp = decl.prop + '',
              copyVal = decl.value + '';

          if (typeof value === 'string') {
            decl.value = value;
            addInfoToValue(decl, ' /* papv - changeValue from [' + copyVal + '] */');
          } else if (typeof value === 'object' || value === undefined) {

            if (!value) {
              decl.prop = prop + '__papv__disable';
            } else if (!value.task) {
              // no task to do  if not set
            } else {

              if (value.whenRegex && typeof value.whenRegex === 'object') {
                regexParser({value: value, decl: decl});
              } else {

                switch (value.task) {
                  case 'remove':
                    if (hasNoFields(value)) {
                      decl.remove();
                    } else if (value.whenValueEquals !== undefined && value.whenValueEquals === decl.value) {
                      decl.remove();
                    }
                    break;
                  case 'cloneBefore':
                    var node = decl.cloneBefore({prop: value.to});
                    break;
                  case 'cloneAfter':
                    var node = decl.cloneAfter({prop: value.to});
                    break;
                  case 'disable':
                    if (hasNoFields(value)) {
                      decl.prop = prop + '__papv_disable';
                    } else if (value.whenValueEquals !== undefined && value.whenValueEquals === decl.value) {
                      decl.prop = prop + '__papv_disable';
                    }
                    break;
                  case 'changeProperty':
                    if (hasNoFields(value)) {
                      decl.prop = value.to;
                      addInfoToValue(decl, ' /* papv - changeProp from [' + copyProp + '] */');
                    } else if (value.whenValueEquals !== undefined && value.whenValueEquals === decl.value) {
                      decl.prop = value.to;
                      addInfoToValue(decl, ' /* papv - changeProp from [' + copyProp + '] */');
                    }
                    break;
                  case 'changeValue':
                    if (hasNoFields(value)) {
                      decl.value = value.to;
                      addInfoToValue(decl, ' /* papv - changeValue from [' + copyVal + '] */');
                    } else if (value.whenValueEquals !== undefined && value.whenValueEquals === decl.value) {
                      decl.value = value.to;
                      addInfoToValue(decl, ' /* papv - changeValue from [' + copyVal + '] */');
                    }
                    break;

                  default:
                    result.warn('unknown task: [' + value.task + ']');
                    break;
                }
              }
            }
          }
        });
    });

  };

  /* Helper utils */

  function regexParser(data) {
    var value = data.value,
        decl = data.decl,
        whenRegex = value.whenRegex;

    if (whenRegex.value === undefined) {
      return; // nothing to do when value is not set
    }

    var copyProp = decl.prop + '',
        copyVal = decl.value + '',
        task = value.task;

    var regex = new RegExp(whenRegex.value, whenRegex.flags || '');

    switch (task) {
      case 'disable':
        if (regex.test(decl.value)) 
          decl.prop = prop + '__papv_disable';
        break;
      case 'remove':
        if (regex.test(decl.value)) 
          decl.remove();
        break;
      case 'changeProperty':
        if (regex.test(decl.value)) {
          decl.prop = value.to;
          addInfoToValue(decl, ' /* papv - changeProp from [' + copyProp + '] */');
        }
        break;
      case 'changeValue':
        switch (whenRegex.mode) {
          case 'partial':
            decl.value = decl.value.replace(regex, value.to);
            addInfoToValue(decl, ' /* --papv - changeValue from [' + copyVal + '] */');
            break;
          case 'replace':
          default:
            if (regex.test(decl.value)) {
              decl.value = value.to;
              addInfoToValue(decl, ' /* papv - changeValue from [' + copyVal + '] */');
            }
            break;
        }
        break;
    }
  }

  function hasNoFields(value) {
    return value.whenValueEquals === undefined && value.whenRegex === undefined;
  }

  function addInfoToValue(decl, str) {
    if (config.addInfo) {
      decl.value += str;
    }
  }

});