Rename file based on regex in Gulp

Say I have a LESS CSS directory structure like this:

less/
    core/
        _main.less
        header.less
        body.less
        footer.less
    contact/
        _main.less
        form.less
        details.less

I want to write a Gulp task that will look for the _main.less files in each subdirectory of the less/ dir, pass this to gulp-less and write the output to the css/ dir like this:

css/
    core.css
    contact.css

Because _main.less includes the other files in it's directory, only the _main.less files will have to be parsed, but I want the output file to have the name of the directory it's in.

So far I have this:

gulp.src('less/*/*/_main.less')
    .pipe(less())
    .pipe(gulp.dest('css'));

But this will create a directory structure like this:

css/
    core/
        _main.css
    contact/
        _main.css

But that's not what I want. I was thinking to use a regex to match the directory name, get this back in a matches var, and rename the file accordingly. Something like this:

gulp.src(/less\/[^\/]+\/([^\/]+)\/_main.less/)
    .pipe(less())
    .pipe(rename(function(context) {
        context.src.matches[1] + '.css'
     }))
    .pipe(gulp.dest('css'));

This code is just an example. I can't figure out how to do something like this, or if it's even possible.

Is this possible? If so, how?

You look like you already have this, but maybe didn't see the gulp-rename plugin?

I don't even think you'll need to use a RegExp, something like this should work:

var rename = require('gulp-rename'),
    path = require('path'); // node Path

//...

gulp.src('less/**/_main.less')
    .pipe(less())
    .pipe(rename(function(filepath) {
        // replace file name to that of the parent directory
        filepath.basename = path.basename(filepath.dirname);
        // remove parent directory from relative path
        filepath.dirname = path.dirname(filepath.dirname);
        // leave extension as-is
     }))
    .pipe(gulp.dest('css'));