scss-use-vars

#!/usr/bin/env python3

"""
Usage:
  find src/app -name "*.scss" -exec ./scss-use-vars -I <your-theme.scss> {} \+

About:
  This is a quick and dirty implementation of part of an SCSS decompiler.
  It parses obvious color definitions, and replaces inline colors with definitions where possible.

Limitations:
  - No attempt is made to ensure that relevant imports exist.
  - Does not understand #FFFFFF is rgb(255, 255, 255) or otherwise normalize color representations. Including capitalization.
  - Does not consider rgb() and rgba(..., 1) calls equivalent.
  - Many more I'm sure you can find
"""

import argparse
import re
import sys


parser = argparse.ArgumentParser()
parser.add_argument("-I", "--incldue", action="append", dest="includes")
parser.add_argument("files", nargs="+")


DEF_PAT = re.compile(r'(?P<name>\$.*?):\s*(?P<val>(#|rgb|rgba|hls|hsv|hwb|cmyk).*?);')

def parse_defs(text: str) -> dict:
    defs = {}
    for match in re.finditer(DEF_PAT, text):
        defs[match.group('name')] = match.group('val')
    return defs

assert(parse_defs("""
// Ignored
$grid-breakpoints: (
  xs: 0,
  sm: 576px,
  md: 768px,
  lg: 992px,
  xl: 1200px
);
// Should match
$elten-red: #EA5454;
$elten-normal-text: rgba(0, 0, 0, 0.6);
$el-important-text: #D84315;
""") == {
    "$elten-red": "#EA5454",
    "$elten-normal-text": "rgba(0, 0, 0, 0.6)",
    "$el-important-text": "#D84315",
})


INSTANCE_PAT = re.compile(r'(?P<val>(#|rgb|rgba|hls|hsv|hwb|cmyk).*?)(?=;)')

def fix_usages(defs: dict, text: str) -> str:
    inv_defs = {v: k for k, v in defs.items()}

    def munge(match: re.Match) -> str:
        return inv_defs.get(match.group(1), match.group(1))

    return re.sub(INSTANCE_PAT, munge, text)

assert(fix_usages({
    "$elten-red": "#EA5454",
    "$elten-normal-text": "rgba(0, 0, 0, 0.6)",
    "$el-important-text": "#D84315",
}, """
.elten-red {
   color: #EA5454;
}
.dv-fill {
   fill-color: #D84315;
}
.mat-border {
   border-color: rgba(0, 0, 0, 0.6);
}
""") == """
.elten-red {
   color: $elten-red;
}
.dv-fill {
   fill-color: $el-important-text;
}
.mat-border {
   border-color: $elten-normal-text;
}
""")


if __name__ == "__main__":
    opts, args = parser.parse_known_args()

    defs = {}
    for f in opts.includes:
        with open(f, "r") as fp:
            defs.update(parse_defs(fp.read()))

    for f in opts.files:
        with open(f, 'r') as fp:
            buff = fp.read()

        with open(f, 'w') as fp:
            fp.write(fix_usages(defs, buff))