moss/src/ast/ruleSet.ts

import * as AST from '../ast';
import Env, { EnvError } from '../env';

export class RuleSet {
  public selectors: AST.Selector[];
  public children: AST.Child[];

  public constructor(selectors: AST.Selector[], children: AST.Child[] = []) {
    this.selectors = selectors;
    this.children = children;
  }

  public compile(env: Env, opts: AST.Opts): string | EnvError {
    const lineSpacer = opts.prettyPrint ? '\n' : '';
    const wordSpacer = opts.prettyPrint ? ' ' : '';
    const indentSpacer = opts.prettyPrint ? Array(opts.depth).fill(' ').join('') : '';
    const [lBrace, rBrace] = ['{', '}'];

    const lineages = ([] as string[]).concat(
      ...this.selectors.map((sel) => sel.getLineages())
    );

    const rules: (String | EnvError)[] = [];
    const children: (String | EnvError)[] = [];

    for (const child of this.children) {
      if (child instanceof AST.Rule) {
        rules.push(child.compile(env, opts));
      } else if (child instanceof RuleSet) {
        children.push(child.compile(env, opts));
      } else if (child instanceof AST.Application) {
        const mixin = env.get(child.name.value);
        if (mixin instanceof EnvError) return mixin;
        if (mixin instanceof AST.Mixin) {
          const expansion = mixin.expand(env, opts, this.selectors, child.arguments);
          if (expansion instanceof EnvError) return expansion;
          expansion.rules.forEach((rule: String | EnvError) => rules.push(rule));
          expansion.children.forEach((child: String | EnvError) => children.push(child));
        }
      }
    }

    const rulesError = rules.find((node) => node instanceof EnvError);
    if (rulesError instanceof EnvError) return rulesError;
    const childrenError = children.find((node) => node instanceof EnvError);
    if (childrenError instanceof EnvError) return childrenError;

    const compiledRules = rules.join(lineSpacer);
    const compiledChildren = children.join(lineSpacer);

    const lineage = lineages.join(`,${wordSpacer}`);
    const frontMatter = `${indentSpacer}${lineage}${wordSpacer}${lBrace}${lineSpacer}`;
    const backMatter = `${lineSpacer}${indentSpacer}${rBrace}${
      compiledChildren.length ? lineSpacer : ''
    }`;
    return rules.length
      ? `${frontMatter}${compiledRules}${backMatter}${compiledChildren}`
      : compiledChildren;
  }
}