flat.js

#!env node

let path = require('path');
let fs = require('fs').promises;


async function run(build, contract) {
  let buildJson = JSON.parse(await fs.readFile(build, 'utf8'));

  let contracts = buildJson['contracts'];

  let contractPair = Object.entries(contracts).find(([k, v]) => k.split(':')[1] === contract);

  if (!contractPair) {
    throw new Error(`Could not find contract \`${contract}\` in build \`${build}\``);
  }

  let [contractFilePair, contractData] = contractPair;
  let metadata = JSON.parse(contractData.metadata);
  let sources =  metadata['sources'];
  let contractFile = contractFilePair.split(':')[0];

  let target = sources[contractFile].content;

  function resolveImports(current, currentFile, included) {
    if (!current.includes('import')) {
      return [current, included];
    }

    let importRegex = /import\s+["']([^"']+)["']\s*;/im;
    let nextIncluded = [];
    let next = current.replace(importRegex, (match, contractName) => {
      let resolvedContract = path.join(currentFile, '..', contractName);
      // Uck, we have to change the relative resolves here

      if (included.includes(resolvedContract)) {
        return "";
      } else {
        let content = sources[resolvedContract].content;

        let [res, newIncluded] = resolveImports(
          content
            .replace(/pragma[^;]*;\n+/g, '')
            .replace(/\/\/\s*SPDX-License-Identifier[^\n]*\n+/g, ''),
          resolvedContract,
          included,
          false);
        nextIncluded = [resolvedContract, ...newIncluded];
        return res;
      }
    });

    return resolveImports(next, currentFile, nextIncluded);
  }

  let [file, _included] = resolveImports(target, contractFile, [contractFile]);

  console.log(file);
}

let [_n, _f, build, contract] = process.argv;

if (!build || !contract) {
  console.error(`usage: ${path.relative(process.cwd(), _f)} <build file> <contract name>`);
  process.exit(1);
}

run(build, contract);