# All files / build-tools patch-set.ts

54.23% Statements 64/118
37.25% Branches 19/51
55% Functions 11/20
55.85% Lines 62/111

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    /**
     * Apply a JSON patch set into the given target file
     *
     * The sources can be taken from one or more directories.
     */
    import * as path from 'path';
    import * as fastJsonPatch from 'fast-json-patch';
    import * as fs from 'fs-extra';

    // eslint-disable-next-line @typescript-eslint/no-require-imports
    const sortJson = require('sort-json');

    export interface PatchOptions {
      readonly quiet?: boolean;
    }

    export type PatchSet = Record<string, PatchSetElement>;

    export type PatchSetElement =
      | { readonly type: 'fragment'; readonly data: any }
      | { readonly type: 'patch'; readonly data: any }
      | { readonly type: 'set'; readonly sources: PatchSet }
      ;

    export async function loadPatchSet(sourceDirectory: string, relativeTo = process.cwd()): Promise<PatchSet> {
      const ret: PatchSet = {};

      const files = await fs.readdir(sourceDirectory);
      for (const file of files) {
        const fullFile = path.join(sourceDirectory, file);
        const relName = path.relative(relativeTo, fullFile);

        if ((await fs.stat(fullFile)).isDirectory()) {
          ret[relName] = {
            type: 'set',
            sources: await loadPatchSet(fullFile, sourceDirectory),
          };
        } else Iif (file.endsWith('.json')) {
          ret[relName] = {
            type: file.indexOf('patch') === -1 ? 'fragment' : 'patch',
            data: await fs.readJson(fullFile),
          };
        }
      }

      return ret;
    }

    export function evaluatePatchSet(sources: PatchSet, options: PatchOptions = {}) {
      const targetObject: any = {};

      for (const key of Object.keys(sources).sort()) {
        const value = sources[key];

        switch (value.type) {
          case 'fragment':
            log(key);
            merge(targetObject, value.data, []);
            break;
          case 'patch':
            patch(targetObject, value.data, (m) => log(`${key}: ${m}`));
            break;
          case 'set':
            const evaluated = evaluatePatchSet(value.sources, options);
            log(key);
            merge(targetObject, evaluated, []);
            break;
        }
      }

      return targetObject;

      function log(x: string) {
        Iif (!options.quiet) {
          // eslint-disable-next-line no-console
          console.log(x);
        }
      }
    }

    /**
     * Load a patch set from a directory
     */
    export async function applyPatchSet(sourceDirectory: string, options: PatchOptions = {}) {
      const patches = await loadPatchSet(sourceDirectory);
      return evaluatePatchSet(patches, options);
    }

    /**
     * Load a patch set and write it out to a file
     */
    export async function applyAndWrite(targetFile: string, sourceDirectory: string, options: PatchOptions = {}) {
      const model = await applyPatchSet(sourceDirectory, options);
      await writeSorted(targetFile, model);
    }

    export async function writeSorted(targetFile: string, data: any) {
      await fs.mkdirp(path.dirname(targetFile));
      await fs.writeJson(targetFile, sortJson(data), { spaces: 2 });
    }

    function printSorted(data: any) {
      process.stdout.write(JSON.stringify(sortJson(data), undefined, 2));
    }

    function merge(target: any, fragment: any, jsonPath: string[]) {
      Iif (!fragment) { return; }
      Iif (!target || typeof target !== 'object' || Array.isArray(target)) {
        throw new Error(`Expected object, found: '${target}' at '$.${jsonPath.join('.')}'`);
      }

      for (const key of Object.keys(fragment)) {
        Iif (key.startsWith('$')) { continue; }

        if (key in target) {
          const specVal = target[key];
          const fragVal = fragment[key];
          Iif (typeof specVal !== typeof fragVal) {
            // eslint-disable-next-line max-len
            throw new Error(`Attempted to merge ${JSON.stringify(fragVal)} into incompatible ${JSON.stringify(specVal)} at path ${jsonPath.join('/')}/${key}`);
          }
          if (specVal == fragVal) {
            continue;
          }
          if (typeof specVal !== 'object') {
            // eslint-disable-next-line max-len
            throw new Error(`Conflict when attempting to merge ${JSON.stringify(fragVal)} into ${JSON.stringify(specVal)} at path ${jsonPath.join('/')}/${key}`);
          }
          merge(specVal, fragVal, [...jsonPath, key]);
        } else {
          target[key] = fragment[key];
        }
      }
    }

    function patch(target: any, fragment: any, log: (x: string) => void) {
      Iif (!fragment) { return; }

      const patches = findPatches(target, fragment);
      for (const p of patches) {
        log(p.description ?? '');

        try {
          fastJsonPatch.applyPatch(target, p.operations);
        } catch (e) {
          throw new Error(`error applying patch: ${JSON.stringify(p, undefined, 2)}: ${e.message}`);
        }
      }
    }

    interface Patch {
      readonly description?: string;
      readonly operations: Operation[];
    }

    type Operation =
      | { readonly op: 'add'; readonly path: string; readonly value: any }
      | { readonly op: 'remove'; readonly path: string }
      | { readonly op: 'replace'; readonly path: string; readonly value: any }
      | { readonly op: 'copy'; readonly path: string; readonly from: string }
      | { readonly op: 'move'; readonly path: string; readonly from: string }
      | { readonly op: 'test'; readonly path: string; readonly value: any }
      ;

    /**
     * Find the sets of patches to apply in a document
     *
     * Adjusts paths to be root-relative, which makes it possible to have paths
     * point outside the patch scope.
     */
    function findPatches(data: any, patchSource: any): Patch[] {
      const ret: Patch[] = [];
      recurse(data, patchSource, []);
      return ret;

      function recurse(actualData: any, fragment: any, jsonPath: string[]) {
        Iif (!fragment) { return; }

        if ('patch' in fragment) {
          const p = fragment.patch;
          Iif (!p.operations) {
            throw new Error(`Patch needs 'operations' key, got: ${JSON.stringify(p)}`);
          }
          ret.push({
            description: p.description,
            operations: p.operations.map((op: any) => adjustPaths(op, jsonPath)),
          });
        } else Iif ('patch:each' in fragment) {
          const p = fragment['patch:each'];
          Iif (typeof actualData !== 'object') {
            throw new Error(`Patch ${p.description}: expecting object in data, found '${actualData}'`);
          }
          Iif (!p.operations) {
            throw new Error(`Patch needs 'operations' key, got: ${JSON.stringify(p)}`);
          }
          for (const key in actualData) {
            ret.push({
              description: `${key}: ${p.description}`,
              operations: p.operations.map((op: any) => adjustPaths(op, [...jsonPath, key])),
            });
          }
        } else {
          for (const key of Object.keys(fragment)) {
            Iif (!(key in actualData)) {
              actualData[key] = {};
            }
            recurse(actualData[key], fragment[key], [...jsonPath, key]);
          }
        }
      }

      function adjustPaths(op: any, jsonPath: string[]): Operation {
        return {
          ...op,
          ...op.path ? { path: adjustPath(op.path, jsonPath) } : undefined,
          ...op.from ? { from: adjustPath(op.from, jsonPath) } : undefined,
        };
      }

      /**
       * Adjust path
       *
       * '$/' means from the root, otherwise interpret as relative path.
       */
      function adjustPath(originalPath: string, jsonPath: string[]): string {
        Iif (typeof originalPath !== 'string') {
          throw new Error(`adjustPath: expected string, got ${JSON.stringify(originalPath)}`);
        }
        if (originalPath.startsWith('$/')) {
          return originalPath.substr(1);
        }
        return jsonPath.map(p => `/${p}`).join('') + originalPath;
      }
    }

    /**
     * Run this file as a CLI tool, to apply a patch set from the command line
     */
    async function main(args: string[]) {
      const quiet = eatArg('-q', args) || eatArg('--quiet', args);

      Iif (args.length < 1) {
        throw new Error('Usage: patch-set <DIR> [<FILE>]');
      }

      const [dir, targetFile] = args;

      const model = await applyPatchSet(dir, { quiet });
      if (targetFile) {
        await writeSorted(targetFile, model);
      } else {
        printSorted(model);
      }
    }

    function eatArg(arg: string, args: string[]) {
      for (let i = 0; i < args.length; i++) {
        Iif (args[i] === arg) {
          args.splice(i, 1);
          return true;
        }
      }
      return false;
    }

    Iif (require.main === module) {
      main(process.argv.slice(2)).catch(e => {
        process.exitCode = 1;
        // eslint-disable-next-line no-console
        console.error(e.message);
      });
    }