benjamine/jsondiffpatch

import type DiffContext from '../contexts/diff.js';
import type PatchContext from '../contexts/patch.js';
import type ReverseContext from '../contexts/reverse.js';
import type {
  AddedDelta,
  DeletedDelta,
  Filter,
  ModifiedDelta,
  MovedDelta,
  TextDiffDelta,
} from '../types.js';

export const diffFilter: Filter<DiffContext> =
  function trivialMatchesDiffFilter(context) {
    if (context.left === context.right) {
      context.setResult(undefined).exit();
      return;
    }
    if (typeof context.left === 'undefined') {
      if (typeof context.right === 'function') {
        throw new Error('functions are not supported');
      }
      context.setResult([context.right]).exit();
      return;
    }
    if (typeof context.right === 'undefined') {
      context.setResult([context.left, 0, 0]).exit();
      return;
    }
    if (
      typeof context.left === 'function' ||
      typeof context.right === 'function'
    ) {
      throw new Error('functions are not supported');
    }
    context.leftType = context.left === null ? 'null' : typeof context.left;
    context.rightType = context.right === null ? 'null' : typeof context.right;
    if (context.leftType !== context.rightType) {
      context.setResult([context.left, context.right]).exit();
      return;
    }
    if (context.leftType === 'boolean' || context.leftType === 'number') {
      context.setResult([context.left, context.right]).exit();
      return;
    }
    if (context.leftType === 'object') {
      context.leftIsArray = Array.isArray(context.left);
    }
    if (context.rightType === 'object') {
      context.rightIsArray = Array.isArray(context.right);
    }
    if (context.leftIsArray !== context.rightIsArray) {
      context.setResult([context.left, context.right]).exit();
      return;
    }

    if (context.left instanceof RegExp) {
      if (context.right instanceof RegExp) {
        context
          .setResult([context.left.toString(), context.right.toString()])
          .exit();
      } else {
        context.setResult([context.left, context.right]).exit();
      }
    }
  };
diffFilter.filterName = 'trivial';

export const patchFilter: Filter<PatchContext> =
  function trivialMatchesPatchFilter(context) {
    if (typeof context.delta === 'undefined') {
      context.setResult(context.left).exit();
      return;
    }
    context.nested = !Array.isArray(context.delta);
    if (context.nested) {
      return;
    }
    const nonNestedDelta = context.delta as
      | AddedDelta
      | ModifiedDelta
      | DeletedDelta
      | MovedDelta
      | TextDiffDelta;
    if (nonNestedDelta.length === 1) {
      context.setResult(nonNestedDelta[0]).exit();
      return;
    }
    if (nonNestedDelta.length === 2) {
      if (context.left instanceof RegExp) {
        const regexArgs = /^\/(.*)\/([gimyu]+)$/.exec(
          nonNestedDelta[1] as string,
        );
        if (regexArgs) {
          context.setResult(new RegExp(regexArgs[1], regexArgs[2])).exit();
          return;
        }
      }
      context.setResult(nonNestedDelta[1]).exit();
      return;
    }
    if (nonNestedDelta.length === 3 && nonNestedDelta[2] === 0) {
      context.setResult(undefined).exit();
    }
  };
patchFilter.filterName = 'trivial';

export const reverseFilter: Filter<ReverseContext> =
  function trivialReferseFilter(context) {
    if (typeof context.delta === 'undefined') {
      context.setResult(context.delta).exit();
      return;
    }
    context.nested = !Array.isArray(context.delta);
    if (context.nested) {
      return;
    }
    const nonNestedDelta = context.delta as
      | AddedDelta
      | ModifiedDelta
      | DeletedDelta
      | MovedDelta
      | TextDiffDelta;
    if (nonNestedDelta.length === 1) {
      context.setResult([nonNestedDelta[0], 0, 0]).exit();
      return;
    }
    if (nonNestedDelta.length === 2) {
      context.setResult([nonNestedDelta[1], nonNestedDelta[0]]).exit();
      return;
    }
    if (nonNestedDelta.length === 3 && nonNestedDelta[2] === 0) {
      context.setResult([nonNestedDelta[0]]).exit();
    }
  };
reverseFilter.filterName = 'trivial';