src/base/string_utils.ts

// Copyright (C) 2019 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

import {
  decode as b64Decode,
  encode as b64Encode,
  length as b64Len,
} from '@protobufjs/base64';
import {assertTrue} from './logging';

// Lazy initialize at first use.
let textDecoder: TextDecoder | undefined = undefined;
let textEncoder: TextEncoder | undefined = undefined;

export function base64Encode(buffer: Uint8Array): string {
  return b64Encode(buffer, 0, buffer.length);
}

export function base64Decode(str: string): Uint8Array {
  // if the string is in base64url format, convert to base64
  const b64 = str.replaceAll('-', '+').replaceAll('_', '/');
  const arr = new Uint8Array(b64Len(b64));
  const written = b64Decode(b64, arr, 0);
  assertTrue(written === arr.length);
  return arr;
}

// encode binary array to hex string
export function hexEncode(bytes: Uint8Array): string {
  return bytes.reduce(
    (prev, cur) => prev + ('0' + cur.toString(16)).slice(-2),
    '',
  );
}

export function utf8Encode(str: string): Uint8Array {
  textEncoder = textEncoder ?? new TextEncoder();
  return textEncoder.encode(str);
}

// Note: not all byte sequences can be converted to<>from UTF8. This can be
// used only with valid unicode strings, not arbitrary byte buffers.
export function utf8Decode(buffer: Uint8Array | ArrayBuffer): string {
  textDecoder = textDecoder ?? new TextDecoder();
  return textDecoder.decode(buffer);
}

// The binaryEncode/Decode functions below allow to encode an arbitrary binary
// buffer into a string that can be JSON-encoded. binaryEncode() applies
// UTF-16 encoding to each byte individually.
// Unlike utf8Encode/Decode, any arbitrary byte sequence can be converted into a
// valid string, and viceversa.
// This should be only used when a byte array needs to be transmitted over an
// interface that supports only JSON serialization (e.g., postmessage to a
// chrome extension).

export function binaryEncode(buf: Uint8Array): string {
  let str = '';
  for (let i = 0; i < buf.length; i++) {
    str += String.fromCharCode(buf[i]);
  }
  return str;
}

export function binaryDecode(str: string): Uint8Array {
  const buf = new Uint8Array(str.length);
  const strLen = str.length;
  for (let i = 0; i < strLen; i++) {
    buf[i] = str.charCodeAt(i);
  }
  return buf;
}

// A function used to interpolate strings into SQL query. The only replacement
// is done is that single quote replaced with two single quotes, according to
// SQLite documentation:
// https://www.sqlite.org/lang_expr.html#literal_values_constants_
//
// The purpose of this function is to use in simple comparisons, to escape
// strings used in GLOB clauses see escapeQuery function.
export function sqliteString(str: string): string {
  return `'${str.replaceAll("'", "''")}'`;
}

// Makes a string safe to be used as a SQL table/view/function name.
export function sqlNameSafe(str: string): string {
  return str.replace(/[^a-zA-Z0-9_]+/g, '_');
}

// Chat apps (including G Chat) sometimes replace ASCII characters with similar
// looking unicode characters that break code snippets.
// This function attempts to undo these replacements.
export function undoCommonChatAppReplacements(str: string): string {
  // Replace non-breaking spaces with normal spaces.
  return str.replaceAll('\u00A0', ' ');
}

export function cropText(str: string, charWidth: number, rectWidth: number) {
  let displayText = '';
  const maxLength = Math.floor(rectWidth / charWidth) - 1;
  if (str.length <= maxLength) {
    displayText = str;
  } else {
    let limit = maxLength;
    let maybeTripleDot = '';
    if (maxLength > 1) {
      limit = maxLength - 1;
      maybeTripleDot = '\u2026';
    }
    // Javascript strings are UTF-16. |limit| could point in the middle of a
    // 32-bit double-wchar codepoint (e.g., an emoji). Here we detect if the
    // |limit|-th wchar is a leading surrogate and attach the trailing one.
    const lastCharCode = str.charCodeAt(limit - 1);
    limit += lastCharCode >= 55296 && lastCharCode < 56320 ? 1 : 0;
    displayText = str.substring(0, limit) + maybeTripleDot;
  }
  return displayText;
}