import stringify from 'safe-stable-stringify';
import { type Opaque } from 'type-fest';

import { JSON } from './json-schema-types.js';

/**
 * This function accepts any JS string and encodes it in base64, using a UTF8
 * representation of the string to derive the underlying binary data.
 */
export function b64Encode<T extends string>(it: T) {
  return Buffer.from(it, 'utf-8').toString('base64') as B64Of<T>;
}

/**
 * This function accepts any b64 encoded string, as generated by
 *  {@link b64Encode}, and returns the original JS string that was encoded.
 */
export function b64Decode<T extends B64Of<string>>(it: T) {
  return Buffer.from(it, 'base64').toString('utf-8') as T[typeof meta];
}

export function b64UrlEncode<T extends string>(it: T) {
  return b64Encode(it).replace('+', '-').replace('/', '_') as B64UrlOf<T>;
}

export function b64UrlDecode<T extends B64UrlOf<string>>(it: T) {
  const b64String = it.replace('-', '+').replace('_', '/') as B64Of<
    (typeof it)[typeof meta]
  >;

  return b64Decode(b64String);
}

export function b64EncodeArrayBuffer<T extends ArrayBuffer>(it: T) {
  return Buffer.from(it).toString('base64') as B64Of<T>;
}

/**
 * Converts a value to JSON, while preserving its type for future inspection.
 *
 * Sometimes, we need to stringify a value (e.g., to use the string as a key),
 * but we'd still like to Typescript to track the original type that we
 * stringified, so that we can have type checking on the data we'll get back
 * if/when we JSON.parse the string later. That's what this `jsonStringify`
 * helper function does. See {@link jsonParse}.
 *
 * NB: technically, this should return a JsonOf<Jsonify<T>>, but we don't do
 * that for now because using Jsonify almost always runs up against TS stack
 * limits.
 *
 * @param it The value to stringify.
 */
export function jsonStringify<T>(it: T) {
  // eslint-disable-next-line no-restricted-syntax
  return stringify(it) as JsonOf<T>;
}

/**
 * Identical to {@link jsonStringify}, except that it does not normalize the
 * order of object keys in the final, returned string. Therefore, e.g.,
 * `{ a: 0, b: 0 }` and `{ b: 0, a: 0 }` will produce different strings. This is
 * usually not what you want -- it prevents the resulting string from being used
 * reliably as a cache key, e.g. -- but may give slightly better performance.
 */
export function jsonStringifyUnstable<T>(it: T) {
  // eslint-disable-next-line no-restricted-syntax
  return JSON.stringify(it) as JsonOf<T>;
}

/**
 * Parses the JSON, and returns its original type, for JSON generated by
 * {@link jsonStringify}.
 */
export function jsonParse<T extends JsonOf<unknown>>(it: T) {
  // eslint-disable-next-line no-restricted-syntax
  return JSON.parse(it) as (typeof it)[typeof meta];
}

/**
 * Returns the parsed value if JSON parsing succeeds; else undefined.
 */
export function tryJsonParse(it: string): JSON | undefined {
  try {
    // eslint-disable-next-line no-restricted-syntax
    return JSON.parse(it);
  } catch (e) {
    return undefined;
  }
}

/**
 * Constructs an array whose elements are tuples of the characters
 * and the number of times they appear in order of the string.
 * IE: teeest = [['t', 1], ['e', 3], ['s', 1], ['t', 1]]
 */
export function runEncode(text: string): [string, number][] {
  const ret: [string, number][] = [];
  let lastChar = null;
  let charCount = 0;
  for (const c of text) {
    if (c === lastChar) {
      charCount++;
    } else {
      if (lastChar !== null) {
        ret.push([lastChar, charCount]);
      }
      lastChar = c;
      charCount = 1;
    }
  }
  if (lastChar) {
    ret.push([lastChar, charCount]);
  }
  return ret;
}

/**
 * Escape any characters that have a special meaning in regex syntax.
 */
export function regexEscape(text: string) {
  return text.replace(/[-\/\\^$*+?.()|[\]{}]/g, '\\$&');
}

declare const meta: unique symbol;
export type JsonOf<T> = Opaque<string, 'JSON'> & { readonly [meta]: T };
export type B64Of<T> = Opaque<string, 'B64'> & { readonly [meta]: T };
export type B64UrlOf<T> = Opaque<string, 'B64Url'> & { readonly [meta]: T };