// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
// This module is browser compatible.
/**
 * {@linkcode parse} function for parsing
 * {@link https://code.visualstudio.com/docs/languages/json#_json-with-comments | JSONC}
 * (JSON with Comments) strings.
 *
 * This module is browser compatible.
 *
 * @module
 */ import { assert } from "../assert/assert.ts";
/**
 * Converts a JSON with Comments (JSONC) string into an object.
 * If a syntax error is found, throw a {@linkcode SyntaxError}.
 *
 * @example
 * ```ts
 * import { parse } from "https://deno.land/std@$STD_VERSION/jsonc/mod.ts";
 *
 * console.log(parse('{"foo": "bar", } // comment')); // { foo: "bar" }
 * console.log(parse('{"foo": "bar", } /* comment *\/')); // { foo: "bar" }
 * console.log(parse('{"foo": "bar" } // comment', {
 *   allowTrailingComma: false,
 * })); // { foo: "bar" }
 * ```
 *
 * @param text A valid JSONC string.
 */ export function parse(text, { allowTrailingComma = true } = {}) {
  if (new.target) {
    throw new TypeError("parse is not a constructor");
  }
  return new JSONCParser(text, {
    allowTrailingComma
  }).parse();
}
const originalJSONParse = globalThis.JSON.parse;
// First tokenize and then parse the token.
class JSONCParser {
  #whitespace = new Set(" \t\r\n");
  #numberEndToken = new Set([
    ..."[]{}:,/",
    ...this.#whitespace
  ]);
  #text;
  #length;
  #tokenized;
  #options;
  constructor(text, options){
    this.#text = `${text}`;
    this.#length = this.#text.length;
    this.#tokenized = this.#tokenize();
    this.#options = options;
  }
  parse() {
    const token = this.#getNext();
    const res = this.#parseJsonValue(token);
    // make sure all characters have been read
    const { done, value } = this.#tokenized.next();
    if (!done) {
      throw new SyntaxError(buildErrorMessage(value));
    }
    return res;
  }
  /** Read the next token. If the token is read to the end, it throws a SyntaxError. */ #getNext() {
    const { done, value } = this.#tokenized.next();
    if (done) {
      throw new SyntaxError("Unexpected end of JSONC input");
    }
    return value;
  }
  /** Split the JSONC string into token units. Whitespace and comments are skipped. */ *#tokenize() {
    for(let i = 0; i < this.#length; i++){
      // skip whitespace
      if (this.#whitespace.has(this.#text[i])) {
        continue;
      }
      // skip multi line comment (`/*...*/`)
      if (this.#text[i] === "/" && this.#text[i + 1] === "*") {
        i += 2;
        let hasEndOfComment = false;
        for(; i < this.#length; i++){
          if (this.#text[i] === "*" && this.#text[i + 1] === "/") {
            hasEndOfComment = true;
            break;
          }
        }
        if (!hasEndOfComment) {
          throw new SyntaxError("Unexpected end of JSONC input");
        }
        i++;
        continue;
      }
      // skip single line comment (`//...`)
      if (this.#text[i] === "/" && this.#text[i + 1] === "/") {
        i += 2;
        for(; i < this.#length; i++){
          if (this.#text[i] === "\n" || this.#text[i] === "\r") {
            break;
          }
        }
        continue;
      }
      switch(this.#text[i]){
        case "{":
          yield {
            type: "BeginObject",
            position: i
          };
          break;
        case "}":
          yield {
            type: "EndObject",
            position: i
          };
          break;
        case "[":
          yield {
            type: "BeginArray",
            position: i
          };
          break;
        case "]":
          yield {
            type: "EndArray",
            position: i
          };
          break;
        case ":":
          yield {
            type: "NameSeparator",
            position: i
          };
          break;
        case ",":
          yield {
            type: "ValueSeparator",
            position: i
          };
          break;
        case '"':
          {
            const startIndex = i;
            // Need to handle consecutive backslashes correctly
            // '"\\""' => '"'
            // '"\\\\"' => '\\'
            // '"\\\\\\""' => '\\"'
            // '"\\\\\\\\"' => '\\\\'
            let shouldEscapeNext = false;
            i++;
            for(; i < this.#length; i++){
              if (this.#text[i] === '"' && !shouldEscapeNext) {
                break;
              }
              shouldEscapeNext = this.#text[i] === "\\" && !shouldEscapeNext;
            }
            yield {
              type: "String",
              sourceText: this.#text.substring(startIndex, i + 1),
              position: startIndex
            };
            break;
          }
        default:
          {
            const startIndex = i;
            for(; i < this.#length; i++){
              if (this.#numberEndToken.has(this.#text[i])) {
                break;
              }
            }
            i--;
            yield {
              type: "NullOrTrueOrFalseOrNumber",
              sourceText: this.#text.substring(startIndex, i + 1),
              position: startIndex
            };
          }
      }
    }
  }
  #parseJsonValue(value) {
    switch(value.type){
      case "BeginObject":
        return this.#parseObject();
      case "BeginArray":
        return this.#parseArray();
      case "NullOrTrueOrFalseOrNumber":
        return this.#parseNullOrTrueOrFalseOrNumber(value);
      case "String":
        return this.#parseString(value);
      default:
        throw new SyntaxError(buildErrorMessage(value));
    }
  }
  #parseObject() {
    const target = {};
    //   ┌─token1
    // { }
    //      ┌─────────────token1
    //      │   ┌─────────token2
    //      │   │   ┌─────token3
    //      │   │   │   ┌─token4
    //  { "key" : value }
    //      ┌───────────────token1
    //      │   ┌───────────token2
    //      │   │   ┌───────token3
    //      │   │   │   ┌───token4
    //      │   │   │   │ ┌─token1
    //  { "key" : value , }
    //      ┌─────────────────────────────token1
    //      │   ┌─────────────────────────token2
    //      │   │   ┌─────────────────────token3
    //      │   │   │   ┌─────────────────token4
    //      │   │   │   │   ┌─────────────token1
    //      │   │   │   │   │   ┌─────────token2
    //      │   │   │   │   │   │   ┌─────token3
    //      │   │   │   │   │   │   │   ┌─token4
    //  { "key" : value , "key" : value }
    for(let isFirst = true;; isFirst = false){
      const token1 = this.#getNext();
      if ((isFirst || this.#options.allowTrailingComma) && token1.type === "EndObject") {
        return target;
      }
      if (token1.type !== "String") {
        throw new SyntaxError(buildErrorMessage(token1));
      }
      const key = this.#parseString(token1);
      const token2 = this.#getNext();
      if (token2.type !== "NameSeparator") {
        throw new SyntaxError(buildErrorMessage(token2));
      }
      const token3 = this.#getNext();
      Object.defineProperty(target, key, {
        value: this.#parseJsonValue(token3),
        writable: true,
        enumerable: true,
        configurable: true
      });
      const token4 = this.#getNext();
      if (token4.type === "EndObject") {
        return target;
      }
      if (token4.type !== "ValueSeparator") {
        throw new SyntaxError(buildErrorMessage(token4));
      }
    }
  }
  #parseArray() {
    const target = [];
    //   ┌─token1
    // [ ]
    //      ┌─────────────token1
    //      │   ┌─────────token2
    //  [ value ]
    //      ┌───────token1
    //      │   ┌───token2
    //      │   │ ┌─token1
    //  [ value , ]
    //      ┌─────────────token1
    //      │   ┌─────────token2
    //      │   │   ┌─────token1
    //      │   │   │   ┌─token2
    //  [ value , value ]
    for(let isFirst = true;; isFirst = false){
      const token1 = this.#getNext();
      if ((isFirst || this.#options.allowTrailingComma) && token1.type === "EndArray") {
        return target;
      }
      target.push(this.#parseJsonValue(token1));
      const token2 = this.#getNext();
      if (token2.type === "EndArray") {
        return target;
      }
      if (token2.type !== "ValueSeparator") {
        throw new SyntaxError(buildErrorMessage(token2));
      }
    }
  }
  #parseString(value) {
    let parsed;
    try {
      // Use JSON.parse to handle `\u0000` etc. correctly.
      parsed = originalJSONParse(value.sourceText);
    } catch  {
      throw new SyntaxError(buildErrorMessage(value));
    }
    assert(typeof parsed === "string");
    return parsed;
  }
  #parseNullOrTrueOrFalseOrNumber(value) {
    if (value.sourceText === "null") {
      return null;
    }
    if (value.sourceText === "true") {
      return true;
    }
    if (value.sourceText === "false") {
      return false;
    }
    let parsed;
    try {
      // Use JSON.parse to handle `+100`, `Infinity` etc. correctly.
      parsed = originalJSONParse(value.sourceText);
    } catch  {
      throw new SyntaxError(buildErrorMessage(value));
    }
    assert(typeof parsed === "number");
    return parsed;
  }
}
function buildErrorMessage({ type, sourceText, position }) {
  let token = "";
  switch(type){
    case "BeginObject":
      token = "{";
      break;
    case "EndObject":
      token = "}";
      break;
    case "BeginArray":
      token = "[";
      break;
    case "EndArray":
      token = "]";
      break;
    case "NameSeparator":
      token = ":";
      break;
    case "ValueSeparator":
      token = ",";
      break;
    case "NullOrTrueOrFalseOrNumber":
    case "String":
      // Truncate the string so that it is within 30 lengths.
      token = 30 < sourceText.length ? `${sourceText.slice(0, 30)}...` : sourceText;
      break;
    default:
      throw new Error("unreachable");
  }
  return `Unexpected token ${token} in JSONC at position ${position}`;
}
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