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// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.import { toTransformStream } from "../streams/to_transform_stream.ts";import type { JsonValue, ParseStreamOptions } from "./common.ts";import { parse } from "./_common.ts";
function isBlankChar(char: string | undefined) {  return char !== undefined && [" ", "\t", "\r", "\n"].includes(char);}
const primitives = new Map(  (["null", "true", "false"] as const).map((v) => [v[0], v]),);
/** * Stream to parse {@link https://en.wikipedia.org/wiki/JSON_streaming#Concatenated_JSON|Concatenated JSON}. * * @example * ```ts * import { ConcatenatedJsonParseStream } from "https://deno.land/std@$STD_VERSION/json/concatenated_json_parse_stream.ts"; * * const url = "https://deno.land/std@$STD_VERSION/json/testdata/test.concatenated-json"; * const { body } = await fetch(url); * * const readable = body! *   .pipeThrough(new TextDecoderStream()) // convert Uint8Array to string *   .pipeThrough(new ConcatenatedJsonParseStream()); // parse Concatenated JSON * * for await (const data of readable) { *   console.log(data); * } * ``` */export class ConcatenatedJsonParseStream  implements TransformStream<string, JsonValue> {  /** A writable stream of byte data. */  readonly writable: WritableStream<string>;  /** A readable stream of byte data. */  readonly readable: ReadableStream<JsonValue>;
  /** Constructs a new instance. */  constructor({ writableStrategy, readableStrategy }: ParseStreamOptions = {}) {    const { writable, readable } = toTransformStream(      this.#concatenatedJSONIterator,      writableStrategy,      readableStrategy,    );    this.writable = writable;    this.readable = readable;  }
  async *#concatenatedJSONIterator(src: AsyncIterable<string>) {    // Counts the number of '{', '}', '[', ']', and when the nesting level reaches 0, concatenates and returns the string.    let targetString = "";    let hasValue = false;    let nestCount = 0;    let readingString = false;    let escapeNext = false;    let readingPrimitive: false | "null" | "true" | "false" = false;    let positionInPrimitive = 0;    for await (const string of src) {      let sliceStart = 0;      for (let i = 0; i < string.length; i++) {        const char = string[i];
        // We're reading a primitive at the top level        if (readingPrimitive) {          if (char === readingPrimitive[positionInPrimitive]) {            positionInPrimitive++;
            // Emit the primitive when done reading            if (positionInPrimitive === readingPrimitive.length) {              yield parse(targetString + string.slice(sliceStart, i + 1));              hasValue = false;              readingPrimitive = false;              positionInPrimitive = 0;              targetString = "";              sliceStart = i + 1;            }          } else {            // If the primitive is malformed, keep reading, maybe the next characters can be useful in the syntax error.            readingPrimitive = false;            positionInPrimitive = 0;          }          continue;        }
        if (readingString) {          if (char === '"' && !escapeNext) {            readingString = false;
            // When the nesting level is 0, it returns a string when '"' comes.            if (nestCount === 0 && hasValue) {              yield parse(targetString + string.slice(sliceStart, i + 1));              hasValue = false;              targetString = "";              sliceStart = i + 1;            }          }          escapeNext = !escapeNext && char === "\\";          continue;        }
        // Parses number with a nesting level of 0.        // example: '0["foo"]' => 0, ["foo"]        // example: '3.14{"foo": "bar"}' => 3.14, {foo: "bar"}        if (          hasValue && nestCount === 0 &&          (char === "{" || char === "[" || char === '"' || char === " " ||            char === "n" || char === "t" || char === "f")        ) {          yield parse(targetString + string.slice(sliceStart, i));          hasValue = false;          readingString = false;          targetString = "";          sliceStart = i;          i--;          continue;        }
        switch (char) {          case '"':            readingString = true;            escapeNext = false;            break;          case "{":          case "[":            nestCount++;            break;          case "}":          case "]":            nestCount--;            break;        }
        if (nestCount === 0 && primitives.has(char)) {          // The first letter of a primitive at top level was found          readingPrimitive = primitives.get(char)!;          positionInPrimitive = 1;        }
        // parse object or array        if (          hasValue && nestCount === 0 &&          (char === "}" || char === "]")        ) {          yield parse(targetString + string.slice(sliceStart, i + 1));          hasValue = false;          targetString = "";          sliceStart = i + 1;          continue;        }
        if (!hasValue && !isBlankChar(char)) {          // We want to ignore the character string with only blank, so if there is a character other than blank, record it.          hasValue = true;        }      }      targetString += string.slice(sliceStart);    }    if (hasValue) {      yield parse(targetString);    }  }}