import { parse as partialParse } from "partial-json";
const VALID_JSON_ESCAPES = new Set(['"', "\\", "/", "b", "f", "n", "r", "t", "u"]);
function isControlCharacter(char: string): boolean {
const codePoint = char.codePointAt(0);
return codePoint !== undefined && codePoint >= 0x00 && codePoint <= 0x1f;
}
function escapeControlCharacter(char: string): string {
switch (char) {
case "\b":
return "\\b";
case "\f":
return "\\f";
case "\n":
return "\\n";
case "\r":
return "\\r";
case "\t":
return "\\t";
default:
return `\\u${char.codePointAt(0)?.toString(16).padStart(4, "0") ?? "0000"}`;
}
}
/**
* Repairs malformed JSON string literals by:
* - escaping raw control characters inside strings
* - doubling backslashes before invalid escape characters
*/
export function repairJson(json: string): string {
let repaired = "";
let inString = false;
for (let index = 0; index < json.length; index++) {
const char = json[index];
if (!inString) {
repaired += char;
if (char === '"') {
inString = true;
}
continue;
}
if (char === '"') {
repaired += char;
inString = false;
continue;
}
if (char === "\\") {
const nextChar = json[index + 1];
if (nextChar === undefined) {
repaired += "\\\\";
continue;
}
if (nextChar === "u") {
const unicodeDigits = json.slice(index + 2, index + 6);
if (/^[0-9a-fA-F]{4}$/.test(unicodeDigits)) {
repaired += `\\u${unicodeDigits}`;
index += 5;
continue;
}
}
if (VALID_JSON_ESCAPES.has(nextChar)) {
repaired += `\\${nextChar}`;
index += 1;
continue;
}
repaired += "\\\\";
continue;
}
repaired += isControlCharacter(char) ? escapeControlCharacter(char) : char;
}
return repaired;
}
export function parseJsonWithRepair<T>(json: string): T {
try {
return JSON.parse(json) as T;
} catch (error) {
const repairedJson = repairJson(json);
if (repairedJson !== json) {
return JSON.parse(repairedJson) as T;
}
throw error;
}
}
/**
* Attempts to parse potentially incomplete JSON during streaming.
* Always returns a valid object, even if the JSON is incomplete.
*
* @param partialJson The partial JSON string from streaming
* @returns Parsed object or empty object if parsing fails
*/
export function parseStreamingJson<T = Record<string, unknown>>(partialJson: string | undefined): T {
if (!partialJson || partialJson.trim() === "") {
return {} as T;
}
try {
return parseJsonWithRepair<T>(partialJson);
} catch {
try {
const result = partialParse(partialJson);
return (result ?? {}) as T;
} catch {
try {
const result = partialParse(repairJson(partialJson));
return (result ?? {}) as T;
} catch {
return {} as T;
}
}
}
}