@langchain/core
Version:
Core LangChain.js abstractions and schemas
211 lines (209 loc) • 6.74 kB
JavaScript
//#region src/utils/json.ts
function parseJsonMarkdown(s, parser = parsePartialJson) {
s = s.trim();
const firstFenceIndex = s.indexOf("```");
if (firstFenceIndex === -1) return parser(s);
let contentAfterFence = s.substring(firstFenceIndex + 3);
if (contentAfterFence.startsWith("json\n")) contentAfterFence = contentAfterFence.substring(5);
else if (contentAfterFence.startsWith("json")) contentAfterFence = contentAfterFence.substring(4);
else if (contentAfterFence.startsWith("\n")) contentAfterFence = contentAfterFence.substring(1);
const closingFenceIndex = contentAfterFence.indexOf("```");
let finalContent = contentAfterFence;
if (closingFenceIndex !== -1) finalContent = contentAfterFence.substring(0, closingFenceIndex);
return parser(finalContent.trim());
}
/**
* Recursive descent partial JSON parser.
* @param s - The string to parse.
* @returns The parsed value.
* @throws Error if the input is a malformed JSON string.
*/
function strictParsePartialJson(s) {
try {
return JSON.parse(s);
} catch {}
const buffer = s.trim();
if (buffer.length === 0) throw new Error("Unexpected end of JSON input");
let pos = 0;
function skipWhitespace() {
while (pos < buffer.length && /\s/.test(buffer[pos])) pos += 1;
}
function parseString() {
if (buffer[pos] !== "\"") throw new Error(`Expected '"' at position ${pos}, got '${buffer[pos]}'`);
pos += 1;
let result = "";
let escaped = false;
while (pos < buffer.length) {
const char = buffer[pos];
if (escaped) {
if (char === "n") result += "\n";
else if (char === "t") result += " ";
else if (char === "r") result += "\r";
else if (char === "\\") result += "\\";
else if (char === "\"") result += "\"";
else if (char === "b") result += "\b";
else if (char === "f") result += "\f";
else if (char === "/") result += "/";
else if (char === "u") {
const hex = buffer.substring(pos + 1, pos + 5);
if (/^[0-9A-Fa-f]{0,4}$/.test(hex)) {
if (hex.length === 4) result += String.fromCharCode(Number.parseInt(hex, 16));
else result += `u${hex}`;
pos += hex.length;
} else throw new Error(`Invalid unicode escape sequence '\\u${hex}' at position ${pos}`);
} else throw new Error(`Invalid escape sequence '\\${char}' at position ${pos}`);
escaped = false;
} else if (char === "\\") escaped = true;
else if (char === "\"") {
pos += 1;
return result;
} else result += char;
pos += 1;
}
if (escaped) result += "\\";
return result;
}
function parseNumber() {
const start = pos;
let numStr = "";
if (buffer[pos] === "-") {
numStr += "-";
pos += 1;
}
if (pos < buffer.length && buffer[pos] === "0") {
numStr += "0";
pos += 1;
if (buffer[pos] >= "0" && buffer[pos] <= "9") throw new Error(`Invalid number at position ${start}`);
}
if (pos < buffer.length && buffer[pos] >= "1" && buffer[pos] <= "9") while (pos < buffer.length && buffer[pos] >= "0" && buffer[pos] <= "9") {
numStr += buffer[pos];
pos += 1;
}
if (pos < buffer.length && buffer[pos] === ".") {
numStr += ".";
pos += 1;
while (pos < buffer.length && buffer[pos] >= "0" && buffer[pos] <= "9") {
numStr += buffer[pos];
pos += 1;
}
}
if (pos < buffer.length && (buffer[pos] === "e" || buffer[pos] === "E")) {
numStr += buffer[pos];
pos += 1;
if (pos < buffer.length && (buffer[pos] === "+" || buffer[pos] === "-")) {
numStr += buffer[pos];
pos += 1;
}
while (pos < buffer.length && buffer[pos] >= "0" && buffer[pos] <= "9") {
numStr += buffer[pos];
pos += 1;
}
}
if (numStr === "-") return -0;
const num = Number.parseFloat(numStr);
if (Number.isNaN(num)) {
pos = start;
throw new Error(`Invalid number '${numStr}' at position ${start}`);
}
return num;
}
function parseValue() {
skipWhitespace();
if (pos >= buffer.length) throw new Error(`Unexpected end of input at position ${pos}`);
const char = buffer[pos];
if (char === "{") return parseObject();
if (char === "[") return parseArray();
if (char === "\"") return parseString();
if ("null".startsWith(buffer.substring(pos, pos + 4))) {
pos += Math.min(4, buffer.length - pos);
return null;
}
if ("true".startsWith(buffer.substring(pos, pos + 4))) {
pos += Math.min(4, buffer.length - pos);
return true;
}
if ("false".startsWith(buffer.substring(pos, pos + 5))) {
pos += Math.min(5, buffer.length - pos);
return false;
}
if (char === "-" || char >= "0" && char <= "9") return parseNumber();
throw new Error(`Unexpected character '${char}' at position ${pos}`);
}
function parseArray() {
if (buffer[pos] !== "[") throw new Error(`Expected '[' at position ${pos}, got '${buffer[pos]}'`);
const arr = [];
pos += 1;
skipWhitespace();
if (pos >= buffer.length) return arr;
if (buffer[pos] === "]") {
pos += 1;
return arr;
}
while (pos < buffer.length) {
skipWhitespace();
if (pos >= buffer.length) return arr;
arr.push(parseValue());
skipWhitespace();
if (pos >= buffer.length) return arr;
if (buffer[pos] === "]") {
pos += 1;
return arr;
} else if (buffer[pos] === ",") {
pos += 1;
continue;
}
throw new Error(`Expected ',' or ']' at position ${pos}, got '${buffer[pos]}'`);
}
return arr;
}
function parseObject() {
if (buffer[pos] !== "{") throw new Error(`Expected '{' at position ${pos}, got '${buffer[pos]}'`);
const obj = {};
pos += 1;
skipWhitespace();
if (pos >= buffer.length) return obj;
if (buffer[pos] === "}") {
pos += 1;
return obj;
}
while (pos < buffer.length) {
skipWhitespace();
if (pos >= buffer.length) return obj;
const key = parseString();
skipWhitespace();
if (pos >= buffer.length) return obj;
if (buffer[pos] !== ":") throw new Error(`Expected ':' at position ${pos}, got '${buffer[pos]}'`);
pos += 1;
skipWhitespace();
if (pos >= buffer.length) return obj;
obj[key] = parseValue();
skipWhitespace();
if (pos >= buffer.length) return obj;
if (buffer[pos] === "}") {
pos += 1;
return obj;
} else if (buffer[pos] === ",") {
pos += 1;
continue;
}
throw new Error(`Expected ',' or '}' at position ${pos}, got '${buffer[pos]}'`);
}
return obj;
}
const value = parseValue();
skipWhitespace();
if (pos < buffer.length) throw new Error(`Unexpected character '${buffer[pos]}' at position ${pos}`);
return value;
}
function parsePartialJson(s) {
try {
if (typeof s === "undefined") return null;
return strictParsePartialJson(s);
} catch {
return null;
}
}
//#endregion
exports.parseJsonMarkdown = parseJsonMarkdown;
exports.parsePartialJson = parsePartialJson;
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