94 lines
3.9 KiB
JavaScript
94 lines
3.9 KiB
JavaScript
import { Document } from "@langchain/core/documents";
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import { getEnv } from "@langchain/core/utils/env";
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import { BaseDocumentLoader } from "../base.js";
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/**
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* A class that extends the `BaseDocumentLoader` class. It represents a
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* document loader that loads documents from a text file. The `load()`
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* method is implemented to read the text from the file or blob, parse it
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* using the `parse()` method, and create a `Document` instance for each
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* parsed page. The metadata includes the source of the text (file path or
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* blob) and, if there are multiple pages, the line number of each page.
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* @example
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* ```typescript
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* const loader = new TextLoader("src/document_loaders/example_data/example.txt");
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* const docs = await loader.load();
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* ```
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*/
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export class TextLoader extends BaseDocumentLoader {
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constructor(filePathOrBlob) {
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super();
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Object.defineProperty(this, "filePathOrBlob", {
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enumerable: true,
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configurable: true,
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writable: true,
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value: filePathOrBlob
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});
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}
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/**
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* A protected method that takes a `raw` string as a parameter and returns
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* a promise that resolves to an array containing the raw text as a single
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* element.
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* @param raw The raw text to be parsed.
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* @returns A promise that resolves to an array containing the raw text as a single element.
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*/
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async parse(raw) {
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return [raw];
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}
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/**
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* A method that loads the text file or blob and returns a promise that
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* resolves to an array of `Document` instances. It reads the text from
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* the file or blob using the `readFile` function from the
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* `node:fs/promises` module or the `text()` method of the blob. It then
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* parses the text using the `parse()` method and creates a `Document`
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* instance for each parsed page. The metadata includes the source of the
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* text (file path or blob) and, if there are multiple pages, the line
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* number of each page.
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* @returns A promise that resolves to an array of `Document` instances.
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*/
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async load() {
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let text;
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let metadata;
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if (typeof this.filePathOrBlob === "string") {
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const { readFile } = await TextLoader.imports();
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text = await readFile(this.filePathOrBlob, "utf8");
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metadata = { source: this.filePathOrBlob };
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}
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else {
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text = await this.filePathOrBlob.text();
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metadata = { source: "blob", blobType: this.filePathOrBlob.type };
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}
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const parsed = await this.parse(text);
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parsed.forEach((pageContent, i) => {
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if (typeof pageContent !== "string") {
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throw new Error(`Expected string, at position ${i} got ${typeof pageContent}`);
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}
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});
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return parsed.map((pageContent, i) => new Document({
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pageContent,
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metadata: parsed.length === 1
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? metadata
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: {
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...metadata,
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line: i + 1,
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},
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}));
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}
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/**
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* A static method that imports the `readFile` function from the
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* `node:fs/promises` module. It is used to dynamically import the
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* function when needed. If the import fails, it throws an error
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* indicating that the `fs/promises` module is not available in the
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* current environment.
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* @returns A promise that resolves to an object containing the `readFile` function from the `node:fs/promises` module.
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*/
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static async imports() {
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try {
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const { readFile } = await import("node:fs/promises");
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return { readFile };
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}
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catch (e) {
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console.error(e);
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throw new Error(`Failed to load fs/promises. TextLoader available only on environment 'node'. It appears you are running environment '${getEnv()}'. See https://<link to docs> for alternatives.`);
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}
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}
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}
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