MetadataExtractor.ts•3.36 kB
/**
* MetadataExtractor - Extract and validate frontmatter metadata
* Converts frontmatter to MarkdownMetadata entries for storage
*/
import { nanoid } from "nanoid";
import type {
Frontmatter,
MarkdownMetadata,
} from "../markdown/types.js";
/**
* MetadataExtractor class
*/
export class MetadataExtractor {
/**
* Convert frontmatter to metadata entries
*/
extractMetadata(
fileId: string,
frontmatter: Frontmatter
): MarkdownMetadata[] {
const metadata: MarkdownMetadata[] = [];
for (const [key, value] of Object.entries(frontmatter)) {
metadata.push({
id: nanoid(),
file_id: fileId,
key,
value: this.serializeValue(value),
});
}
return metadata;
}
/**
* Serialize metadata value to string
*/
private serializeValue(value: unknown): string {
if (Array.isArray(value)) {
return JSON.stringify(value);
}
if (typeof value === "object" && value !== null) {
return JSON.stringify(value);
}
return String(value);
}
/**
* Deserialize metadata value from string
*/
deserializeValue(value: string): unknown {
// Try to parse as JSON first
try {
return JSON.parse(value);
} catch {
// If not JSON, return as string
return value;
}
}
/**
* Get metadata by key
*/
getMetadataValue(
metadata: MarkdownMetadata[],
key: string
): unknown | null {
const entry = metadata.find((m) => m.key === key);
if (!entry) {
return null;
}
return this.deserializeValue(entry.value);
}
/**
* Validate required metadata fields
*/
validateMetadata(
frontmatter: Frontmatter,
requiredFields: string[]
): { valid: boolean; missing: string[] } {
const missing: string[] = [];
for (const field of requiredFields) {
if (!(field in frontmatter) || frontmatter[field] === undefined || frontmatter[field] === null) {
missing.push(field);
}
}
return {
valid: missing.length === 0,
missing,
};
}
/**
* Extract common metadata fields
*/
extractCommonFields(frontmatter: Frontmatter): {
title?: string;
author?: string;
date?: string;
tags?: string[];
draft?: boolean;
description?: string;
} {
return {
title: this.getString(frontmatter.title),
author: this.getString(frontmatter.author),
date: this.getString(frontmatter.date),
tags: this.getStringArray(frontmatter.tags),
draft: this.getBoolean(frontmatter.draft),
description: this.getString(frontmatter.description),
};
}
/**
* Get string value from unknown type
*/
private getString(value: unknown): string | undefined {
if (typeof value === "string") {
return value;
}
return undefined;
}
/**
* Get string array value from unknown type
*/
private getStringArray(value: unknown): string[] | undefined {
if (Array.isArray(value)) {
const strings = value.filter((v) => typeof v === "string") as string[];
return strings.length > 0 ? strings : undefined;
}
return undefined;
}
/**
* Get boolean value from unknown type
*/
private getBoolean(value: unknown): boolean | undefined {
if (typeof value === "boolean") {
return value;
}
return undefined;
}
}