import { existsSync } from 'node:fs';
import { join } from 'node:path';
import nunjucks from 'nunjucks';
/**
* Renders a named Nunjucks template with raw JSON text.
* Returns the rendered string, or null if no template exists or the text is not valid JSON.
*/
type TemplateRenderFn = (toolName: string, rawText: string) => string | null;
/**
* Creates a template renderer function bound to a views directory.
* Returns a function that checks for a matching template, parses the JSON text,
* and renders it — or returns null if no template exists or parsing fails.
*/
export function createTemplateRenderer(viewsDir: string): TemplateRenderFn {
const env = nunjucks.configure(viewsDir, {
autoescape: false,
noCache: false,
throwOnUndefined: false,
});
// Render empty string instead of "undefined" for missing values
env.addFilter('default', (val: unknown, defaultVal: string = '') =>
val === undefined || val === null ? defaultVal : val
);
return (toolName: string, rawText: string): string | null => {
const templatePath = join(viewsDir, `${toolName}.njk`);
if (!existsSync(templatePath)) return null;
try {
const data = JSON.parse(rawText);
return env.render(`${toolName}.njk`, data as Record<string, unknown>);
} catch {
return null;
}
};
}
