import { BadRequestException, Injectable, PipeTransform } from '@nestjs/common';
import type { ZodTypeAny, z } from 'zod';

/**
 * Validates request bodies against a shared Zod schema. Failures become a
 * 400 with field-level details: { field: [i18nKey, …] } — the web client
 * renders the keys next to the matching inputs.
 */
@Injectable()
export class ZodValidationPipe<Schema extends ZodTypeAny> implements PipeTransform {
  constructor(private readonly schema: Schema) {}

  transform(value: unknown): z.infer<Schema> {
    const result = this.schema.safeParse(value);
    if (result.success) return result.data;

    const details: Record<string, string[]> = {};
    for (const issue of result.error.issues) {
      const field = issue.path.join('.') || '_';
      (details[field] ??= []).push(issue.message);
    }
    throw new BadRequestException({ code: 'bad_request', details });
  }
}