import { Injectable, type PipeTransform } from '@nestjs/common';
import type { ZodType } from 'zod';

import type { ApiFieldErrors } from '@sport/types';

import { AppException } from '../errors/app.exception';

/**
 * Validates a request payload with a Zod schema from @sport/validation and
 * returns the *parsed* value (with coercions and defaults applied).
 *
 * Chosen over class-validator so that exactly one schema governs both the API
 * and the frontend forms. See ADR-0006.
 *
 *     @Post()
 *     create(@Body(new ZodValidationPipe(createProductSchema)) body: CreateProductInput) {}
 */
@Injectable()
export class ZodValidationPipe<TSchema extends ZodType> implements PipeTransform {
  constructor(private readonly schema: TSchema) {}

  transform(value: unknown): unknown {
    const result = this.schema.safeParse(value);

    if (!result.success) {
      throw AppException.validation(toFieldErrors(result.error.issues));
    }

    return result.data;
  }
}

interface ZodIssueLike {
  path: PropertyKey[];
  message: string;
}

/** `items.0.quantity` → ["Must be at least 1"] — directly consumable by forms. */
function toFieldErrors(issues: readonly ZodIssueLike[]): ApiFieldErrors {
  const fields: Record<string, string[]> = {};

  for (const issue of issues) {
    const key = issue.path.map(String).join('.') || '_';
    (fields[key] ??= []).push(issue.message);
  }

  return fields;
}