import type { Field } from "payload";

function slugify(value: string): string {
  return value
    .toLowerCase()
    .trim()
    .replace(/ä/g, "ae")
    .replace(/ö/g, "oe")
    .replace(/ü/g, "ue")
    .replace(/ß/g, "ss")
    .replace(/[^a-z0-9]+/g, "-")
    .replace(/^-+|-+$/g, "");
}

/**
 * A "Slug" field that auto-fills itself from `sourceField` (usually the
 * title) whenever left empty, so the admin never has to think about URLs.
 */
export function slugField(sourceField = "title"): Field {
  return {
    name: "slug",
    type: "text",
    label: "Slug (URL)",
    unique: true,
    index: true,
    admin: {
      position: "sidebar",
      description: "Wird automatisch aus dem Titel erzeugt, kann aber angepasst werden.",
    },
    hooks: {
      beforeValidate: [
        ({ value, data }) => {
          if (value) return slugify(String(value));
          const source = data?.[sourceField];
          return typeof source === "string" ? slugify(source) : value;
        },
      ],
    },
  };
}