/**
 * Helper for spinning up a real `@suaveplan/i18n` `I18nInstance` plus
 * its bundled translations under a fresh `I18nInstance` per test. No
 * mocks — every consumer of an i18n instance in the test suite uses
 * this helper so the wiring matches production exactly.
 *
 * The bundled `react-ui` JSON files ship FLAT keys
 * (`"react-ui.button.iconOnly.fallback": "Action"`). The catalog's `t()`
 * walks dot-separated paths, so we nest the flat bag into a deep
 * record (`{ react-ui: { button: { iconOnly: { fallback: "Action" } } } }`)
 * before merging into the catalog. This mirrors the chassis
 * `ReactUiProvider`'s `nestFlatKeys` step exactly so production and
 * tests resolve keys via the same pathway.
 */

import { createI18n, type I18nInstance } from "@suaveplan/i18n/plugin";
import { reactUiBundles } from "../../src/locales/index.js";

export interface CreateTestI18nOptions {
    readonly locale?: "en-GB" | "zh-CN" | "ar-AE" | "cy-GB" | "ru-RU";
}

type NestedTranslationRecord = {
    [key: string]: string | NestedTranslationRecord;
};

function nestFlatKeys(bag: Record<string, string>): NestedTranslationRecord {
    const out: NestedTranslationRecord = {};
    for (const [flatKey, value] of Object.entries(bag)) {
        const parts = flatKey.split(".");
        let cursor: NestedTranslationRecord = out;
        for (let i = 0; i < parts.length - 1; i += 1) {
            const seg = parts[i] as string;
            const existing = cursor[seg];
            if (
                typeof existing !== "object" ||
                existing === null ||
                Array.isArray(existing)
            ) {
                cursor[seg] = {};
            }
            cursor = cursor[seg] as NestedTranslationRecord;
        }
        cursor[parts[parts.length - 1] as string] = value;
    }
    return out;
}

/**
 * Build an `I18nInstance` seeded with the chassis locale bundles.
 * Useful for tests that need a Provider but want deterministic
 * translations.
 */
export async function createTestI18n(
    options: CreateTestI18nOptions = {}
): Promise<I18nInstance> {
    const locale = options.locale ?? "en-GB";
    const i18n = createI18n({
        defaultLocale: locale,
        fallbackLocale: "en-GB",
    });
    for (const code of ["en-GB", "zh-CN", "ar-AE", "cy-GB", "ru-RU"] as const) {
        const bundle = await reactUiBundles[code]();
        const nested = nestFlatKeys(bundle as Record<string, string>);
        i18n.catalog.mergeMessages(code, nested as Record<string, unknown>);
    }
    return i18n;
}