import type { LocaleDetector } from "../detector.types.js";
import { acceptLanguageDetector } from "../detectors/accept-language/accept-language.js";
import { cloudflareIpGeoDetector } from "../detectors/cloudflare-ip-geo/cloudflare-ip-geo.js";
import { cookieDetector } from "../detectors/cookie/cookie.js";
import { fallbackDetector } from "../detectors/fallback/fallback.js";
import { htmlLangDetector } from "../detectors/html-lang/html-lang.js";
import { localStorageDetector } from "../detectors/local-storage/local-storage.js";
import { navigatorDetector } from "../detectors/navigator/navigator.js";
import { querystringDetector } from "../detectors/querystring/querystring.js";
import { userPreferenceDetector } from "../detectors/user-preference/user-preference.js";
import type { DefaultDetectorChainOptions } from "./default-chain.types.js";

/**
 * Build the canonical 9-entry (or 8-entry) detector chain consumed
 * by `<TranslationProvider>` and `useLocaleDetection`.
 *
 * Order (per spec "Default chain order"):
 *
 * 1. `querystring`
 * 2. `userPreference` — only when `opts.userPreferenceEndpoint` is set
 * 3. `cookie`
 * 4. `localStorage`
 * 5. `htmlLang`
 * 6. `acceptLanguage`
 * 7. `navigator`
 * 8. `cloudflareIpGeo`
 * 9. `fallback`
 *
 * The chain is returned as a fresh array on every call so callers
 * can mutate or filter the result without affecting subsequent
 * invocations.
 */
export function defaultDetectorChain(
    options: DefaultDetectorChainOptions
): LocaleDetector[] {
    const detectors: LocaleDetector[] = [querystringDetector()];
    if (
        typeof options.userPreferenceEndpoint === "string" &&
        options.userPreferenceEndpoint !== ""
    ) {
        detectors.push(
            userPreferenceDetector({
                endpoint: options.userPreferenceEndpoint,
            })
        );
    }
    detectors.push(cookieDetector());
    detectors.push(localStorageDetector());
    detectors.push(htmlLangDetector());
    detectors.push(acceptLanguageDetector());
    detectors.push(navigatorDetector());
    detectors.push(cloudflareIpGeoDetector());
    detectors.push(fallbackDetector(options.fallback));
    return detectors;
}