import {NextRequest} from "next/server";

function decodeB64Json(b64: string) {
    try {
        const s = b64.replace(/-/g, "+").replace(/_/g, "/");
        const pad = s.length % 4 === 2 ? "=="
            : s.length % 4 === 3 ? "="
                : "";
        const json = Buffer.from(s + pad, "base64").toString("utf8");
        return JSON.parse(json);
    } catch {
        return null;
    }
}

export function resolveTenantFromRequest(req: NextRequest): string {
    const ui = req.cookies.get("user_info")?.value;
    if (ui) {
        try {
            const parsed = JSON.parse(Buffer.from(ui, "base64").toString("utf8"));
            if (parsed?.tenantKey && typeof parsed.tenantKey === "string") return parsed.tenantKey;
        } catch {
        }
    }

    const access = req.cookies.get("access_token")?.value;
    if (access && access.split(".").length >= 2) {
        const payloadB64 = access.split(".")[1];
        const payload = decodeB64Json(payloadB64);
        const tk = payload?.tenant_key ?? payload?.tenantKey;
        if (typeof tk === "string" && tk) return tk;
    }

    const host = req.headers.get("host") ?? "";
    const parts = host.split(".");
    if (parts.length >= 3) return parts[0];

    if (process.env.DEFAULT_TENANT_KEY) return process.env.DEFAULT_TENANT_KEY;

    return "default";
}