/**
 * CFG-30 — the single place that decides whether Gaunt Sloth emits ANSI colour.
 *
 * Everything this decision depends on arrives as an argument: no `process.env`, no `stdout`, no
 * config merge. That keeps the ladder unit-testable rung by rung without touching process globals,
 * and keeps the one mutation site ({@link setUseColour}, called from `mergeConfig`) unchanged.
 */
/** Everything the colour decision depends on. See {@link resolveUseColour}. */
export interface UseColourInput {
    /**
     * Raw `FORCE_COLOR` environment value; `undefined` when the variable is not set at all.
     * The empty string is a SET value (`FORCE_COLOR=` on the command line) and means colour on.
     */
    forceColor?: string;
    /** Raw `NO_COLOR` environment value; `undefined` when the variable is not set at all. */
    noColor?: string;
    /**
     * `useColour` as the user actually wrote it — read from the RAW config, BEFORE `DEFAULT_CONFIG`
     * is merged in. `undefined` means the user set nothing, which is what rung 3 tests for; after the
     * default merge an explicit `true` is indistinguishable from the default `true`, so this value
     * must be captured pre-merge or the rung collapses.
     */
    explicitUseColour?: boolean;
    /** Whether stdout is a terminal. Rung 4's auto-detection; stdout, not stdin. */
    stdoutIsTTY: boolean;
}
/**
 * Resolve the effective colour setting from the four-rung precedence ladder, highest wins:
 *
 *   1. `FORCE_COLOR` is set — `"0"` or `"false"` turn colour OFF, ANY other value (including the
 *      empty string) turns it ON. This rung outranks everything below it, `NO_COLOR` included.
 *   2. `NO_COLOR` is set and non-empty — colour OFF (the no-color.org convention: the variable's
 *      presence is the signal, its value is not, but an empty value does not count as set).
 *   3. `useColour` was set explicitly in config — use it verbatim.
 *   4. Otherwise auto-detect — colour ON when stdout is a terminal, OFF when it is piped or
 *      redirected, so captured output stays clean without any configuration.
 */
export declare function resolveUseColour(input: UseColourInput): boolean;