import type { JSONValue } from "ai";

export type ToolErrorOutput =
    | { type: "error-text"; value: string }
    | { type: "error-json"; value: JSONValue };

export const serializeToolError = (error: unknown): string => {
    if (error instanceof Error) {
        return error.message;
    }
    if (typeof error === "string") {
        return error;
    }
    try {
        return JSON.stringify(error) ?? "An unknown tool error occurred";
    } catch {
        return "The tool returned an error that could not be serialized";
    }
};

export const readStoredToolError = (
    error: Readonly<{ type: string; value: string }> | null | undefined,
): ToolErrorOutput => {
    if (!error) {
        return { type: "error-text", value: "An unknown tool error occurred" };
    }
    if (error.type === "json") {
        try {
            const value: JSONValue = JSON.parse(error.value);
            return { type: "error-json", value };
        } catch {
            // Older tool failures were saved as JSON even when their value was plain text.
        }
    }
    return { type: "error-text", value: error.value };
};