export interface ActivationItem {
    name: string;
    descriptor: string;
}

/**
 * Contains information about the error which occurred during service activation.
 * 
 * Information about activation error includes original exception which has
 * occurred, the name of the service being activated and activation stack of
 * services.
 */
export class ActivationError {
    /**
     * Stack of services being activating
     */
    readonly activationStack: ActivationItem[];

    /**
     * The exception which occurred during activation of the service
     */
    readonly innerException: unknown;

    /**
     * Error message
     */
    readonly message: string;

    constructor(message: string, activationStack: ActivationItem[], innerException?: unknown) {
        this.message = message;
        this.activationStack = activationStack;
        this.innerException = innerException;
    }

    toString() {
        const parts = [this.message];

        if (this.activationStack && this.activationStack.length) {
            const [{ name, descriptor }, ...before] = this.activationStack;

            parts.push(`when activating: ${name}, ${descriptor}`);

            if (before) {
                parts.push("at");
                parts.push.apply(
                    null,
                    before.map(({ name: name, descriptor: service }) => `    ${name} ${service}`)
                );
            }
        }

        if (this.innerException)
            parts.push(`caused by: ${String(this.innerException)}`);

        return parts.join("\n");
    }
}