import { type Address, getAddressEncoder, getProgramDerivedAddress } from '@solana/kit';

/** Maximum `period_hours` supported by the subscriptions program. */
const MAX_PERIOD_HOURS = 8760;

/**
 * Map the shared subscription period to the subscriptions program's
 * `period_hours` value. The Solana profile only supports `day` and `week`;
 * `month` cannot be represented exactly because the on-chain program uses
 * fixed elapsed seconds.
 *
 * @throws If the inputs cannot be represented on-chain.
 */
export function mapSubscriptionPeriodToHours(periodUnit: 'day' | 'week', periodCount: number): number {
    if (!Number.isInteger(periodCount) || periodCount <= 0) {
        throw new Error(`periodCount must be a positive integer, got ${periodCount}`);
    }
    if (periodUnit === 'day') {
        if (periodCount > 365) {
            throw new Error(`periodCount=${periodCount} for periodUnit="day" exceeds 365`);
        }
        return periodCount * 24;
    }
    if (periodUnit === 'week') {
        if (periodCount > 52) {
            throw new Error(`periodCount=${periodCount} for periodUnit="week" exceeds 52`);
        }
        return periodCount * 168;
    }
    // The Zod schema rejects `month` at the framework boundary; this branch
    // exists for defense-in-depth and as a clear error for direct callers.
    throw new Error(`Solana subscription profile rejects periodUnit="${String(periodUnit)}"`);
}

/** Verify the computed `period_hours` is within the on-chain program's [1, 8760] bound. */
export function assertPeriodHoursInRange(periodHours: number): void {
    if (!Number.isInteger(periodHours) || periodHours < 1 || periodHours > MAX_PERIOD_HOURS) {
        throw new Error(`period_hours ${periodHours} out of [1, ${MAX_PERIOD_HOURS}] range`);
    }
}

/**
 * Derive the `SubscriptionAuthority` PDA for a given subscriber and mint.
 * Seeds: `["SubscriptionAuthority", subscriber, mint]`.
 */
export async function deriveSubscriptionAuthorityPda(params: {
    mint: Address;
    programId: Address;
    subscriber: Address;
}): Promise<Address> {
    const encoder = getAddressEncoder();
    const [pda] = await getProgramDerivedAddress({
        programAddress: params.programId,
        seeds: [
            new TextEncoder().encode('SubscriptionAuthority'),
            encoder.encode(params.subscriber),
            encoder.encode(params.mint),
        ],
    });
    return pda;
}

/**
 * Derive the `SubscriptionDelegation` PDA for a given plan and subscriber.
 * Seeds: `["subscription", plan_pda, subscriber]`.
 */
export async function deriveSubscriptionPda(params: {
    planPda: Address;
    programId: Address;
    subscriber: Address;
}): Promise<Address> {
    const encoder = getAddressEncoder();
    const [pda] = await getProgramDerivedAddress({
        programAddress: params.programId,
        seeds: [
            new TextEncoder().encode('subscription'),
            encoder.encode(params.planPda),
            encoder.encode(params.subscriber),
        ],
    });
    return pda;
}