const {
    PermissionFlagsBits,
    MessageFlags
} = require(
    "discord.js"
);


/*
 * ============================================================
 * CONFIG
 * ============================================================
 *
 * .env:
 *
 * BOT_AUTHOR_ID=123456789012345678
 *
 * Do not hard-code the author ID into commands.
 */

function getBotAuthorId() {
    return (
        process.env.BOT_AUTHOR_ID
        ??
        null
    );
}


/*
 * ============================================================
 * BOT AUTHOR
 * ============================================================
 */

function isBotAuthor(
    userId
) {
    const authorId =
        getBotAuthorId();


    if (
        !authorId
        ||
        !userId
    ) {
        return false;
    }


    return (
        String(
            userId
        )
        ===
        String(
            authorId
        )
    );
}


/*
 * ============================================================
 * GUILD ADMINISTRATOR
 * ============================================================
 */

function isAdministrator(
    interaction
) {
    if (
        !interaction
            ?.memberPermissions
    ) {
        return false;
    }


    return interaction
        .memberPermissions
        .has(
            PermissionFlagsBits.Administrator
        );
}


/*
 * ============================================================
 * ADMIN COMMAND ACCESS
 * ============================================================
 *
 * Access is granted when:
 *
 * - the user is the configured bot author
 * OR
 * - the user has Discord Administrator
 *
 * Bot author is checked first so the owner can use admin
 * utilities even without Discord Administrator in the guild.
 */

function canUseAdminCommands(
    interaction
) {
    if (
        !interaction
            ?.user
            ?.id
    ) {
        return false;
    }


    return (
        isBotAuthor(
            interaction.user.id
        )
        ||
        isAdministrator(
            interaction
        )
    );
}


/*
 * ============================================================
 * STANDARD ACCESS DENIAL
 * ============================================================
 *
 * Administrative access failures are intentionally ephemeral.
 */

async function denyAdminAccess(
    interaction,
    message =
        "You don't have permission to use this command."
) {
    const payload = {
        content:
            message,

        flags:
            MessageFlags.Ephemeral
    };


    if (
        interaction.replied
        ||
        interaction.deferred
    ) {
        return interaction.followUp(
            payload
        );
    }


    return interaction.reply(
        payload
    );
}


/*
 * ============================================================
 * REQUIRE ADMIN ACCESS
 * ============================================================
 *
 * Convenience helper:
 *
 * if (!await requireAdminAccess(interaction)) {
 *     return;
 * }
 */

async function requireAdminAccess(
    interaction
) {
    if (
        canUseAdminCommands(
            interaction
        )
    ) {
        return true;
    }


    await denyAdminAccess(
        interaction
    );


    return false;
}


/*
 * ============================================================
 * EXPORTS
 * ============================================================
 */

module.exports = {
    getBotAuthorId,

    isBotAuthor,
    isAdministrator,

    canUseAdminCommands,
    requireAdminAccess,

    denyAdminAccess
};