feat: build out initial prototype (#1)

### Explanation

_No response_

### Issue

_No response_

### Attestations

- [ ] I have read and agree to the [Code of Conduct](https://docs.nhcarrigan.com/community/coc/)
- [ ] I have read and agree to the [Community Guidelines](https://docs.nhcarrigan.com/community/guide/).
- [ ] My contribution complies with the [Contributor Covenant](https://docs.nhcarrigan.com/dev/covenant/).

### Dependencies

- [ ] I have pinned the dependencies to a specific patch version.

### Style

- [ ] I have run the linter and resolved any errors.
- [ ] My pull request uses an appropriate title, matching the conventional commit standards.
- [ ] My scope of feat/fix/chore/etc. correctly matches the nature of changes in my pull request.

### Tests

- [ ] My contribution adds new code, and I have added tests to cover it.
- [ ] My contribution modifies existing code, and I have updated the tests to reflect these changes.
- [ ] All new and existing tests pass locally with my changes.
- [ ] Code coverage remains at or above the configured threshold.

### Documentation

_No response_

### Versioning

_No response_

Reviewed-on: #1
Co-authored-by: Naomi Carrigan <commits@nhcarrigan.com>
Co-committed-by: Naomi Carrigan <commits@nhcarrigan.com>

src/modules/getEntitlement.ts

@@ -0,0 +1,51 @@
+/**
+ * @copyright nhcarrigan
+ * @license Naomi's Public License
+ * @author Naomi Carrigan
+ */
+
+import { type Entitlement, EntitlementType } from "discord.js";
+import { SKU } from "../interfaces/skus.js";
+import type { Lynira } from "../interfaces/lynira.js";
+
+/**
+ * Fetches an entitlement for a user. Only looks at the first ACTIVE entitlement.
+ * @param lynira - Lynira's Discord instance.
+ * @param userId - The ID of the user to fetch the entitlement for.
+ * @returns The entitlement if found, or null if not found.
+ */
+export const getEntitlement = async(
+  lynira: Lynira,
+  userId: string,
+): Promise<Entitlement | null> => {
+  if (userId === "465650873650118659") {
+    // eslint-disable-next-line @typescript-eslint/consistent-type-assertions -- Mock entitlement for Naomi.
+    return {
+      applicationId: lynira.discord.application?.id ?? "",
+      consumed:      false,
+      deleted:       false,
+      endsAt:        null,
+      endsTimestamp: null,
+      guild:         null,
+      guildId:       null,
+      id:            "enterprise-entitlement-id",
+      isActive:      () => {
+        return true;
+      },
+      skuId:           SKU.ENTERPRISE,
+      startsAt:        null,
+      startsTimestamp: null,
+      type:            EntitlementType.ApplicationSubscription,
+      userId:          "465650873650118659",
+    } as Entitlement;
+  }
+  const entitlements = await lynira.discord.application?.entitlements.fetch({
+    excludeDeleted: true,
+    excludeEnded:   true,
+    user:           userId,
+  }).catch(() => {
+    return null;
+  });
+
+  return entitlements?.first() ?? null;
+};

src/modules/getLinkComponents.ts

@@ -0,0 +1,33 @@
+/**
+ * @copyright nhcarrigan
+ * @license Naomi's Public License
+ * @author Naomi Carrigan
+ */
+
+import { ContainerBuilder, TextDisplayBuilder } from "discord.js";
+import type { Links } from "@prisma/client";
+
+/**
+ * Generates an array of components for displaying users' short URLs.
+ * @param links - The array of links to display.
+ * @returns An array of ContainerBuilder components.
+ */
+export const getLinkComponents
+  = (links: Array<Links>): Array<ContainerBuilder> => {
+    const components: Array<ContainerBuilder> = [];
+    while (links.length > 0) {
+      const slice = links.splice(0, 50);
+      components.push(
+        new ContainerBuilder().
+          addTextDisplayComponents(
+            new TextDisplayBuilder().setContent(
+              slice.map((link) => {
+                return `- \`${link.slug}\`: ${link.url}`;
+              }).
+                join("\n"),
+            ),
+          ),
+      );
+    }
+    return components;
+  };

src/modules/getSkuLimit.ts

@@ -0,0 +1,32 @@
+/**
+ * @copyright nhcarrigan
+ * @license Naomi's Public License
+ * @author Naomi Carrigan
+ */
+/* eslint-disable @typescript-eslint/no-unsafe-enum-comparison -- We want this function to accept arbitrary SKU IDs. */
+
+import { SKU } from "../interfaces/skus.js";
+
+/**
+ * Get the URL limit for a given SKU.
+ * @param sku - The SKU to check.
+ * @returns The URL limit for the SKU. Returns 0 if the SKU is not recognized.
+ */
+export const getSkuLimit = (sku: SKU | string): number => {
+  if (sku === SKU.PERSONAL) {
+    return 10;
+  }
+  if (sku === SKU.PROFESSIONAL) {
+    return 25;
+  }
+  if (sku === SKU.BUSINESS) {
+    return 100;
+  }
+  if (sku === SKU.ORGANISATION) {
+    return 250;
+  }
+  if (sku === SKU.ENTERPRISE) {
+    return 1000;
+  }
+  return 0;
+};

src/modules/processCommand.ts

@@ -0,0 +1,23 @@
+/**
+ * @copyright nhcarrigan
+ * @license Naomi's Public License
+ * @author Naomi Carrigan
+ */
+
+import { MessageFlags } from "discord.js";
+import { handlers } from "../config/handlers.js";
+import type { Command } from "../interfaces/command.js";
+
+/**
+ * Process a command interaction.
+ * @param lynira - The Lynira instance.
+ * @param interaction - The interaction to process.
+ */
+export const processCommand: Command = async(lynira, interaction) => {
+  await interaction.deferReply({
+    flags: [ MessageFlags.Ephemeral ],
+  });
+  const { commandName } = interaction;
+  // eslint-disable-next-line no-underscore-dangle -- Accessing private property for command handler.
+  await (handlers[commandName] ?? handlers._default)(lynira, interaction);
+};

src/modules/sendUnintitledResponse.ts

@@ -0,0 +1,48 @@
+/**
+ * @copyright nhcarrigan
+ * @license Naomi's Public License
+ * @author Naomi Carrigan
+ */
+
+import {
+  ActionRowBuilder,
+  ButtonBuilder,
+  ButtonStyle,
+  MessageFlags,
+  TextDisplayBuilder,
+  type ChatInputCommandInteraction,
+} from "discord.js";
+import { SKU } from "../interfaces/skus.js";
+
+/**
+ * Responds with a default image and a button to subscribe.
+ * @param interaction - The interaction object from Discord.
+ */
+export const sendUnentitledResponse = async(
+  interaction: ChatInputCommandInteraction,
+): Promise<void> => {
+  const components = [
+    new TextDisplayBuilder().setContent(
+      // eslint-disable-next-line stylistic/max-len -- Big boi string.
+      "Hmm, you do not seem to have an active subscription. If you wish to continue using my services, you will need to rectify that.",
+    ),
+    new ActionRowBuilder<ButtonBuilder>().addComponents(
+      new ButtonBuilder().
+        setStyle(ButtonStyle.Premium).
+        setSKUId(SKU.PERSONAL),
+      new ButtonBuilder().
+        setStyle(ButtonStyle.Premium).
+        setSKUId(SKU.PROFESSIONAL),
+      new ButtonBuilder().
+        setStyle(ButtonStyle.Premium).
+        setSKUId(SKU.BUSINESS),
+      new ButtonBuilder().
+        setStyle(ButtonStyle.Premium).
+        setSKUId(SKU.ENTERPRISE),
+    ),
+  ];
+  await interaction.editReply({
+    components: components,
+    flags:      [ MessageFlags.IsComponentsV2 ],
+  });
+};