import type { AstroIntegration } from 'astro';
import debugC from 'debug';

const debug = debugC('inox-tools:astro-when');

const VIRTUAL_MODULE_ID = '@it-astro:when';
const RESOLVED_MODULE_ID = `\x00${VIRTUAL_MODULE_ID}`;

// Globally indicate to the virtual module that it is in the same context as the build system.
const key = Symbol.for('astro:when/buildContext');

export default function astroWhen(): AstroIntegration {
	return {
		name: '@inox-tools/astro-when',
		hooks: {
			'astro:config:setup': (params) => {
				(globalThis as any)[key] = params.command === 'build';

				debug('Adding Vite plugin');
				params.updateConfig({
					vite: {
						plugins: [
							{
								name: '@inox-tools/astro-when',
								resolveId(id) {
									if (id === VIRTUAL_MODULE_ID) {
										debug('Resolving virtual module ID');
										return RESOLVED_MODULE_ID;
									}
								},
								load(id, options) {
									if (id !== RESOLVED_MODULE_ID) return;

									const preamble = `
										export const When = {
											Client: 'client',
											Server: 'server',
											Prerender: 'prerender',
											StaticBuild: 'staticBuild',
											DevServer: 'devServer',
										};
									`;

									if (options?.ssr !== true) {
										debug('Generating module for client');
										return `${preamble} export const whenAmI = When.Client;`;
									}

									if (params.command === 'dev') {
										debug('Generating module for dev server');
										return `${preamble} export const whenAmI = When.DevServer;`;
									}

									if (!params.config.adapter) {
										debug('Generating module for static build');
										return `${preamble} export const whenAmI = When.StaticBuild;`;
									}

									debug('Generating module for live server');
									return `${preamble}
										const isBuildContext = Symbol.for('astro:when/buildContext');
										export const whenAmI = globalThis[isBuildContext] ? When.Prerender : When.Server;
									`;
								},
							},
						],
					},
				});
			},
			'astro:config:done': (params) => {
				// Check if the version of Astro being used has the `injectTypes` utility.
				if (typeof params.injectTypes === 'function') {
					debug('Injecting types in .astro structure');
					params.injectTypes({
						filename: 'types.d.ts',
						content: "import '@inox-tools/astro-when';",
					});
				}
			},
			'astro:build:done': () => {
				delete (globalThis as any)[key];
			},
		},
	};
}