import fs from "fs/promises";
import {IndexHtmlTransformContext, Plugin, ServerOptions, UserConfig} from "vite";

let htmlCache: string | undefined = undefined;

const getUrlFromServer = (server: ServerOptions): string => {
    const protocol = server.https ? 'https' : 'http';
    const host = server.origin ?? 'localhost';
    const port = server.port;

    return `${protocol}://${host}:${port}`;
}

const vitePluginWriteIndexToDisk: () => Plugin = () => ({
    name: 'vite-plugin-write-index-to-disk',
    apply: 'serve',
    order: 'pre',
    config(config: UserConfig) {
        // warmup triggers transformIndexHtml on start
        if(config?.server?.warmup?.clientFiles && !config.server.warmup.clientFiles.includes('index.html')) {
            config.server.warmup.clientFiles.push('index.html')
        } else {
            if(!config.server) {
                config.server = {};
            }

            config.server.warmup = {
                clientFiles: [
                    'index.html'
                ]
            };
        }
    },
    async handleHotUpdate({ server, modules }) {
        if(modules.length === 0) {
            const url = getUrlFromServer(server.config.server);
            // fetch triggers transformIndexHtml after the initial warmup
            await fetch(url);
        }
    },
    transformIndexHtml(html: string, ctx: IndexHtmlTransformContext) {
        if(!ctx.server) {
            return;
        }

        const {build, server} = ctx.server.config;
        const outDir = build.outDir;
        const url = getUrlFromServer(server);

        if(html !== htmlCache) {
            htmlCache = html;

            fs.writeFile(
                `./${outDir}/index.html`,
                html
                    .replaceAll('src="', `src="${url}`)
                    .replaceAll('href="', `href="${url}`)
            );
        }
    },
});

export default vitePluginWriteIndexToDisk;