export interface Theme {
  bg: string;
  fg: string;
  primary?: string;
  h1?: string;
}

export function stringifyTheme(theme: Theme) {
  return [
    ":root {",
    "--bg: " + theme.bg + ";",
    "--fg: " + theme.fg + ";",
    theme.primary ? "--primary: " + theme.primary + ";" : null,
    "}",
    theme.h1 ? "h1 { color: " + theme.h1 + "}" : null,
  ].filter(Boolean).join("\n");
}

export function preprocess(css: string, theme: Theme): string {
  const keys = Object.keys(theme);
  const regex = new RegExp(
    `([{};\\n][^{};\\n]*var\\(--(${keys.join("|")})\\).*?(?=[;{}\\n]))`,
    "gs",
  );
  const regex2 = new RegExp(`var\\(--(${keys.join("|")})\\)`);
  return css.replace(
    regex,
    (_, line) =>
      line.replace(regex2, (_: string, varName: string) => theme[varName]) +
      ";" + line.slice(1),
  );
}

export async function bundleCssFiles(
  cssImports: string[],
  theme: Theme,
  dev: boolean = false,
): Promise<string> {
  const plugin = {
    name: "clover",
    setup(b) {
      b.onResolve(
        { filter: /^\$input\$$/ },
        () => ({ path: ".", namespace: "input" }),
      );
      b.onLoad(
        { filter: /./, namespace: "input" },
        () => ({
          loader: "css",
          contents:
            cssImports.map((path) => `@import url(${JSON.stringify(path)});`)
              .join("\n") + stringifyTheme(theme),
          resolveDir: ".",
        }),
      );
      b.onLoad(
        { filter: /\.css$/ },
        async ({ path: file }) => ({
          loader: "css",
          contents: preprocess(await fs.readFile(file, "utf-8"), theme),
        }),
      );
    },
  } satisfies Plugin;
  const build = await esbuild.build({
    bundle: true,
    entryPoints: ["$input$"],
    write: false,
    external: ["*.woff2"],
    target: ["ie11"],
    plugins: [plugin],
    minify: !dev,
  });
  const { errors, warnings, outputFiles } = build;
  if (errors.length > 0) {
    throw new AggregateError(errors, "CSS Build Failed");
  }
  if (warnings.length > 0) {
    throw new AggregateError(warnings, "CSS Build Failed");
  }
  if (outputFiles.length > 1) throw new Error("Too many output files");
  return outputFiles[0].text;
}

import type { Plugin } from "esbuild";
import * as esbuild from "esbuild";
import * as fs from "./fs.ts";