import { UnpluginInstance, createUnplugin } from "unplugin";
import { createFilter } from "@rollup/pluginutils";
import { type Options, resolveOption, defaultInclude } from "./core/options";
import { transformAsync } from "@babel/core";
import transformReactSlots from "@beqa/babel-plugin-transform-react-slots";
import SyntaxTypescript from "@babel/plugin-syntax-typescript";

// Matches @disable-transform-react-slots at the very start. Only line comments or block comments can precede it
const isDisabledRegex =
  /^(?:\s*(?:\/\/[^\n\r]*|\/\*(?:.|[\n\r])*?\*\/))*\s*\/\/\s*@disable-transform-react-slots\W/;

function appendTestComment(code: string, isDisabled: boolean): string {
  if (isDisabled) {
    code +=
      "/* slot transformation skipped by unplugin-transform-react-slots */";
  } else {
    code += "/* slot transformation done by unplugin-transform-react-slots */";
  }
  return code;
}

export default createUnplugin<Options | undefined, false>((rawOptions) => {
  const options = resolveOption(rawOptions);
  const filter = createFilter(options.include, options.exclude);

  return {
    name: "unplugin-transform-react-slots",

    enforce: "pre",

    transformInclude(id) {
      return filter(id);
    },

    async transform(code, id) {
      if (id.endsWith(".ts")) {
        return appendTestComment(code, true);
      }

      if (isDisabledRegex.test(code)) {
        return appendTestComment(code, true);
      }

      if (!(code.includes("@beqa/react-slots") && code.includes("useSlot"))) {
        return appendTestComment(code, true);
      }

      const transformed = await transformAsync(code, {
        plugins: [
          id.endsWith(".tsx") ? [SyntaxTypescript, { isTSX: true }] : "",
          transformReactSlots,
        ].filter(Boolean),
        filename: id,
      });

      if (!transformed) {
        throw new Error(
          "unplugin-transform-react-slots failed to transform file: " + id,
        );
      }

      // TODO: test if returning babel sourcemap makes it better or worse
      return transformed.code && appendTestComment(transformed.code, false);
    },

    esbuild: {
      onLoadFilter:
        !!options.include && !Array.isArray(options.include)
          ? options.include
          : defaultInclude,
      loader(code, id) {
        if (id.endsWith("tsx")) {
          return "tsx";
        }

        if (id.endsWith("ts")) {
          return "ts";
        }

        return "jsx";
      },
    },
  };
}) as Pick<
  UnpluginInstance<Options | undefined, false>,
  "esbuild" | "rollup" | "vite" | "webpack"
>;