import { readFileSync } from "node:fs";
import { parse } from "@kitchen-md/core";
import { err, ok, type Result } from "neverthrow";
import { render } from "./render.ts";

export type ViewError = { tag: "read-failed"; path: string; cause: string };

export function viewFile(path: string): Result<string, ViewError> {
  return readFile(path).map((content) => render(parse(content)));
}

export function formatViewError(error: ViewError): string {
  switch (error.tag) {
    case "read-failed":
      return `cannot read '${error.path}': ${error.cause}`;
  }
}

// The one place a throwing API is turned into a Result; nothing above this leaks exceptions.
function readFile(path: string): Result<string, ViewError> {
  try {
    return ok(readFileSync(path, "utf8"));
  } catch (error) {
    const cause = error instanceof Error ? error.message : String(error);
    return err({ tag: "read-failed", path, cause });
  }
}