import * as fs from "node:fs";
import * as path from "node:path";
import nunjucks, { ConfigureOptions } from "nunjucks";

import { deepMerge } from "./deepMerge";
import { RenderContext } from "./getRenderContext";
import { sortDependencies } from "./sortDependencies";
import {
  camelCase,
  kebabCase,
  pascalCase,
  snakeCase,
  titleCase,
} from "./strings";

/**
 * Renders a template folder/file to the provided destination,
 * by recursively copying all files under the source directory,
 * with the following exception:
 *   - `_filename` are renamed to `.filename`.
 *   - `package.json` files are merged.
 *   - `.gitignore` files are concatenated.
 *   - `.njk` files are rendered as nunjucks templates
 *     and saved without the `.njk` extension.
 */
export function renderTemplate(ctx: RenderContext, src: string, dest: string) {
  const stats = fs.statSync(src);

  // Recursively render directories.
  if (stats.isDirectory()) {
    // Skip node_module.
    if (path.basename(src) === "node_modules") return;

    // Render its subdirectories and files recursively.
    fs.mkdirSync(dest, { recursive: true });
    for (const file of fs.readdirSync(src)) {
      renderTemplate(ctx, path.resolve(src, file), path.resolve(dest, file));
    }
    return;
  }

  const filename = path.basename(src);

  // Merge package.json files.
  if (filename === "package.json" && fs.existsSync(dest)) {
    const existing = JSON.parse(fs.readFileSync(dest, "utf8"));
    const newPackage = JSON.parse(fs.readFileSync(src, "utf8"));
    const pkg = sortDependencies(deepMerge(existing, newPackage));
    fs.writeFileSync(dest, JSON.stringify(pkg, null, 2) + "\n");
    return;
  }

  // Rename `_file` to `.file`.
  if (filename.startsWith("_")) {
    dest = path.resolve(path.dirname(dest), filename.replace(/^_/, "."));
  }

  // Append to existing .gitignore.
  if (filename === "_gitignore" && fs.existsSync(dest)) {
    const existing = fs.readFileSync(dest, "utf8");
    const newGitignore = fs.readFileSync(src, "utf8");
    fs.writeFileSync(dest, existing + "\n" + newGitignore);
    return;
  }

  // Render nunjucks templates.
  if (filename.endsWith(".njk")) {
    dest = dest.replace(/\.njk$/, "");
    fs.writeFileSync(dest, resolveNunjunksTemplate(src, ctx));
    return;
  }

  fs.copyFileSync(src, dest);
}

function resolveNunjunksTemplate(
  file: string,
  context?: object,
  options?: ConfigureOptions
): string {
  const directory = path.dirname(file);
  const filename = path.basename(file);
  const env = nunjucks.configure(directory, {
    trimBlocks: true,
    autoescape: false,
    ...options,
  });
  env.addFilter("pascalCase", pascalCase);
  env.addFilter("camelCase", camelCase);
  env.addFilter("snakeCase", snakeCase);
  env.addFilter("kebabCase", kebabCase);
  env.addFilter("titleCase", titleCase);
  return env.render(filename, context);
}