import cds from "@sap/cds";
import {struct} from "@sap/cds/apis/csn";
import fs from "fs/promises";
import {toSnakeCase} from "js-convert-case";

import {Command} from "commander";
const program = new Command();

interface Options {
  schema: string;
  namespace: string;
  prefix: string;
  case: string;
}

program
  .option("-s, --schema <schema>", "imported CDS")
  .option("-n, --namespace <namespace>", "imported namespace")
  .option("-p, --prefix <prefix>", "new namespace")
  .option("-c, --case <case>", "case to use: camel|snake|kebab")
  .parse(process.argv);

class Main {
  static async formatCDS(options: Options) {
    let {schema, namespace, prefix} = options;
    const csn = await cds.load(schema);

    let model = `using {${namespace}} from './${schema.replace(
      ".cds",
      ""
    )}';\n`;

    Object.keys(csn.definitions)
      .filter((key) => key.startsWith(`${namespace}.`))
      .forEach((key) => {
        let entity = csn.definitions[key] as struct;

        switch (entity.kind) {
          case "entity":
            model += `entity ${prefix}.${key} as projection on ${key} {\n`;
            Object.keys(entity.elements).forEach((element, index, array) => {
              // to be extended with more cases if needed
              let alias =
                options.case === "snake" ? toSnakeCase(element) : element;
              //tab
              model += "\t";
              // element or alias
              model += element === alias ? element : `${element} as ${alias}`;
              // no comma for last element
              index === array.length || (model += ",");
              // line brake
              model += "\n";
            });
            model += "};\n";

            break;
          default:
            break;
        }
      });

    fs.writeFile(`${prefix}.cds`, model);
  }
}

//console.log(program.opts());

Main.formatCDS(program.opts() as Options);