Webpack Plugin, From CSV To Typescript

csv_import_with_typescript.js

var file_path = "/Users/stevezelaznik/src/gnar/aarp-foundation-pta/app/javascript/src/tools/mn-2023/tables/renters_refund_table.csv"
var fs = require("fs");
var Papa = require("papaparse");
var sourceText = fs.readFileSync(file_path).toString();

function hydrateType(types, cell, column_index) {
  const type = typeof cell

  switch(type) {
    case 'string':
      types[column_index]['string'] = true;
      break;

    case 'number':
      types[column_index]['number'] = true;
      break;

    default:
      throw new Error(`Unsupported type ${type}`);
  }
}

function makeType(type_columns) {
  var lines = [];

  return '[' + type_columns.map(col => {
    var keys = Object.keys(col);

    if (keys.length > 1) {
      var col_type = keys.sort().join(" | ");
      return '(' + col_type + ')';
    } else {
      return keys[0];
    }
  }).join(', ') + ']';
}

function process(sourceText, /*sourePath, options*/) {
  var data = Papa.parse(sourceText, {
    dynamicTyping: true,
    skipEmptyLines: true
  }).data

  // Create an array of empty object [ {}, {}, {}, {} ]
  // those will be used to get a unique set of types used across all rows
  // something like [ { string: true }, { string: true, number: true } ]
  var header_types = data[0].map(() => ({}));
  var value_types = data[1].map(() => ({}));

  // get the header types
  data[0].forEach((cell, i) => hydrateType(header_types, cell, i));

  // get the types for each column in the data
  data.slice(1).forEach((row) => {
    row.forEach((cell, i) => hydrateType(value_types, cell, i));
  });

  var code = [
    `type CsvHeader = [${header_types.map(t => Object.keys(t).sort().join(" | ")).join(', ')}]`,
    `type CsvRow = [${value_types.map(t => Object.keys(t).sort().join(" | ")).join(', ')}]`,
    "",
    "type CsvFile = [CsvHeader, ...CsvRow[]]",
    "",
    "const data: CsvFile = [",
    data.slice(0, 20).map(row => "  " + JSON.stringify(row) + ",").join("\n"),
    "];",
    "",
    "export default data;"
  ]

  return {
    code: code.join("\n")
  }
}