function lowerToPascalCase(str: string) {
  return str.replace(/(?:^|\s)\w/g, (match) => match.toUpperCase()).replaceAll(
    " ",
    "",
  );
}
function lowerToTrainCase(str: string) {
  return str.replace(/(?:^|\s)\w/g, (match) => match.toUpperCase()).replaceAll(
    " ",
    "-",
  );
}

function lowerToCamelCase(str: string) {
  return str.trim().replace(/(?:\s)\w/g, (match) => match.toUpperCase())
    .replaceAll(" ", "");
}

function lowerToSnakeCase(str: string) {
  return str.replace(" ", "_");
}

function lowerToKebabCase(str: string) {
  return str.replace(" ", "-");
}

function lowerToMacroCase(str: string) {
  return str.replace(/\w\S*/g, (match) => match.toUpperCase()).replaceAll(
    " ",
    "_",
  );
}

function lowerToTitleCase(str: string) {
  return str.replace(/(?:^|\s)\w/g, (match) => match.toUpperCase());
}

type CaseType =
  | "pascal"
  | "camel"
  | "snake"
  | "kebab"
  | "macro"
  | "upper"
  | "lower"
  | "train"
  | "title"
  | "";

function parseCase(str: string) {
  const isCaseMap = new Map<CaseType, (str: string) => boolean>([
    ["pascal", (str: string) => {
      return /^[A-Z][a-zA-Z]*$/.test(str);
    }],
    ["camel", (str: string) => {
      return /^[a-z][a-zA-Z]*$/.test(str);
    }],
    ["snake", (str: string) => {
      return /^[a-z][a-z0-9_]*$/.test(str);
    }],
    ["kebab", (str: string) => {
      return /^[a-z][a-z0-9-]*$/.test(str);
    }],
    ["macro", (str: string) => {
      return /^[A-Z]*$/.test(str);
    }],
    ["upper", (str: string) => {
      return /^[A-Z]*$/.test(str);
    }],
    ["lower", (str: string) => {
      return /^[a-z]*$/.test(str);
    }],
    ["train", (str: string) => {
      return /([A-Z][a-z]*(?:-|$))+/.test(str);
    }],
  ]);
  for (const [key, value] of isCaseMap) {
    if (value(str)) return key;
  }
  return "";
}

function coerceCaseToLower(str: string, caseType: CaseType) {
  switch (caseType) {
    case "pascal":
    case "camel":
      return str.replace(/[A-Z]/g, (match) => " " + match.toLowerCase().trim());
    case "macro":
    case "snake":
    case "upper":
      return str.replace("_", " ").toLowerCase();
    case "train":
    case "kebab":
      return str.replace("-", " ").toLowerCase();
    default:
      return str.toLowerCase();
  }
}

export function toCase(str: string, toCase: CaseType) {
  const caseType = parseCase(str) || "";
  if (caseType === toCase) return str;
  const lowerStr = coerceCaseToLower(str, caseType);
  switch (toCase) {
    case "pascal":
      return lowerToPascalCase(lowerStr);
    case "camel":
      return lowerToCamelCase(lowerStr);
    case "snake":
      return lowerToSnakeCase(lowerStr);
    case "kebab":
      return lowerToKebabCase(lowerStr);
    case "macro":
      return lowerToMacroCase(lowerStr);
    case "upper":
      return lowerStr.toUpperCase();
    case "lower":
      return lowerStr.toLowerCase();
    case "train":
      return lowerToTrainCase(lowerStr);
    case "title":
      return lowerToTitleCase(lowerStr);
    default:
      return str;
  }
}