import Context from "../context-detection";
import { PostProcessor } from "../types";


class RemoveOverlap implements PostProcessor {
  process(
    prefix: string,
    suffix: string,
    completion: string,
    context: Context
  ): string {
    completion = removeWordOverlapPrefix(prefix, completion);
    completion = removeWordOverlapSuffix(completion, suffix);
    completion = removeWhiteSpaceOverlapPrefix(suffix, completion);
    completion = removeWhiteSpaceOverlapSuffix(completion, suffix);

    return completion;
  }
}


function removeWhiteSpaceOverlapPrefix(prefix: string, completion: string): string {
  let prefixIdx = prefix.length - 1;
  while (completion.length > 0 && completion[0] === prefix[prefixIdx]) {
    completion = completion.slice(1);
    prefixIdx--;
  }
  return completion;
}


function removeWhiteSpaceOverlapSuffix(completion: string, suffix: string): string {
  let suffixIdx = 0;
  while (completion.length > 0 && completion[completion.length - 1] === suffix[suffixIdx]) {
    completion = completion.slice(0, -1);
    suffixIdx++;
  }
  return completion;
}

function removeWordOverlapPrefix(prefix: string, completion: string): string {
  const rightTrimmed = completion.trimStart();

  const startIdxOfEachWord = startLocationOfEachWord(prefix);

  while (startIdxOfEachWord.length > 0) {
    const idx = startIdxOfEachWord.pop();
    const leftSubstring = prefix.slice(idx);
    if (rightTrimmed.startsWith(leftSubstring)) {
      return rightTrimmed.replace(leftSubstring, "");
    }
  }

  return completion;
}

function removeWordOverlapSuffix(completion: string, suffix: string): string {
  const suffixTrimmed = removeLeadingWhiteSpace(suffix);

  const startIdxOfEachWord = startLocationOfEachWord(completion);

  while (startIdxOfEachWord.length > 0) {
    const idx = startIdxOfEachWord.pop();
    const suffixSubstring = completion.slice(idx);
    if (suffixTrimmed.startsWith(suffixSubstring)) {
      return completion.replace(suffixSubstring, "");
    }
  }

  return completion;
}

function removeLeadingWhiteSpace(completion: string): string {
  return completion.replace(/^[ \t\f\r\v]+/, "");
}

function startLocationOfEachWord(text: string): number[] {
  const locations: number[] = [];
  if (text.length > 0 && !isWhiteSpaceChar(text[0])) {
    locations.push(0);
  }

  for (let i = 1; i < text.length; i++) {
    if (isWhiteSpaceChar(text[i - 1]) && !isWhiteSpaceChar(text[i])) {
      locations.push(i);
    }
  }

  return locations;
}

function isWhiteSpaceChar(char: string | undefined): boolean {
  return char !== undefined && (/\s/.exec(char)) !== null;
}

export default RemoveOverlap;