import { ExternalTokenizer, ContextTracker } from '@lezer/lr';
import {
  newline as newlineToken,
  newlineEmpty,
  indent,
  LineText1,
  LineText2,
  LineText3,
  LineText4,
  LineText5,
} from './mindmap.grammar.terms';

import type { InputStream } from '@lezer/lr';

type InputStreamWithRead = InputStream & {
  read: (inputPosition: number, stackPosition: number) => string;
};

const LineTextTokens = [LineText1, LineText2, LineText3, LineText4, LineText5];

const newline = 10,
  carriageReturn = 13,
  space = 32,
  tab = 9,
  hash = 35,
  colon = 58,
  parenL = 40,
  parenR = 41,
  bracketL = 91,
  bracketR = 93,
  braceL = 123,
  braceR = 125;

export const newlines = new ExternalTokenizer(
  (input, _stack) => {
    if (input.next < 0) return;
    else {
      input.advance();
      let spaces = 0;
      while ((input.next as number) == space || (input.next as number) == tab) {
        input.advance();
        spaces++;
      }
      let empty =
        input.next == newline ||
        input.next == carriageReturn ||
        input.next == hash;
      input.acceptToken(empty ? newlineEmpty : newlineToken, -spaces);
    }
  },
  { contextual: true, fallback: true }
);

export const lineTextType = new ExternalTokenizer((input, stack) => {
  let chars = 0;

  while (input.next > -1 && input.next !== newline) {
    if (input.next === colon) return;

    if (
      input.next === parenL ||
      input.next === bracketL ||
      input.next === braceL
    ) {
      if (chars > 0) {
        input.acceptToken(stack.context.lineType);
        return;
      } else return;
    }

    if (
      (input.next === parenR ||
        input.next === bracketR ||
        input.next === braceR) &&
      chars > 0
    ) {
      input.acceptToken(stack.context.lineType);
      return;
    }

    input.advance();
    chars++;
  }

  input.acceptToken(stack.context.lineType);
});

const tabDepth = (depth: number) => {
  return 4 - (depth % 4);
};

export const indentation = new ExternalTokenizer((input, _stack) => {
  let prev = input.peek(-1);
  if (prev == newline || prev == carriageReturn) {
    let depth = 0;
    let chars = 0;

    while (true) {
      if (input.next == space) depth++;
      else if (input.next == tab) depth += tabDepth(depth);
      else break;
      input.advance();
      chars++;
    }

    if (
      input.next != newline &&
      input.next != carriageReturn &&
      input.next != hash
    ) {
      input.acceptToken(indent);
    }
  }
});

const indentTracker = {
  lineType: LineText1,
};

const countIndent = (space: string) => {
  let depth = 0;
  for (let i = 0; i < space.length; i++)
    depth += space.charCodeAt(i) == tab ? tabDepth(depth) : 1;
  return depth;
};

const getLineType = (depth: number) => {
  return LineTextTokens[depth % 5];
};

export const trackIndent = new ContextTracker({
  start: indentTracker,
  shift(context, term, stack, input: InputStreamWithRead) {
    if (term === indent) {
      const depth = countIndent(input.read(input.pos, stack.pos));
      context.lineType = getLineType(depth);
    }
    return context;
  },
});