import { EditorState, TextSelection } from "prosemirror-state";
import isInCode from "../queries/isInCode";
import { Dispatch } from "../types";

/**
 * Moves the current selection to the previous newline, this is used inside
 * code fences only, prosemirror handles this functionality fine in other nodes.
 *
 * @returns A prosemirror command.
 */
export const moveToPreviousNewline = (
  state: EditorState,
  dispatch: Dispatch
) => {
  if (!isInCode(state)) {
    return false;
  }

  const $pos = state.selection.$from;
  if (!$pos.parent.type.isTextblock) {
    return false;
  }

  // The easiest way to find the previous newline is to reverse the string and
  // perform a forward seach as if looking for the next newline.
  const beginningOfNode = $pos.pos - $pos.parentOffset;
  const startOfLine = $pos.parent.textContent
    .split("")
    .reverse()
    .join("")
    .indexOf("\n", $pos.parent.nodeSize - $pos.parentOffset - 2);

  if (startOfLine === -1) {
    return false;
  }

  dispatch(
    state.tr.setSelection(
      TextSelection.create(
        state.doc,
        beginningOfNode + ($pos.parent.nodeSize - startOfLine - 2)
      )
    )
  );

  return true;
};

/**
 * Moves the current selection to the next newline, this is used inside code
 * fences only, prosemirror handles this functionality fine in other nodes.
 *
 * @returns A prosemirror command.
 */
export const moveToNextNewline = (state: EditorState, dispatch: Dispatch) => {
  if (!isInCode(state)) {
    return false;
  }

  const $pos = state.selection.$to;
  if (!$pos.parent.type.isTextblock) {
    return false;
  }

  // find next newline
  const beginningOfNode = $pos.pos - $pos.parentOffset;
  const endOfLine = $pos.parent.textContent.indexOf("\n", $pos.parentOffset);
  if (endOfLine === -1) {
    return false;
  }

  dispatch(
    state.tr.setSelection(
      TextSelection.create(state.doc, beginningOfNode + endOfLine)
    )
  );

  return true;
};

/**
 * Replace the selection with a newline character preceeded by a number of
 * spaces to have the new line align with the code on the previous. This is
 * standard code editor behavior.
 *
 * @returns A prosemirror command
 */
export const newlineInCode = (state: EditorState, dispatch: Dispatch) => {
  if (!isInCode(state)) {
    return false;
  }
  const { tr, selection } = state;
  const text = selection?.$anchor?.nodeBefore?.text;

  let newText = "\n";

  if (text) {
    const splitByNewLine = text.split("\n");
    const numOfSpaces = splitByNewLine[splitByNewLine.length - 1].search(
      /\S|$/
    );
    newText += " ".repeat(numOfSpaces);
  }

  dispatch(tr.insertText(newText, selection.from, selection.to));
  return true;
};

/**
 * Insert two spaces to simulate the tab key.
 *
 * @returns A prosemirror command
 */
export const insertSpaceTab = (state: EditorState, dispatch: Dispatch) => {
  if (!isInCode(state)) {
    return false;
  }

  const { tr, selection } = state;
  dispatch(tr.insertText("  ", selection.from, selection.to));
  return true;
};