import { post } from "../ui/postToTerminal";

import {
  containsAllStrings,
  longestCommonStart,
} from "../../utils/StringHelperFunctions";

/**
 * Implements tab completion for the Terminal
 *
 * @param command {string} Terminal command, excluding the last incomplete argument
 * @param arg {string} Last argument that is being completed
 * @param allPossibilities {string[]} All values that `arg` can complete to
 */
export function tabCompletion(
  command: string,
  arg: string,
  allPossibilities: string[],
): void {
  if (!(allPossibilities.constructor === Array)) {
    return;
  }
  if (!containsAllStrings(allPossibilities)) {
    return;
  }

  // Remove all options in allPossibilities that do not match the current string
  // that we are attempting to autocomplete
  if (arg === "") {
    for (let i = allPossibilities.length - 1; i >= 0; --i) {
      if (
        !allPossibilities[i].toLowerCase().startsWith(command.toLowerCase())
      ) {
        allPossibilities.splice(i, 1);
      }
    }
  } else {
    for (let i = allPossibilities.length - 1; i >= 0; --i) {
      if (!allPossibilities[i].toLowerCase().startsWith(arg.toLowerCase())) {
        allPossibilities.splice(i, 1);
      }
    }
  }

  const textBoxElem = document.getElementById("terminal-input-text-box");
  if (textBoxElem == null) {
    console.warn(
      `Couldn't find terminal input DOM element (id=terminal-input-text-box) when trying to autocomplete`,
    );
    return;
  }
  const textBox = textBoxElem as HTMLInputElement;

  const oldValue = textBox.value;
  const semiColonIndex = oldValue.lastIndexOf(";");

  let val = "";
  if (allPossibilities.length === 0) {
    return;
  } else if (allPossibilities.length === 1) {
    if (arg === "") {
      //Autocomplete command
      val = allPossibilities[0] + " ";
    } else {
      val = command + " " + allPossibilities[0];
    }

    if (semiColonIndex === -1) {
      // No semicolon, so replace the whole command
      textBox.value = val;
    } else {
      // Replace only after the last semicolon
      textBox.value = textBox.value.slice(0, semiColonIndex + 1) + " " + val;
    }

    textBox.focus();
  } else {
    const longestStartSubstr = longestCommonStart(allPossibilities);
    /**
     * If the longest common starting substring of remaining possibilities is the same
     * as whatevers already in terminal, just list all possible options. Otherwise,
     * change the input in the terminal to the longest common starting substr
     */
    let allOptionsStr = "";
    for (let i = 0; i < allPossibilities.length; ++i) {
      allOptionsStr += allPossibilities[i];
      allOptionsStr += "   ";
    }
    if (arg === "") {
      if (longestStartSubstr === command) {
        post("> " + command);
        post(allOptionsStr);
      } else {
        if (semiColonIndex === -1) {
          // No semicolon, so replace the whole command
          textBox.value = longestStartSubstr;
        } else {
          // Replace only after the last semicolon
          textBox.value = `${textBox.value.slice(
            0,
            semiColonIndex + 1,
          )} ${longestStartSubstr}`;
        }

        textBox.focus();
      }
    } else {
      if (longestStartSubstr === arg) {
        // List all possible options
        post("> " + command + " " + arg);
        post(allOptionsStr);
      } else {
        if (semiColonIndex == -1) {
          // No semicolon, so replace the whole command
          textBox.value = `${command} ${longestStartSubstr}`;
        } else {
          // Replace only after the last semicolon
          textBox.value = `${textBox.value.slice(
            0,
            semiColonIndex + 1,
          )} ${command} ${longestStartSubstr}`;
        }

        textBox.focus();
      }
    }
  }
}