linkify

import 'package:engine_io_client/engine_io_client.dart';
import 'package:flutter/gestures.dart';
import 'package:flutter/material.dart';

final RegExp urlRegEx = new RegExp(r'(https?://)?(www\.)?([\w]+\.)+[‌​\w]{2,63}/?');
final RegExp phoneRegEx =
    new RegExp(r'(([(]?(\d{2,4})[)]?)|(\d{2,4})|([+1-9]+\d{1,2}))?[-\s]?(\d{2,3})?[-\s]?((\d{7,8})|(\d{3,4}[-\s]\d{3,4}))');

RegExp emailRegEx = new RegExp(r'[a-zA-Z0-9-_.]+@[a-zA-Z0-9-_.]+');

RegExp underline = new RegExp(r'__(.*?)__');
RegExp italic = new RegExp(r'_(.*?)_');
RegExp bold = new RegExp(r'\*(.*?)\*');
RegExp strikethrough = new RegExp(r'~(.*?)~');

enum ItemType { email, url, phone }

typedef void OnItemTapped(String item, ItemType type);

class MessagesParser {
  static final Log log = new Log('MessagesParser');

  const MessagesParser();

  static TextSpan parse(String message, OnItemTapped onItemTapped) {
    return _match(
      regex: emailRegEx,
      text: message,
      style: const TextStyle(
        color: Colors.blue,
        decoration: TextDecoration.underline,
      ),
      onItemTapped: onItemTapped,
      nextMatcher: (String text) {
        return _match(
          regex: urlRegEx,
          text: text,
          style: const TextStyle(
            color: Colors.blue,
            decoration: TextDecoration.underline,
          ),
          onItemTapped: onItemTapped,
          nextMatcher: (String text) {
            return _match(
              regex: phoneRegEx,
              text: text,
              style: const TextStyle(
                color: Colors.blue,
                decoration: TextDecoration.underline,
              ),
              onItemTapped: onItemTapped,
              nextMatcher: (String text) {
                return _match(
                  regex: underline,
                  text: text,
                  style: const TextStyle(
                    decoration: TextDecoration.underline,
                  ),
                  onItemTapped: onItemTapped,
                  nextMatcher: (String text) {
                    return _match(
                      regex: italic,
                      text: text,
                      style: const TextStyle(
                        fontStyle: FontStyle.italic,
                      ),
                      onItemTapped: onItemTapped,
                      nextMatcher: (String text) {
                        return _match(
                          regex: bold,
                          text: text,
                          style: const TextStyle(
                            fontWeight: FontWeight.bold,
                          ),
                          onItemTapped: onItemTapped,
                          nextMatcher: (String text) {
                            return _match(
                              regex: strikethrough,
                              text: text,
                              style: const TextStyle(
                                decoration: TextDecoration.lineThrough,
                              ),
                              onItemTapped: onItemTapped,
                            );
                          },
                        );
                      },
                    );
                  },
                );
              },
            );
          },
        );
      },
    );
  }

  static TextSpan _match({
    RegExp regex,
    String text,
    TextStyle style,
    OnItemTapped onItemTapped,
    TextSpan nextMatcher(String text) = _nextMatcher,
  }) {
    final List<Match> matches = regex.allMatches(text).toList(growable: false);

    TextSpan textSpan =
        new TextSpan(children: <TextSpan>[].toList(growable: true), style: const TextStyle(color: Colors.black87));

    if (matches.isNotEmpty) {
      int previousEnd = 0;
      for (Match m in matches) {

        final String beforePart = text.substring(previousEnd, m.start);
        if (beforePart.isNotEmpty) textSpan.children.add(nextMatcher(beforePart));
        textSpan.children.add(
          new TextSpan(
            text: m.groupCount == 1 ? m.group(1) : m.group(0),
            style: style,
            recognizer: new TapGestureRecognizer()
              ..onTap = () {
                final ItemType itemType =
                    regex == emailRegEx ? ItemType.email : regex == urlRegEx ? ItemType.url : ItemType.phone;
                onItemTapped(m.group(0), itemType);
              },
          ),
        );

        if (m == matches.last) {
          final String afterPart = text.substring(m.end);
          if (afterPart.isNotEmpty) textSpan.children.add(nextMatcher(afterPart));
        }

        previousEnd = m.end;
      }
    } else {
      textSpan = nextMatcher(text);
    }

    return textSpan;
  }

  static TextSpan _nextMatcher(String text) => new TextSpan(text: text);
}