Add is valid hashtag check

is_valid_hashtag.kt.diff

@Composable
private fun PostHashtags(
    hashtags: ImmutableList<String>,
    onAddHashTag: (String) -> Unit,
    modifier: Modifier
) {
    var inputHashTag by remember(hashtags) { mutableStateOf("") }
+   val isValidHashtag: Boolean by remember {
+       derivedStateOf {
+           !inputHashTag.contains(" ")
+       }
+   }

    Column(modifier = modifier) {
        OutlinedTextField(
            value = inputHashTag,
            onValueChange = { inputHashTag = it },
            leadingIcon = { Text(text = "#", fontWeight = FontWeight.Bold) },
            placeholder = { Text(text = "Type a hashtag here") },
            trailingIcon = {
+               AnimatedVisibility(
+                   visible = inputHashTag.isNotEmpty() && isValidHashtag,
+                   enter = fadeIn(),
+                   exit = fadeOut()
+               ) {
                    IconButton(onClick = { onAddHashTag(inputHashTag) }) {
                        Icon(imageVector = Icons.Default.AddCircle,
                            contentDescription = "Add hashtag")
                    }
                }
            },
+           isError = !isValidHashtag,
        )
+       AnimatedVisibility(visible = !isValidHashtag) {
+           Text(
+               text = "Hashtag cannot have a space",
+               style = MaterialTheme.typography.labelSmall,
+               modifier = Modifier.padding(vertical = 2.dp)
+           )
+       }
        ReusableVerticalLazyList(content = hashtags)
    }
}