// TouchPoint Example
// Source code file: MainActivity.kt
// Draw a circle when a user touches (clicks)
// on the Canvas element.  Passing Unit as a
// key to Modifier.pointerInput prevents the
// gesture detector from resetting across
// standard recompositions.

// Reference for example: Google AI Overview
// using the search key "jetpack compose 
// detect a tap gesture draw point"

package it372.ssmith.touchpoints2
import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.activity.enableEdgeToEdge
import androidx.compose.foundation.Canvas
import androidx.compose.foundation.background
import androidx.compose.foundation.gestures.detectTapGestures
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.padding
import androidx.compose.runtime.Composable
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.setValue
import androidx.compose.ui.Modifier
import androidx.compose.ui.geometry.Offset
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.input.pointer.pointerInput
import androidx.compose.ui.tooling.preview.Preview
import androidx.compose.ui.unit.dp

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        enableEdgeToEdge()
        setContent {
            TapToDrawPointScreen( )
        }
    }
}

@Composable
fun TapToDrawPointScreen() {
    // Stores the coordinate of the last tapped position
    var tapOffset by remember { mutableStateOf<Offset?>(null) }

    Column(modifier = Modifier
        .background(Color(0xFFC0C0C0))
        .padding(all = 30.dp)) {
        Canvas(
            modifier = Modifier
                .fillMaxSize()
                .background(Color.White)
                .pointerInput(Unit) {
                    // Detects individual tap events on the screen
                    detectTapGestures(
                        onTap = {
                            tapOffset = it
                        }
                    )
                }
        ) {
            // Draw the point only if the user has tapped
            // the screen
            tapOffset?.let { offset ->
                drawCircle(
                    color = Color.Blue,
                    radius = 75f,
                    center = offset
                )
            }
        }
    }
}

@Preview(showBackground = true)
@Composable
fun MainLayoutPreview() {
    TapToDrawPointScreen( )
}