Apply terrain exaggeration

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/* Copyright 2025 Esri
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

package com.esri.arcgismaps.sample.applyterrainexaggeration.components

import android.app.Application
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableFloatStateOf
import androidx.compose.runtime.setValue
import androidx.lifecycle.AndroidViewModel
import androidx.lifecycle.viewModelScope
import com.arcgismaps.geometry.Point
import com.arcgismaps.geometry.SpatialReference
import com.arcgismaps.mapping.ArcGISScene
import com.arcgismaps.mapping.ArcGISTiledElevationSource
import com.arcgismaps.mapping.BasemapStyle
import com.arcgismaps.mapping.Surface
import com.arcgismaps.mapping.Viewpoint
import com.arcgismaps.mapping.view.Camera
import com.esri.arcgismaps.sample.sampleslib.components.MessageDialogViewModel
import kotlinx.coroutines.launch

/**
 * ViewModel that prepares a Scene with an elevation source and exposes
 * an elevation exaggeration value that the UI can update.
 */
class ApplyTerrainExaggerationViewModel(app: Application) : AndroidViewModel(app) {

    // Elevation source used by the scene's base surface.
    private val elevationSource: ArcGISTiledElevationSource = ArcGISTiledElevationSource(
        uri = "https://elevation3d.arcgis.com/arcgis/rest/services/WorldElevation3D/Terrain3D/ImageServer"
    )

    // Expose the elevation exaggeration as a mutable state.
    var currentElevationExaggeration by mutableFloatStateOf(1f)

    // Set the camera location to center on Levering, WA.
    private val camera = Camera(
        lookAtPoint = Point(
            x = -119.9489,
            y = 46.75792,
            spatialReference = SpatialReference.wgs84()
        ),
        distance = 15000.0,
        heading = 40.0,
        pitch = 60.0,
        roll = 0.0
    )

    // Create a scene with a topographic basemap and a surface that holds the elevation source.
    val arcGISScene: ArcGISScene = ArcGISScene(BasemapStyle.ArcGISTopographic).apply {
        baseSurface = Surface().apply {
            elevationSources.add(elevationSource)
            // Initial exaggeration value.
            elevationExaggeration = currentElevationExaggeration
        }
        // Set the initial viewpoint using the camera.
        initialViewpoint = Viewpoint(camera = camera, boundingGeometry = camera.location)
    }

    // Dialog helper for showing errors.
    val messageDialogVM = MessageDialogViewModel()

    init {
        // Load the scene.
        viewModelScope.launch {
            arcGISScene.load().onFailure { messageDialogVM.showMessageDialog(it) }
        }
    }

    /**
     * Update exaggeration using an increment or decrement amount.
     * Value is expected between 1 and 10, clamped for the sample.
     */
    fun updateElevationExaggeration(amount: Float) {
        // Update current elevation state with the exaggeration amount
        currentElevationExaggeration = (currentElevationExaggeration + amount).coerceIn(1f, 10f)
        // Update the base surface to honor the current elevation state
        arcGISScene.baseSurface.elevationExaggeration = currentElevationExaggeration
    }
}