tilt-shift-camera/app/src/main/java/no/naiv/tiltshift/ui/TiltShiftOverlay.kt

package no.naiv.tiltshift.ui

import androidx.compose.foundation.Canvas
import androidx.compose.foundation.gestures.awaitEachGesture
import androidx.compose.foundation.gestures.awaitFirstDown
import androidx.compose.foundation.gestures.calculateCentroid
import androidx.compose.foundation.gestures.calculateRotation
import androidx.compose.foundation.gestures.calculateZoom
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.runtime.Composable
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableFloatStateOf
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.graphics.PathEffect
import androidx.compose.ui.graphics.drawscope.DrawScope
import androidx.compose.ui.graphics.drawscope.Stroke
import androidx.compose.ui.graphics.drawscope.rotate
import androidx.compose.ui.input.pointer.PointerEventType
import androidx.compose.ui.input.pointer.pointerInput
import androidx.compose.ui.unit.dp
import no.naiv.tiltshift.effect.BlurParameters
import kotlin.math.PI
import kotlin.math.cos
import kotlin.math.sin

/**
 * Type of gesture being performed.
 */
private enum class GestureType {
    NONE,
    DRAG_POSITION,      // Single finger drag to move focus position
    ROTATE,             // Two-finger rotation
    PINCH_SIZE,         // Pinch near blur edges to resize
    PINCH_ZOOM          // Pinch in center to zoom camera
}

// Sensitivity factors for gesture controls (lower = less sensitive)
private const val POSITION_SENSITIVITY = 0.15f   // Drag to move focus line
private const val ROTATION_SENSITIVITY = 0.2f    // Two-finger rotation
private const val SIZE_SENSITIVITY = 0.25f       // Pinch to resize blur zone
private const val ZOOM_SENSITIVITY = 0.4f        // Pinch to zoom camera

/**
 * Overlay that shows tilt-shift effect controls and handles gestures.
 */
@Composable
fun TiltShiftOverlay(
    params: BlurParameters,
    onParamsChange: (BlurParameters) -> Unit,
    onZoomChange: (Float) -> Unit,
    modifier: Modifier = Modifier
) {
    var currentGesture by remember { mutableStateOf(GestureType.NONE) }
    var initialZoom by remember { mutableFloatStateOf(1f) }
    var initialAngle by remember { mutableFloatStateOf(0f) }
    var initialSize by remember { mutableFloatStateOf(0.3f) }
    var initialPosition by remember { mutableFloatStateOf(0.5f) }

    Canvas(
        modifier = modifier
            .fillMaxSize()
            .pointerInput(Unit) {
                awaitEachGesture {
                    val firstDown = awaitFirstDown(requireUnconsumed = false)
                    currentGesture = GestureType.NONE

                    var previousCentroid = firstDown.position
                    var previousPointerCount = 1
                    var accumulatedRotation = 0f
                    var accumulatedZoom = 1f
                    var accumulatedDragY = 0f

                    initialAngle = params.angle
                    initialSize = params.size
                    initialPosition = params.position
                    initialZoom = 1f

                    do {
                        val event = awaitPointerEvent()
                        val pointers = event.changes.filter { it.pressed }

                        if (pointers.isEmpty()) break

                        val centroid = if (pointers.size >= 2) {
                            event.calculateCentroid()
                        } else {
                            pointers.first().position
                        }

                        when {
                            // Two or more fingers
                            pointers.size >= 2 -> {
                                val rotation = event.calculateRotation()
                                val zoom = event.calculateZoom()

                                // Determine gesture type based on touch positions
                                if (currentGesture == GestureType.NONE || currentGesture == GestureType.DRAG_POSITION) {
                                    currentGesture = determineGestureType(
                                        centroid,
                                        size.width.toFloat(),
                                        size.height.toFloat(),
                                        params
                                    )
                                }

                                when (currentGesture) {
                                    GestureType.ROTATE -> {
                                        // Apply dampening to rotation
                                        accumulatedRotation += rotation * ROTATION_SENSITIVITY
                                        val newAngle = initialAngle + accumulatedRotation
                                        onParamsChange(params.copy(angle = newAngle))
                                    }
                                    GestureType.PINCH_SIZE -> {
                                        // Apply dampening to size change
                                        val dampenedZoom = 1f + (zoom - 1f) * SIZE_SENSITIVITY
                                        accumulatedZoom *= dampenedZoom
                                        val newSize = (initialSize * accumulatedZoom)
                                            .coerceIn(BlurParameters.MIN_SIZE, BlurParameters.MAX_SIZE)
                                        onParamsChange(params.copy(size = newSize))
                                    }
                                    GestureType.PINCH_ZOOM -> {
                                        // Apply dampening to camera zoom
                                        val dampenedZoom = 1f + (zoom - 1f) * ZOOM_SENSITIVITY
                                        onZoomChange(dampenedZoom)
                                    }
                                    else -> {}
                                }
                            }

                            // Single finger
                            pointers.size == 1 -> {
                                if (currentGesture == GestureType.NONE) {
                                    currentGesture = GestureType.DRAG_POSITION
                                }

                                if (currentGesture == GestureType.DRAG_POSITION) {
                                    // Apply dampening to position drag
                                    val deltaY = (centroid.y - previousCentroid.y) / size.height
                                    accumulatedDragY += deltaY * POSITION_SENSITIVITY
                                    val newPosition = (initialPosition + accumulatedDragY).coerceIn(0f, 1f)
                                    onParamsChange(params.copy(position = newPosition))
                                }
                            }
                        }

                        previousCentroid = centroid
                        previousPointerCount = pointers.size

                        // Consume all pointer changes
                        pointers.forEach { it.consume() }
                    } while (event.type != PointerEventType.Release)

                    currentGesture = GestureType.NONE
                }
            }
    ) {
        drawTiltShiftOverlay(params)
    }
}

/**
 * Determines the type of two-finger gesture based on touch position.
 */
private fun determineGestureType(
    centroid: Offset,
    width: Float,
    height: Float,
    params: BlurParameters
): GestureType {
    // Calculate distance from focus center line
    val focusCenterY = height * params.position
    val focusHalfHeight = height * params.size * 0.5f

    // Rotate centroid to align with focus line
    val dx = centroid.x - width / 2f
    val dy = centroid.y - focusCenterY
    val rotatedY = -dx * sin(params.angle) + dy * cos(params.angle)

    val distFromCenter = kotlin.math.abs(rotatedY)

    return when {
        // Near the edges of the blur zone -> size adjustment
        distFromCenter > focusHalfHeight * 0.7f && distFromCenter < focusHalfHeight * 1.5f -> {
            GestureType.PINCH_SIZE
        }
        // Inside the focus zone -> rotation
        distFromCenter < focusHalfHeight * 0.7f -> {
            GestureType.ROTATE
        }
        // Outside -> camera zoom
        else -> {
            GestureType.PINCH_ZOOM
        }
    }
}

/**
 * Draws the tilt-shift visualization overlay.
 * Uses extended geometry so rotated elements don't clip at screen edges.
 */
private fun DrawScope.drawTiltShiftOverlay(params: BlurParameters) {
    val width = size.width
    val height = size.height

    val centerX = width / 2f
    val centerY = height * params.position
    val focusHalfHeight = height * params.size * 0.5f
    val angleDegrees = params.angle * (180f / PI.toFloat())

    // Colors for overlay
    val focusLineColor = Color(0xFFFFB300)  // Amber
    val blurZoneColor = Color(0x40FFFFFF)    // Semi-transparent white
    val dashEffect = PathEffect.dashPathEffect(floatArrayOf(20f, 10f), 0f)

    // Calculate diagonal for extended drawing (ensures coverage when rotated)
    val diagonal = kotlin.math.sqrt(width * width + height * height)
    val extendedHalf = diagonal  // Extend lines/rects well beyond screen

    rotate(angleDegrees, pivot = Offset(centerX, centerY)) {
        // Draw blur zone indicators (top and bottom) - extended horizontally
        // Top blur zone: from far above to the top edge of focus area
        drawRect(
            color = blurZoneColor,
            topLeft = Offset(centerX - extendedHalf, centerY - focusHalfHeight - extendedHalf),
            size = androidx.compose.ui.geometry.Size(extendedHalf * 2, extendedHalf)
        )
        // Bottom blur zone: from bottom edge of focus area to far below
        drawRect(
            color = blurZoneColor,
            topLeft = Offset(centerX - extendedHalf, centerY + focusHalfHeight),
            size = androidx.compose.ui.geometry.Size(extendedHalf * 2, extendedHalf)
        )

        // Draw focus zone boundary lines - extended horizontally
        drawLine(
            color = focusLineColor,
            start = Offset(centerX - extendedHalf, centerY - focusHalfHeight),
            end = Offset(centerX + extendedHalf, centerY - focusHalfHeight),
            strokeWidth = 2.dp.toPx(),
            pathEffect = dashEffect
        )
        drawLine(
            color = focusLineColor,
            start = Offset(centerX - extendedHalf, centerY + focusHalfHeight),
            end = Offset(centerX + extendedHalf, centerY + focusHalfHeight),
            strokeWidth = 2.dp.toPx(),
            pathEffect = dashEffect
        )

        // Draw center focus line - extended horizontally
        drawLine(
            color = focusLineColor,
            start = Offset(centerX - extendedHalf, centerY),
            end = Offset(centerX + extendedHalf, centerY),
            strokeWidth = 3.dp.toPx()
        )

        // Draw rotation indicator at center
        val indicatorRadius = 30.dp.toPx()
        drawCircle(
            color = focusLineColor.copy(alpha = 0.5f),
            radius = indicatorRadius,
            center = Offset(centerX, centerY),
            style = Stroke(width = 2.dp.toPx())
        )

        // Draw angle tick mark
        val tickLength = 15.dp.toPx()
        drawLine(
            color = focusLineColor,
            start = Offset(centerX, centerY - indicatorRadius + tickLength),
            end = Offset(centerX, centerY - indicatorRadius - 5.dp.toPx()),
            strokeWidth = 3.dp.toPx()
        )
    }
}