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.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.rememberUpdatedState
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.atan2
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 center
    ROTATE,             // Two-finger rotation
    PINCH_SIZE,         // Pinch near blur edges to resize
    PINCH_ZOOM          // Pinch in center to zoom camera
}

// Sensitivity factor for size pinch (lower = less sensitive)
private const val SIZE_SENSITIVITY = 0.3f
private const val ZOOM_SENSITIVITY = 0.5f

/**
 * Calculates the angle between two touch points.
 */
private fun angleBetweenPoints(p1: Offset, p2: Offset): Float {
    return atan2(p2.y - p1.y, p2.x - p1.x)
}

/**
 * Overlay that shows tilt-shift effect controls and handles gestures.
 */
@Composable
fun TiltShiftOverlay(
    params: BlurParameters,
    onParamsChange: (BlurParameters) -> Unit,
    onZoomChange: (Float) -> Unit,
    modifier: Modifier = Modifier
) {
    // Use rememberUpdatedState to always get latest values inside pointerInput
    val currentParams by rememberUpdatedState(params)
    val currentOnParamsChange by rememberUpdatedState(onParamsChange)
    val currentOnZoomChange by rememberUpdatedState(onZoomChange)

    var currentGesture by remember { mutableStateOf(GestureType.NONE) }

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

                    // Capture initial state at gesture start
                    val gestureStartParams = currentParams
                    var initialTouchAngle = 0f
                    var initialDragCentroid = firstDown.position
                    var accumulatedZoom = 1f
                    var rotationInitialized = false
                    var dragInitialized = false

                    var previousCentroid = firstDown.position

                    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 p1 = pointers[0].position
                                val p2 = pointers[1].position
                                val currentTouchAngle = angleBetweenPoints(p1, p2)
                                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(),
                                        currentParams
                                    )
                                    rotationInitialized = false
                                }

                                when (currentGesture) {
                                    GestureType.ROTATE -> {
                                        if (!rotationInitialized) {
                                            initialTouchAngle = currentTouchAngle
                                            rotationInitialized = true
                                        } else {
                                            val angleDelta = currentTouchAngle - initialTouchAngle
                                            val newAngle = gestureStartParams.angle + angleDelta
                                            currentOnParamsChange(currentParams.copy(angle = newAngle))
                                        }
                                    }
                                    GestureType.PINCH_SIZE -> {
                                        val dampenedZoom = 1f + (zoom - 1f) * SIZE_SENSITIVITY
                                        accumulatedZoom *= dampenedZoom
                                        val newSize = (gestureStartParams.size * accumulatedZoom)
                                            .coerceIn(BlurParameters.MIN_SIZE, BlurParameters.MAX_SIZE)
                                        currentOnParamsChange(currentParams.copy(size = newSize))
                                    }
                                    GestureType.PINCH_ZOOM -> {
                                        val dampenedZoom = 1f + (zoom - 1f) * ZOOM_SENSITIVITY
                                        currentOnZoomChange(dampenedZoom)
                                    }
                                    else -> {}
                                }
                            }

                            // Single finger - drag to move focus center 1:1
                            pointers.size == 1 -> {
                                if (currentGesture == GestureType.NONE) {
                                    currentGesture = GestureType.DRAG_POSITION
                                    dragInitialized = false
                                }

                                if (currentGesture == GestureType.DRAG_POSITION) {
                                    if (!dragInitialized) {
                                        initialDragCentroid = centroid
                                        dragInitialized = true
                                    } else {
                                        // Calculate total drag from initial touch point
                                        val totalDragX = (centroid.x - initialDragCentroid.x) / size.width
                                        val totalDragY = (centroid.y - initialDragCentroid.y) / size.height
                                        val newX = (gestureStartParams.positionX + totalDragX).coerceIn(0f, 1f)
                                        val newY = (gestureStartParams.positionY + totalDragY).coerceIn(0f, 1f)
                                        currentOnParamsChange(currentParams.copy(positionX = newX, positionY = newY))
                                    }
                                }
                            }
                        }

                        previousCentroid = centroid
                        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.
 *
 * Zones (from center outward):
 * - Very center (< 30% of focus height): Rotation
 * - Near focus line (30% - 200% of focus height): Size adjustment
 * - Far outside (> 200%): Camera zoom
 */
private fun determineGestureType(
    centroid: Offset,
    width: Float,
    height: Float,
    params: BlurParameters
): GestureType {
    // Calculate distance from focus center
    val focusCenterX = width * params.positionX
    val focusCenterY = height * params.positionY
    val focusHalfHeight = height * params.size * 0.5f

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

    val distFromCenter = kotlin.math.abs(rotatedY)

    return when {
        // Very center of focus zone -> rotation (small area)
        distFromCenter < focusHalfHeight * 0.3f -> {
            GestureType.ROTATE
        }
        // Anywhere near the blur effect -> size adjustment (large area)
        distFromCenter < focusHalfHeight * 2.0f -> {
            GestureType.PINCH_SIZE
        }
        // Far 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 * params.positionX
    val centerY = height * params.positionY
    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
        drawRect(
            color = blurZoneColor,
            topLeft = Offset(centerX - extendedHalf, centerY - focusHalfHeight - extendedHalf),
            size = androidx.compose.ui.geometry.Size(extendedHalf * 2, extendedHalf)
        )
        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()
        )
    }
}