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.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
) {
    var currentGesture by remember { mutableStateOf(GestureType.NONE) }
    var initialAngle by remember { mutableFloatStateOf(0f) }
    var initialTouchAngle by remember { mutableFloatStateOf(0f) }
    var initialSize by remember { mutableFloatStateOf(0.3f) }
    var initialPositionX by remember { mutableFloatStateOf(0.5f) }
    var initialPositionY 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 accumulatedZoom = 1f
                    var rotationInitialized = false

                    initialAngle = params.angle
                    initialSize = params.size
                    initialPositionX = params.positionX
                    initialPositionY = params.positionY

                    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(),
                                        params
                                    )
                                    rotationInitialized = false
                                }

                                when (currentGesture) {
                                    GestureType.ROTATE -> {
                                        // Initialize rotation reference on first frame
                                        if (!rotationInitialized) {
                                            initialTouchAngle = currentTouchAngle
                                            initialAngle = params.angle
                                            rotationInitialized = true
                                        } else {
                                            // Direct angle mapping: effect angle = initial + (current touch angle - initial touch angle)
                                            val angleDelta = currentTouchAngle - initialTouchAngle
                                            val newAngle = initialAngle + angleDelta
                                            onParamsChange(params.copy(angle = newAngle))
                                        }
                                    }
                                    GestureType.PINCH_SIZE -> {
                                        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 -> {
                                        val dampenedZoom = 1f + (zoom - 1f) * ZOOM_SENSITIVITY
                                        onZoomChange(dampenedZoom)
                                    }
                                    else -> {}
                                }
                            }

                            // Single finger - drag to move focus center 1:1
                            pointers.size == 1 -> {
                                if (currentGesture == GestureType.NONE) {
                                    currentGesture = GestureType.DRAG_POSITION
                                    // Reset initial position at drag start
                                    initialPositionX = params.positionX
                                    initialPositionY = params.positionY
                                    previousCentroid = centroid
                                }

                                if (currentGesture == GestureType.DRAG_POSITION) {
                                    // 1:1 drag - finger movement directly maps to position change
                                    val deltaX = (centroid.x - previousCentroid.x) / size.width
                                    val deltaY = (centroid.y - previousCentroid.y) / size.height
                                    val newX = (params.positionX + deltaX).coerceIn(0f, 1f)
                                    val newY = (params.positionY + deltaY).coerceIn(0f, 1f)
                                    onParamsChange(params.copy(positionX = newX, positionY = newY))
                                }
                            }
                        }

                        previousCentroid = centroid

                        // 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.
 *
 * 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()
        )
    }
}