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
}

/**
 * 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) }

    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

                    initialAngle = params.angle
                    initialSize = params.size
                    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 -> {
                                        accumulatedRotation += rotation
                                        val newAngle = initialAngle + accumulatedRotation
                                        onParamsChange(params.copy(angle = newAngle))
                                    }
                                    GestureType.PINCH_SIZE -> {
                                        accumulatedZoom *= zoom
                                        val newSize = (initialSize * accumulatedZoom)
                                            .coerceIn(BlurParameters.MIN_SIZE, BlurParameters.MAX_SIZE)
                                        onParamsChange(params.copy(size = newSize))
                                    }
                                    GestureType.PINCH_ZOOM -> {
                                        onZoomChange(zoom)
                                    }
                                    else -> {}
                                }
                            }

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

                                if (currentGesture == GestureType.DRAG_POSITION) {
                                    val deltaY = (centroid.y - previousCentroid.y) / size.height
                                    val newPosition = (params.position + deltaY).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.
 */
private fun DrawScope.drawTiltShiftOverlay(params: BlurParameters) {
    val width = size.width
    val height = size.height

    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)

    rotate(angleDegrees, pivot = Offset(width / 2f, centerY)) {
        // Draw blur zone indicators (top and bottom)
        drawRect(
            color = blurZoneColor,
            topLeft = Offset(0f, 0f),
            size = androidx.compose.ui.geometry.Size(width, centerY - focusHalfHeight)
        )
        drawRect(
            color = blurZoneColor,
            topLeft = Offset(0f, centerY + focusHalfHeight),
            size = androidx.compose.ui.geometry.Size(width, height - (centerY + focusHalfHeight))
        )

        // Draw focus zone boundary lines
        drawLine(
            color = focusLineColor,
            start = Offset(0f, centerY - focusHalfHeight),
            end = Offset(width, centerY - focusHalfHeight),
            strokeWidth = 2.dp.toPx(),
            pathEffect = dashEffect
        )
        drawLine(
            color = focusLineColor,
            start = Offset(0f, centerY + focusHalfHeight),
            end = Offset(width, centerY + focusHalfHeight),
            strokeWidth = 2.dp.toPx(),
            pathEffect = dashEffect
        )

        // Draw center focus line
        drawLine(
            color = focusLineColor,
            start = Offset(0f, centerY),
            end = Offset(width, 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(width / 2f, centerY),
            style = Stroke(width = 2.dp.toPx())
        )

        // Draw angle tick mark
        val tickLength = 15.dp.toPx()
        drawLine(
            color = focusLineColor,
            start = Offset(width / 2f, centerY - indicatorRadius + tickLength),
            end = Offset(width / 2f, centerY - indicatorRadius - 5.dp.toPx()),
            strokeWidth = 3.dp.toPx()
        )
    }
}