orx/orx-mesh-generators/src/commonMain/kotlin/MeshGenerators.kt

package org.openrndr.extra.meshgenerators

import org.openrndr.draw.*
import org.openrndr.math.Vector2
import org.openrndr.math.Vector3
import org.openrndr.math.mod
import org.openrndr.shape.Shape
import org.openrndr.shape.triangulate

/**
 * Vertex writer function interface
 */
typealias VertexWriter = (position: Vector3, normal: Vector3, texCoord: Vector2) -> Unit

/**
 * create a [VertexWriter] that writes into a [java.nio.ByteBuffer] through [BufferWriter]
 */
fun bufferWriter(bw: BufferWriter): VertexWriter {
    return { p, n, t ->
        bw.write(p)
        bw.write(n)
        bw.write(t)
    }
}

/**
 * Creates a [VertexBuffer] that is suited for holding meshes.
 * Each vertex contains:
 * - `position` (vec3)
 * - `normal` (vec3)
 * - `textureCoordinate` (vec2)
 */
fun meshVertexBuffer(size: Int): VertexBuffer {
    return vertexBuffer(vertexFormat(BufferAlignment.STD430) {
        position(3)
        normal(3)
        textureCoordinate(2)
    }, size)
}

/**
 * Creates a [VertexBuffer] that is suited for holding meshes.
 * Each vertex contains:
 * - `position` (vec3)
 * - `normal` (vec3)
 * - `textureCoordinate` (vec2)
 * - `color` (vec4)
 */
fun meshVertexBufferWithColor(size: Int): VertexBuffer {
    return vertexBuffer(vertexFormat(BufferAlignment.STD430) {
        position(3)
        normal(3)
        textureCoordinate(2)
        color(4)
    }, size)
}


@Deprecated("binary compatibility only")
fun extrudeShape(
    shape: Shape,
    front: Double,
    back: Double,
    distanceTolerance: Double = 0.5,
    writer: VertexWriter
) {
    extrudeShape(
        shape,
        front,
        back,
        distanceTolerance = distanceTolerance,
        flipNormals = false,
        writer = writer
    )
}


/**
 * Extrudes a [Shape] from its triangulations
 *
 * @param baseTriangles triangle vertices for the caps
 * @param contours contour vertices for the sides
 * @param front the `z` position of the front
 * @param back the `z` position of the back
 * @param frontScale scale factor for the front cap
 * @param backScale scale factor for the back cap
 * @param frontCap add a front cap if true
 * @param backCap add a back cap if true
 * @param sides add the sides if true
 * @param flipNormals generates inside-out geometry if true
 * @param writer the vertex writer function
 */

fun extrudeShape(
    baseTriangles: List<Vector2>,
    contours: List<List<Vector2>>,
    front: Double,
    back: Double,
    frontScale: Double = 1.0,
    backScale: Double = 1.0,
    frontCap: Boolean = true,
    backCap: Boolean = true,
    sides: Boolean = true,
    flipNormals: Boolean = false,
    writer: VertexWriter
) {

    val depth = back - front
    val flip = if (flipNormals) 1.0 else -1.0

    run {
        val normal = Vector3(0.0, 0.0, depth).normalized * flip
        val negativeNormal = normal * -1.0

        if (frontCap) {
            baseTriangles.reversed().forEach {
                writer(
                    (it * frontScale).vector3(z = front),
                    normal,
                    Vector2.ZERO
                )
            }
        }
        if (backCap) {
            baseTriangles.forEach {
                writer(
                    (it * backScale).vector3(z = back),
                    negativeNormal,
                    Vector2.ZERO
                )
            }
        }
    }

    if (sides) {
        contours.forEach {
            val points = it

            val normals = (points.indices).map { index ->
                val a = mod(index + 1, points.size)
                val b = mod(index - 1, points.size)
                (points[a] - points[b]).safeNormalized * -flip
            }
            val forward = Vector3(0.0, 0.0, depth)
            val base = Vector3(0.0, 0.0, front)

            var offset = 0.0
            (points zip normals).zipWithNext().forEach { (left, right) ->

                val width = right.first.distanceTo(left.first)

                val frontRight = (right.first * frontScale).xy0 + base
                val frontLeft = (left.first * frontScale).xy0 + base


                val backRight = (right.first * backScale).xy0 + base + forward
                val backLeft = (left.first * backScale).xy0 + base + forward

                val height = frontRight.distanceTo(backRight)


                val backRightUV = Vector2(offset + width, 0.0)
                val backLeftUV = Vector2(offset, 0.0)

                val frontLeftUV = Vector2(offset, height)
                val frontRightUV = Vector2(offset + width, height)


                val lnormal =
                    (frontLeft - backLeft).normalized.cross(left.second.xy0)
                val rnormal =
                    (frontRight - backRight).normalized.cross(right.second.xy0)

                writer(frontLeft, lnormal, frontLeftUV)
                writer(frontRight, rnormal, frontRightUV)
                writer(backRight, rnormal, backRightUV)

                writer(backRight, rnormal, backRightUV)
                writer(backLeft, lnormal, backLeftUV)
                writer(frontLeft, lnormal, frontLeftUV)

                offset += width
            }
        }
    }
}


/**
 * Extrudes a [shape] by triangulating it and creating side- and cap geometry.
 * @param front the `z` position of the front
 * @param back the `z` position of the back
 * @param frontScale scale factor for the front cap
 * @param backScale scale factor for the back cap
 * @param frontCap add a front cap if true
 * @param backCap add a back cap if true
 * @param sides add the sides if true
 * @param distanceTolerance
 * @param flipNormals generates inside-out geometry if true
 * @param writer the vertex writer function
 */
fun extrudeShape(
    shape: Shape,
    front: Double,
    back: Double,
    frontScale: Double = 1.0,
    backScale: Double = 1.0,
    frontCap: Boolean = true,
    backCap: Boolean = true,
    sides: Boolean = true,
    distanceTolerance: Double = 0.5,
    flipNormals: Boolean = false,
    writer: VertexWriter
) {
    val baseTriangles = triangulate(shape, distanceTolerance)
    val points = shape.contours.map { it.adaptivePositions(distanceTolerance) }

    extrudeShape(
        baseTriangles = baseTriangles,
        contours = points,
        front = front,
        back = back,
        frontScale = frontScale,
        backScale = backScale,
        frontCap = frontCap,
        backCap = backCap,
        sides = sides,
        flipNormals = flipNormals,
        writer = writer
    )
}

/**
 * Extrudes all [shapes]. Uses [writer] to write the resulting
 * 3D meshes. The arguments are passed unmodified to [extrudeShape].
 */
fun extrudeShapes(
    shapes: List<Shape>,
    front: Double,
    back: Double,
    frontScale: Double = 1.0,
    backScale: Double = 1.0,
    frontCap: Boolean = true,
    backCap: Boolean = true,
    sides: Boolean = true,
    distanceTolerance: Double = 0.5,
    flipNormals: Boolean = false,
    writer: VertexWriter
) {
    shapes.forEach {
        extrudeShape(
            shape = it,
            front = front,
            back = back,
            frontScale = frontScale,
            backScale = backScale,
            frontCap = frontCap,
            backCap = backCap,
            sides = sides,
            distanceTolerance = distanceTolerance,
            flipNormals = flipNormals,
            writer = writer
        )
    }
}

/**
 * Return a normalized [Vector2], or [Vector2.ZERO] if the vector is too small
 */
private val Vector2.safeNormalized: Vector2
    get() {
        return if (length > 0.0001) {
            normalized
        } else {
            Vector2.ZERO
        }
    }