package org.openrndr.extras.meshgenerators

import org.openrndr.draw.VertexBuffer
import org.openrndr.math.Matrix44
import org.openrndr.math.Vector2
import org.openrndr.math.Vector3
import org.openrndr.math.mix
import org.openrndr.math.transforms.rotateZ

fun cylinderMesh(sides: Int = 16, segments: Int = 16, radius: Double = 1.0, length: Double, invert: Boolean = false): VertexBuffer {
    val vertexCount = 6 * sides * segments
    val vb = meshVertexBuffer(vertexCount)
    vb.put {
        generateCylinder(sides, segments, radius, length, invert, bufferWriter(this))
    }
    return vb
}

fun generateCylinder(sides: Int, segments: Int, radius: Double, length: Double, invert: Boolean = false, vertexWriter: VertexWriter) {
    return generateTaperedCylinder(sides, segments, radius, radius, length, invert, vertexWriter)
}

fun generateTaperedCylinder(sides: Int, segments: Int, radiusStart: Double, radiusEnd:Double, length: Double, invert: Boolean = false, vertexWriter: VertexWriter) {
    val dphi = (Math.PI * 2) / sides
    val ddeg = (360.0) / sides

    val invertFactor = if (invert) -1.0 else 1.0

    val dr = radiusEnd - radiusStart

    val baseNormal = Vector2(length, dr).normalized.perpendicular.let { Vector3(x=it.y, y=0.0, z=it.x)}
    //val baseNormal = Vector3(1.0, 0.0, 0.0)

    for (segment in 0 until segments) {

        val radius0 = mix(radiusStart, radiusEnd, segment*1.0/segments)
        val radius1 = mix(radiusStart, radiusEnd, (segment+1)*1.0/segments)
        val z0 = (length / segments) * segment - length/2.0
        val z1 = (length / segments) * (segment + 1) - length/2.0


        for (side in 0 until sides) {
            val x00 = Math.cos(side * dphi) * radius0
            val x10 = Math.cos(side * dphi + dphi) * radius0
            val y00 = Math.sin(side * dphi) * radius0
            val y10 = Math.sin(side * dphi + dphi) * radius0

            val x01 = Math.cos(side * dphi) * radius1
            val x11 = Math.cos(side * dphi + dphi) * radius1
            val y01 = Math.sin(side * dphi) * radius1
            val y11 = Math.sin(side * dphi + dphi) * radius1


            val u0 = (segment + 0.0) / segments
            val u1 = (segment + 1.0) / segments
            val v0 = (side + 0.0) / sides
            val v1 = (side + 1.0) / sides


            val n0 = (Matrix44.rotateZ(side * ddeg) * baseNormal.xyz0).xyz.normalized * invertFactor
            val n1 = (Matrix44.rotateZ((side+1) * ddeg) * baseNormal.xyz0).xyz.normalized * invertFactor


            if (!invert) {
                vertexWriter(Vector3(x00, y00, z0), n0, Vector2(u0, v0))
                vertexWriter(Vector3(x10, y10, z0), n1, Vector2(u0, v1))
                vertexWriter(Vector3(x11, y11, z1), n1, Vector2(u1, v1))

                vertexWriter(Vector3(x11, y11, z1), n1, Vector2(u1, v1))
                vertexWriter(Vector3(x01, y01, z1), n0, Vector2(u1, v0))
                vertexWriter(Vector3(x00, y00, z0), n0, Vector2(u0, v0))
            } else {
                vertexWriter(Vector3(x00, y00, z0), n0, Vector2(u0, v0))
                vertexWriter(Vector3(x01, y01, z1), n0, Vector2(u1, v0))
                vertexWriter(Vector3(x11, y11, z1), n1, Vector2(u1, v1))

                vertexWriter(Vector3(x11, y11, z1), n1, Vector2(u1, v1))
                vertexWriter(Vector3(x10, y10, z0), n1, Vector2(u0, v1))
                vertexWriter(Vector3(x00, y00, z0), n0, Vector2(u0, v0))
            }
        }
    }
}