package org.openrndr.extra.meshgenerators

import org.openrndr.draw.VertexBuffer
import org.openrndr.math.Spherical
import org.openrndr.math.Vector2
import kotlin.math.max

/**
 * Returns a sphere mesh
 *
 * @param sides The number of steps around its axis.
 * @param segments The number of steps from pole to pole.
 * @param radius The radius of the sphere.
 * @param flipNormals Create an inside-out shape if true.
 */
fun sphereMesh(
    sides: Int = 16,
    segments: Int = 16,
    radius: Double = 1.0,
    flipNormals: Boolean = false
): VertexBuffer {
    val vertexCount = 2 * sides * 3 + max(0, (segments - 2)) * sides * 6
    val vb = meshVertexBuffer(vertexCount)
    vb.put {
        generateSphere(sides, segments, radius, flipNormals, bufferWriter(this))
    }
    return vb
}

/**
 * Generate sphere centered at the origin.
 *
 * @param sides The number of steps around its axis.
 * @param segments The number of steps from pole to pole.
 * @param radius The radius of the sphere.
 * @param flipNormals Create an inside-out shape if true.
 * @param writer The vertex writer function
 */
fun generateSphere(
    sides: Int,
    segments: Int,
    radius: Double = 1.0,
    flipNormals: Boolean = false,
    writer: VertexWriter
) {
    val invertFactor = if (flipNormals) -1.0 else 1.0
    for (t in 0 until segments) {
        for (s in 0 until sides) {
            val st00 = Spherical(s * 180.0 * 2.0 / sides, t * 180.0 / segments, radius)
            val st01 = Spherical(s * 180.0 * 2.0 / sides, (t + 1) * 180.0 / segments, radius)
            val st10 = Spherical((s + 1) * 180.0 * 2.0 / sides, t * 180.0 / segments, radius)
            val st11 = Spherical((s + 1) * 180.0 * 2.0 / sides, (t + 1) * 180.0 / segments, radius)

            val thetaMax = 180.0 * 2.0
            val phiMax = 180.0

            when (t) {
                0 -> {
                    writer(st00.cartesian, st00.cartesian.normalized * invertFactor, Vector2(st00.theta / thetaMax, 1.0 - st00.phi / phiMax))
                    writer(st01.cartesian, st01.cartesian.normalized * invertFactor, Vector2(st01.theta / thetaMax, 1.0 - st01.phi / phiMax))
                    writer(st11.cartesian, st11.cartesian.normalized * invertFactor, Vector2(st11.theta / thetaMax, 1.0 - st11.phi / phiMax))
                }
                segments - 1 -> {
                    writer(st11.cartesian, st11.cartesian.normalized * invertFactor, Vector2(st11.theta / thetaMax, 1.0 - st11.phi / phiMax))
                    writer(st10.cartesian, st10.cartesian.normalized * invertFactor, Vector2(st10.theta / thetaMax, 1.0 - st10.phi / phiMax))
                    writer(st00.cartesian, st00.cartesian.normalized * invertFactor, Vector2(st00.theta / thetaMax, 1.0 - st00.phi / phiMax))
                }
                else -> {
                    writer(st00.cartesian, st00.cartesian.normalized * invertFactor, Vector2(st00.theta / thetaMax, 1.0 - st00.phi / phiMax))
                    writer(st01.cartesian, st01.cartesian.normalized * invertFactor, Vector2(st01.theta / thetaMax, 1.0 - st01.phi / phiMax))
                    writer(st11.cartesian, st11.cartesian.normalized * invertFactor, Vector2(st11.theta / thetaMax, 1.0 - st11.phi / phiMax))

                    writer(st11.cartesian, st11.cartesian.normalized * invertFactor, Vector2(st11.theta / thetaMax, 1.0 - st11.phi / phiMax))
                    writer(st10.cartesian, st10.cartesian.normalized * invertFactor, Vector2(st10.theta / thetaMax, 1.0 - st10.phi / phiMax))
                    writer(st00.cartesian, st00.cartesian.normalized * invertFactor, Vector2(st00.theta / thetaMax, 1.0 - st00.phi / phiMax))
                }
            }
        }
    }
}

/**
 * Generate hemisphere centered at the origin.
 *
 * @param sides The number of steps around its axis.
 * @param segments The number of steps from pole to pole.
 * @param radius The radius of the sphere.
 * @param flipNormals Create an inside-out shape if true.
 * @param writer The vertex writer function
 */
fun generateHemisphere(
    sides: Int,
    segments: Int,
    radius: Double = 1.0,
    flipNormals: Boolean = false,
    writer: VertexWriter
) {
    val invertFactor = if (flipNormals) -1.0 else 1.0
    for (t in 0 until segments) {
        for (s in 0 until sides) {
            val st00 = Spherical(s * 180.0 * 2.0 / sides, t * 180.0 / segments, radius)
            val st01 = Spherical(s * 180.0 * 2.0 / sides, (t + 1) * 180.0 / segments, radius)
            val st10 = Spherical((s + 1) * 180.0 * 2.0 / sides, t * 180.0 / segments, radius)
            val st11 = Spherical((s + 1) * 180.0 * 2.0 / sides, (t + 1) * 180.0 / segments, radius)

            val thetaMax = 180.0 * 2.0
            val phiMax = 180.0 * 0.5

            when (t) {
                0 -> {
                    writer(st00.cartesian, st00.cartesian.normalized * invertFactor, Vector2(st00.theta / thetaMax + 0.5, 1.0 - st00.phi / phiMax))
                    writer(st01.cartesian, st01.cartesian.normalized * invertFactor, Vector2(st01.theta / thetaMax + 0.5, 1.0 - st01.phi / phiMax))
                    writer(st11.cartesian, st11.cartesian.normalized * invertFactor, Vector2(st11.theta / thetaMax + 0.5, 1.0 - st11.phi / phiMax))
                }
                else -> {
                    writer(st00.cartesian, st00.cartesian.normalized * invertFactor, Vector2(st00.theta / thetaMax + 0.5, 1.0 - st00.phi / phiMax))
                    writer(st01.cartesian, st01.cartesian.normalized * invertFactor, Vector2(st01.theta / thetaMax + 0.5, 1.0 - st01.phi / phiMax))
                    writer(st11.cartesian, st11.cartesian.normalized * invertFactor, Vector2(st11.theta / thetaMax + 0.5, 1.0 - st11.phi / phiMax))

                    writer(st11.cartesian, st11.cartesian.normalized * invertFactor, Vector2(st11.theta / thetaMax + 0.5, 1.0 - st11.phi / phiMax))
                    writer(st10.cartesian, st10.cartesian.normalized * invertFactor, Vector2(st10.theta / thetaMax + 0.5, 1.0 - st10.phi / phiMax))
                    writer(st00.cartesian, st00.cartesian.normalized * invertFactor, Vector2(st00.theta / thetaMax + 0.5, 1.0 - st00.phi / phiMax))
                }
            }
        }
    }
}