// PropLinePlacer - a tool for placing lines of prefabs
// By Jon Manning

// MIT License

// Copyright (c) 2019 Secret Lab Pty Ltd

// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:

// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
// IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
// TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
// SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

using UnityEngine;

public class PropLinePlacer : MonoBehaviour
{
    /// <summary>
    /// The end point of the line, in local space.
    /// </summary>
    /// <remarks>The start point is the transform of this object.</remarks>
    public Vector3 endPoint = new Vector3(1, 0, 0);

    /// <summary>
    /// The possible prefabs that this line should contain. Prefabs will be
    /// randomly selected from this list.
    /// </summary>
    public GameObject[] prefabs;

    /// <summary>
    /// The number of objects that should be created.
    /// </summary>
    public uint numberOfObjects = 3;

    /// <summary>
    /// If true, the created objects will be randomly rotated around the Y
    /// axis.
    /// </summary>
    public bool randomizeYRotation = true;

    /// <summary>
    /// The amount of distance, in the X and Z directions, to randomly
    /// offset our objects.
    /// </summary>
    public float randomXZDistance = 0.05f;

    /// <summary>
    /// The degree of distance along the line to shift our objects.
    /// </summary>
    public float maxLineDisplacement = 0f;

    /// <summary>
    /// A list of materials to randomly assign to the created objects.
    /// </summary>
    /// <remarks>If this array is empty, the created objects will not have
    /// their materials changed.</remarks>
    public Material[] materials;

    /// <summary>
    /// Produces an array of positions, in world space, for objects to be
    /// created at.
    /// </summary>
    /// <returns>The positions, in world space, for objects to be
    /// placed.</returns>
    public Vector3[] GetSpawnPositions()
    {
        // Early out if we're producing zero objects.
        if (numberOfObjects == 0)
        {
            return new Vector3[0];
        }

        var result = new Vector3[numberOfObjects];

        // Save the state of the random number generator, because we're
        // about to blow it away
        var state = UnityEngine.Random.state;

        // Reset the random number generator so that it's consistent
        // between frames
        Random.InitState(0);

        // For each object we want to create, calculate its position
        for (int i = 0; i < numberOfObjects; i++)
        {
            // Figure out how far along the line we are, from 0 to 1
            var t = i / (float)(numberOfObjects - 1);

            // Randomly displace this along the line (this is why we're
            // preserving random state, otherwise the positions would
            // change every frame that the object is selected in the
            // editor)
            t += Random.Range(-maxLineDisplacement, maxLineDisplacement) * 1f / numberOfObjects;

            // Calculate this position along the line!
            var position = Vector3.Lerp(
                transform.position, // start point
                endPoint + transform.position, // end point
                t // position on the line (from 0 to 1)
            );

            result[i] = position;
        }

        // Restore the random state we saved earlier
        Random.state = state;

        // Return the list of positions!
        return result;
    }
}