using System;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Experimental.Perception.Randomization.Samplers;

namespace UnityEngine.Experimental.Perception.Randomization.Parameters
{
    /// <summary>
    /// Parameters, in conjunction with a parameter configuration, are used to create convenient interfaces for
    /// randomizing simulations.
    /// </summary>
    [Serializable]
    public abstract class Parameter
    {
        [HideInInspector, SerializeField] internal bool collapsed;

        /// <summary>
        /// The sample type generated by this parameter
        /// </summary>
        public abstract Type sampleType { get; }

        /// <summary>
        /// Returns an IEnumerable that iterates over each sampler field in this parameter
        /// </summary>
        internal abstract IEnumerable<ISampler> samplers { get; }

        /// <summary>
        /// Constructs a new parameter
        /// </summary>
        protected Parameter()
        {
            InitializeSamplers();
        }

        /// <summary>
        /// Returns the display name of a parameter type
        /// </summary>
        /// <param name="type">A subclass of Parameter</param>
        /// <returns>The parameter type's display name</returns>
        public static string GetDisplayName(Type type)
        {
            return type.Name.Replace("Parameter", "");
        }

        /// <summary>
        /// Deterministically ensures that no sampler shares the same seed when a parameter is initialized
        /// </summary>
        void InitializeSamplers()
        {
            var i = 0;
            foreach (var sampler in samplers)
            {
                sampler.IterateState(i++);
                sampler.ResetState();
            }
        }

        internal void RandomizeSamplers()
        {
            foreach (var sampler in samplers)
            {
                sampler.baseSeed = SamplerUtility.GenerateRandomSeed();
                sampler.ResetState();
            }
        }

        /// <summary>
        /// Resets the state of each sampler employed by this parameter
        /// </summary>
        public void ResetState()
        {
            foreach (var sampler in samplers)
                sampler.ResetState();
        }

        /// <summary>
        /// Offsets the state of each sampler employed by this parameter
        /// </summary>
        /// <param name="offsetIndex">Often the current scenario iteration</param>
        public void IterateState(int offsetIndex)
        {
            foreach (var sampler in samplers)
                sampler.IterateState(offsetIndex);
        }

        /// <summary>
        /// Generates a generic sample
        /// </summary>
        /// <returns>The generated sample</returns>
        public abstract object GenericSample();

        /// <summary>
        /// Validates parameter settings
        /// </summary>
        public virtual void Validate() { }
    }
}