using System;
using UnityEngine;
using UnityEngine.Perception.Randomization.Samplers;

namespace UnityEngine.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
    {
        /// <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", "");
        }

        [HideInInspector, SerializeField] internal bool collapsed;

        /// <summary>
        /// The name of the parameter
        /// </summary>
        [HideInInspector] public string name = "Parameter";

        /// <summary>
        /// The target this parameter apply a sample to
        /// </summary>
        [HideInInspector, SerializeField] public ParameterTarget target = new ParameterTarget();

        /// <summary>
        /// Indicates whether this parameter has a target GameObject
        /// </summary>
        public bool hasTarget => target.gameObject != null;

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

        /// <summary>
        /// An array containing a reference to each sampler field in this parameter
        /// </summary>
        public abstract ISampler[] samplers { get; }

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

        /// <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.Rebase(SamplerUtility.IterateSeed((uint)i++, SamplerUtility.largePrime));
                sampler.ResetState();
            }
        }

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

        /// <summary>
        /// Resets sampler states and then offsets those states using the current scenario iteration
        /// </summary>
        /// <param name="scenarioIteration">The current scenario iteration</param>
        public void ResetState(int scenarioIteration)
        {
            foreach (var sampler in samplers)
                sampler.ResetState(scenarioIteration);
        }

        /// <summary>
        /// Applies one sampled value to this parameters assigned target gameobject
        /// </summary>
        internal abstract void ApplyToTarget(int seedOffset);

        /// <summary>
        /// Validates parameter settings
        /// </summary>
        internal virtual void Validate()
        {
            if (hasTarget)
            {
                if (target.component == null)
                    throw new ParameterValidationException($"Null component target on parameter \"{name}\"");
                if (string.IsNullOrEmpty(target.propertyName))
                    throw new ParameterValidationException($"Invalid property target on parameter \"{name}\"");
            }
        }
    }
}