using Prefab.Domain.Common;

namespace Prefab.Catalog.Domain.Entities;

/// <summary>
/// Identifies what entity a rule set controls (option definition vs individual value).
/// </summary>
public enum OptionRuleTargetKind : byte
{
    OptionDefinition = 0,
    OptionValue = 1
}

/// <summary>
/// Result to apply when rule conditions evaluate to true.
/// </summary>
public enum RuleEffect : byte
{
    Show = 0,
    Enable = 1,
    Require = 2
}

/// <summary>
/// Defines whether all or any conditions must be satisfied.
/// </summary>
public enum RuleMode : byte
{
    All = 0,
    Any = 1
}

/// <summary>
/// Operators supported when evaluating rule conditions against shopper selections.
/// </summary>
public enum RuleOperator : byte
{
    Equal = 0,
    NotEqual = 1,
    InList = 2,
    NotInList = 3,
    GreaterThan = 4,
    GreaterThanOrEqual = 5,
    LessThan = 6,
    LessThanOrEqual = 7,
    Between = 8
}

/// <summary>
/// Groups conditions that control visibility, enablement, or requirement for an option or value.
/// </summary>
public class OptionRuleSet : EntityWithAuditAndStatus<Guid>
{
    private OptionRuleSet()
    {
    }

    public Guid ProductId { get; internal set; }

    public Product Product { get; internal set; } = null!;

    public OptionRuleTargetKind TargetKind { get; internal set; }

    public Guid TargetId { get; internal set; }

    public RuleEffect Effect { get; internal set; }

    public RuleMode Mode { get; internal set; }

    public List<OptionRuleCondition> Conditions { get; } = [];

    public static OptionRuleSet Create(
        Product product,
        OptionRuleTargetKind targetKind,
        Guid targetId,
        RuleEffect effect,
        RuleMode mode)
    {
        ArgumentNullException.ThrowIfNull(product);

        if (targetKind == OptionRuleTargetKind.OptionDefinition)
        {
            _ = product.Options.FirstOrDefault(o => o.Id == targetId)
                ?? throw new ArgumentException($"Option definition '{targetId}' does not belong to product '{product.Id}'.", nameof(targetId));
        }
        else
        {
            var ownsValue = product.Options
                .SelectMany(o => o.Values)
                .Any(v => v.Id == targetId);
            if (!ownsValue)
            {
                throw new ArgumentException($"Option value '{targetId}' does not belong to product '{product.Id}'.", nameof(targetId));
            }
        }

        var ruleSet = new OptionRuleSet
        {
            Id = Guid.NewGuid(),
            Product = product,
            ProductId = product.Id,
            TargetKind = targetKind,
            TargetId = targetId,
            Effect = effect,
            Mode = mode
        };

        product.RuleSets.Add(ruleSet);
        return ruleSet;
    }

    public OptionRuleCondition AddCondition(
        OptionDefinition leftOptionDefinition,
        RuleOperator @operator,
        Guid? rightOptionValueId = null,
        string? rightList = null,
        decimal? rightNumber = null,
        decimal? rightMin = null,
        decimal? rightMax = null)
    {
        ArgumentNullException.ThrowIfNull(leftOptionDefinition);
        if (leftOptionDefinition.ProductId != ProductId)
        {
            throw new ArgumentException($"Option definition '{leftOptionDefinition.Id}' does not belong to product '{ProductId}'.", nameof(leftOptionDefinition));
        }

        ValidateRightHandSide(leftOptionDefinition, @operator, rightOptionValueId, rightList, rightNumber, rightMin, rightMax);

        OptionValue? rightOptionValue = null;
        if (rightOptionValueId.HasValue)
        {
            rightOptionValue = leftOptionDefinition.Values.FirstOrDefault(v => v.Id == rightOptionValueId.Value);
            if (rightOptionValue is null)
            {
                rightOptionValue = Product.Options
                    .SelectMany(o => o.Values)
                    .FirstOrDefault(v => v.Id == rightOptionValueId.Value)
                    ?? throw new ArgumentException($"Option value '{rightOptionValueId.Value}' was not found for product '{ProductId}'.", nameof(rightOptionValueId));
            }
        }

        var condition = new OptionRuleCondition
        {
            Id = Guid.NewGuid(),
            RuleSet = this,
            RuleSetId = Id,
            LeftOptionDefinition = leftOptionDefinition,
            LeftOptionDefinitionId = leftOptionDefinition.Id,
            Operator = @operator,
            RightOptionValue = rightOptionValue,
            RightOptionValueId = rightOptionValueId,
            RightList = string.IsNullOrWhiteSpace(rightList) ? null : rightList,
            RightNumber = rightNumber,
            RightMin = rightMin,
            RightMax = rightMax
        };

        Conditions.Add(condition);
        return condition;
    }

    private static void ValidateRightHandSide(
        OptionDefinition leftOptionDefinition,
        RuleOperator @operator,
        Guid? rightOptionValueId,
        string? rightList,
        decimal? rightNumber,
        decimal? rightMin,
        decimal? rightMax)
    {
        var isChoice = leftOptionDefinition.DataType == OptionDataType.Choice;

        switch (@operator)
        {
            case RuleOperator.Equal:
            case RuleOperator.NotEqual:
                if (isChoice)
                {
                    if (rightOptionValueId is null && string.IsNullOrWhiteSpace(rightList))
                    {
                        throw new ArgumentException("Choice comparisons require a right option value identifier or list.", nameof(rightOptionValueId));
                    }
                }
                else if (rightNumber is null)
                {
                    throw new ArgumentException("Numeric comparisons require a numeric value.", nameof(rightNumber));
                }
                break;

            case RuleOperator.InList:
            case RuleOperator.NotInList:
                if (string.IsNullOrWhiteSpace(rightList))
                {
                    throw new ArgumentException("List-based comparisons require a comma delimited list.", nameof(rightList));
                }
                break;

            case RuleOperator.GreaterThan:
            case RuleOperator.GreaterThanOrEqual:
            case RuleOperator.LessThan:
            case RuleOperator.LessThanOrEqual:
                if (rightNumber is null)
                {
                    throw new ArgumentException("Range comparisons require a numeric value.", nameof(rightNumber));
                }
                break;

            case RuleOperator.Between:
                if (rightMin is null || rightMax is null)
                {
                    throw new ArgumentException("Between comparisons require both minimum and maximum values.", nameof(rightMin));
                }
                break;
            default:
                throw new ArgumentOutOfRangeException(nameof(@operator), @operator, "Unsupported rule operator.");
        }
    }
}

/// <summary>
/// A single conditional expression applied to option selections.
/// </summary>
public class OptionRuleCondition : EntityWithAuditAndStatus<Guid>
{
    internal OptionRuleCondition()
    {
    }

    public Guid RuleSetId { get; internal set; }

    public OptionRuleSet RuleSet { get; internal set; } = null!;

    public Guid LeftOptionDefinitionId { get; internal set; }

    public OptionDefinition LeftOptionDefinition { get; internal set; } = null!;

    public RuleOperator Operator { get; internal set; }

    public Guid? RightOptionValueId { get; internal set; }

    public OptionValue? RightOptionValue { get; internal set; }

    public string? RightList { get; internal set; }

    public decimal? RightNumber { get; internal set; }

    public decimal? RightMin { get; internal set; }

    public decimal? RightMax { get; internal set; }
}

/// <summary>
/// Records which option value combination maps to an individual variant SKU.
/// </summary>
public class VariantAxisValue
{
    public Guid ProductVariantId { get; set; }

    public Product ProductVariant { get; set; } = null!;

    public Guid OptionDefinitionId { get; set; }

    public OptionDefinition OptionDefinition { get; set; } = null!;

    public Guid OptionValueId { get; set; }

    public OptionValue OptionValue { get; set; } = null!;
}