using Core.Entities;

namespace Core.Validation.Rules.BaseRules;

/// <summary>
/// Base class for validation rules that check event counts against thresholds
/// Eliminates duplication across TooManyEvents, TooFewEvents, and TooManyRegionalEvents rules
/// </summary>
public abstract class EventCountThresholdRuleBase : IValidationRule<StudentEventStatistics>
{
    /// <summary>
    /// Get the actual count to validate
    /// </summary>
    protected abstract int GetCount(StudentEventStatistics statistics);

    /// <summary>
    /// Get the threshold value from configuration
    /// </summary>
    protected abstract int GetThreshold(ValidationConfiguration config);

    /// <summary>
    /// Check if the count violates the threshold
    /// </summary>
    protected abstract bool ViolatesThreshold(int count, int threshold);

    /// <summary>
    /// Get the base severity from configuration (can be overridden for critical thresholds)
    /// </summary>
    protected abstract ValidationSeverity GetBaseSeverity(ValidationConfiguration config);

    /// <summary>
    /// Optionally check for critical threshold that escalates to Error severity
    /// Returns null if no critical threshold applies
    /// </summary>
    protected virtual int? GetCriticalThreshold(ValidationConfiguration config) => null;

    /// <summary>
    /// Check if count violates critical threshold (for escalation to Error)
    /// </summary>
    protected virtual bool ViolatesCriticalThreshold(int count, int criticalThreshold) => false;

    /// <summary>
    /// The validation warning code
    /// </summary>
    protected abstract string Code { get; }

    /// <summary>
    /// Build the display message
    /// </summary>
    protected abstract string GetMessage(int count, int threshold);

    /// <summary>
    /// Icon identifier for the warning (can be null)
    /// </summary>
    protected virtual string? IconIdentifier => null;

    /// <summary>
    /// Build additional metadata beyond the standard fields
    /// </summary>
    protected virtual Dictionary<string, object> BuildAdditionalMetadata(StudentEventStatistics statistics, ValidationConfiguration config)
    {
        return new Dictionary<string, object>();
    }

    public ValidationWarning? Validate(StudentEventStatistics entity, ValidationConfiguration config)
    {
        var count = GetCount(entity);
        var threshold = GetThreshold(config);

        if (!ViolatesThreshold(count, threshold))
            return null;

        // Check for critical threshold escalation
        var severity = GetBaseSeverity(config);
        var criticalThreshold = GetCriticalThreshold(config);
        if (criticalThreshold.HasValue && ViolatesCriticalThreshold(count, criticalThreshold.Value))
        {
            severity = ValidationSeverity.Error;
        }

        var metadata = new Dictionary<string, object>
        {
            { "StudentId", entity.Student.Id },
            { "StudentName", entity.Student.FirstNameLastName },
            { "EventCount", entity.EventCount }
        };

        // Add any additional metadata from derived class
        foreach (var kvp in BuildAdditionalMetadata(entity, config))
        {
            metadata[kvp.Key] = kvp.Value;
        }

        return new ValidationWarning
        {
            Code = Code,
            Message = GetMessage(count, threshold),
            Severity = severity,
            Context = ValidationContext.StudentAssignment,
            IconIdentifier = IconIdentifier,
            Metadata = metadata
        };
    }

    public bool AppliesTo(ValidationContext context) =>
        context == ValidationContext.StudentAssignment ||
        context == ValidationContext.StudentRegistration;
}