/*
* SPDX-License-Identifier: AGPL-3.0-or-later
* Copyright (C) 2025 Sergej Görzen <sergej.goerzen@gmail.com>
* This file is part of OmiLAXR.
*/

using OmiLAXR.Actors.StressLevel;
using UnityEngine;

namespace OmiLAXR.Facial
{
    /// <summary>
    /// Facial expression data provider for stress level detection and analysis.
    /// Analyzes facial features, particularly eyebrow tension, to determine stress indicators.
    /// Implements the StressLevelDataProvider interface to contribute to overall stress assessment.
    /// Currently contains placeholder implementation awaiting facial recognition integration.
    /// </summary>
    internal class FacialExpressionProvider : ActorDataProvider, IStressLevelDataProvider
    {
        /// <summary>
        /// Identifier name for this data provider within the stress level system.
        /// Used for logging, debugging, and system identification purposes.
        /// </summary>
        /// <returns>The string "FacialExpression" as the provider identifier</returns>
        public string Name => "FacialExpression";

        /// <summary>
        /// Indicates whether this provider is currently active and providing data.
        /// Always returns true in this implementation, assuming facial tracking is available.
        /// In a complete implementation, this would check for camera availability and face detection.
        /// </summary>
        /// <returns>True if the provider is active and can provide stress level data</returns>
        public bool IsActive => true;

        /// <summary>
        /// Weighting factor for this provider's contribution to overall stress calculation.
        /// Higher weight (1.2f) indicates that facial expressions are considered a strong indicator
        /// of stress levels compared to other data sources with default weight of 1.0f.
        /// This reflects the psychological significance of facial micro-expressions in stress detection.
        /// </summary>
        /// <returns>Weight factor of 1.2f for facial expression contribution</returns>
        public float Weight => 1.2f;

        /// <summary>
        /// Calculates and returns the current stress level based on facial expression analysis.
        /// Currently implements a placeholder that always returns 0 (no stress detected).
        /// 
        /// In a complete implementation, this method would:
        /// - Capture facial image data from camera input
        /// - Analyze facial landmarks and muscle tension patterns
        /// - Focus on eyebrow position, eye strain, and jaw tension
        /// - Calculate stress indicators from micro-expressions
        /// - Return normalized stress value between 0.0 (relaxed) and 1.0 (highly stressed)
        /// 
        /// The placeholder focuses on brow tension as a primary stress indicator,
        /// as furrowed brows and eyebrow positioning are well-documented stress markers.
        /// </summary>
        /// <returns>
        /// Nullable float representing stress level:
        /// - null: Unable to determine stress level (no face detected, poor lighting, etc.)
        /// - 0.0f: No stress detected, relaxed facial expression
        /// - 1.0f: Maximum stress detected, high tension in facial muscles
        /// Currently always returns 0.0f due to placeholder implementation
        /// </returns>
        public float? GetStressLevel()
        {
            // TODO: Implement actual facial expression analysis
            // This is a placeholder implementation awaiting:
            // - Camera integration for facial capture
            // - Facial landmark detection system
            // - Machine learning model for expression analysis
            // - Calibration system for individual baseline expressions
            
            // Placeholder variable for eyebrow tension measurement
            // In actual implementation, this would be calculated from:
            // - Distance between eyebrows and eyes
            // - Angle of eyebrow arch
            // - Forehead wrinkle detection
            // - Comparison to user's baseline relaxed state
            float browTension = 0;
            
            // Ensure the returned value is within valid range [0, 1]
            // Clamp01 ensures any calculated stress value stays within bounds
            // even if the underlying facial analysis produces values outside this range
            return Mathf.Clamp01(browTension); // Already normalized to 0-1 range
        }
    }
}