use serde::{Deserialize, Serialize};

/// 趋势方向
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum TrendDirection {
    Improving,
    Stable,
    Worsening,
}

/// 单项指标变化
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct MetricChange {
    pub metric: String,
    pub baseline_value: f64,
    pub current_value: f64,
    pub change_percent: f64,
    pub trend: TrendDirection,
}

/// 前后对比报告
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ComparisonReport {
    pub baseline: serde_json::Value,
    pub current: serde_json::Value,
    pub changes: Vec<MetricChange>,
    pub overall_trend: TrendDirection,
}

/// 对比 baseline 和当前数据生成变化报告。
pub fn generate_comparison(
    baseline: &serde_json::Value,
    current: &serde_json::Value,
) -> ComparisonReport {
    let mut changes = Vec::new();

    // 提取可比较的数值指标
    if let (Some(b_obj), Some(c_obj)) = (baseline.as_object(), current.as_object()) {
        for key in b_obj.keys() {
            if let (Some(b_val), Some(c_val)) = (b_obj.get(key), c_obj.get(key)) {
                if let (Some(b_num), Some(c_num)) = (b_val.as_f64(), c_val.as_f64()) {
                    let change_pct = if b_num.abs() > 0.0001 {
                        ((c_num - b_num) / b_num.abs()) * 100.0
                    } else {
                        0.0
                    };
                    let trend = if change_pct.abs() > 5.0 {
                        TrendDirection::Worsening
                    } else {
                        TrendDirection::Stable
                    };
                    changes.push(MetricChange {
                        metric: key.clone(),
                        baseline_value: b_num,
                        current_value: c_num,
                        change_percent: change_pct,
                        trend,
                    });
                }
            }
        }
    }

    // 综合趋势判断
    let changed = changes.iter().filter(|c| c.trend == TrendDirection::Worsening).count();
    let overall = if changed > 0 {
        TrendDirection::Worsening
    } else {
        TrendDirection::Stable
    };

    ComparisonReport {
        baseline: baseline.clone(),
        current: current.clone(),
        changes,
        overall_trend: overall,
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn generate_comparison_detects_significant_change() {
        let baseline = serde_json::json!({"systolic_bp": 160.0, "heart_rate": 95.0});
        let current = serde_json::json!({"systolic_bp": 130.0, "heart_rate": 80.0});
        let report = generate_comparison(&baseline, &current);
        assert_eq!(report.overall_trend, TrendDirection::Worsening);
        assert_eq!(report.changes.len(), 2);
    }

    #[test]
    fn generate_comparison_detects_single_change() {
        let baseline = serde_json::json!({"systolic_bp": 130.0});
        let current = serde_json::json!({"systolic_bp": 160.0});
        let report = generate_comparison(&baseline, &current);
        assert_eq!(report.overall_trend, TrendDirection::Worsening);
    }

    #[test]
    fn generate_comparison_detects_stable() {
        let baseline = serde_json::json!({"heart_rate": 75.0});
        let current = serde_json::json!({"heart_rate": 76.0});
        let report = generate_comparison(&baseline, &current);
        assert_eq!(report.overall_trend, TrendDirection::Stable);
    }

    #[test]
    fn generate_comparison_empty_data() {
        let baseline = serde_json::json!({});
        let current = serde_json::json!({});
        let report = generate_comparison(&baseline, &current);
        assert_eq!(report.overall_trend, TrendDirection::Stable);
        assert!(report.changes.is_empty());
    }

    #[test]
    fn generate_comparison_mixed_metrics() {
        let baseline = serde_json::json!({"systolic_bp": 150.0, "heart_rate": 80.0, "spo2": 96.0});
        let current = serde_json::json!({"systolic_bp": 140.0, "heart_rate": 95.0, "spo2": 90.0});
        let report = generate_comparison(&baseline, &current);
        // bp: -6.7% changed, hr: +18.75% changed, spo2: -6.25% changed → has changes
        assert_eq!(report.overall_trend, TrendDirection::Worsening);
        assert_eq!(report.changes.len(), 3);
    }
}