//! SYNSPEC 氢线窗口初始化。
//!
//! 重构自 SYNSPEC 54 的 HYLSEW 子程序。

/// 氢线窗口参数
#[derive(Debug, Clone)]
pub struct HylsewOutput {
    /// 是否包含氢线 (0=否, 1=是)
    pub ihylw: i32,
    /// 线数参数
    pub m20w: i32,
    /// 最低主量子数索引
    pub ilowhw: i32,
    /// 线翼参数
    pub m10w: i32,
}

/// 初始化氢线处理窗口。
///
/// 根据频率和重力加速度判断是否包含氢线，并设置相关参数。
///
/// # Arguments
/// * `ij` - 频率索引
/// * `freq` - 频率值 (Hz)
/// * `grav` - 重力加速度 (log g)
///
/// # Returns
/// 氢线窗口参数
pub fn hylsew(_ij: usize, freq: f64, grav: f64) -> HylsewOutput {
    let mut output = HylsewOutput {
        ihylw: 0,
        m20w: 0,
        ilowhw: 0,
        m10w: 0,
    };

    // 检查频率是否在氢线范围内
    if freq >= 3.28805e15 {
        return output;
    }

    let al0 = 2.997925e17 / freq;
    let al1 = al0;

    // 根据重力加速度检查波长范围
    if grav < 6.0 {
        if al0 > 160.0 && al1 < 364.6 {
            return output;
        }
        if al0 > 506.0 && al1 < 630.0 {
            return output;
        }
        if al0 > 680.0 && al1 < 820.3 {
            return output;
        }
    } else {
        if al0 > 540.0 && al1 < 600.0 {
            return output;
        }
        if al0 > 720.0 && al1 < 820.3 {
            return output;
        }
    }

    // 包含氢线
    output.ihylw = 1;
    output.m20w = 40;

    // 确定最低主量子数
    let frion = if al1 < 364.6 {
        output.ilowhw = 1;
        3.28805e15
    } else if al1 < 820.0 {
        output.ilowhw = 2;
        8.2225e14
    } else if al1 < 1458.0 {
        output.ilowhw = 3;
        3.6544142e14
    } else if al1 < 2278.0 {
        output.ilowhw = 4;
        2.0555837e14
    } else if al1 < 3281.0 {
        output.ilowhw = 5;
        1.315589e14
    } else if al1 < 4466.0 {
        output.ilowhw = 6;
        9.136394e13
    } else {
        output.ilowhw = 7;
        6.7120228e13
    };

    // 计算线翼参数
    if frion > freq {
        output.m10w = (3.289017e15 / (frion - freq).abs()).sqrt() as i32;
    }

    output
}

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

    #[test]
    fn test_hylsew_high_freq() {
        // 频率太高，不包含氢线
        let result = hylsew(1, 4.0e15, 4.0);
        assert_eq!(result.ihylw, 0);
    }

    #[test]
    fn test_hylsew_lyman_region() {
        // Lyman 系区域
        let result = hylsew(1, 3.0e15, 4.0);
        assert_eq!(result.ihylw, 1);
        assert_eq!(result.ilowhw, 1);
    }

    #[test]
    fn test_hylsew_balmer_region() {
        // Balmer 系区域 (500 Å，在 Lyman 极限和 Balmer 极限之间)
        let freq = 2.997925e17 / 500.0;
        let result = hylsew(1, freq, 4.0);
        assert_eq!(result.ihylw, 1);
        assert_eq!(result.ilowhw, 2);
    }

    #[test]
    fn test_hylsew_high_gravity() {
        // 高重力情况
        let freq = 2.997925e17 / 550.0;
        let result = hylsew(1, freq, 7.0);
        assert_eq!(result.ihylw, 0);
    }
}