//! System statistics retrieval functions and associated data types.

use std::result::Result;

#[cfg(feature = "miniserde_support")]
use miniserde::{Deserialize, Serialize};

#[cfg(feature = "serde_support")]
use serde::{Deserialize, Serialize};

use probes::{cpu, disk_usage, load, memory};
use systemstat::{Platform, System};

use crate::error::StatsError;

/// CPU statistics.
#[derive(Debug)]
#[cfg_attr(feature = "miniserde_support", derive(Serialize, Deserialize))]
#[cfg_attr(feature = "serde_support", derive(Serialize, Deserialize))]
pub struct CpuStat {
    /// Time spent running user space (application) code.
    pub user: u64,
    /// Time spent running kernel code.
    pub system: u64,
    /// Time spent doing nothing.
    pub idle: u64,
    /// Time spent running user space processes which have been niced.
    pub nice: u64,
}

/// CPU statistics as percentages.
#[derive(Debug)]
#[cfg_attr(feature = "miniserde_support", derive(Serialize, Deserialize))]
#[cfg_attr(feature = "serde_support", derive(Serialize, Deserialize))]
pub struct CpuStatPercentages {
    /// Time spent running user space (application) code.
    pub user: f32,
    /// Time spent running kernel code.
    pub system: f32,
    /// Time spent doing nothing.
    pub idle: f32,
    /// Time spent running user space processes which have been niced.
    pub nice: f32,
}

/// Disk usage statistics.
#[derive(Debug)]
#[cfg_attr(feature = "miniserde_support", derive(Serialize, Deserialize))]
#[cfg_attr(feature = "serde_support", derive(Serialize, Deserialize))]
pub struct DiskUsage {
    /// Filesystem device path.
    pub filesystem: Option<String>,
    /// Total amount of disk space as a number of 1,000 kilobyte blocks.
    pub one_k_blocks: u64,
    /// Total amount of used disk space as a number of 1,000 kilobyte blocks.
    pub one_k_blocks_used: u64,
    /// Total amount of free / available disk space as a number of 1,000 kilobyte blocks.
    pub one_k_blocks_free: u64,
    /// Total amount of used disk space as a percentage.
    pub used_percentage: u32,
    /// Mountpoint of the disk / partition.
    pub mountpoint: String,
}

/// Load average statistics.
#[derive(Debug)]
#[cfg_attr(feature = "miniserde_support", derive(Serialize, Deserialize))]
#[cfg_attr(feature = "serde_support", derive(Serialize, Deserialize))]
pub struct LoadAverage {
    /// Average computational work performed over the past minute.
    pub one: f32,
    /// Average computational work performed over the past five minutes.
    pub five: f32,
    /// Average computational work performed over the past fifteen minutes.
    pub fifteen: f32,
}

/// Memory statistics.
#[derive(Debug)]
#[cfg_attr(feature = "miniserde_support", derive(Serialize, Deserialize))]
#[cfg_attr(feature = "serde_support", derive(Serialize, Deserialize))]
pub struct MemStat {
    /// Total amount of physical memory in kilobytes.
    pub total: u64,
    /// Total amount of free / available physical memory in kilobytes.
    pub free: u64,
    /// Total amount of used physical memory in kilobytes.
    pub used: u64,
}

/// Retrieve the current CPU statistics.
pub fn cpu_stats() -> Result<CpuStat, StatsError> {
    let cpu_stats = cpu::proc::read().map_err(StatsError::CpuStat)?;
    let s = cpu_stats.stat;
    let cpu = CpuStat {
        user: s.user,
        system: s.system,
        nice: s.nice,
        idle: s.idle,
    };

    Ok(cpu)
}

/// Retrieve the current CPU statistics as percentages.
pub fn cpu_stats_percent() -> Result<CpuStatPercentages, StatsError> {
    let cpu_stats = cpu::proc::read().map_err(StatsError::CpuStat)?;
    let s = cpu_stats.stat.in_percentages();
    let cpu = CpuStatPercentages {
        user: s.user,
        system: s.system,
        nice: s.nice,
        idle: s.idle,
    };

    Ok(cpu)
}

/// Retrieve the current disk usage statistics for each available disk / partition.
pub fn disk_usage() -> Result<Vec<DiskUsage>, StatsError> {
    let disks = disk_usage::read().map_err(StatsError::DiskUsage)?;
    let mut disk_usages = Vec::new();
    for d in disks {
        let disk = DiskUsage {
            filesystem: d.filesystem,
            one_k_blocks: d.one_k_blocks,
            one_k_blocks_used: d.one_k_blocks_used,
            one_k_blocks_free: d.one_k_blocks_free,
            used_percentage: d.used_percentage,
            mountpoint: d.mountpoint,
        };
        disk_usages.push(disk);
    }

    Ok(disk_usages)
}

/// Retrieve the current load average statistics.
pub fn load_average() -> Result<LoadAverage, StatsError> {
    let l = load::read().map_err(StatsError::LoadAvg)?;
    let load_avg = LoadAverage {
        one: l.one,
        five: l.five,
        fifteen: l.fifteen,
    };

    Ok(load_avg)
}

/// Retrieve the current memory usage statistics.
pub fn mem_stats() -> Result<MemStat, StatsError> {
    let m = memory::read().map_err(StatsError::MemStat)?;
    let mem = MemStat {
        total: m.total(),
        free: m.free(),
        used: m.used(),
    };

    Ok(mem)
}

/// Retrieve the system uptime in seconds.
pub fn uptime() -> Result<u64, StatsError> {
    let sys = System::new();
    let uptime = sys.uptime().map_err(StatsError::Uptime)?;
    let uptime_secs = uptime.as_secs();

    Ok(uptime_secs)
}