//! This module contains the implementation of the `cpuset` cgroup subsystem.
//!
//! See the Kernel's documentation for more information about this subsystem, found at:
//!  [Documentation/cgroup-v1/cpusets.txt](https://www.kernel.org/doc/Documentation/cgroup-v1/cpusets.txt)
use std::fs::File;
use std::io::{Read, Write};
use std::path::PathBuf;

use error::*;
use error::ErrorKind::*;

use {
    ControllIdentifier, ControllerInternal, Controllers, CpuResources, Resources, Subsystem,
};

/// A controller that allows controlling the `cpuset` subsystem of a Cgroup.
///
/// In essence, this controller is responsible for restricting the tasks in the control group to a
/// set of CPUs and/or memory nodes.
#[derive(Debug, Clone)]
pub struct CpuSetController {
    base: PathBuf,
    path: PathBuf,
}

/// The current state of the `cpuset` controller for this control group.
pub struct CpuSet {
    /// If true, no other control groups can share the CPUs listed in the `cpus` field.
    pub cpu_exclusive: bool,
    /// The list of CPUs the tasks of the control group can run on.
    ///
    /// This is a vector of `(start, end)` tuples, where each tuple is a range of CPUs where the
    /// control group is allowed to run on. Both sides of the range are inclusive.
    pub cpus: Vec<(u64, u64)>,
    /// The list of CPUs that the tasks can effectively run on. This removes the list of CPUs that
    /// the parent (and all of its parents) cannot run on from the `cpus` field of this control
    /// group.
    pub effective_cpus: Vec<(u64, u64)>,
    /// The list of memory nodes that the tasks can effectively use. This removes the list of nodes that
    /// the parent (and all of its parents) cannot use from the `mems` field of this control
    /// group.
    pub effective_mems: Vec<(u64, u64)>,
    /// If true, no other control groups can share the memory nodes listed in the `mems` field.
    pub mem_exclusive: bool,
    /// If true, the control group is 'hardwalled'. Kernel memory allocations (except for a few
    /// minor exceptions) are made from the memory nodes designated in the `mems` field.
    pub mem_hardwall: bool,
    /// If true, whenever `mems` is changed via `set_mems()`, the memory stored on the previous
    /// nodes are migrated to the new nodes selected by the new `mems`.
    pub memory_migrate: bool,
    /// Running average of the memory pressured faced by the tasks in the control group.
    pub memory_pressure: u64,
    /// This field is only at the root control group and controls whether the kernel will compute
    /// the memory pressure for control groups or not.
    pub memory_pressure_enabled: Option<bool>,
    /// If true, filesystem buffers are spread across evenly between the nodes specified in `mems`.
    pub memory_spread_page: bool,
    /// If true, kernel slab caches for file I/O are spread across evenly between the nodes
    /// specified in `mems`.
    pub memory_spread_slab: bool,
    /// The list of memory nodes the tasks of the control group can use.
    ///
    /// The format is the same as the `cpus`, `effective_cpus` and `effective_mems` fields.
    pub mems: Vec<(u64, u64)>,
    /// If true, the kernel will attempt to rebalance the load between the CPUs specified in the
    /// `cpus` field of this control group.
    pub sched_load_balance: bool,
    /// Represents how much work the kernel should do to rebalance this cpuset.
    ///
    /// | `sched_load_balance` | Effect |
    /// | -------------------- | ------ |
    /// |          -1          | Use the system default value |
    /// |           0          | Only balance loads periodically |
    /// |           1          | Immediately balance the load across tasks on the same core |
    /// |           2          | Immediately balance the load across cores in the same CPU package |
    /// |           4          | Immediately balance the load across CPUs on the same node |
    /// |           5          | Immediately balance the load between CPUs even if the system is NUMA |
    /// |           6          | Immediately balance the load between all CPUs |
    pub sched_relax_domain_level: u64,
}

impl ControllerInternal for CpuSetController {
    fn control_type(&self) -> Controllers {
        Controllers::CpuSet
    }
    fn get_path(&self) -> &PathBuf {
        &self.path
    }
    fn get_path_mut(&mut self) -> &mut PathBuf {
        &mut self.path
    }
    fn get_base(&self) -> &PathBuf {
        &self.base
    }

    fn apply(&self, res: &Resources) -> Result<()> {
        // get the resources that apply to this controller
        let res: &CpuResources = &res.cpu;

        if res.update_values {
            let _ = self.set_cpus(&res.cpus);
            let _ = self.set_mems(&res.mems);
        }

        Ok(())
    }
}

impl ControllIdentifier for CpuSetController {
    fn controller_type() -> Controllers {
        Controllers::CpuSet
    }
}

impl<'a> From<&'a Subsystem> for &'a CpuSetController {
    fn from(sub: &'a Subsystem) -> &'a CpuSetController {
        unsafe {
            match sub {
                Subsystem::CpuSet(c) => c,
                _ => {
                    assert_eq!(1, 0);
                    ::std::mem::uninitialized()
                }
            }
        }
    }
}

fn read_string_from(mut file: File) -> Result<String> {
    let mut string = String::new();
    match file.read_to_string(&mut string) {
        Ok(_) => Ok(string.trim().to_string()),
        Err(e) => Err(Error::with_cause(ReadFailed, e)),
    }
}

fn read_u64_from(mut file: File) -> Result<u64> {
    let mut string = String::new();
    match file.read_to_string(&mut string) {
        Ok(_) => string.trim().parse().map_err(|e| Error::with_cause(ParseError, e)),
        Err(e) => Err(Error::with_cause(ReadFailed, e)),
    }
}

/// Parse a string like "1,2,4-5,8" into a list of (start, end) tuples.
fn parse_range(s: String) -> Result<Vec<(u64, u64)>> {
    let mut fin = Vec::new();

    if s == "".to_string() {
        return Ok(fin);
    }

    // first split by commas
    let comma_split = s.split(",");

    for sp in comma_split {
        if sp.contains("-") {
            // this is a true range
            let dash_split = sp.split("-").collect::<Vec<_>>();
            if dash_split.len() != 2 {
                return Err(Error::new(ParseError));
            }
            let first = dash_split[0].parse::<u64>();
            let second = dash_split[1].parse::<u64>();
            if first.is_err() || second.is_err() {
                return Err(Error::new(ParseError));
            }
            fin.push((first.unwrap(), second.unwrap()));
        } else {
            // this is just a single number
            let num = sp.parse::<u64>();
            if num.is_err() {
                return Err(Error::new(ParseError));
            }
            fin.push((num.clone().unwrap(), num.clone().unwrap()));
        }
    }

    Ok(fin)
}

impl CpuSetController {
    /// Contructs a new `CpuSetController` with `oroot` serving as the root of the control group.
    pub fn new(oroot: PathBuf) -> Self {
        let mut root = oroot;
        root.push(Self::controller_type().to_string());
        Self {
            base: root.clone(),
            path: root,
        }
    }

    /// Returns the statistics gathered by the kernel for this control group. See the struct for
    /// more information on what information this entails.
    pub fn cpuset(&self) -> CpuSet {
        CpuSet {
            cpu_exclusive: {
                self.open_path("cpuset.cpu_exclusive", false)
                    .and_then(|file| read_u64_from(file))
                    .map(|x| x == 1)
                    .unwrap_or(false)
            },
            cpus: {
                self.open_path("cpuset.cpus", false)
                    .and_then(read_string_from)
                    .and_then(parse_range)
                    .unwrap_or(Vec::new())
            },
            effective_cpus: {
                self.open_path("cpuset.effective_cpus", false)
                    .and_then(read_string_from)
                    .and_then(parse_range)
                    .unwrap_or(Vec::new())
            },
            effective_mems: {
                self.open_path("cpuset.effective_mems", false)
                    .and_then(read_string_from)
                    .and_then(parse_range)
                    .unwrap_or(Vec::new())
            },
            mem_exclusive: {
                self.open_path("cpuset.mem_exclusive", false)
                    .and_then(read_u64_from)
                    .map(|x| x == 1)
                    .unwrap_or(false)
            },
            mem_hardwall: {
                self.open_path("cpuset.mem_hardwall", false)
                    .and_then(read_u64_from)
                    .map(|x| x == 1)
                    .unwrap_or(false)
            },
            memory_migrate: {
                self.open_path("cpuset.memory_migrate", false)
                    .and_then(read_u64_from)
                    .map(|x| x == 1)
                    .unwrap_or(false)
            },
            memory_pressure: {
                self.open_path("cpuset.memory_pressure", false)
                    .and_then(read_u64_from)
                    .unwrap_or(0)
            },
            memory_pressure_enabled: {
                self.open_path("cpuset.memory_pressure_enabled", false)
                    .and_then(read_u64_from)
                    .map(|x| x == 1)
                    .ok()
            },
            memory_spread_page: {
                self.open_path("cpuset.memory_spread_page", false)
                    .and_then(read_u64_from)
                    .map(|x| x == 1)
                    .unwrap_or(false)
            },
            memory_spread_slab: {
                self.open_path("cpuset.memory_spread_slab", false)
                    .and_then(read_u64_from)
                    .map(|x| x == 1)
                    .unwrap_or(false)
            },
            mems: {
                self.open_path("cpuset.mems", false)
                    .and_then(read_string_from)
                    .and_then(parse_range)
                    .unwrap_or(Vec::new())
            },
            sched_load_balance: {
                self.open_path("cpuset.sched_load_balance", false)
                    .and_then(read_u64_from)
                    .map(|x| x == 1)
                    .unwrap_or(false)
            },
            sched_relax_domain_level: {
                self.open_path("cpuset.sched_relax_domain_level", false)
                    .and_then(read_u64_from)
                    .unwrap_or(0)
            },
        }
    }

    /// Control whether the CPUs selected via `set_cpus()` should be exclusive to this control
    /// group or not.
    pub fn set_cpu_exclusive(&self, b: bool) -> Result<()> {
        self.open_path("cpuset.cpu_exclusive", true)
            .and_then(|mut file| {
                if b {
                    file.write_all(b"1").map_err(|e| Error::with_cause(WriteFailed, e))
                } else {
                    file.write_all(b"0").map_err(|e| Error::with_cause(WriteFailed, e))
                }
            })
    }

    /// Control whether the memory nodes selected via `set_memss()` should be exclusive to this control
    /// group or not.
    pub fn set_mem_exclusive(&self, b: bool) -> Result<()> {
        self.open_path("cpuset.mem_exclusive", true)
            .and_then(|mut file| {
                if b {
                    file.write_all(b"1").map_err(|e| Error::with_cause(WriteFailed, e))
                } else {
                    file.write_all(b"0").map_err(|e| Error::with_cause(WriteFailed, e))
                }
            })
    }

    /// Set the CPUs that the tasks in this control group can run on.
    ///
    /// Syntax is a comma separated list of CPUs, with an additional extension that ranges can
    /// be represented via dashes.
    pub fn set_cpus(&self, cpus: &str) -> Result<()> {
        self.open_path("cpuset.cpus", true).and_then(|mut file| {
            file.write_all(cpus.as_ref())
                .map_err(|e| Error::with_cause(WriteFailed, e))
        })
    }

    /// Set the memory nodes that the tasks in this control group can use.
    ///
    /// Syntax is the same as with `set_cpus()`.
    pub fn set_mems(&self, mems: &str) -> Result<()> {
        self.open_path("cpuset.mems", true).and_then(|mut file| {
            file.write_all(mems.as_ref())
                .map_err(|e| Error::with_cause(WriteFailed, e))
        })
    }

    /// Controls whether the control group should be "hardwalled", i.e., whether kernel allocations
    /// should exclusively use the memory nodes set via `set_mems()`.
    ///
    /// Note that some kernel allocations, most notably those that are made in interrupt handlers
    /// may disregard this.
    pub fn set_hardwall(&self, b: bool) -> Result<()> {
        self.open_path("cpuset.mem_hardwall", true)
            .and_then(|mut file| {
                if b {
                    file.write_all(b"1").map_err(|e| Error::with_cause(WriteFailed, e))
                } else {
                    file.write_all(b"0").map_err(|e| Error::with_cause(WriteFailed, e))
                }
            })
    }

    /// Controls whether the kernel should attempt to rebalance the load between the CPUs specified in the
    /// `cpus` field of this control group.
    pub fn set_load_balancing(&self, b: bool) -> Result<()> {
        self.open_path("cpuset.sched_load_balance", true)
            .and_then(|mut file| {
                if b {
                    file.write_all(b"1").map_err(|e| Error::with_cause(WriteFailed, e))
                } else {
                    file.write_all(b"0").map_err(|e| Error::with_cause(WriteFailed, e))
                }
            })
    }

    /// Contorl how much effort the kernel should invest in rebalacing the control group.
    ///
    /// See @CpuSet 's similar field for more information.
    pub fn set_rebalance_relax_domain_level(&self, i: i64) -> Result<()> {
        self.open_path("cpuset.sched_relax_domain_level", true)
            .and_then(|mut file| {
                file.write_all(i.to_string().as_ref())
                    .map_err(|e| Error::with_cause(WriteFailed, e))
            })
    }

    /// Control whether when using `set_mems()` the existing memory used by the tasks should be
    /// migrated over to the now-selected nodes.
    pub fn set_memory_migration(&self, b: bool) -> Result<()> {
        self.open_path("cpuset.memory_migrate", true)
            .and_then(|mut file| {
                if b {
                    file.write_all(b"1").map_err(|e| Error::with_cause(WriteFailed, e))
                } else {
                    file.write_all(b"0").map_err(|e| Error::with_cause(WriteFailed, e))
                }
            })
    }

    /// Control whether filesystem buffers should be evenly split across the nodes selected via
    /// `set_mems()`.
    pub fn set_memory_spread_page(&self, b: bool) -> Result<()> {
        self.open_path("cpuset.memory_spread_page", true)
            .and_then(|mut file| {
                if b {
                    file.write_all(b"1").map_err(|e| Error::with_cause(WriteFailed, e))
                } else {
                    file.write_all(b"0").map_err(|e| Error::with_cause(WriteFailed, e))
                }
            })
    }

    /// Control whether the kernel's slab cache for file I/O should be evenly split across the
    /// nodes selected via `set_mems()`.
    pub fn set_memory_spread_slab(&self, b: bool) -> Result<()> {
        self.open_path("cpuset.memory_spread_slab", true)
            .and_then(|mut file| {
                if b {
                    file.write_all(b"1").map_err(|e| Error::with_cause(WriteFailed, e))
                } else {
                    file.write_all(b"0").map_err(|e| Error::with_cause(WriteFailed, e))
                }
            })
    }

    /// Control whether the kernel should collect information to calculate memory pressure for
    /// control groups.
    ///
    /// Note: This will fail with `InvalidOperation` if the current congrol group is not the root
    /// control group.
    pub fn set_enable_memory_pressure(&self, b: bool) -> Result<()> {
        if !self.path_exists("cpuset.memory_pressure_enabled") {
            return Err(Error::new(InvalidOperation));
        }
        self.open_path("cpuset.memory_pressure_enabled", true)
            .and_then(|mut file| {
                if b {
                    file.write_all(b"1").map_err(|e| Error::with_cause(WriteFailed, e))
                } else {
                    file.write_all(b"0").map_err(|e| Error::with_cause(WriteFailed, e))
                }
            })
    }
}

#[cfg(test)]
mod tests {
    use cpuset;
    #[test]
    fn test_parse_range() {
        let test_cases = vec![
            "1,2,4-6,9".to_string(),
            "".to_string(),
            "1".to_string(),
            "1-111".to_string(),
            "1,2,3,4".to_string(),
            "1-5,6-7,8-9".to_string(),
        ];
        let expecteds = vec![
            vec![(1, 1), (2, 2), (4, 6), (9, 9)],
            vec![],
            vec![(1, 1)],
            vec![(1, 111)],
            vec![(1, 1), (2, 2), (3, 3), (4, 4)],
            vec![(1, 5), (6, 7), (8, 9)],
        ];

        for (i, case) in test_cases.into_iter().enumerate() {
            let range = cpuset::parse_range(case.clone());
            println!("{:?} => {:?}", case, range);
            assert!(range.is_ok());
            assert_eq!(range.unwrap(), expecteds[i]);
        }
    }
}