// Copyright (c) 2018 Levente Kurusa
// Copyright (c) 2020 Ant Group
//
// SPDX-License-Identifier: Apache-2.0 or MIT
//

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

use crate::error::ErrorKind::*;
use crate::error::*;
use crate::{flat_keyed_to_vec, read_u64_from};

use crate::{
    ControllIdentifier, ControllerInternal, Controllers, HugePageResources, Resources, Subsystem,
};

/// A controller that allows controlling the `hugetlb` subsystem of a Cgroup.
///
/// In essence, using this controller it is possible to limit the use of hugepages in the tasks of
/// the control group.
#[derive(Debug, Clone)]
pub struct HugeTlbController {
    base: PathBuf,
    path: PathBuf,
    sizes: Vec<String>,
    v2: bool,
}

impl ControllerInternal for HugeTlbController {
    fn control_type(&self) -> Controllers {
        Controllers::HugeTlb
    }
    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 is_v2(&self) -> bool {
        self.v2
    }

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

        for i in &res.limits {
            let _ = self.set_limit_in_bytes(&i.size, i.limit);
            if self.limit_in_bytes(&i.size)? != i.limit {
                return Err(Error::new(Other));
            }
        }

        Ok(())
    }
}

impl ControllIdentifier for HugeTlbController {
    fn controller_type() -> Controllers {
        Controllers::HugeTlb
    }
}

impl<'a> From<&'a Subsystem> for &'a HugeTlbController {
    fn from(sub: &'a Subsystem) -> &'a HugeTlbController {
        unsafe {
            match sub {
                Subsystem::HugeTlb(c) => c,
                _ => {
                    assert_eq!(1, 0);
                    let v = std::mem::MaybeUninit::uninit();
                    v.assume_init()
                }
            }
        }
    }
}

impl HugeTlbController {
    /// Constructs a new `HugeTlbController` with `root` serving as the root of the control group.
    pub fn new(point: PathBuf, root: PathBuf, v2: bool) -> Self {
        let sizes = get_hugepage_sizes();
        Self {
            base: root,
            path: point,
            sizes,
            v2,
        }
    }

    /// Whether the system supports `hugetlb_size` hugepages.
    pub fn size_supported(&self, hugetlb_size: &str) -> bool {
        for s in &self.sizes {
            if s == hugetlb_size {
                return true;
            }
        }
        false
    }

    pub fn get_sizes(&self) -> Vec<String> {
        self.sizes.clone()
    }

    fn failcnt_v2(&self, hugetlb_size: &str) -> Result<u64> {
        self.open_path(&format!("hugetlb.{}.events", hugetlb_size), false)
            .and_then(flat_keyed_to_vec)
            .and_then(|x| {
                if x.is_empty() {
                    return Err(Error::from_string(format!(
                        "get empty from hugetlb.{}.events",
                        hugetlb_size
                    )));
                }
                Ok(x[0].1 as u64)
            })
    }

    /// Check how many times has the limit of `hugetlb_size` hugepages been hit.
    pub fn failcnt(&self, hugetlb_size: &str) -> Result<u64> {
        if self.v2 {
            return self.failcnt_v2(hugetlb_size);
        }
        self.open_path(&format!("hugetlb.{}.failcnt", hugetlb_size), false)
            .and_then(read_u64_from)
    }

    /// Get the limit (in bytes) of how much memory can be backed by hugepages of a certain size
    /// (`hugetlb_size`).
    pub fn limit_in_bytes(&self, hugetlb_size: &str) -> Result<u64> {
        let mut file_name = format!("hugetlb.{}.limit_in_bytes", hugetlb_size);
        if self.v2 {
            file_name = format!("hugetlb.{}.max", hugetlb_size);
        }
        self.open_path(&file_name, false).and_then(read_u64_from)
    }

    /// Get the current usage of memory that is backed by hugepages of a certain size
    /// (`hugetlb_size`).
    pub fn usage_in_bytes(&self, hugetlb_size: &str) -> Result<u64> {
        let mut file = format!("hugetlb.{}.usage_in_bytes", hugetlb_size);
        if self.v2 {
            file = format!("hugetlb.{}.current", hugetlb_size);
        }
        self.open_path(&file, false).and_then(read_u64_from)
    }

    /// Get the maximum observed usage of memory that is backed by hugepages of a certain size
    /// (`hugetlb_size`).
    pub fn max_usage_in_bytes(&self, hugetlb_size: &str) -> Result<u64> {
        self.open_path(
            &format!("hugetlb.{}.max_usage_in_bytes", hugetlb_size),
            false,
        )
        .and_then(read_u64_from)
    }

    /// Set the limit (in bytes) of how much memory can be backed by hugepages of a certain size
    /// (`hugetlb_size`).
    pub fn set_limit_in_bytes(&self, hugetlb_size: &str, limit: u64) -> Result<()> {
        let mut file_name = format!("hugetlb.{}.limit_in_bytes", hugetlb_size);
        if self.v2 {
            file_name = format!("hugetlb.{}.max", hugetlb_size);
        }
        self.open_path(&file_name, true).and_then(|mut file| {
            file.write_all(limit.to_string().as_ref()).map_err(|e| {
                Error::with_cause(WriteFailed(file_name.to_string(), limit.to_string()), e)
            })
        })
    }
}

pub const HUGEPAGESIZE_DIR: &str = "/sys/kernel/mm/hugepages";
use std::collections::HashMap;
use std::fs;

fn get_hugepage_sizes() -> Vec<String> {
    let dirs = fs::read_dir(HUGEPAGESIZE_DIR);
    if dirs.is_err() {
        return Vec::new();
    }

    dirs.unwrap()
        .filter_map(|e| {
            let entry = e.map_err(|e| warn!("readdir error: {:?}", e)).ok()?;
            let name = entry.file_name().into_string().unwrap();
            let parts: Vec<&str> = name.split('-').collect();
            if parts.len() != 2 {
                return None;
            }
            let bmap = get_binary_size_map();
            let size = parse_size(parts[1], &bmap)
                .map_err(|e| warn!("parse_size error: {:?}", e))
                .ok()?;
            let dabbrs = get_decimal_abbrs();

            Some(custom_size(size as f64, 1024.0, &dabbrs))
        })
        .collect()
}

pub const KB: u128 = 1000;
pub const MB: u128 = 1000 * KB;
pub const GB: u128 = 1000 * MB;
pub const TB: u128 = 1000 * GB;
pub const PB: u128 = 1000 * TB;

#[allow(non_upper_case_globals)]
pub const KiB: u128 = 1024;
#[allow(non_upper_case_globals)]
pub const MiB: u128 = 1024 * KiB;
#[allow(non_upper_case_globals)]
pub const GiB: u128 = 1024 * MiB;
#[allow(non_upper_case_globals)]
pub const TiB: u128 = 1024 * GiB;
#[allow(non_upper_case_globals)]
pub const PiB: u128 = 1024 * TiB;

pub fn get_binary_size_map() -> HashMap<String, u128> {
    let mut m = HashMap::new();
    m.insert("k".to_string(), KiB);
    m.insert("m".to_string(), MiB);
    m.insert("g".to_string(), GiB);
    m.insert("t".to_string(), TiB);
    m.insert("p".to_string(), PiB);
    m
}

pub fn get_decimal_size_map() -> HashMap<String, u128> {
    let mut m = HashMap::new();
    m.insert("k".to_string(), KB);
    m.insert("m".to_string(), MB);
    m.insert("g".to_string(), GB);
    m.insert("t".to_string(), TB);
    m.insert("p".to_string(), PB);
    m
}

pub fn get_decimal_abbrs() -> Vec<String> {
    let m = vec![
        "B".to_string(),
        "KB".to_string(),
        "MB".to_string(),
        "GB".to_string(),
        "TB".to_string(),
        "PB".to_string(),
        "EB".to_string(),
        "ZB".to_string(),
        "YB".to_string(),
    ];
    m
}

fn parse_size(s: &str, m: &HashMap<String, u128>) -> Result<u128> {
    // Remove leading/trailing whitespace.
    let s = s.trim();

    // Remove an optional trailing 'b' or 'B'
    let s = if let Some(stripped) = s.strip_suffix('b').or_else(|| s.strip_suffix('B')) {
        stripped
    } else {
        s
    };

    // Ensure that the string is not empty after stripping.
    if s.is_empty() {
        return Err(Error::new(InvalidBytesSize));
    }

    // The last character should be the multiplier letter.
    let last_char = s.chars().last().unwrap();
    if !"kKmMgGtTpP".contains(last_char) {
        return Err(Error::new(InvalidBytesSize));
    }

    // The numeric part is everything before the multiplier letter.
    let num_part = &s[..s.len() - last_char.len_utf8()];
    if num_part.trim().is_empty() {
        return Err(Error::new(InvalidBytesSize));
    }

    // Parse the numeric part into a u128.
    let number: u128 = num_part
        .trim()
        .parse()
        .map_err(|_| Error::new(InvalidBytesSize))?;

    // Look up the multiplier in the provided HashMap.
    let multiplier_key = last_char.to_string();
    let multiplier = m
        .get(&multiplier_key)
        .ok_or_else(|| Error::new(InvalidBytesSize))?;

    Ok(number * multiplier)
}

fn custom_size(mut size: f64, base: f64, m: &[String]) -> String {
    let mut i = 0;
    while size >= base && i < m.len() - 1 {
        size /= base;
        i += 1;
    }

    format!("{}{}", size, m[i].as_str())
}

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

    #[test]
    fn test_binary_size_valid() {
        let m = get_binary_size_map();
        // Valid inputs must include a multiplier letter.
        assert_eq!(parse_size("1k", &m).unwrap(), KiB);
        assert_eq!(parse_size("2m", &m).unwrap(), 2 * MiB);
        assert_eq!(parse_size("3g", &m).unwrap(), 3 * GiB);
        assert_eq!(parse_size("4t", &m).unwrap(), 4 * TiB);
        assert_eq!(parse_size("5p", &m).unwrap(), 5 * PiB);
    }

    #[test]
    fn test_decimal_size_valid() {
        let m = get_decimal_size_map();
        assert_eq!(parse_size("1k", &m).unwrap(), KB);
        assert_eq!(parse_size("2m", &m).unwrap(), 2 * MB);
        assert_eq!(parse_size("3g", &m).unwrap(), 3 * GB);
        assert_eq!(parse_size("4t", &m).unwrap(), 4 * TB);
        assert_eq!(parse_size("5p", &m).unwrap(), 5 * PB);
    }

    #[test]
    fn test_trailing_b_suffix() {
        let m = get_binary_size_map();
        // Trailing 'b' or 'B' should be accepted.
        assert_eq!(parse_size("1kb", &m).unwrap(), KiB);
        assert_eq!(parse_size("2mB", &m).unwrap(), 2 * MiB);
    }

    #[test]
    fn test_invalid_inputs() {
        let m = get_binary_size_map();
        // Missing multiplier letter results in error.
        assert!(parse_size("1", &m).is_err());
        // Invalid multiplier letter.
        assert!(parse_size("10x", &m).is_err());
        // Non-numeric input.
        assert!(parse_size("abc", &m).is_err());
        // Only multiplier letter with no number.
        assert!(parse_size("k", &m).is_err());
        // Number with an invalid trailing character.
        assert!(parse_size("123z", &m).is_err());
    }

    #[test]
    fn test_uppercase_multiplier_fails() {
        let m = get_binary_size_map();
        // Although the regex matches uppercase letters, the provided map only contains lowercase keys.
        // Therefore, "1K" does not match any key and should produce an error.
        assert!(parse_size("1K", &m).is_err());
    }
}