/*!
Read data from `/proc/meminfo` into the struct [`ProcMemInfo`].

The processor of `/proc/meminfo` takes the values for the memory areas specified, and puts them in the
struct [`ProcMemInfo`]. The values are in kilobytes (kB), just like the values in the original `/proc/meminfo`
file.

Here is an example obtaining the data from `/proc/meminfo`:
```no_run
use proc_sys_parser::{meminfo, meminfo::ProcMemInfo};

let proc_meminfo = meminfo::read();

println!("{:#?}", proc_meminfo);
```
Example output:
```text
ProcMemInfo {
    memtotal: 3997876,
    memfree: 2415136,
    memavailable: 3654096,
    buffers: 37492,
    cached: 1305568,
    swapcached: 0,
    active: 880772,
    inactive: 549432,
    active_anon: 86968,
    inactive_anon: 5196,
    active_file: 793804,
    inactive_file: 544236,
    unevictable: 4000,
    mlocked: 0,
    swaptotal: 0,
    swapfree: 0,
    zswap: 0,
    zswapped: 0,
    dirty: 0,
    writeback: 0,
    anonpages: 91144,
    mapped: 140948,
    shmem: 5020,
    kreclaimable: 56680,
    slab: 93916,
    sreclaimable: 56680,
    sunreclaim: 37236,
    kernelstack: 3256,
    shadowcallstack: 828,
    pagetables: 2884,
    secpagetables: 0,
    nfs_unstable: 0,
    bounce: 0,
    writebacktmp: 0,
    commitlimit: 1998936,
    committed_as: 944240,
    vmalloctotal: 133141626880,
    vmallocused: 14124,
    vmallocchunk: 0,
    percpu: 2280,
    hardwarecorrupted: 0,
    anonhugepages: 4096,
    shmemhugepages: 0,
    shmempmdmapped: 0,
    filehugepages: 0,
    filepmdmapped: 0,
    cmatotal: 32768,
    cmafree: 31232,
    hugepages_total: 0,
    hugepages_free: 0,
    hugepages_rsvd: 0,
    hugepages_surp: 0,
    hugepagesize: 2048,
    hugetlb: 0
}
```
(edited for readability)

If you want to change th path and/or file that is read for [`ProcMemInfo`], which is `/proc/meminfo`
by default, use:
```no_run
use proc_sys_parser::{meminfo, meminfo::{ProcMemInfo, Builder}};

let proc_meminfo = Builder::new().file_name("/myproc/meminfo").read();
```

*/
use std::fs::read_to_string;

/// Struct for holding `/proc/meminfo` statistics
#[derive(Debug, PartialEq)]
pub struct ProcMemInfo {
    pub memtotal: u64,
    pub memfree: u64,
    pub memavailable: u64,
    pub buffers: u64,
    pub cached: u64,
    pub swapcached: u64,
    pub active: u64,
    pub inactive: u64,
    pub active_anon: u64,
    pub inactive_anon: u64,
    pub active_file: u64,
    pub inactive_file: u64,
    pub unevictable: u64,
    pub mlocked: u64,
    pub swaptotal: u64,
    pub swapfree: u64,
    pub zswap: u64,
    pub zswapped: u64,
    pub dirty: u64,
    pub writeback: u64,
    pub anonpages: u64,
    pub mapped: u64,
    pub shmem: u64,
    pub kreclaimable: u64,
    pub slab: u64,
    pub sreclaimable: u64,
    pub sunreclaim: u64,
    pub kernelstack: u64,
    pub shadowcallstack: u64,
    pub pagetables: u64,
    pub secpagetables: u64,
    pub nfs_unstable: u64,
    pub bounce: u64,
    pub writebacktmp: u64,
    pub commitlimit: u64,
    pub committed_as: u64,
    pub vmalloctotal: u64,
    pub vmallocused: u64,
    pub vmallocchunk: u64,
    pub percpu: u64,
    pub hardwarecorrupted: u64,
    pub anonhugepages: u64,
    pub shmemhugepages: u64,
    pub shmempmdmapped: u64,
    pub filehugepages: u64,
    pub filepmdmapped: u64,
    pub cmatotal: u64,
    pub cmafree: u64,
    pub hugepages_total: u64,
    pub hugepages_free: u64,
    pub hugepages_rsvd: u64,
    pub hugepages_surp: u64,
    pub hugepagesize: u64,
    pub hugetlb: u64,
}

/// Builder pattern for [`ProcMemInfo`]
pub struct Builder
{
    pub proc_meminfo_file: String
}

impl Default for Builder
{
    fn default() -> Self
    {
        Self::new()
    }
}

impl Builder
{
    pub fn new() -> Builder
    {
        Builder { proc_meminfo_file: "/proc/meminfo".to_string() }
    }

    pub fn file_name(mut self, proc_meminfo_file: &str) -> Builder
    {
        self.proc_meminfo_file = proc_meminfo_file.to_string();
        self
    }
    pub fn read(self) -> ProcMemInfo
    {
        ProcMemInfo::read_proc_meminfo(&self.proc_meminfo_file)
    }
}

/// The main function for building a [`ProcMemInfo`] struct with current data.
/// This uses the Builder pattern, which allows settings such as the filename to specified.
pub fn read() -> ProcMemInfo
{
   Builder::new().read()
}

impl Default for ProcMemInfo {
    fn default() -> Self {
        Self::new()
    }
}
impl ProcMemInfo {
    pub fn new() -> ProcMemInfo {
        ProcMemInfo {
            memtotal: 0,
            memfree: 0,
            memavailable: 0,
            buffers: 0,
            cached: 0,
            swapcached: 0,
            active: 0,
            inactive: 0,
            active_anon: 0,
            inactive_anon: 0,
            active_file: 0,
            inactive_file: 0,
            unevictable: 0,
            mlocked: 0,
            swaptotal: 0,
            swapfree: 0,
            zswap: 0,
            zswapped: 0,
            dirty: 0,
            writeback: 0,
            anonpages: 0,
            mapped: 0,
            shmem: 0,
            kreclaimable: 0,
            slab: 0,
            sreclaimable: 0,
            sunreclaim: 0,
            kernelstack: 0,
            shadowcallstack: 0,
            pagetables: 0,
            secpagetables: 0,
            nfs_unstable: 0,
            bounce: 0,
            writebacktmp: 0,
            commitlimit: 0,
            committed_as: 0,
            vmalloctotal: 0,
            vmallocused: 0,
            vmallocchunk: 0,
            percpu: 0,
            hardwarecorrupted: 0,
            anonhugepages: 0,
            shmemhugepages: 0,
            shmempmdmapped: 0,
            filehugepages: 0,
            filepmdmapped: 0,
            cmatotal: 0,
            cmafree: 0,
            hugepages_total: 0,
            hugepages_free: 0,
            hugepages_rsvd: 0,
            hugepages_surp: 0,
            hugepagesize: 0,
            hugetlb: 0,
        }
    }
    pub fn parse_proc_meminfo_output(
        proc_meminfo: &str,
    ) -> ProcMemInfo
    {
        let mut procmeminfo = ProcMemInfo::new();
        for line in proc_meminfo.lines()
        {
            match line
            {
                line if line.starts_with("MemTotal:") => procmeminfo.memtotal = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("MemFree:") => procmeminfo.memfree = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("MemAvailable:") => procmeminfo.memavailable = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("Buffers:") => procmeminfo.buffers = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("Cached:") => procmeminfo.cached = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("SwapCached:") => procmeminfo.swapcached = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("Active:") => procmeminfo.active = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("Inactive:") => procmeminfo.inactive = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("Active(anon):") => procmeminfo.active_anon = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("Inactive(anon):") => procmeminfo.inactive_anon = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("Active(file):") => procmeminfo.active_file = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("Inactive(file):") => procmeminfo.inactive_file = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("Unevictable:") => procmeminfo.unevictable = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("Mlocked:") => procmeminfo.mlocked = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("SwapTotal:") => procmeminfo.swaptotal = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("SwapFree:") => procmeminfo.swapfree = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("Zswap:") => procmeminfo.zswap = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("Zswapped:") => procmeminfo.zswapped = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("Dirty:") => procmeminfo.dirty = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("Writeback:") => procmeminfo.writeback = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("AnonPages:") => procmeminfo.anonpages = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("Mapped:") => procmeminfo.mapped = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("Shmem:") => procmeminfo.shmem = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("KReclaimable:") => procmeminfo.kreclaimable = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("Slab:") => procmeminfo.slab = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("SReclaimable:") => procmeminfo.sreclaimable = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("SUnreclaim:") => procmeminfo.sunreclaim = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("KernelStack:") => procmeminfo.kernelstack = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("ShadowCallStack:") => procmeminfo.shadowcallstack = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("PageTables:") => procmeminfo.pagetables = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("SecPageTables:") => procmeminfo.secpagetables = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("NFS_Unstable:") => procmeminfo.nfs_unstable = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("Bounce:") => procmeminfo.bounce = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("WritebackTmp:") => procmeminfo.writebacktmp = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("CommitLimit:") => procmeminfo.commitlimit = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("Committed_AS:") => procmeminfo.committed_as = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("VmallocTotal:") => procmeminfo.vmalloctotal = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("VmallocUsed:") => procmeminfo.vmallocused = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("VmallocChunk:") => procmeminfo.vmallocchunk = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("Percpu:") => procmeminfo.percpu = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("HardwareCorrupted:") => procmeminfo.hardwarecorrupted = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("AnonHugePages:") => procmeminfo.anonhugepages = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("ShmemHugePages:") => procmeminfo.shmemhugepages = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("ShmemPmdMapped:") => procmeminfo.shmempmdmapped = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("FileHugePages:") => procmeminfo.filehugepages = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("FilePmdMapped:") => procmeminfo.filepmdmapped = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("CmaTotal:") => procmeminfo.cmatotal = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("CmaFree:") => procmeminfo.cmafree = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("HugePages_Total:") => procmeminfo.hugepages_total = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("HugePages_Free:") => procmeminfo.hugepages_free = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("HugePages_Rsvd:") => procmeminfo.hugepages_rsvd = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("HugePages_Surp:") => procmeminfo.hugepages_surp = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("Hugepagesize:") => procmeminfo.hugepagesize = ProcMemInfo::parse_proc_meminfo_line(line),
                line if line.starts_with("Hugetlb:") => procmeminfo.hugetlb = ProcMemInfo::parse_proc_meminfo_line(line),
                _  => panic!("Unknown line found in stat: {}", line),
            }
        }
        procmeminfo
    }
    fn parse_proc_meminfo_line(proc_meminfo_line: &str) -> u64
    {
        proc_meminfo_line.split_whitespace()
            .skip(1)
            .map(|number| number.parse::<u64>().unwrap())
            .nth(0)
            .unwrap_or(0)
    }
    pub fn read_proc_meminfo(proc_meminfo_file: &str) -> ProcMemInfo
    {
        //let proc_stat_file = proc_stat_file.unwrap_or("/proc/stat");
        let proc_meminfo_output = read_to_string(proc_meminfo_file).unwrap_or_else(|error|panic!("Error {} reading file: {}", error, proc_meminfo_file));
        ProcMemInfo::parse_proc_meminfo_output(&proc_meminfo_output)
    }
}

#[cfg(test)]
mod tests {
    use std::fs::{write, remove_dir_all, create_dir_all};
    use rand::{thread_rng, Rng};
    use rand::distributions::Alphanumeric;
    use super::*;

    #[test]
    fn parse_meminfo_line() {
        let meminfo_line = "MemTotal:        3997876 kB";
        let result = ProcMemInfo::parse_proc_meminfo_line(&meminfo_line);
        assert_eq!(result, 3997876_u64);
    }

    #[test]
    fn parse_full_proc_meminfo_file() {
        let proc_meminfo = "MemTotal:        3997876 kB
MemFree:         2415136 kB
MemAvailable:    3654096 kB
Buffers:           37492 kB
Cached:          1305568 kB
SwapCached:            0 kB
Active:           880772 kB
Inactive:         549432 kB
Active(anon):      86968 kB
Inactive(anon):     5196 kB
Active(file):     793804 kB
Inactive(file):   544236 kB
Unevictable:        4000 kB
Mlocked:               0 kB
SwapTotal:             0 kB
SwapFree:              0 kB
Zswap:                 0 kB
Zswapped:              0 kB
Dirty:                 0 kB
Writeback:             0 kB
AnonPages:         91144 kB
Mapped:           140948 kB
Shmem:              5020 kB
KReclaimable:      56680 kB
Slab:              93916 kB
SReclaimable:      56680 kB
SUnreclaim:        37236 kB
KernelStack:        3256 kB
ShadowCallStack:     828 kB
PageTables:         2884 kB
SecPageTables:         0 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:     1998936 kB
Committed_AS:     944240 kB
VmallocTotal:   133141626880 kB
VmallocUsed:       14124 kB
VmallocChunk:          0 kB
Percpu:             2280 kB
HardwareCorrupted:     0 kB
AnonHugePages:      4096 kB
ShmemHugePages:        0 kB
ShmemPmdMapped:        0 kB
FileHugePages:         0 kB
FilePmdMapped:         0 kB
CmaTotal:          32768 kB
CmaFree:           31232 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
Hugetlb:               0 kB";
        let result = ProcMemInfo::parse_proc_meminfo_output(proc_meminfo);
        assert_eq!(result, ProcMemInfo {
            memtotal: 3997876,
            memfree: 2415136,
            memavailable: 3654096,
            buffers: 37492,
            cached: 1305568,
            swapcached: 0,
            active: 880772,
            inactive: 549432,
            active_anon: 86968,
            inactive_anon: 5196,
            active_file: 793804,
            inactive_file: 544236,
            unevictable: 4000,
            mlocked: 0,
            swaptotal: 0,
            swapfree: 0,
            zswap: 0,
            zswapped: 0,
            dirty: 0,
            writeback: 0,
            anonpages: 91144,
            mapped: 140948,
            shmem: 5020,
            kreclaimable: 56680,
            slab: 93916,
            sreclaimable: 56680,
            sunreclaim: 37236,
            kernelstack: 3256,
            shadowcallstack: 828,
            pagetables: 2884,
            secpagetables: 0,
            nfs_unstable: 0,
            bounce: 0,
            writebacktmp: 0,
            commitlimit: 1998936,
            committed_as: 944240,
            vmalloctotal: 133141626880,
            vmallocused: 14124,
            vmallocchunk: 0,
            percpu: 2280,
            hardwarecorrupted: 0,
            anonhugepages: 4096,
            shmemhugepages: 0,
            shmempmdmapped: 0,
            filehugepages: 0,
            filepmdmapped: 0,
            cmatotal: 32768,
            cmafree: 31232,
            hugepages_total: 0,
            hugepages_free: 0,
            hugepages_rsvd: 0,
            hugepages_surp: 0,
            hugepagesize: 2048,
            hugetlb: 0
        });
    }

    #[test]
    fn create_proc_meminfo_file_and_read() {
        let proc_meminfo = "MemTotal:        3997876 kB
MemFree:         2415136 kB
MemAvailable:    3654096 kB
Buffers:           37492 kB
Cached:          1305568 kB
SwapCached:            0 kB
Active:           880772 kB
Inactive:         549432 kB
Active(anon):      86968 kB
Inactive(anon):     5196 kB
Active(file):     793804 kB
Inactive(file):   544236 kB
Unevictable:        4000 kB
Mlocked:               0 kB
SwapTotal:             0 kB
SwapFree:              0 kB
Zswap:                 0 kB
Zswapped:              0 kB
Dirty:                 0 kB
Writeback:             0 kB
AnonPages:         91144 kB
Mapped:           140948 kB
Shmem:              5020 kB
KReclaimable:      56680 kB
Slab:              93916 kB
SReclaimable:      56680 kB
SUnreclaim:        37236 kB
KernelStack:        3256 kB
ShadowCallStack:     828 kB
PageTables:         2884 kB
SecPageTables:         0 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:     1998936 kB
Committed_AS:     944240 kB
VmallocTotal:   133141626880 kB
VmallocUsed:       14124 kB
VmallocChunk:          0 kB
Percpu:             2280 kB
HardwareCorrupted:     0 kB
AnonHugePages:      4096 kB
ShmemHugePages:        0 kB
ShmemPmdMapped:        0 kB
FileHugePages:         0 kB
FilePmdMapped:         0 kB
CmaTotal:          32768 kB
CmaFree:           31232 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
Hugetlb:               0 kB";
        let directory_suffix: String = thread_rng().sample_iter(&Alphanumeric).take(8).map(char::from).collect();
        let test_path = format!("/tmp/test.{}", directory_suffix);
        create_dir_all(format!("{}", test_path)).expect("Error creating mock directory.");

        write(format!("{}/meminfo", test_path), proc_meminfo).expect(format!("Error writing to {}/meminfo", test_path).as_str());
        let result = Builder::new().file_name(format!("{}/meminfo", test_path).as_str()).read();

        remove_dir_all(test_path).unwrap();

        assert_eq!(result, ProcMemInfo {
            memtotal: 3997876,
            memfree: 2415136,
            memavailable: 3654096,
            buffers: 37492,
            cached: 1305568,
            swapcached: 0,
            active: 880772,
            inactive: 549432,
            active_anon: 86968,
            inactive_anon: 5196,
            active_file: 793804,
            inactive_file: 544236,
            unevictable: 4000,
            mlocked: 0,
            swaptotal: 0,
            swapfree: 0,
            zswap: 0,
            zswapped: 0,
            dirty: 0,
            writeback: 0,
            anonpages: 91144,
            mapped: 140948,
            shmem: 5020,
            kreclaimable: 56680,
            slab: 93916,
            sreclaimable: 56680,
            sunreclaim: 37236,
            kernelstack: 3256,
            shadowcallstack: 828,
            pagetables: 2884,
            secpagetables: 0,
            nfs_unstable: 0,
            bounce: 0,
            writebacktmp: 0,
            commitlimit: 1998936,
            committed_as: 944240,
            vmalloctotal: 133141626880,
            vmallocused: 14124,
            vmallocchunk: 0,
            percpu: 2280,
            hardwarecorrupted: 0,
            anonhugepages: 4096,
            shmemhugepages: 0,
            shmempmdmapped: 0,
            filehugepages: 0,
            filepmdmapped: 0,
            cmatotal: 32768,
            cmafree: 31232,
            hugepages_total: 0,
            hugepages_free: 0,
            hugepages_rsvd: 0,
            hugepages_surp: 0,
            hugepagesize: 2048,
            hugetlb: 0
        });
    }
}