// Take a look at the license at the top of the repository in the LICENSE file.

use crate::{LoadAvg, Networks, Pid, ProcessExt, ProcessRefreshKind, RefreshKind, SystemExt, User};
use winapi::um::winreg::HKEY_LOCAL_MACHINE;

use crate::sys::component::{self, Component};
use crate::sys::disk::Disk;
use crate::sys::process::{get_handle, update_memory, Process};
use crate::sys::processor::*;
use crate::sys::tools::*;
use crate::sys::users::get_users;
use crate::sys::utils::get_now;

use crate::utils::into_iter;

use std::cell::UnsafeCell;
use std::collections::HashMap;
use std::ffi::OsStr;
use std::mem::{size_of, zeroed};
use std::os::windows::ffi::OsStrExt;
use std::slice::from_raw_parts;
use std::time::SystemTime;

use ntapi::ntexapi::{
    NtQuerySystemInformation, SystemProcessInformation, SYSTEM_PROCESS_INFORMATION,
};
use winapi::ctypes::wchar_t;
use winapi::shared::minwindef::{DWORD, FALSE, HKEY, LPBYTE, TRUE};
use winapi::shared::ntdef::{PVOID, ULONG};
use winapi::shared::ntstatus::STATUS_INFO_LENGTH_MISMATCH;
use winapi::shared::winerror;
use winapi::um::minwinbase::STILL_ACTIVE;
use winapi::um::processthreadsapi::GetExitCodeProcess;
use winapi::um::psapi::{GetPerformanceInfo, PERFORMANCE_INFORMATION};
use winapi::um::sysinfoapi::{
    ComputerNamePhysicalDnsHostname, GetComputerNameExW, GetTickCount64, GlobalMemoryStatusEx,
    MEMORYSTATUSEX,
};
use winapi::um::winnt::{HANDLE, KEY_READ};
use winapi::um::winreg::{RegOpenKeyExW, RegQueryValueExW};

#[doc = include_str!("../../md_doc/system.md")]
pub struct System {
    process_list: HashMap<usize, Process>,
    mem_total: u64,
    mem_available: u64,
    swap_total: u64,
    swap_used: u64,
    processors: ProcessorsWrapper,
    components: Vec<Component>,
    disks: Vec<Disk>,
    query: Option<Query>,
    networks: Networks,
    boot_time: u64,
    users: Vec<User>,
}

// Useful for parallel iterations.
struct Wrap<T>(T);

#[allow(clippy::non_send_fields_in_send_ty)]
unsafe impl<T> Send for Wrap<T> {}
unsafe impl<T> Sync for Wrap<T> {}

unsafe fn boot_time() -> u64 {
    match SystemTime::now().duration_since(SystemTime::UNIX_EPOCH) {
        Ok(n) => n.as_secs() - GetTickCount64() / 1000,
        Err(_e) => {
            sysinfo_debug!("Failed to compute boot time: {:?}", _e);
            0
        }
    }
}

impl SystemExt for System {
    const IS_SUPPORTED: bool = true;

    #[allow(non_snake_case)]
    fn new_with_specifics(refreshes: RefreshKind) -> System {
        let mut s = System {
            process_list: HashMap::with_capacity(500),
            mem_total: 0,
            mem_available: 0,
            swap_total: 0,
            swap_used: 0,
            processors: ProcessorsWrapper::new(),
            components: Vec::new(),
            disks: Vec::with_capacity(2),
            query: None,
            networks: Networks::new(),
            boot_time: unsafe { boot_time() },
            users: Vec::new(),
        };
        s.refresh_specifics(refreshes);
        s
    }

    fn refresh_cpu(&mut self) {
        if self.query.is_none() {
            self.query = Query::new();
            if let Some(ref mut query) = self.query {
                add_english_counter(
                    r"\Processor(_Total)\% Processor Time".to_string(),
                    query,
                    get_key_used(self.processors.global_processor_mut()),
                    "tot_0".to_owned(),
                );
                for (pos, proc_) in self.processors.iter_mut().enumerate() {
                    add_english_counter(
                        format!(r"\Processor({})\% Processor Time", pos),
                        query,
                        get_key_used(proc_),
                        format!("{}_0", pos),
                    );
                }
            }
        }
        if let Some(ref mut query) = self.query {
            query.refresh();
            let mut used_time = None;
            if let Some(ref key_used) = *get_key_used(self.processors.global_processor_mut()) {
                used_time = Some(
                    query
                        .get(&key_used.unique_id)
                        .expect("global_key_idle disappeared"),
                );
            }
            if let Some(used_time) = used_time {
                self.processors
                    .global_processor_mut()
                    .set_cpu_usage(used_time);
            }
            for p in self.processors.iter_mut() {
                let mut used_time = None;
                if let Some(ref key_used) = *get_key_used(p) {
                    used_time = Some(
                        query
                            .get(&key_used.unique_id)
                            .expect("key_used disappeared"),
                    );
                }
                if let Some(used_time) = used_time {
                    p.set_cpu_usage(used_time);
                }
            }
        }
    }

    fn refresh_memory(&mut self) {
        let mut mem_info: MEMORYSTATUSEX = unsafe { zeroed() };
        mem_info.dwLength = size_of::<MEMORYSTATUSEX>() as u32;
        unsafe {
            GlobalMemoryStatusEx(&mut mem_info);
        }
        self.mem_total = auto_cast!(mem_info.ullTotalPhys, u64) / 1_000;
        self.mem_available = auto_cast!(mem_info.ullAvailPhys, u64) / 1_000;
        let mut perf_info: PERFORMANCE_INFORMATION = unsafe { zeroed() };
        if unsafe {
            GetPerformanceInfo(&mut perf_info, size_of::<PERFORMANCE_INFORMATION>() as u32)
        } == TRUE
        {
            let swap_total = perf_info.PageSize
                * perf_info
                    .CommitLimit
                    .saturating_sub(perf_info.PhysicalTotal);
            let swap_used = perf_info.PageSize
                * perf_info
                    .CommitTotal
                    .saturating_sub(perf_info.PhysicalTotal);
            self.swap_total = (swap_total / 1000) as u64;
            self.swap_used = (swap_used / 1000) as u64;
        }
    }

    fn refresh_components_list(&mut self) {
        self.components = component::get_components();
    }

    #[allow(clippy::map_entry)]
    fn refresh_process_specifics(&mut self, pid: Pid, refresh_kind: ProcessRefreshKind) -> bool {
        if self.process_list.contains_key(&pid) {
            if !refresh_existing_process(self, pid, refresh_kind) {
                self.process_list.remove(&pid);
                return false;
            }
            return true;
        }
        let now = get_now();
        if let Some(mut p) = Process::new_from_pid(pid, now) {
            p.update(refresh_kind, self.processors.len() as u64, now);
            self.process_list.insert(pid, p);
            true
        } else {
            false
        }
    }

    #[allow(clippy::cast_ptr_alignment)]
    fn refresh_processes_specifics(&mut self, refresh_kind: ProcessRefreshKind) {
        // Windows 10 notebook requires at least 512KiB of memory to make it in one go
        let mut buffer_size: usize = 512 * 1024;
        let now = get_now();

        loop {
            let mut process_information: Vec<u8> = Vec::with_capacity(buffer_size);

            let mut cb_needed = 0;
            let ntstatus = unsafe {
                process_information.set_len(buffer_size);
                NtQuerySystemInformation(
                    SystemProcessInformation,
                    process_information.as_mut_ptr() as PVOID,
                    buffer_size as ULONG,
                    &mut cb_needed,
                )
            };

            if ntstatus != STATUS_INFO_LENGTH_MISMATCH {
                if ntstatus < 0 {
                    sysinfo_debug!(
                        "Couldn't get process infos: NtQuerySystemInformation returned {}",
                        ntstatus
                    );
                }

                // Parse the data block to get process information
                let mut process_ids = Vec::with_capacity(500);
                let mut process_information_offset = 0;
                loop {
                    let p = unsafe {
                        process_information
                            .as_ptr()
                            .offset(process_information_offset)
                            as *const SYSTEM_PROCESS_INFORMATION
                    };
                    let pi = unsafe { &*p };

                    process_ids.push(Wrap(p));

                    if pi.NextEntryOffset == 0 {
                        break;
                    }

                    process_information_offset += pi.NextEntryOffset as isize;
                }
                let process_list = Wrap(UnsafeCell::new(&mut self.process_list));
                let nb_processors = if refresh_kind.cpu() {
                    self.processors.len() as u64
                } else {
                    0
                };

                #[cfg(feature = "multithread")]
                use rayon::iter::ParallelIterator;

                // TODO: instead of using parallel iterator only here, would be better to be able
                //       to run it over `process_information` directly!
                let processes = into_iter(process_ids)
                    .filter_map(|pi| unsafe {
                        let pi = *pi.0;
                        let pid = pi.UniqueProcessId as usize;
                        if let Some(proc_) = (*process_list.0.get()).get_mut(&pid) {
                            proc_.memory = (pi.WorkingSetSize as u64) / 1_000;
                            proc_.virtual_memory = (pi.VirtualSize as u64) / 1_000;
                            proc_.update(refresh_kind, nb_processors, now);
                            return None;
                        }
                        let name = get_process_name(&pi, pid);
                        let mut p = Process::new_full(
                            pid,
                            if pi.InheritedFromUniqueProcessId as usize != 0 {
                                Some(pi.InheritedFromUniqueProcessId as usize)
                            } else {
                                None
                            },
                            (pi.WorkingSetSize as u64) / 1_000,
                            (pi.VirtualSize as u64) / 1_000,
                            name,
                            now,
                        );
                        p.update(refresh_kind, nb_processors, now);
                        Some(p)
                    })
                    .collect::<Vec<_>>();
                self.process_list.retain(|_, v| {
                    let x = v.updated;
                    v.updated = false;
                    x
                });
                for p in processes.into_iter() {
                    self.process_list.insert(p.pid(), p);
                }

                break;
            }

            // GetNewBufferSize
            if cb_needed == 0 {
                buffer_size *= 2;
                continue;
            }
            // allocating a few more kilo bytes just in case there are some new process
            // kicked in since new call to NtQuerySystemInformation
            buffer_size = (cb_needed + (1024 * 10)) as usize;
        }
    }

    fn refresh_disks_list(&mut self) {
        self.disks = unsafe { get_disks() };
    }

    fn refresh_users_list(&mut self) {
        self.users = unsafe { get_users() };
    }

    fn processes(&self) -> &HashMap<Pid, Process> {
        &self.process_list
    }

    fn process(&self, pid: Pid) -> Option<&Process> {
        self.process_list.get(&(pid as usize))
    }

    fn global_processor_info(&self) -> &Processor {
        self.processors.global_processor()
    }

    fn processors(&self) -> &[Processor] {
        self.processors.processors()
    }

    fn physical_core_count(&self) -> Option<usize> {
        get_physical_core_count()
    }

    fn total_memory(&self) -> u64 {
        self.mem_total
    }

    fn free_memory(&self) -> u64 {
        // MEMORYSTATUSEX doesn't report free memory
        self.mem_available
    }

    fn available_memory(&self) -> u64 {
        self.mem_available
    }

    fn used_memory(&self) -> u64 {
        self.mem_total - self.mem_available
    }

    fn total_swap(&self) -> u64 {
        self.swap_total
    }

    fn free_swap(&self) -> u64 {
        self.swap_total - self.swap_used
    }

    fn used_swap(&self) -> u64 {
        self.swap_used
    }

    fn components(&self) -> &[Component] {
        &self.components
    }

    fn components_mut(&mut self) -> &mut [Component] {
        &mut self.components
    }

    fn disks(&self) -> &[Disk] {
        &self.disks
    }

    fn disks_mut(&mut self) -> &mut [Disk] {
        &mut self.disks
    }

    fn users(&self) -> &[User] {
        &self.users
    }

    fn networks(&self) -> &Networks {
        &self.networks
    }

    fn networks_mut(&mut self) -> &mut Networks {
        &mut self.networks
    }

    fn uptime(&self) -> u64 {
        unsafe { GetTickCount64() / 1000 }
    }

    fn boot_time(&self) -> u64 {
        self.boot_time
    }

    fn load_average(&self) -> LoadAvg {
        get_load_average()
    }

    fn name(&self) -> Option<String> {
        Some("Windows".to_owned())
    }

    fn long_os_version(&self) -> Option<String> {
        get_reg_string_value(
            HKEY_LOCAL_MACHINE,
            "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion",
            "ProductName",
        )
    }

    fn host_name(&self) -> Option<String> {
        get_dns_hostname()
    }

    fn kernel_version(&self) -> Option<String> {
        get_reg_string_value(
            HKEY_LOCAL_MACHINE,
            "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion",
            "CurrentBuildNumber",
        )
    }

    fn os_version(&self) -> Option<String> {
        let major = get_reg_value_u32(
            HKEY_LOCAL_MACHINE,
            "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion",
            "CurrentMajorVersionNumber",
        );

        let build_number = get_reg_string_value(
            HKEY_LOCAL_MACHINE,
            "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion",
            "CurrentBuildNumber",
        );

        Some(format!(
            "{} ({})",
            u32::from_le_bytes(major.unwrap_or_default()),
            build_number.unwrap_or_default()
        ))
    }
}

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

fn is_proc_running(handle: HANDLE) -> bool {
    let mut exit_code = 0;
    let ret = unsafe { GetExitCodeProcess(handle, &mut exit_code) };
    !(ret == FALSE || exit_code != STILL_ACTIVE)
}

fn refresh_existing_process(s: &mut System, pid: Pid, refresh_kind: ProcessRefreshKind) -> bool {
    if let Some(ref mut entry) = s.process_list.get_mut(&(pid as usize)) {
        if !is_proc_running(get_handle(entry)) {
            return false;
        }
        update_memory(entry);
        entry.update(refresh_kind, s.processors.len() as u64, get_now());
        true
    } else {
        false
    }
}

#[allow(clippy::size_of_in_element_count)]
//^ needed for "name.Length as usize / std::mem::size_of::<u16>()"
pub(crate) fn get_process_name(process: &SYSTEM_PROCESS_INFORMATION, process_id: usize) -> String {
    let name = &process.ImageName;
    if name.Buffer.is_null() {
        match process_id {
            0 => "Idle".to_owned(),
            4 => "System".to_owned(),
            _ => format!("<no name> Process {}", process_id),
        }
    } else {
        let slice = unsafe {
            std::slice::from_raw_parts(
                name.Buffer,
                // The length is in bytes, not the length of string
                name.Length as usize / std::mem::size_of::<u16>(),
            )
        };

        String::from_utf16_lossy(slice)
    }
}

fn utf16_str<S: AsRef<OsStr> + ?Sized>(text: &S) -> Vec<u16> {
    OsStr::new(text)
        .encode_wide()
        .chain(Some(0).into_iter())
        .collect::<Vec<_>>()
}

fn get_reg_string_value(hkey: HKEY, path: &str, field_name: &str) -> Option<String> {
    let c_path = utf16_str(path);
    let c_field_name = utf16_str(field_name);

    let mut new_hkey: HKEY = std::ptr::null_mut();
    if unsafe { RegOpenKeyExW(hkey, c_path.as_ptr(), 0, KEY_READ, &mut new_hkey) } != 0 {
        return None;
    }

    let mut buf_len: DWORD = 2048;
    let mut buf_type: DWORD = 0;
    let mut buf: Vec<u8> = Vec::with_capacity(buf_len as usize);
    loop {
        match unsafe {
            RegQueryValueExW(
                new_hkey,
                c_field_name.as_ptr(),
                std::ptr::null_mut(),
                &mut buf_type,
                buf.as_mut_ptr() as LPBYTE,
                &mut buf_len,
            ) as DWORD
        } {
            0 => break,
            winerror::ERROR_MORE_DATA => {
                buf.reserve(buf_len as _);
            }
            _ => return None,
        }
    }

    unsafe {
        buf.set_len(buf_len as _);
    }

    let words = unsafe { from_raw_parts(buf.as_ptr() as *const u16, buf.len() / 2) };
    let mut s = String::from_utf16_lossy(words);
    while s.ends_with('\u{0}') {
        s.pop();
    }
    Some(s)
}

fn get_reg_value_u32(hkey: HKEY, path: &str, field_name: &str) -> Option<[u8; 4]> {
    let c_path = utf16_str(path);
    let c_field_name = utf16_str(field_name);

    let mut new_hkey: HKEY = std::ptr::null_mut();
    if unsafe { RegOpenKeyExW(hkey, c_path.as_ptr(), 0, KEY_READ, &mut new_hkey) } != 0 {
        return None;
    }

    let mut buf_len: DWORD = 4;
    let mut buf_type: DWORD = 0;
    let mut buf = [0u8; 4];

    match unsafe {
        RegQueryValueExW(
            new_hkey,
            c_field_name.as_ptr(),
            std::ptr::null_mut(),
            &mut buf_type,
            buf.as_mut_ptr() as LPBYTE,
            &mut buf_len,
        ) as DWORD
    } {
        0 => Some(buf),
        _ => None,
    }
}

fn get_dns_hostname() -> Option<String> {
    let mut buffer_size = 0;
    // Running this first to get the buffer size since the DNS name can be longer than MAX_COMPUTERNAME_LENGTH
    // setting the `lpBuffer` to null will return the buffer size
    // https://docs.microsoft.com/en-us/windows/win32/api/sysinfoapi/nf-sysinfoapi-getcomputernameexw
    unsafe {
        GetComputerNameExW(
            ComputerNamePhysicalDnsHostname,
            std::ptr::null_mut(),
            &mut buffer_size,
        )
    };

    // Setting the buffer with the new length
    let mut buffer = vec![0_u16; buffer_size as usize];

    // https://docs.microsoft.com/en-us/windows/win32/api/sysinfoapi/ne-sysinfoapi-computer_name_format
    if unsafe {
        GetComputerNameExW(
            ComputerNamePhysicalDnsHostname,
            buffer.as_mut_ptr() as *mut wchar_t,
            &mut buffer_size,
        )
    } == TRUE
    {
        if let Some(pos) = buffer.iter().position(|c| *c == 0) {
            buffer.resize(pos, 0);
        }

        String::from_utf16(&buffer).ok()
    } else {
        sysinfo_debug!("Failed to get computer hostname");
        None
    }
}