//----------------------------------------------------------------------------
// Example: List all processes owning a specific file
//
// Depends on "winapi" crate (tested version 0.3.9) with features
// "impl-default", "restartmanager" and "winerror" enabled.
//----------------------------------------------------------------------------

use std::ffi::{OsStr, OsString};
use std::io::{Error, Result};
use std::iter::once;
use std::os::windows::prelude::*;
use std::ptr::null_mut;

//----------------------------------------------------------------------------
// Helper functions

fn string_from_wide(wide: &[u16]) -> String {
    let os_str = OsString::from_wide(wide);
    let result = os_str.to_string_lossy();
    if let Some(i) = result.find('\0') {
        result[0..i].to_string()
    } else {
        result.to_string()
    }
}

fn wide_from_string(val: &str) -> Vec<u16> {
    let os_str = OsStr::new(val);
    os_str.encode_wide().chain(once(0)).collect()
}

struct ProcessInfo {
    pid: u32,
    app_name: String,
}

fn file_owner_process_info(file_name: &str) -> Result<Vec<ProcessInfo>> {
    use winapi::shared::winerror::ERROR_SUCCESS;
    use winapi::um::restartmanager::*;

    let mut result = Vec::new();
    let mut handle = 0;
    let mut session_key = vec![0; CCH_RM_SESSION_KEY];

    let mut errno = unsafe {
        RmStartSession(&mut handle, 0, session_key.as_mut_ptr())
    };
    if errno != ERROR_SUCCESS {
        return Err(Error::from_raw_os_error(errno as i32));
    }

    let file_name = wide_from_string(file_name);
    let mut file_names = vec![file_name.as_ptr()];
    errno = unsafe{
        RmRegisterResources(handle, 1, file_names.as_mut_ptr(), 0, null_mut(), 0, null_mut())
    };
    if errno == ERROR_SUCCESS {
        let mut proc_info = vec![RM_PROCESS_INFO::default(); 100];
        let mut proc_info_needed = 0;
        let mut proc_info_count = proc_info.len() as u32;
        let mut reboot_reasons = 0;
        errno = unsafe {
            RmGetList(handle, &mut proc_info_needed, &mut proc_info_count, proc_info.as_mut_ptr(), &mut reboot_reasons)
        };
        if errno == ERROR_SUCCESS {
            for i in 0..proc_info_count {
                let info = &proc_info[i as usize];
                let pid = info.Process.dwProcessId;
                let app_name = string_from_wide(&info.strAppName);
                result.push(ProcessInfo { pid, app_name });
            }
        }
    }

    unsafe { RmEndSession(handle) };
    if errno != ERROR_SUCCESS {
        return Err(Error::from_raw_os_error(errno as i32));
    }

    Ok(result)
}

//----------------------------------------------------------------------------

fn main() -> Result<()> {
    let args : Vec<_> = std::env::args().collect();
    let file_name = args.get(1).map(|v| v.as_str())
        .unwrap_or("C:\\Windows\\system32\\cmd.exe");

    println!("Owners of {}:", file_name);
    for info in file_owner_process_info(file_name)? {
        println!("pid: {},\tname: {}", info.pid, info.app_name);
    }
    Ok(())
}

//----------------------------------------------------------------------------