module os

import strings

fn C.GenerateConsoleCtrlEvent(event u32, pgid u32) bool
fn C.GetModuleHandleA(name &char) HMODULE
fn C.GetProcAddress(handle voidptr, procname &u8) voidptr
fn C.TerminateProcess(process HANDLE, exit_code u32) bool
fn C.PeekNamedPipe(hNamedPipe voidptr, lpBuffer voidptr, nBufferSize int, lpBytesRead voidptr, lpTotalBytesAvail voidptr, lpBytesLeftThisMessage voidptr) bool

type FN_NTSuspendResume = fn (voidptr)

fn ntdll_fn(name &u8) FN_NTSuspendResume {
    ntdll := C.GetModuleHandleA(c'NTDLL')
    if ntdll == 0 {
        return FN_NTSuspendResume(0)
    }
    the_fn := FN_NTSuspendResume(C.GetProcAddress(ntdll, name))
    return the_fn
}

fn failed_cfn_report_error(ok bool, label string) {
    if ok {
        return
    }
    error_num := int(C.GetLastError())
    error_msg := get_error_msg(error_num)
    eprintln('failed ${label}: ${error_msg}')
    exit(1)
}

type PU32 = &u32

// TODO: the PU32 alias is used to compensate for the wrong number of &/*
// that V does when doing: `h := &&u32(p)`, which should have casted
// p to a double pointer.
fn close_valid_handle(p voidptr) {
    h := &PU32(p)
    if *h != &u32(0) {
        C.CloseHandle(*h)
        unsafe {
            *h = &u32(0)
        }
    }
}

pub struct WProcess {
pub mut:
    proc_info    ProcessInformation
    command_line [65536]u8
    child_stdin  &u32 = unsafe { nil }
    //
    child_stdout_read  &u32 = unsafe { nil }
    child_stdout_write &u32 = unsafe { nil }
    //
    child_stderr_read  &u32 = unsafe { nil }
    child_stderr_write &u32 = unsafe { nil }
}

[manualfree]
fn (mut p Process) win_spawn_process() int {
    mut to_be_freed := []voidptr{cap: 5}
    defer {
        for idx := to_be_freed.len - 1; idx >= 0; idx-- {
            unsafe { free(to_be_freed[idx]) }
        }
        unsafe { to_be_freed.free() }
    }
    p.filename = abs_path(p.filename) // expand the path to an absolute one, in case we later change the working folder
    mut wdata := &WProcess{
        child_stdin: 0
        child_stdout_read: 0
        child_stdout_write: 0
        child_stderr_read: 0
        child_stderr_write: 0
    }
    p.wdata = voidptr(wdata)
    mut start_info := StartupInfo{
        lp_reserved2: 0
        lp_reserved: 0
        lp_desktop: 0
        lp_title: 0
        cb: sizeof(C.PROCESS_INFORMATION)
    }
    if p.use_stdio_ctl {
        mut sa := SecurityAttributes{}
        sa.n_length = sizeof(C.SECURITY_ATTRIBUTES)
        sa.b_inherit_handle = true
        create_pipe_ok1 := C.CreatePipe(voidptr(&wdata.child_stdout_read), voidptr(&wdata.child_stdout_write),
            voidptr(&sa), 0)
        failed_cfn_report_error(create_pipe_ok1, 'CreatePipe stdout')
        set_handle_info_ok1 := C.SetHandleInformation(wdata.child_stdout_read, C.HANDLE_FLAG_INHERIT,
            0)
        failed_cfn_report_error(set_handle_info_ok1, 'SetHandleInformation')
        create_pipe_ok2 := C.CreatePipe(voidptr(&wdata.child_stderr_read), voidptr(&wdata.child_stderr_write),
            voidptr(&sa), 0)
        failed_cfn_report_error(create_pipe_ok2, 'CreatePipe stderr')
        set_handle_info_ok2 := C.SetHandleInformation(wdata.child_stderr_read, C.HANDLE_FLAG_INHERIT,
            0)
        failed_cfn_report_error(set_handle_info_ok2, 'SetHandleInformation stderr')
        start_info.h_std_input = wdata.child_stdin
        start_info.h_std_output = wdata.child_stdout_write
        start_info.h_std_error = wdata.child_stderr_write
        start_info.dw_flags = u32(C.STARTF_USESTDHANDLES)
    }
    cmd := '${p.filename} ' + p.args.join(' ')
    cmd_wide_ptr := cmd.to_wide()
    to_be_freed << cmd_wide_ptr
    C.ExpandEnvironmentStringsW(cmd_wide_ptr, voidptr(&wdata.command_line[0]), 32768)

    mut creation_flags := if p.create_no_window {
        int(C.CREATE_NO_WINDOW)
    } else {
        int(C.NORMAL_PRIORITY_CLASS)
    }
    if p.use_pgroup {
        creation_flags |= C.CREATE_NEW_PROCESS_GROUP
    }

    mut work_folder_ptr := voidptr(unsafe { nil })
    if p.work_folder != '' {
        work_folder_ptr = p.work_folder.to_wide()
        to_be_freed << work_folder_ptr
    }

    create_process_ok := C.CreateProcessW(0, &wdata.command_line[0], 0, 0, C.TRUE, creation_flags,
        0, work_folder_ptr, voidptr(&start_info), voidptr(&wdata.proc_info))
    failed_cfn_report_error(create_process_ok, 'CreateProcess')
    if p.use_stdio_ctl {
        close_valid_handle(&wdata.child_stdout_write)
        close_valid_handle(&wdata.child_stderr_write)
    }
    p.pid = int(wdata.proc_info.dw_process_id)
    return p.pid
}

fn (mut p Process) win_stop_process() {
    the_fn := ntdll_fn(c'NtSuspendProcess')
    if voidptr(the_fn) == 0 {
        return
    }
    wdata := unsafe { &WProcess(p.wdata) }
    the_fn(wdata.proc_info.h_process)
}

fn (mut p Process) win_resume_process() {
    the_fn := ntdll_fn(c'NtResumeProcess')
    if voidptr(the_fn) == 0 {
        return
    }
    wdata := unsafe { &WProcess(p.wdata) }
    the_fn(wdata.proc_info.h_process)
}

fn (mut p Process) win_kill_process() {
    wdata := unsafe { &WProcess(p.wdata) }
    C.TerminateProcess(wdata.proc_info.h_process, 3)
}

fn (mut p Process) win_kill_pgroup() {
    wdata := unsafe { &WProcess(p.wdata) }
    C.GenerateConsoleCtrlEvent(C.CTRL_BREAK_EVENT, wdata.proc_info.dw_process_id)
    C.Sleep(20)
    C.TerminateProcess(wdata.proc_info.h_process, 3)
}

fn (mut p Process) win_wait() {
    exit_code := u32(1)
    mut wdata := unsafe { &WProcess(p.wdata) }
    if p.wdata != 0 {
        C.WaitForSingleObject(wdata.proc_info.h_process, C.INFINITE)
        C.GetExitCodeProcess(wdata.proc_info.h_process, voidptr(&exit_code))
        close_valid_handle(&wdata.child_stdin)
        close_valid_handle(&wdata.child_stdout_write)
        close_valid_handle(&wdata.child_stderr_write)
        close_valid_handle(&wdata.proc_info.h_process)
        close_valid_handle(&wdata.proc_info.h_thread)
    }
    p.status = .exited
    p.code = int(exit_code)
}

fn (mut p Process) win_is_alive() bool {
    exit_code := u32(0)
    wdata := unsafe { &WProcess(p.wdata) }
    C.GetExitCodeProcess(wdata.proc_info.h_process, voidptr(&exit_code))
    if exit_code == C.STILL_ACTIVE {
        return true
    }
    return false
}

///////////////

fn (mut p Process) win_write_string(idx int, s string) {
    panic('Process.write_string ${idx} is not implemented yet')
}

fn (mut p Process) win_read_string(idx int, maxbytes int) (string, int) {
    mut wdata := unsafe { &WProcess(p.wdata) }
    if unsafe { wdata == 0 } {
        return '', 0
    }
    mut rhandle := &u32(0)
    if idx == 1 {
        rhandle = wdata.child_stdout_read
    }
    if idx == 2 {
        rhandle = wdata.child_stderr_read
    }
    if rhandle == 0 {
        return '', 0
    }
    mut bytes_avail := int(0)
    if !C.PeekNamedPipe(rhandle, unsafe { nil }, int(0), unsafe { nil }, &bytes_avail,
        unsafe { nil }) {
        return '', 0
    }
    if bytes_avail == 0 {
        return '', 0
    }

    mut bytes_read := int(0)
    buf := []u8{len: bytes_avail + 300}
    unsafe {
        C.ReadFile(rhandle, &buf[0], buf.cap, voidptr(&bytes_read), 0)
    }
    return buf[..bytes_read].bytestr(), bytes_read
}

fn (mut p Process) win_slurp(idx int) string {
    mut wdata := unsafe { &WProcess(p.wdata) }
    if unsafe { wdata == 0 } {
        return ''
    }
    mut rhandle := &u32(0)
    if idx == 1 {
        rhandle = wdata.child_stdout_read
    }
    if idx == 2 {
        rhandle = wdata.child_stderr_read
    }
    if rhandle == 0 {
        return ''
    }
    mut bytes_read := u32(0)
    buf := [4096]u8{}
    mut read_data := strings.new_builder(1024)
    for {
        mut result := false
        unsafe {
            result = C.ReadFile(rhandle, &buf[0], 1000, voidptr(&bytes_read), 0)
            read_data.write_ptr(&buf[0], int(bytes_read))
        }
        if result == false || int(bytes_read) == 0 {
            break
        }
    }
    soutput := read_data.str()
    unsafe { read_data.free() }
    //    if idx == 1 {
    //        close_valid_handle(&wdata.child_stdout_read)
    //    }
    //    if idx == 2 {
    //        close_valid_handle(&wdata.child_stderr_read)
    //    }
    return soutput
}

//
// these are here to make v_win.c/v.c generation work in all cases:
fn (mut p Process) unix_spawn_process() int {
    return 0
}

fn (mut p Process) unix_stop_process() {
}

fn (mut p Process) unix_resume_process() {
}

fn (mut p Process) unix_kill_process() {
}

fn (mut p Process) unix_kill_pgroup() {
}

fn (mut p Process) unix_wait() {
}

fn (mut p Process) unix_is_alive() bool {
    return false
}