module os

#include <dirent.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/utsname.h>
#include <sys/types.h>
#include <sys/statvfs.h>
#include <sys/wait.h>
#include <utime.h>
#insert "@VEXEROOT/vlib/os/execute_capture_nix.h"

// short_path is a Windows-only helper that returns the DOS 8.3 short path.
// On non-Windows platforms it simply returns the given path unchanged,
// so that callers guarded by `$if windows { ... }` type-check on other targets.
pub fn short_path(path string) string {
    return path
}

// path_separator is the platform specific separator string, used between the folders and filenames in a path. It is '/' on POSIX, and '\\' on Windows.
pub const path_separator = '/'

// path_delimiter is the platform specific delimiter string, used between the paths in environment variables like PATH. It is ':' on POSIX, and ';' on Windows.
pub const path_delimiter = ':'

// path_devnull is a platform-specific file path of the null device.
// It is '/dev/null' on POSIX, and r'\\.\nul' on Windows.
pub const path_devnull = '/dev/null'

const executable_suffixes = ['']

const stdin_value = 0
const stdout_value = 1
const stderr_value = 2

// (Must be realized in Syscall) (Must be specified)
// ref: http://www.ccfit.nsu.ru/~deviv/courses/unix/unix/ng7c229.html
pub const s_ifmt = 0xF000 // type of file
pub const s_ifdir = 0x4000 // directory
pub const s_ifreg = 0x8000 // regular file
pub const s_iflnk = 0xa000 // link
pub const s_isuid = 0o4000 // SUID
pub const s_isgid = 0o2000 // SGID
pub const s_isvtx = 0o1000 // Sticky
pub const s_irusr = 0o0400 // Read by owner
pub const s_iwusr = 0o0200 // Write by owner
pub const s_ixusr = 0o0100 // Execute by owner
pub const s_irgrp = 0o0040 // Read by group
pub const s_iwgrp = 0o0020 // Write by group
pub const s_ixgrp = 0o0010 // Execute by group
pub const s_iroth = 0o0004 // Read by others
pub const s_iwoth = 0o0002 // Write by others
pub const s_ixoth = 0o0001

fn C.utime(&char, &C.utimbuf) i32

fn C.uname(name &C.utsname) i32

fn C.symlink(&char, &char) i32

fn C.readlink(&char, &char, i32) i32

fn C.link(&char, &char) i32

fn C.gethostname(&char, i32) i32

// Note: not available on Android fn C.getlogin_r(&char, int) int
fn C.getlogin() &char

fn C.getppid() i32

fn C.getgid() i32

fn C.getegid() i32

fn C.v_os_execute_capture_start(cmd &char, child_pid &int, read_fd &int) int

fn C.v_os_exec_capture_start(argv &&char, child_pid &int, read_fd &int) int

enum GlobMatch {
    exact
    ends_with
    starts_with
    start_and_ends_with
    contains
    any
}

fn glob_match(dir string, pattern string, next_pattern string, mut matches []string) []string {
    mut subdirs := []string{}
    if is_file(dir) {
        return subdirs
    }
    mut files := ls(dir) or { return subdirs }
    mut mode := GlobMatch.exact
    mut pat := pattern
    if pat == '*' {
        mode = GlobMatch.any
        if next_pattern != pattern && next_pattern != '' {
            for file in files {
                if is_dir('${dir}/${file}') {
                    subdirs << '${dir}/${file}'
                }
            }
            return subdirs
        }
    }
    if pat == '**' {
        files = walk_ext(dir, '')
        pat = next_pattern
    }
    if pat.starts_with('*') {
        mode = .ends_with
        pat = pat[1..]
    }
    if pat.ends_with('*') {
        mode = if mode == .ends_with { GlobMatch.contains } else { GlobMatch.starts_with }
        pat = pat[..pat.len - 1]
    }
    if pat.contains('*') {
        mode = .start_and_ends_with
    }
    for file in files {
        mut fpath := file
        f := if file.contains(path_separator) {
            pathwalk := file.split(path_separator)
            pathwalk[pathwalk.len - 1]
        } else {
            fpath = if dir == '.' { file } else { '${dir}/${file}' }
            file
        }
        if f in ['.', '..'] || f == '' {
            continue
        }
        hit := match mode {
            .any {
                true
            }
            .exact {
                f == pat
            }
            .starts_with {
                f.starts_with(pat)
            }
            .ends_with {
                f.ends_with(pat)
            }
            .start_and_ends_with {
                p := pat.split('*')
                f.starts_with(p[0]) && f.ends_with(p[1])
            }
            .contains {
                f.contains(pat)
            }
        }

        if hit {
            if is_dir(fpath) {
                subdirs << fpath
                if next_pattern == pattern && next_pattern != '' {
                    matches << '${fpath}${path_separator}'
                }
            } else {
                matches << fpath
            }
        }
    }
    return subdirs
}

fn native_glob_pattern(pattern string, mut matches []string) ! {
    steps := pattern.split(path_separator)
    cwd := if pattern.starts_with(path_separator) { path_separator } else { '.' }
    mut subdirs := [cwd]
    for i := 0; i < steps.len; i++ {
        step := steps[i]
        step2 := if i + 1 == steps.len { step } else { steps[i + 1] }
        if step == '' {
            continue
        }
        if is_dir('${cwd}${path_separator}${step}') {
            dd := if cwd == '/' {
                step
            } else {
                if cwd == '.' || cwd == '' {
                    step
                } else {
                    if step == '.' || step == '/' { cwd } else { '${cwd}/${step}' }
                }
            }
            if i + 1 != steps.len {
                if dd !in subdirs {
                    subdirs << dd
                }
            }
        }
        mut subs := []string{}
        for sd in subdirs {
            d := if cwd == '/' {
                sd
            } else {
                if cwd == '.' || cwd == '' {
                    sd
                } else {
                    if sd == '.' || sd == '/' { cwd } else { '${cwd}/${sd}' }
                }
            }
            subs << glob_match(d.replace('//', '/'), step, step2, mut matches)
        }
        subdirs = subs.clone()
    }
}

// utime changes the access and modification times of the inode specified by path.
// It returns POSIX error message, if it can not do so.
pub fn utime(path string, actime i64, modtime i64) ! {
    u := C.utimbuf{actime, modtime}
    if C.utime(&char(path.str), &u) != 0 {
        return error_with_code(posix_get_error_msg(C.errno), C.errno)
    }
}

// uname returns information about the platform on which the program is running.
// For example:
// os.Uname{
//    sysname: 'Linux'
//    nodename: 'nemesis'
//    release: '5.15.0-57-generic'
//    version: '#63~20.04.1-Ubuntu SMP Wed Nov 30 13:40:16 UTC 2022'
//    machine: 'x86_64'
// }
// where the fields have the following meaning:
//    sysname is the name of this implementation of the operating system
//    nodename is the name of this node within an implementation-dependent communications network
//    release is the current release level of this implementation
//    version is the current version level of this release
//    machine is the name of the hardware type, on which the system is running
// See also https://pubs.opengroup.org/onlinepubs/7908799/xsh/sysutsname.h.html
pub fn uname() Uname {
    mut u := Uname{}
    unsafe {
        d := &C.utsname(malloc_noscan(int(sizeof(C.utsname))))
        if C.uname(d) == 0 {
            u.sysname = cstring_to_vstring(d.sysname)
            u.nodename = cstring_to_vstring(d.nodename)
            u.release = cstring_to_vstring(d.release)
            u.version = cstring_to_vstring(d.version)
            u.machine = cstring_to_vstring(d.machine)
        }
        free(d)
    }
    return u
}

// hostname returns the hostname (system's DNS name) or POSIX error message if the hostname call fails.
pub fn hostname() !string {
    mut hstnme := ''
    size := 256
    buf := unsafe { &char(malloc_noscan(size)) }
    if C.gethostname(buf, size) == 0 {
        hstnme = unsafe { cstring_to_vstring(buf) }
        unsafe { free(buf) }
        return hstnme
    }
    return error(posix_get_error_msg(C.errno))
}

// loginname returns the name of the user logged in on the controlling terminal of the process.
// It returns a POSIX error message, if the getlogin call fails.
pub fn loginname() !string {
    x := C.getlogin()
    if !isnil(x) {
        return unsafe { cstring_to_vstring(x) }
    }
    return error(posix_get_error_msg(C.errno))
}

// ls returns ![]string of the files and dirs in the given `path` ( os.ls uses C.readdir ). Symbolic links are returned to be files. For recursive list see os.walk functions.
// See also: `os.walk`, `os.walk_ext`, `os.is_dir`, `os.is_file`
// Example:
// ```
//   entries := os.ls(os.home_dir()) or { [] }
//   for entry in entries {
//     if os.is_dir(os.join_path(os.home_dir(), entry)) {
//       println('dir: ${entry}')
//     } else {
//       println('file: ${entry}')
//     }
//   }
// ```
@[manualfree]
pub fn ls(path string) ![]string {
    if path == '' {
        return error('ls() expects a folder, not an empty string')
    }
    mut res := []string{cap: 50}
    dir_ptr := unsafe { C.opendir(&char(path.str)) }
    if isnil(dir_ptr) {
        return error_posix(msg: 'ls() couldnt open dir "${path}"')
    }
    mut ent := &C.dirent(unsafe { nil })
    for {
        ent = C.readdir(dir_ptr)
        if isnil(ent) {
            break
        }
        unsafe {
            bptr := &u8(&ent.d_name[0])
            // vfmt off
            if bptr[0] == 0 || (bptr[0] == `.` && bptr[1] == 0) || (bptr[0] == `.` && bptr[1] == `.` && bptr[2] == 0) {
                continue
            }
            res << tos_clone(bptr)
            // vfmt on
        }
    }
    C.closedir(dir_ptr)
    return res
}

// mkdir creates a new directory with the specified path.
pub fn mkdir(path string, params MkdirParams) ! {
    if path == '.' {
        return
    }
    apath := real_path(path)
    r := unsafe { C.mkdir(&char(apath.str), params.mode) }
    if r == -1 {
        return error(posix_get_error_msg(C.errno))
    }
}

// execute starts the specified command, waits for it to complete, and returns its output.
pub fn execute(cmd string) Result {
    mut pid := 0
    mut read_fd := -1
    v_os_execute_lock()
    rc := C.v_os_execute_capture_start(&char(cmd.str), &pid, &read_fd)
    v_os_execute_unlock()
    if rc != 0 {
        return Result{
            exit_code: -1
            output:    'exec("${cmd}") failed'
        }
    }
    soutput := fd_slurp(read_fd).join('')
    fd_close(read_fd)
    mut status := 0
    for {
        C.errno = 0
        if C.waitpid(pid, &status, 0) != -1 {
            break
        }
        if C.errno == C.EINTR {
            continue
        }
        return Result{
            exit_code: -1
            output:    soutput
        }
    }
    exit_code, _ := posix_wait4_to_exit_status(status)
    return Result{
        exit_code: exit_code
        output:    soutput
    }
}

// exec starts the specified command with arguments, waits for it to complete, and returns its output.
pub fn exec(args []string) Result {
    if args.len == 0 {
        return Result{
            exit_code: -1
            output:    'exec requires at least one argument'
        }
    }
    mut cargs := []&char{cap: args.len + 1}
    for arg in args {
        cargs << &char(arg.str)
    }
    cargs << &char(unsafe { nil })
    mut pid := 0
    mut read_fd := -1
    v_os_execute_lock()
    rc := C.v_os_exec_capture_start(cargs.data, &pid, &read_fd)
    v_os_execute_unlock()
    if rc != 0 {
        return Result{
            exit_code: -1
            output:    'exec("${args[0]}") failed'
        }
    }
    soutput := fd_slurp(read_fd).join('')
    fd_close(read_fd)
    mut status := 0
    for {
        C.errno = 0
        if C.waitpid(pid, &status, 0) != -1 {
            break
        }
        if C.errno == C.EINTR {
            continue
        }
        return Result{
            exit_code: -1
            output:    soutput
        }
    }
    exit_code, _ := posix_wait4_to_exit_status(status)
    return Result{
        exit_code: exit_code
        output:    soutput
    }
}

// raw_execute does the same as `execute` on Unix platforms.
// On Windows raw_execute starts the specified command, waits for it to complete, and returns its output.
// It's marked as `unsafe` to help emphasize the problems that may arise by allowing, for example,
// user provided escape sequences.
@[unsafe]
pub fn raw_execute(cmd string) Result {
    return execute(cmd)
}

// symlink creates a symbolic link named link_name, which points to target.
// It returns a POSIX error message, if it can not do so.
pub fn symlink(target string, link_name string) ! {
    res := C.symlink(&char(target.str), &char(link_name.str))
    if res == 0 {
        return
    }
    return error(posix_get_error_msg(C.errno))
}

// readlink reads the target of a symbolic link.
// It returns a POSIX error message if it can not do so.
//
// Note that the target of a symbolic link can be any string:
// it is often used to point to another path, but the target is not guaranteed
// to resolve as a path, nor to point to a path that exists.
@[manualfree]
pub fn readlink(path string) !string {
    // Use a region of stack to get information into; we'll return new memory of more precise size later.
    mut buf := [max_path_buffer_size]u8{}
    // readlink returns the number of bytes written into buf, or -1 for errors.
    res := C.readlink(&char(path.str), &char(&buf[0]), max_path_buffer_size)
    if res < 0 {
        return last_error()
    }
    // Common case: we got a complete read into our buffer on the stack.
    // In this case, copy the data into a new heap-allocated string that's right-sized
    // (we can't return memory from our stack).
    if res < max_path_buffer_size {
        return unsafe { (&buf[0]).vstring_with_len(res).clone() }
    }
    // If the number of bytes read wasn't less than as many as we said we'd accept: that means we might not have gotten a complete read.
    // In this case, we have to start doing heap allocations, increasingly large, and simply check until we get a complete one.
    // Whenever we do succeed: we'll return a string that refers to a subset of that possibly excessively sized buffer,
    // because we're already on the heap and returning it is valid; and because allocating a new buffer just
    // to save some resident memory is usually a poor trade of spending of time just to reclaim a very minor amount of space.
    mut size := max_path_buffer_size
    for {
        size *= 2
        mut buf2 := unsafe { &char(malloc_noscan(size)) }
        res2 := C.readlink(&char(path.str), buf2, size)
        if res2 < 0 {
            return last_error()
        }
        if res2 < size {
            unsafe {
                buf2[res2] = 0
                return cstring_to_vstring(buf2)
            }
        }
        unsafe { free(buf2) } // and then loop around to try again with a larger one.
    }
    return error('${@METHOD} unreachable code')
}

// link creates a new link (also known as a hard link) to an existing file.
// It returns a POSIX error message, if it can not do so.
pub fn link(origin string, target string) ! {
    res := C.link(&char(origin.str), &char(target.str))
    if res == 0 {
        return
    }
    return error(posix_get_error_msg(C.errno))
}

// get_error_msg return error code representation in string.
pub fn get_error_msg(code int) string {
    return posix_get_error_msg(code)
}

pub fn (mut f File) close() {
    if !f.is_opened {
        return
    }
    f.is_opened = false
    cfile := f.cfile
    f.cfile = unsafe { nil }
    C.fflush(cfile)
    C.fclose(cfile)
}

fn C.mkstemp(stemplate &u8) i32

// ensure_folder_is_writable checks that `folder` exists, and is writable to the process
// by creating an empty file in it, then deleting it.
@[manualfree]
pub fn ensure_folder_is_writable(folder string) ! {
    if !exists(folder) {
        return error_with_code('`${folder}` does not exist', 1)
    }
    if !is_dir(folder) {
        return error_with_code('`${folder}` is not a folder', 2)
    }
    tmp_perm_check := join_path_single(folder, 'XXXXXX')
    defer {
        unsafe { tmp_perm_check.free() }
    }
    unsafe {
        x := C.mkstemp(&char(tmp_perm_check.str))
        if -1 == x {
            return error_with_code('folder `${folder}` is not writable', 3)
        }
        C.close(x)
    }
    rm(tmp_perm_check)!
}

// getpid returns the process ID (PID) of the calling process.
@[inline]
pub fn getpid() int {
    return C.getpid()
}

// getppid returns the process ID of the parent of the calling process.
@[inline]
pub fn getppid() int {
    return C.getppid()
}

// getuid returns the real user ID of the calling process.
@[inline]
pub fn getuid() int {
    return C.getuid()
}

// geteuid returns the effective user ID of the calling process.
@[inline]
pub fn geteuid() int {
    return C.geteuid()
}

// getgid returns the real group ID of the calling process.
@[inline]
pub fn getgid() int {
    return C.getgid()
}

// getegid returns the effective group ID of the calling process.
@[inline]
pub fn getegid() int {
    return C.getegid()
}

// Turns the given bit on or off, depending on the `enable` parameter.
pub fn posix_set_permission_bit(path_s string, mode u32, enable bool) {
    mut new_mode := u32(0)
    if s := stat(path_s) {
        new_mode = s.mode
    }
    match enable {
        true { new_mode |= mode }
        false { new_mode &= (0o7777 - mode) }
    }

    C.chmod(&char(path_s.str), int(new_mode))
}

// get_long_path has no meaning for *nix, but has for windows, where `c:\folder\some~1` for example
// can be the equivalent of `c:\folder\some spa ces`. On *nix, it just returns a copy of the input path.
fn get_long_path(path string) !string {
    return path
}

fn C.sysconf(name i32) i64

// page_size returns the page size in bytes.
pub fn page_size() int {
    return int(C.sysconf(C._SC_PAGESIZE))
}

struct C.statvfs {
    f_bsize  usize
    f_blocks usize
    f_bfree  usize
    f_bavail usize
}

// disk_usage returns disk usage of `path`.
@[manualfree]
pub fn disk_usage(path string) !DiskUsage {
    mpath := if path == '' { '.' } else { path }
    defer { unsafe { mpath.free() } }
    mut vfs := C.statvfs{}
    ret := unsafe { C.statvfs(&char(mpath.str), &vfs) }
    if ret == -1 {
        return error('cannot get disk usage of path')
    }
    f_bsize := u64(vfs.f_bsize)
    f_blocks := u64(vfs.f_blocks)
    f_bavail := u64(vfs.f_bavail)
    f_bfree := u64(vfs.f_bfree)
    return DiskUsage{
        total:     f_bsize * f_blocks
        available: f_bsize * f_bavail
        used:      f_bsize * (f_blocks - f_bfree)
    }
}