const std = @import("std");
usingnamespace std.c;
const builtin = @import("builtin");
const os = std.os;
const mem = std.mem;
const Stat = std.fs.File.Stat;
const Kind = std.fs.File.Kind;
const StatError = std.fs.File.StatError;
const errno = os.errno;
const zeroes = mem.zeroes;
// int clonefileat(int src_dirfd, const char * src, int dst_dirfd, const char * dst, int flags);
pub extern "c" fn clonefileat(c_int, [*c]const u8, c_int, [*c]const u8, uint32_t: c_int) c_int;
// int fclonefileat(int srcfd, int dst_dirfd, const char * dst, int flags);
pub extern "c" fn fclonefileat(c_int, c_int, [*c]const u8, uint32_t: c_int) c_int;
// int clonefile(const char * src, const char * dst, int flags);
pub extern "c" fn clonefile([*c]const u8, [*c]const u8, uint32_t: c_int) c_int;

pub extern "c" fn chmod([*c]const u8, mode_t) c_int;
pub extern "c" fn fchmod(c_int, mode_t) c_int;
pub extern "c" fn umask(mode_t) mode_t;
pub extern "c" fn fchmodat(c_int, [*c]const u8, mode_t, c_int) c_int;

pub extern "c" fn lstat([*c]const u8, [*c]libc_stat) c_int;
pub extern "c" fn lstat64([*c]const u8, [*c]libc_stat) c_int;

pub fn lstat_absolute(path: [:0]const u8) StatError!Stat {
    if (builtin.os.tag == .windows) {
        var io_status_block: windows.IO_STATUS_BLOCK = undefined;
        var info: windows.FILE_ALL_INFORMATION = undefined;
        const rc = windows.ntdll.NtQueryInformationFile(self.handle, &io_status_block, &info, @sizeOf(windows.FILE_ALL_INFORMATION), .FileAllInformation);
        switch (rc) {
            .SUCCESS => {},
            .BUFFER_OVERFLOW => {},
            .INVALID_PARAMETER => unreachable,
            .ACCESS_DENIED => return error.AccessDenied,
            else => return windows.unexpectedStatus(rc),
        }
        return Stat{
            .inode = info.InternalInformation.IndexNumber,
            .size = @bitCast(u64, info.StandardInformation.EndOfFile),
            .mode = 0,
            .kind = if (info.StandardInformation.Directory == 0) .File else .Directory,
            .atime = windows.fromSysTime(info.BasicInformation.LastAccessTime),
            .mtime = windows.fromSysTime(info.BasicInformation.LastWriteTime),
            .ctime = windows.fromSysTime(info.BasicInformation.CreationTime),
        };
    }

    var st = zeroes(libc_stat);
    switch (errno(lstat64(path.ptr, &st))) {
        .SUCCESS => {},
        // .EINVAL => unreachable,
        .BADF => unreachable, // Always a race condition.
        .NOMEM => return error.SystemResources,
        .ACCES => return error.AccessDenied,
        else => |err| return os.unexpectedErrno(err),
    }

    const atime = st.atime();
    const mtime = st.mtime();
    const ctime = st.ctime();
    return Stat{
        .inode = st.ino,
        .size = @bitCast(u64, st.size),
        .mode = st.mode,
        .kind = switch (builtin.os.tag) {
            .wasi => switch (st.filetype) {
                os.FILETYPE_BLOCK_DEVICE => Kind.BlockDevice,
                os.FILETYPE_CHARACTER_DEVICE => Kind.CharacterDevice,
                os.FILETYPE_DIRECTORY => Kind.Directory,
                os.FILETYPE_SYMBOLIC_LINK => Kind.SymLink,
                os.FILETYPE_REGULAR_FILE => Kind.File,
                os.FILETYPE_SOCKET_STREAM, os.FILETYPE_SOCKET_DGRAM => Kind.UnixDomainSocket,
                else => Kind.Unknown,
            },
            else => switch (st.mode & os.S_IFMT) {
                os.S_IFBLK => Kind.BlockDevice,
                os.S_IFCHR => Kind.CharacterDevice,
                os.S_IFDIR => Kind.Directory,
                os.S_IFIFO => Kind.NamedPipe,
                os.S_IFLNK => Kind.SymLink,
                os.S_IFREG => Kind.File,
                os.S_IFSOCK => Kind.UnixDomainSocket,
                else => Kind.Unknown,
            },
        },
        .atime = @as(i128, atime.tv_sec) * std.time.ns_per_s + atime.tv_nsec,
        .mtime = @as(i128, mtime.tv_sec) * std.time.ns_per_s + mtime.tv_nsec,
        .ctime = @as(i128, ctime.tv_sec) * std.time.ns_per_s + ctime.tv_nsec,
    };
}

pub fn stat_absolute(path: [:0]const u8) StatError!Stat {
    if (builtin.os.tag == .windows) {
        var io_status_block: windows.IO_STATUS_BLOCK = undefined;
        var info: windows.FILE_ALL_INFORMATION = undefined;
        const rc = windows.ntdll.NtQueryInformationFile(self.handle, &io_status_block, &info, @sizeOf(windows.FILE_ALL_INFORMATION), .FileAllInformation);
        switch (rc) {
            .SUCCESS => {},
            .BUFFER_OVERFLOW => {},
            .INVALID_PARAMETER => unreachable,
            .ACCESS_DENIED => return error.AccessDenied,
            else => return windows.unexpectedStatus(rc),
        }
        return Stat{
            .inode = info.InternalInformation.IndexNumber,
            .size = @bitCast(u64, info.StandardInformation.EndOfFile),
            .mode = 0,
            .kind = if (info.StandardInformation.Directory == 0) .File else .Directory,
            .atime = windows.fromSysTime(info.BasicInformation.LastAccessTime),
            .mtime = windows.fromSysTime(info.BasicInformation.LastWriteTime),
            .ctime = windows.fromSysTime(info.BasicInformation.CreationTime),
        };
    }

    var st = zeroes(libc_stat);
    switch (errno(stat(path.ptr, &st))) {
        0 => {},
        // .EINVAL => unreachable,
        .EBADF => unreachable, // Always a race condition.
        .ENOMEM => return error.SystemResources,
        .EACCES => return error.AccessDenied,
        else => |err| return os.unexpectedErrno(err),
    }

    const atime = st.atime();
    const mtime = st.mtime();
    const ctime = st.ctime();
    return Stat{
        .inode = st.ino,
        .size = @bitCast(u64, st.size),
        .mode = st.mode,
        .kind = switch (builtin.os.tag) {
            .wasi => switch (st.filetype) {
                os.FILETYPE_BLOCK_DEVICE => Kind.BlockDevice,
                os.FILETYPE_CHARACTER_DEVICE => Kind.CharacterDevice,
                os.FILETYPE_DIRECTORY => Kind.Directory,
                os.FILETYPE_SYMBOLIC_LINK => Kind.SymLink,
                os.FILETYPE_REGULAR_FILE => Kind.File,
                os.FILETYPE_SOCKET_STREAM, os.FILETYPE_SOCKET_DGRAM => Kind.UnixDomainSocket,
                else => Kind.Unknown,
            },
            else => switch (st.mode & os.S_IFMT) {
                os.S_IFBLK => Kind.BlockDevice,
                os.S_IFCHR => Kind.CharacterDevice,
                os.S_IFDIR => Kind.Directory,
                os.S_IFIFO => Kind.NamedPipe,
                os.S_IFLNK => Kind.SymLink,
                os.S_IFREG => Kind.File,
                os.S_IFSOCK => Kind.UnixDomainSocket,
                else => Kind.Unknown,
            },
        },
        .atime = @as(i128, atime.tv_sec) * std.time.ns_per_s + atime.tv_nsec,
        .mtime = @as(i128, mtime.tv_sec) * std.time.ns_per_s + mtime.tv_nsec,
        .ctime = @as(i128, ctime.tv_sec) * std.time.ns_per_s + ctime.tv_nsec,
    };
}

pub const struct_fstore = extern struct {
    fst_flags: c_uint,
    fst_posmode: c_int,
    fst_offset: off_t,
    fst_length: off_t,
    fst_bytesalloc: off_t,
};
pub const fstore_t = struct_fstore;

pub const F_ALLOCATECONTIG = @as(c_int, 0x00000002);
pub const F_ALLOCATEALL = @as(c_int, 0x00000004);
pub const F_PEOFPOSMODE = @as(c_int, 3);
pub const F_VOLPOSMODE = @as(c_int, 4);

pub fn preallocate_file(fd: os.fd_t, offset: off_t, len: off_t) !void {
    var fstore = zeroes(fstore_t);
    fstore.fst_flags = F_ALLOCATECONTIG;
    fstore.fst_posmode = F_PEOFPOSMODE;
    fstore.fst_offset = 0;
    fstore.fst_length = len + offset;

    // Based on https://api.kde.org/frameworks/kcoreaddons/html/posix__fallocate__mac_8h_source.html
    var rc = os.system.fcntl(fd, os.F_PREALLOCATE, &fstore);

    switch (rc) {
        0 => return,
        else => {
            fstore.fst_flags = F_ALLOCATEALL;
            rc = os.system.fcntl(fd, os.F_PREALLOCATE, &fstore);
        },
    }

    std.mem.doNotOptimizeAway(&fstore);
}