const builtin = @import("builtin");
const std = @import("../../std.zig");
const SYS = std.os.linux.SYS;

pub fn syscall0(number: SYS) u64 {
    return asm volatile ("ecall"
        : [ret] "={x10}" (-> u64),
        : [number] "{x17}" (@intFromEnum(number)),
        : .{ .memory = true });
}

pub fn syscall1(number: SYS, arg1: u64) u64 {
    return asm volatile ("ecall"
        : [ret] "={x10}" (-> u64),
        : [number] "{x17}" (@intFromEnum(number)),
          [arg1] "{x10}" (arg1),
        : .{ .memory = true });
}

pub fn syscall2(number: SYS, arg1: u64, arg2: u64) u64 {
    return asm volatile ("ecall"
        : [ret] "={x10}" (-> u64),
        : [number] "{x17}" (@intFromEnum(number)),
          [arg1] "{x10}" (arg1),
          [arg2] "{x11}" (arg2),
        : .{ .memory = true });
}

pub fn syscall3(number: SYS, arg1: u64, arg2: u64, arg3: u64) u64 {
    return asm volatile ("ecall"
        : [ret] "={x10}" (-> u64),
        : [number] "{x17}" (@intFromEnum(number)),
          [arg1] "{x10}" (arg1),
          [arg2] "{x11}" (arg2),
          [arg3] "{x12}" (arg3),
        : .{ .memory = true });
}

pub fn syscall4(number: SYS, arg1: u64, arg2: u64, arg3: u64, arg4: u64) u64 {
    return asm volatile ("ecall"
        : [ret] "={x10}" (-> u64),
        : [number] "{x17}" (@intFromEnum(number)),
          [arg1] "{x10}" (arg1),
          [arg2] "{x11}" (arg2),
          [arg3] "{x12}" (arg3),
          [arg4] "{x13}" (arg4),
        : .{ .memory = true });
}

pub fn syscall5(number: SYS, arg1: u64, arg2: u64, arg3: u64, arg4: u64, arg5: u64) u64 {
    return asm volatile ("ecall"
        : [ret] "={x10}" (-> u64),
        : [number] "{x17}" (@intFromEnum(number)),
          [arg1] "{x10}" (arg1),
          [arg2] "{x11}" (arg2),
          [arg3] "{x12}" (arg3),
          [arg4] "{x13}" (arg4),
          [arg5] "{x14}" (arg5),
        : .{ .memory = true });
}

pub fn syscall6(
    number: SYS,
    arg1: u64,
    arg2: u64,
    arg3: u64,
    arg4: u64,
    arg5: u64,
    arg6: u64,
) u64 {
    return asm volatile ("ecall"
        : [ret] "={x10}" (-> u64),
        : [number] "{x17}" (@intFromEnum(number)),
          [arg1] "{x10}" (arg1),
          [arg2] "{x11}" (arg2),
          [arg3] "{x12}" (arg3),
          [arg4] "{x13}" (arg4),
          [arg5] "{x14}" (arg5),
          [arg6] "{x15}" (arg6),
        : .{ .memory = true });
}

pub fn clone() callconv(.naked) u64 {
    // __clone(func, stack, flags, arg, ptid, tls, ctid)
    //         a0,   a1,    a2,    a3,  a4,   a5,  a6
    //
    // syscall(SYS_clone, flags, stack, ptid, tls, ctid)
    //         a7         a0,    a1,    a2,   a3,  a4
    asm volatile (
        \\    # Save func and arg to stack
        \\    addi a1, a1, -16
        \\    sd a0, 0(a1)
        \\    sd a3, 8(a1)
        \\
        \\    # Call SYS_clone
        \\    mv a0, a2
        \\    mv a2, a4
        \\    mv a3, a5
        \\    mv a4, a6
        \\    li a7, 220 # SYS_clone
        \\    ecall
        \\
        \\    beqz a0, 1f
        \\    # Parent
        \\    ret
        \\
        \\    # Child
        \\1:
    );
    if (builtin.unwind_tables != .none or !builtin.strip_debug_info) asm volatile (
        \\    .cfi_undefined ra
    );
    asm volatile (
        \\    mv fp, zero
        \\    mv ra, zero
        \\
        \\    ld a1, 0(sp)
        \\    ld a0, 8(sp)
        \\    jalr a1
        \\
        \\    # Exit
        \\    li a7, 93 # SYS_exit
        \\    ecall
    );
}

pub const blksize_t = i32;
pub const nlink_t = u32;
pub const time_t = i64;
pub const mode_t = u32;
pub const off_t = i64;
pub const ino_t = u64;
pub const dev_t = u64;
pub const blkcnt_t = i64;

// The `stat` definition used by the Linux kernel.
pub const Stat = extern struct {
    dev: dev_t,
    ino: ino_t,
    mode: mode_t,
    nlink: nlink_t,
    uid: std.os.linux.uid_t,
    gid: std.os.linux.gid_t,
    rdev: dev_t,
    __pad: u64,
    size: off_t,
    blksize: blksize_t,
    __pad2: i32,
    blocks: blkcnt_t,
    atim: std.os.linux.timespec,
    mtim: std.os.linux.timespec,
    ctim: std.os.linux.timespec,
    __unused: [2]u32,

    pub fn atime(self: @This()) std.os.linux.timespec {
        return self.atim;
    }

    pub fn mtime(self: @This()) std.os.linux.timespec {
        return self.mtim;
    }

    pub fn ctime(self: @This()) std.os.linux.timespec {
        return self.ctim;
    }
};

pub const VDSO = struct {
    pub const CGT_SYM = "__vdso_clock_gettime";
    pub const CGT_VER = "LINUX_4.15";
};