// wasi_snapshot_preview1 spec available (in witx format) here:
// * typenames -- https://github.com/WebAssembly/WASI/blob/master/phases/snapshot/witx/typenames.witx
// * module -- https://github.com/WebAssembly/WASI/blob/master/phases/snapshot/witx/wasi_snapshot_preview1.witx
const std = @import("std");
const mem = std.mem;
const assert = std.debug.assert;

pub usingnamespace @import("bits.zig");

comptime {
    assert(@alignOf(i8) == 1);
    assert(@alignOf(u8) == 1);
    assert(@alignOf(i16) == 2);
    assert(@alignOf(u16) == 2);
    assert(@alignOf(i32) == 4);
    assert(@alignOf(u32) == 4);
    // assert(@alignOf(i64) == 8);
    // assert(@alignOf(u64) == 8);
}

pub const iovec_t = iovec;
pub const ciovec_t = iovec_const;

fn is_prefix(preopen: []const u8, path: []const u8) bool {
    if (preopen.len > path.len) {
        return false;
    }
    var i: usize = 0;
    while (i < preopen.len) {
        std.debug.warn("{} == {}", .{ preopen[i], path[i] });
        if (preopen[i] != path[i]) {
            return false;
        }
        i += 1;
    }
    return true;
}

pub fn resolve_preopen(path: []const u8, dirfd: *fd_t, prefix: *usize) errno_t {
    var fd: fd_t = 3; // start fd has to be beyond stdio fds
    var preopen_path = [_]u8{0} ** PATH_MAX;

    while (true) {
        var buf: prestat_t = undefined;
        switch (fd_prestat_get(fd, &buf)) {
            ESUCCESS => {},
            EBADF => {
                break;
            },
            else => |err| return err,
        }
        const preopen_len = buf.u.dir.pr_name_len;
        switch (fd_prestat_dir_name(fd, &preopen_path, preopen_len)) {
            ESUCCESS => {},
            else => |err| return err,
        }
        if (is_prefix(preopen_path[0..preopen_len], path)) {
            dirfd.* = fd;
            prefix.* = preopen_len;
            return ESUCCESS;
        }
        std.mem.set(u8, &preopen_path, 0);
        fd += 1;
    }

    return ENOTCAPABLE;
}

pub const PreopenType = enum {
    Dir,
};

pub const Preopen = struct {
    fd: fd_t,
    @"type": union(PreopenType) {
        Dir: []const u8,
    },

    const Self = @This();

    pub fn newDir(fd: fd_t, path: []const u8) Self {
        return Self{
            .fd = fd,
            .@"type" = .{ .Dir = path },
        };
    }
};

pub const GetPreopenError = std.os.UnexpectedError || mem.Allocator.Error;

pub fn getPreopens(allocator: *mem.Allocator) GetPreopenError![]Preopen {
    var preopens = std.ArrayList(Preopen).init(allocator);
    errdefer freePreopens(allocator, preopens);
    var fd: fd_t = 3; // start fd has to be beyond stdio fds

    while (true) {
        var buf: prestat_t = undefined;
        switch (fd_prestat_get(fd, &buf)) {
            ESUCCESS => {},
            ENOTSUP => {
                // not a preopen, so keep going
                continue;
            },
            EBADF => {
                // OK, no more fds available
                break;
            },
            else => |err| return std.os.unexpectedErrno(err),
        }
        const preopen_len = buf.u.dir.pr_name_len;
        const path_buf = try allocator.alloc(u8, preopen_len);
        mem.set(u8, path_buf, 0);
        switch (fd_prestat_dir_name(fd, path_buf.ptr, preopen_len)) {
            ESUCCESS => {},
            else => |err| return std.os.unexpectedErrno(err),
        }
        const preopen = Preopen.newDir(fd, path_buf);
        try preopens.append(preopen);
        fd += 1;
    }

    return preopens.toOwnedSlice();
}

pub fn freePreopens(allocator: *mem.Allocator, preopens: std.ArrayList(Preopen)) void {
    for (preopens.items) |preopen| {
        switch (preopen.@"type") {
            PreopenType.Dir => |path| allocator.free(path),
        }
    }
    preopens.deinit();
}

pub extern "wasi_snapshot_preview1" fn args_get(argv: [*][*:0]u8, argv_buf: [*]u8) errno_t;
pub extern "wasi_snapshot_preview1" fn args_sizes_get(argc: *usize, argv_buf_size: *usize) errno_t;

pub extern "wasi_snapshot_preview1" fn clock_res_get(clock_id: clockid_t, resolution: *timestamp_t) errno_t;
pub extern "wasi_snapshot_preview1" fn clock_time_get(clock_id: clockid_t, precision: timestamp_t, timestamp: *timestamp_t) errno_t;

pub extern "wasi_snapshot_preview1" fn environ_get(environ: [*][*:0]u8, environ_buf: [*]u8) errno_t;
pub extern "wasi_snapshot_preview1" fn environ_sizes_get(environ_count: *usize, environ_buf_size: *usize) errno_t;

pub extern "wasi_snapshot_preview1" fn fd_advise(fd: fd_t, offset: filesize_t, len: filesize_t, advice: advice_t) errno_t;
pub extern "wasi_snapshot_preview1" fn fd_allocate(fd: fd_t, offset: filesize_t, len: filesize_t) errno_t;
pub extern "wasi_snapshot_preview1" fn fd_close(fd: fd_t) errno_t;
pub extern "wasi_snapshot_preview1" fn fd_datasync(fd: fd_t) errno_t;
pub extern "wasi_snapshot_preview1" fn fd_pread(fd: fd_t, iovs: [*]const iovec_t, iovs_len: usize, offset: filesize_t, nread: *usize) errno_t;
pub extern "wasi_snapshot_preview1" fn fd_pwrite(fd: fd_t, iovs: [*]const ciovec_t, iovs_len: usize, offset: filesize_t, nwritten: *usize) errno_t;
pub extern "wasi_snapshot_preview1" fn fd_read(fd: fd_t, iovs: [*]const iovec_t, iovs_len: usize, nread: *usize) errno_t;
pub extern "wasi_snapshot_preview1" fn fd_readdir(fd: fd_t, buf: [*]u8, buf_len: usize, cookie: dircookie_t, bufused: *usize) errno_t;
pub extern "wasi_snapshot_preview1" fn fd_renumber(from: fd_t, to: fd_t) errno_t;
pub extern "wasi_snapshot_preview1" fn fd_seek(fd: fd_t, offset: filedelta_t, whence: whence_t, newoffset: *filesize_t) errno_t;
pub extern "wasi_snapshot_preview1" fn fd_sync(fd: fd_t) errno_t;
pub extern "wasi_snapshot_preview1" fn fd_tell(fd: fd_t, newoffset: *filesize_t) errno_t;
pub extern "wasi_snapshot_preview1" fn fd_write(fd: fd_t, iovs: [*]const ciovec_t, iovs_len: usize, nwritten: *usize) errno_t;

pub extern "wasi_snapshot_preview1" fn fd_fdstat_get(fd: fd_t, buf: *fdstat_t) errno_t;
pub extern "wasi_snapshot_preview1" fn fd_fdstat_set_flags(fd: fd_t, flags: fdflags_t) errno_t;
pub extern "wasi_snapshot_preview1" fn fd_fdstat_set_rights(fd: fd_t, fs_rights_base: rights_t, fs_rights_inheriting: rights_t) errno_t;

pub extern "wasi_snapshot_preview1" fn fd_filestat_get(fd: fd_t, buf: *filestat_t) errno_t;
pub extern "wasi_snapshot_preview1" fn fd_filestat_set_size(fd: fd_t, st_size: filesize_t) errno_t;
pub extern "wasi_snapshot_preview1" fn fd_filestat_set_times(fd: fd_t, st_atim: timestamp_t, st_mtim: timestamp_t, fstflags: fstflags_t) errno_t;

pub extern "wasi_snapshot_preview1" fn fd_prestat_get(fd: fd_t, buf: *prestat_t) errno_t;
pub extern "wasi_snapshot_preview1" fn fd_prestat_dir_name(fd: fd_t, path: [*]u8, path_len: usize) errno_t;

pub extern "wasi_snapshot_preview1" fn path_create_directory(fd: fd_t, path: [*]const u8, path_len: usize) errno_t;
pub extern "wasi_snapshot_preview1" fn path_filestat_get(fd: fd_t, flags: lookupflags_t, path: [*]const u8, path_len: usize, buf: *filestat_t) errno_t;
pub extern "wasi_snapshot_preview1" fn path_filestat_set_times(fd: fd_t, flags: lookupflags_t, path: [*]const u8, path_len: usize, st_atim: timestamp_t, st_mtim: timestamp_t, fstflags: fstflags_t) errno_t;
pub extern "wasi_snapshot_preview1" fn path_link(old_fd: fd_t, old_flags: lookupflags_t, old_path: [*]const u8, old_path_len: usize, new_fd: fd_t, new_path: [*]const u8, new_path_len: usize) errno_t;
pub extern "wasi_snapshot_preview1" fn path_open(dirfd: fd_t, dirflags: lookupflags_t, path: [*]const u8, path_len: usize, oflags: oflags_t, fs_rights_base: rights_t, fs_rights_inheriting: rights_t, fs_flags: fdflags_t, fd: *fd_t) errno_t;
pub extern "wasi_snapshot_preview1" fn path_readlink(fd: fd_t, path: [*]const u8, path_len: usize, buf: [*]u8, buf_len: usize, bufused: *usize) errno_t;
pub extern "wasi_snapshot_preview1" fn path_remove_directory(fd: fd_t, path: [*]const u8, path_len: usize) errno_t;
pub extern "wasi_snapshot_preview1" fn path_rename(old_fd: fd_t, old_path: [*]const u8, old_path_len: usize, new_fd: fd_t, new_path: [*]const u8, new_path_len: usize) errno_t;
pub extern "wasi_snapshot_preview1" fn path_symlink(old_path: [*]const u8, old_path_len: usize, fd: fd_t, new_path: [*]const u8, new_path_len: usize) errno_t;
pub extern "wasi_snapshot_preview1" fn path_unlink_file(fd: fd_t, path: [*]const u8, path_len: usize) errno_t;

pub extern "wasi_snapshot_preview1" fn poll_oneoff(in: *const subscription_t, out: *event_t, nsubscriptions: usize, nevents: *usize) errno_t;

pub extern "wasi_snapshot_preview1" fn proc_exit(rval: exitcode_t) noreturn;

pub extern "wasi_snapshot_preview1" fn random_get(buf: [*]u8, buf_len: usize) errno_t;

pub extern "wasi_snapshot_preview1" fn sched_yield() errno_t;

pub extern "wasi_snapshot_preview1" fn sock_recv(sock: fd_t, ri_data: *const iovec_t, ri_data_len: usize, ri_flags: riflags_t, ro_datalen: *usize, ro_flags: *roflags_t) errno_t;
pub extern "wasi_snapshot_preview1" fn sock_send(sock: fd_t, si_data: *const ciovec_t, si_data_len: usize, si_flags: siflags_t, so_datalen: *usize) errno_t;
pub extern "wasi_snapshot_preview1" fn sock_shutdown(sock: fd_t, how: sdflags_t) errno_t;

/// Get the errno from a syscall return value, or 0 for no error.
pub fn getErrno(r: errno_t) usize {
    return r;
}