const std = @import("std.zig");
const builtin = @import("builtin");
const assert = std.debug.assert;
const net = @This();
const mem = std.mem;
const os = std.os;

pub const TmpWinAddr = struct {
    family: u8,
    data: [14]u8,
};

pub const OsAddress = switch (builtin.os) {
    .windows => TmpWinAddr,
    else => os.sockaddr,
};

/// This data structure is a "view". The underlying data might have references
/// to owned memory which must live longer than this struct.
pub const Address = struct {
    os_addr: OsAddress,

    pub fn initIp4(ip4: u32, _port: u16) Address {
        return Address{
            .os_addr = os.sockaddr{
                .in = os.sockaddr_in{
                    .family = os.AF_INET,
                    .port = mem.nativeToBig(u16, _port),
                    .addr = ip4,
                    .zero = [_]u8{0} ** 8,
                },
            },
        };
    }

    pub fn initIp6(ip6: Ip6Addr, _port: u16) Address {
        return Address{
            .os_addr = os.sockaddr{
                .in6 = os.sockaddr_in6{
                    .family = os.AF_INET6,
                    .port = mem.nativeToBig(u16, _port),
                    .flowinfo = 0,
                    .addr = ip6.addr,
                    .scope_id = ip6.scope_id,
                },
            },
        };
    }

    pub fn port(self: Address) u16 {
        return mem.bigToNative(u16, self.os_addr.in.port);
    }

    pub fn initPosix(addr: os.sockaddr) Address {
        return Address{ .os_addr = addr };
    }

    pub fn format(
        self: Address,
        comptime fmt: []const u8,
        options: std.fmt.FormatOptions,
        context: var,
        comptime Errors: type,
        output: fn (@typeOf(context), []const u8) Errors!void,
    ) !void {
        switch (self.os_addr.in.family) {
            os.AF_INET => {
                const native_endian_port = mem.bigToNative(u16, self.os_addr.in.port);
                const bytes = @ptrCast(*const [4]u8, &self.os_addr.in.addr);
                try std.fmt.format(
                    context,
                    Errors,
                    output,
                    "{}.{}.{}.{}:{}",
                    bytes[0],
                    bytes[1],
                    bytes[2],
                    bytes[3],
                    native_endian_port,
                );
            },
            os.AF_INET6 => {
                const ZeroRun = struct {
                    index: usize,
                    count: usize,
                };
                const native_endian_port = mem.bigToNative(u16, self.os_addr.in6.port);
                const big_endian_parts = &self.os_addr.in6.addr;
                const native_endian_parts = switch (builtin.endian) {
                    .Big => big_endian_parts,
                    .Little => blk: {
                        var buf: [8]u16 = undefined;
                        for (big_endian_parts) |part, i| {
                            buf[i] = mem.bigToNative(u16, part);
                        }
                        break :blk buf;
                    },
                };

                var longest_zero_run: ?ZeroRun = null;
                var this_zero_run: ?ZeroRun = null;
                for (native_endian_parts) |part, i| {
                    if (part == 0) {
                        if (this_zero_run) |*zr| {
                            zr.count += 1;
                        } else {
                            this_zero_run = ZeroRun{
                                .index = i,
                                .count = 1,
                            };
                        }
                    } else if (this_zero_run) |zr| {
                        if (longest_zero_run) |lzr| {
                            if (zr.count > lzr.count and zr.count > 1) {
                                longest_zero_run = zr;
                            }
                        } else {
                            longest_zero_run = zr;
                        }
                    }
                }
                try output(context, "[");
                var i: usize = 0;
                while (i < native_endian_parts.len) {
                    if (i != 0) try output(context, ":");

                    if (longest_zero_run) |lzr| {
                        if (lzr.index == i) {
                            i += lzr.count;
                            continue;
                        }
                    }

                    const part = native_endian_parts[i];
                    try std.fmt.format(context, Errors, output, "{x}", part);
                    i += 1;
                }
                try std.fmt.format(context, Errors, output, "]:{}", native_endian_port);
            },
            else => return output(context, "(unrecognized address family)"),
        }
    }
};

pub fn parseIp4(buf: []const u8) !u32 {
    var result: u32 = undefined;
    const out_ptr = @sliceToBytes((*[1]u32)(&result)[0..]);

    var x: u8 = 0;
    var index: u8 = 0;
    var saw_any_digits = false;
    for (buf) |c| {
        if (c == '.') {
            if (!saw_any_digits) {
                return error.InvalidCharacter;
            }
            if (index == 3) {
                return error.InvalidEnd;
            }
            out_ptr[index] = x;
            index += 1;
            x = 0;
            saw_any_digits = false;
        } else if (c >= '0' and c <= '9') {
            saw_any_digits = true;
            const digit = c - '0';
            if (@mulWithOverflow(u8, x, 10, &x)) {
                return error.Overflow;
            }
            if (@addWithOverflow(u8, x, digit, &x)) {
                return error.Overflow;
            }
        } else {
            return error.InvalidCharacter;
        }
    }
    if (index == 3 and saw_any_digits) {
        out_ptr[index] = x;
        return result;
    }

    return error.Incomplete;
}

pub const Ip6Addr = struct {
    scope_id: u32,
    addr: [8]u16,
};

pub fn parseIp6(buf: []const u8) !Ip6Addr {
    var result: Ip6Addr = undefined;
    result.scope_id = 0;
    const ip_slice = @sliceToBytes(result.addr[0..]);

    var x: u16 = 0;
    var saw_any_digits = false;
    var index: u8 = 0;
    var scope_id = false;
    for (buf) |c| {
        if (scope_id) {
            if (c >= '0' and c <= '9') {
                const digit = c - '0';
                if (@mulWithOverflow(u32, result.scope_id, 10, &result.scope_id)) {
                    return error.Overflow;
                }
                if (@addWithOverflow(u32, result.scope_id, digit, &result.scope_id)) {
                    return error.Overflow;
                }
            } else {
                return error.InvalidCharacter;
            }
        } else if (c == ':') {
            if (!saw_any_digits) {
                return error.InvalidCharacter;
            }
            if (index == 14) {
                return error.InvalidEnd;
            }
            ip_slice[index] = @truncate(u8, x >> 8);
            index += 1;
            ip_slice[index] = @truncate(u8, x);
            index += 1;

            x = 0;
            saw_any_digits = false;
        } else if (c == '%') {
            if (!saw_any_digits) {
                return error.InvalidCharacter;
            }
            if (index == 14) {
                ip_slice[index] = @truncate(u8, x >> 8);
                index += 1;
                ip_slice[index] = @truncate(u8, x);
                index += 1;
            }
            scope_id = true;
            saw_any_digits = false;
        } else {
            const digit = try std.fmt.charToDigit(c, 16);
            if (@mulWithOverflow(u16, x, 16, &x)) {
                return error.Overflow;
            }
            if (@addWithOverflow(u16, x, digit, &x)) {
                return error.Overflow;
            }
            saw_any_digits = true;
        }
    }

    if (!saw_any_digits) {
        return error.Incomplete;
    }

    if (scope_id) {
        return result;
    }

    if (index == 14) {
        ip_slice[14] = @truncate(u8, x >> 8);
        ip_slice[15] = @truncate(u8, x);
        return result;
    }

    return error.Incomplete;
}

test "std.net.parseIp4" {
    assert((try parseIp4("127.0.0.1")) == mem.bigToNative(u32, 0x7f000001));

    testParseIp4Fail("256.0.0.1", error.Overflow);
    testParseIp4Fail("x.0.0.1", error.InvalidCharacter);
    testParseIp4Fail("127.0.0.1.1", error.InvalidEnd);
    testParseIp4Fail("127.0.0.", error.Incomplete);
    testParseIp4Fail("100..0.1", error.InvalidCharacter);
}

fn testParseIp4Fail(buf: []const u8, expected_err: anyerror) void {
    if (parseIp4(buf)) |_| {
        @panic("expected error");
    } else |e| {
        assert(e == expected_err);
    }
}

test "std.net.parseIp6" {
    const ip6 = try parseIp6("FF01:0:0:0:0:0:0:FB");
    const addr = Address.initIp6(ip6, 80);
    var buf: [100]u8 = undefined;
    const printed = try std.fmt.bufPrint(&buf, "{}", addr);
    std.testing.expect(mem.eql(u8, "[ff01::fb]:80", printed));
}

pub fn connectUnixSocket(path: []const u8) !std.fs.File {
    const opt_non_block = if (std.event.Loop.instance != null) os.SOCK_NONBLOCK else 0;
    const sockfd = try os.socket(
        os.AF_UNIX,
        os.SOCK_STREAM | os.SOCK_CLOEXEC | opt_non_block,
        0,
    );
    errdefer os.close(sockfd);

    var sock_addr = os.sockaddr{
        .un = os.sockaddr_un{
            .family = os.AF_UNIX,
            .path = undefined,
        },
    };

    if (path.len > @typeOf(sock_addr.un.path).len) return error.NameTooLong;
    mem.copy(u8, sock_addr.un.path[0..], path);
    const size = @intCast(u32, @sizeOf(os.sa_family_t) + path.len);
    if (std.event.Loop.instance) |loop| {
        try os.connect_async(sockfd, &sock_addr, size);
        try loop.linuxWaitFd(sockfd, os.EPOLLIN | os.EPOLLOUT | os.EPOLLET);
        try os.getsockoptError(sockfd);
    } else {
        try os.connect(sockfd, &sock_addr, size);
    }

    return std.fs.File.openHandle(sockfd);
}

pub const AddressList = struct {
    arena: std.heap.ArenaAllocator,
    addrs: []Address,
    canon_names: []?[]u8,

    fn deinit(self: *AddressList) void {
        // Here we copy the arena allocator into stack memory, because
        // otherwise it would destroy itself while it was still working.
        var arena = self.arena;
        arena.deinit();
        // self is destroyed
    }
};

/// Call `AddressList.deinit` on the result.
pub fn getAddressList(allocator: *mem.Allocator, name: []const u8, port: u16) !*AddressList {
    if (builtin.link_libc) {
        const hints = os.addrinfo{
            .flags = os.AI_NUMERICSERV,
            .family = os.AF_UNSPEC,
            .socktype = os.SOCK_STREAM,
            .protocol = os.IPPROTO_TCP,
            .canonname = null,
            .addr = null,
            .addrlen = 0,
            .next = null,
        };
        const result = blk: {
            var arena = std.heap.ArenaAllocator.init(allocator);
            errdefer arena.deinit();

            const result = try arena.allocator.create(AddressList);
            result.* = AddressList{
                .arena = arena,
                .addrs = undefined,
                .canon_names = undefined,
            };
            break :blk result;
        };
        const arena = &result.arena.allocator;
        errdefer result.arena.deinit();

        const name_c = try std.cstr.addNullByte(allocator, name);
        defer allocator.free(name_c);

        const port_c = try std.fmt.allocPrint(allocator, "{}\x00", port);
        defer allocator.free(port_c);

        var res: *os.addrinfo = undefined;
        switch (os.system.getaddrinfo(name_c.ptr, port_c.ptr, &hints, &res)) {
            0 => {},
            os.EAI_ADDRFAMILY => return error.HostLacksNetworkAddresses,
            os.EAI_AGAIN => return error.TemporaryNameServerFailure,
            os.EAI_BADFLAGS => unreachable, // Invalid hints
            os.EAI_FAIL => return error.NameServerFailure,
            os.EAI_FAMILY => return error.AddressFamilyNotSupported,
            os.EAI_MEMORY => return error.OutOfMemory,
            os.EAI_NODATA => return error.HostLacksNetworkAddresses,
            // The  node or service is not known; or both node and service are NULL; or AI_NUMERICSERV
            // was specified in hints.ai_flags and service was not a numeric port-number string.
            os.EAI_NONAME => unreachable, // Invalid hints
            os.EAI_SERVICE => return error.ServiceUnavailable,
            os.EAI_SOCKTYPE => unreachable, // Invalid socket type requested in hints
            os.EAI_SYSTEM => switch (os.errno(-1)) {
                else => |e| return os.unexpectedErrno(e),
            },
            else => unreachable,
        }
        defer os.system.freeaddrinfo(res);

        const addr_count = blk: {
            var count: usize = 0;
            var it: ?*os.addrinfo = res;
            while (it) |info| : (it = info.next) {
                if (info.addr != null) {
                    count += 1;
                }
            }
            break :blk count;
        };
        result.addrs = try arena.alloc(Address, addr_count);
        result.canon_names = try arena.alloc(?[]u8, addr_count);

        var it: ?*os.addrinfo = res;
        var i: usize = 0;
        while (it) |info| : (it = info.next) {
            const addr = info.addr orelse continue;
            result.addrs[i] = std.net.Address.initPosix(addr.*);
            result.canon_names[i] = null;

            if (info.canonname) |n| {
                const name_len = mem.len(u8, n);
                const new_slice = try arena.alloc(u8, name_len + 1);
                @memcpy(new_slice.ptr, n, name_len + 1);
                result.canon_names[i] = new_slice[0..name_len];
            }
            i += 1;
        }

        return result;
    }
    @compileError("TODO implement std.net.getAddresses for this OS");
}