const std = @import("std");
const log = std.log.scoped(.pgz);
const ByteArrayList = std.ArrayList(u8);
const ProtocolError = @import("../main.zig").ProtocolError;
const ClientError = @import("../main.zig").ClientError;
const enum_from_int = @import("../main.zig").enum_from_int;

pub const Tag: u8 = 'R';

const AuthenticationRequest = @This();

pub const InnerAuthRequestType = enum(u32) {
    AuthRequestTypeOk = 0,
    AuthRequestTypeCleartextPassword = 3,
};
pub const InnerAuthRequest = union {
    ok: AuthRequestOk,
    cleartext_password: AuthRequestCleartextPassword,
};
pub const AuthRequestOk = struct {};
pub const AuthRequestCleartextPassword = struct {};

// Authentication requests have multiple subtypes.
// It's not possible to have a tagged union with a custom backing integer, so do it the long way
inner_type: InnerAuthRequestType,
inner: InnerAuthRequest,

pub fn read(_: std.mem.Allocator, b: []const u8) !AuthenticationRequest {
    if (b.len != 4) {
        log.err("invalid message length, expected 4 got {}", .{b.len});
        return ProtocolError.InvalidMessageLength;
    }
    const inner_type = enum_from_int(InnerAuthRequestType, std.mem.readIntBig(u32, b[0..4])) orelse return ClientError.UnsupportedAuthType;
    var inner: InnerAuthRequest = switch (inner_type) {
        .AuthRequestTypeOk => .{ .ok = AuthRequestOk{} },
        .AuthRequestTypeCleartextPassword => .{ .cleartext_password = AuthRequestCleartextPassword{} },
    };
    return .{
        .inner_type = inner_type,
        .inner = inner,
    };
}

pub fn write(self: AuthenticationRequest, _: std.mem.Allocator, stream_writer: anytype) !void {
    try stream_writer.writeByte(Tag);
    try stream_writer.writeIntBig(u32, 8);
    try stream_writer.writeIntBig(u32, @intFromEnum(self.inner_type));
}

pub fn deinit(_: *AuthenticationRequest, _: std.mem.Allocator) void {}

test "round trip" {
    const allocator = std.testing.allocator;
    var sm = AuthenticationRequest{
        .inner_type = .AuthRequestTypeOk,
        .inner = .{ .ok = AuthRequestOk{} },
    };
    defer sm.deinit(allocator);

    var bal = ByteArrayList.init(allocator);
    defer bal.deinit();
    try sm.write(allocator, bal.writer());

    var fbs = std.io.fixedBufferStream(bal.items);
    var reader = fbs.reader();
    const tag = try reader.readByte();
    try std.testing.expectEqual(Tag, tag);
    const len = try reader.readIntBig(u32);
    const buf = try allocator.alloc(u8, len - 4);
    defer allocator.free(buf);
    try reader.readNoEof(buf);
    var sm2 = try AuthenticationRequest.read(allocator, buf);
    defer sm2.deinit(allocator);
    try std.testing.expectEqual(InnerAuthRequestType.AuthRequestTypeOk, sm2.inner_type);
}