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;
const FormatCode = @import("../main.zig").FormatCode;

pub fn CopyXResponse(comptime tag: u8) type {
    return struct {
        pub const Tag: u8 = tag;

        overall_format_code: u8,
        format_codes: []const FormatCode, // owned

        pub fn read(a: std.mem.Allocator, b: []const u8) !@This() {
            var fbs = std.io.fixedBufferStream(b);
            var reader = fbs.reader();
            const overall_format_code = try reader.readIntBig(u8);
            const n_columns = try reader.readIntBig(u16);
            var format_codes = try a.alloc(FormatCode, n_columns);
            errdefer a.free(format_codes);
            for (0..n_columns) |i| {
                const int_format_code = try reader.readIntBig(u16);
                format_codes[i] = enum_from_int(FormatCode, int_format_code) orelse return ProtocolError.InvalidFormatCode;
            }
            return .{
                .overall_format_code = overall_format_code,
                .format_codes = format_codes,
            };
        }

        pub fn write(self: @This(), a: std.mem.Allocator, stream_writer: anytype) !void {
            try stream_writer.writeIntBig(u8, Tag);
            var al = ByteArrayList.init(a);
            defer al.deinit();
            var cw = std.io.countingWriter(al.writer());
            var writer = cw.writer();
            try writer.writeIntBig(u32, 0); // length placeholder
            try writer.writeIntBig(u8, self.overall_format_code);
            try writer.writeIntBig(u16, @intCast(self.format_codes.len));
            for (self.format_codes) |format_code| {
                try writer.writeIntBig(u16, @intFromEnum(format_code));
            }
            std.mem.writeIntBig(u32, al.items[0..4], @as(u32, @intCast(cw.bytes_written))); // Update length
            try stream_writer.writeAll(al.items);
        }

        pub fn deinit(self: *@This(), a: std.mem.Allocator) void {
            a.free(self.format_codes);
        }
    };
}

test "round trip" {
    const Tag: u8 = 'G';
    const CopyInResponse = CopyXResponse(Tag);
    const allocator = std.testing.allocator;
    var format_codes = try allocator.alloc(FormatCode, 3);
    format_codes[0] = .Binary;
    format_codes[1] = .Binary;
    format_codes[2] = .Text;
    var sm = CopyInResponse{
        .overall_format_code = 1,
        .format_codes = format_codes,
    };
    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 CopyInResponse.read(allocator, buf);
    defer sm2.deinit(allocator);

    try std.testing.expectEqual(FormatCode.Binary, sm2.format_codes[0]);
    try std.testing.expectEqual(FormatCode.Binary, sm2.format_codes[1]);
    try std.testing.expectEqual(FormatCode.Text, sm2.format_codes[2]);
}