iceberg: json serde for data types

Adds JSON serialization for newly added Iceberg data types.

A test is added to demonstrate the roundtrip with a type comprised of
multiple nested fields.

src/v/iceberg/CMakeLists.txt

@@ -29,9 +29,12 @@ v_cc_library(
   SRCS
     ${avro_hdrs}
     datatypes.cc
+    datatypes_json.cc
     json_utils.cc
   DEPS
     v::container
+    v::json
+    v::strings
 )
 
 add_subdirectory(tests)

src/v/iceberg/datatypes_json.cc

@@ -0,0 +1,252 @@
+// Copyright 2024 Redpanda Data, Inc.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.md
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0
+
+#include "iceberg/datatypes_json.h"
+
+#include "iceberg/datatypes.h"
+#include "iceberg/json_utils.h"
+#include "json/document.h"
+#include "strings/string_switch.h"
+
+#include <stdexcept>
+#include <string>
+
+namespace iceberg {
+
+namespace {
+std::string_view
+extract_between(char start_ch, char end_ch, const std::string_view& s) {
+    auto start_pos = s.find(start_ch);
+    auto end_pos = s.find(end_ch, start_pos);
+
+    if (start_pos != std::string::npos && end_pos != std::string::npos) {
+        return s.substr(start_pos + 1, end_pos - start_pos - 1);
+    }
+    throw std::invalid_argument(
+      fmt::format("Missing wrappers '{}' or '{}' in {}", start_ch, end_ch, s));
+}
+
+decimal_type parse_decimal(const std::string_view& type_str) {
+    auto ps_str = extract_between('(', ')', type_str);
+    size_t pos = ps_str.find(',');
+    if (pos != std::string::npos) {
+        // Extract substrings before and after the comma
+        auto p_str = ps_str.substr(0, pos);
+        auto s_str = ps_str.substr(pos + 1);
+        return decimal_type{
+          .precision = static_cast<uint32_t>(std::stoul(ss::sstring(p_str))),
+          .scale = static_cast<uint32_t>(std::stoul(ss::sstring(s_str)))};
+    }
+    throw std::invalid_argument(fmt::format(
+      "Decimal requires format decimal(uint32, uint32): {}", type_str));
+}
+
+fixed_type parse_fixed(const std::string_view& type_str) {
+    auto l_str = extract_between('[', ']', type_str);
+    auto l = std::stoull(ss::sstring(l_str));
+    return fixed_type{l};
+}
+
+} // namespace
+
+struct_type parse_struct(const json::Value& v) {
+    struct_type ret;
+    const auto& fields_json = parse_required(v, "fields");
+    const auto& fields_array = fields_json.GetArray();
+    ret.fields.reserve(fields_array.Size());
+    for (const auto& field_json : fields_array) {
+        ret.fields.emplace_back(parse_field(field_json));
+    }
+    return ret;
+}
+
+list_type parse_list(const json::Value& v) {
+    const auto& element_json = parse_required(v, "element");
+    return list_type::create(
+      parse_required_i32(v, "element-id"),
+      parse_required_bool(v, "element-required") ? field_required::yes
+                                                 : field_required::no,
+      parse_type(element_json));
+}
+
+map_type parse_map(const json::Value& v) {
+    const auto& key_json = parse_required(v, "key");
+    const auto& val_json = parse_required(v, "value");
+    auto value_required = parse_required_bool(v, "value-required");
+    auto key_type = parse_type(key_json);
+    return map_type::create(
+      parse_required_i32(v, "key-id"),
+      parse_type(key_json),
+      parse_required_i32(v, "value-id"),
+      value_required ? field_required::yes : field_required::no,
+      parse_type(val_json));
+}
+
+nested_field_ptr parse_field(const json::Value& v) {
+    auto id = parse_required_i32(v, "id");
+    auto name = parse_required_str(v, "name");
+    auto required = parse_required_bool(v, "required");
+    const auto& type_json = parse_required(v, "type");
+    auto type = parse_type(type_json);
+    return nested_field::create(
+      id,
+      std::move(name),
+      required ? field_required::yes : field_required::no,
+      std::move(type));
+}
+
+field_type parse_type(const json::Value& v) {
+    if (v.IsString()) {
+        auto v_str = std::string_view{v.GetString(), v.GetStringLength()};
+        if (v_str.starts_with("decimal")) {
+            return parse_decimal(v_str);
+        }
+        if (v_str.starts_with("fixed")) {
+            return parse_fixed(v_str);
+        }
+        return string_switch<field_type>(v_str)
+          .match("boolean", boolean_type{})
+          .match("int", int_type{})
+          .match("long", long_type{})
+          .match("float", float_type{})
+          .match("double", double_type{})
+          .match("date", date_type{})
+          .match("time", time_type{})
+          .match("timestamp", timestamp_type{})
+          .match("timestamptz", timestamptz_type{})
+          .match("string", string_type{})
+          .match("uuid", uuid_type{})
+          .match("binary", binary_type{});
+    }
+    if (!v.IsObject()) {
+        throw std::invalid_argument("Expected string or object for type field");
+    }
+    auto type = parse_required_str(v, "type");
+    if (type == "struct") {
+        return parse_struct(v);
+    } else if (type == "list") {
+        return parse_list(v);
+    } else if (type == "map") {
+        return parse_map(v);
+    }
+    throw std::invalid_argument(fmt::format(
+      "Expected type field of 'struct', 'list', or 'map': {}", type));
+}
+
+} // namespace iceberg
+
+namespace json {
+
+namespace {
+class rjson_visitor {
+public:
+    explicit rjson_visitor(json::Writer<json::StringBuffer>& w)
+      : w(w) {}
+    void operator()(const iceberg::boolean_type&) { w.String("boolean"); }
+    void operator()(const iceberg::int_type&) { w.String("int"); }
+    void operator()(const iceberg::long_type&) { w.String("long"); }
+    void operator()(const iceberg::float_type&) { w.String("float"); }
+    void operator()(const iceberg::double_type&) { w.String("double"); }
+    void operator()(const iceberg::decimal_type& t) {
+        w.String("decimal({}, {})", t.precision, t.scale);
+    }
+    void operator()(const iceberg::date_type&) { w.String("date"); }
+    void operator()(const iceberg::time_type&) { w.String("time"); }
+    void operator()(const iceberg::timestamp_type&) { w.String("timestamp"); }
+    void operator()(const iceberg::timestamptz_type&) {
+        w.String("timestamptz");
+    }
+    void operator()(const iceberg::string_type&) { w.String("string"); }
+    void operator()(const iceberg::uuid_type&) { w.String("uuid"); }
+    void operator()(const iceberg::fixed_type& t) {
+        w.String(fmt::format("fixed[{}]", t.length));
+    }
+    void operator()(const iceberg::binary_type&) { w.String("binary"); }
+
+    void operator()(const iceberg::primitive_type& t) { rjson_serialize(w, t); }
+    void operator()(const iceberg::struct_type& t) { rjson_serialize(w, t); }
+    void operator()(const iceberg::list_type& t) { rjson_serialize(w, t); }
+    void operator()(const iceberg::map_type& t) { rjson_serialize(w, t); }
+
+private:
+    json::Writer<json::StringBuffer>& w;
+};
+} // anonymous namespace
+
+void rjson_serialize(
+  json::Writer<json::StringBuffer>& w, const iceberg::nested_field& f) {
+    w.StartObject();
+    w.Key("id");
+    w.Int(f.id());
+    w.Key("name");
+    w.String(f.name);
+    w.Key("required");
+    w.Bool(bool(f.required));
+    w.Key("type");
+    rjson_serialize(w, f.type);
+    w.EndObject();
+}
+
+void rjson_serialize(
+  json::Writer<json::StringBuffer>& w, const iceberg::primitive_type& t) {
+    std::visit(rjson_visitor{w}, t);
+}
+
+void rjson_serialize(
+  json::Writer<json::StringBuffer>& w, const iceberg::struct_type& t) {
+    w.StartObject();
+    w.Key("type");
+    w.String("struct");
+    w.Key("fields");
+    w.StartArray();
+    for (const auto& f : t.fields) {
+        rjson_serialize(w, *f);
+    }
+    w.EndArray();
+    w.EndObject();
+}
+
+void rjson_serialize(
+  json::Writer<json::StringBuffer>& w, const iceberg::list_type& t) {
+    w.StartObject();
+    w.Key("type");
+    w.String("list");
+    w.Key("element-id");
+    w.Int(t.element_field->id);
+    w.Key("element-required");
+    w.Bool(bool(t.element_field->required));
+    w.Key("element");
+    rjson_serialize(w, t.element_field->type);
+    w.EndObject();
+}
+
+void rjson_serialize(
+  json::Writer<json::StringBuffer>& w, const iceberg::map_type& t) {
+    w.StartObject();
+    w.Key("type");
+    w.String("map");
+    w.Key("key-id");
+    w.Int(t.key_field->id);
+    w.Key("value-id");
+    w.Int(t.value_field->id);
+    w.Key("value-required");
+    w.Bool(bool(t.value_field->required));
+    w.Key("key");
+    rjson_serialize(w, t.key_field->type);
+    w.Key("value");
+    rjson_serialize(w, t.value_field->type);
+    w.EndObject();
+}
+
+void rjson_serialize(
+  json::Writer<json::StringBuffer>& w, const iceberg::field_type& t) {
+    std::visit(rjson_visitor{w}, t);
+}
+
+} // namespace json

src/v/iceberg/datatypes_json.h

@@ -0,0 +1,42 @@
+// Copyright 2024 Redpanda Data, Inc.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.md
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0
+#pragma once
+
+#include "iceberg/datatypes.h"
+#include "json/_include_first.h"
+#include "json/document.h"
+#include "json/stringbuffer.h"
+#include "json/writer.h"
+
+namespace iceberg {
+
+struct_type parse_struct(const json::Value&);
+list_type parse_list(const json::Value&);
+map_type parse_map(const json::Value&);
+field_type parse_type(const json::Value&);
+nested_field_ptr parse_field(const json::Value&);
+
+} // namespace iceberg
+
+namespace json {
+
+void rjson_serialize(
+  json::Writer<json::StringBuffer>& w, const iceberg::nested_field& f);
+void rjson_serialize(
+  json::Writer<json::StringBuffer>& w, const iceberg::primitive_type& t);
+void rjson_serialize(
+  json::Writer<json::StringBuffer>& w, const iceberg::struct_type& t);
+void rjson_serialize(
+  json::Writer<json::StringBuffer>& w, const iceberg::list_type& t);
+void rjson_serialize(
+  json::Writer<json::StringBuffer>& w, const iceberg::map_type& t);
+void rjson_serialize(
+  json::Writer<json::StringBuffer>& w, const iceberg::field_type& t);
+
+} // namespace json

src/v/iceberg/tests/CMakeLists.txt

@@ -8,6 +8,7 @@ rp_test(
   SOURCES
     datatypes_test.cc
     manifest_serialization_test.cc
+    datatypes_json_test.cc
   LIBRARIES
     Avro::avro
     v::bytes