exduckdb

#include "duckdb/planner/expression/bound_function_expression.hpp"
#include "duckdb/common/string_util.hpp"
#include "duckdb/parser/expression/bound_expression.hpp"
#include "duckdb/function/scalar/nested_functions.hpp"
#include "duckdb/common/unordered_set.hpp"
#include "duckdb/storage/statistics/struct_statistics.hpp"
#include "duckdb/planner/expression_binder.hpp"

namespace duckdb {

static void StructPackFunction(DataChunk &args, ExpressionState &state, Vector &result) {
#ifdef DEBUG
	auto &func_expr = (BoundFunctionExpression &)state.expr;
	auto &info = (VariableReturnBindData &)*func_expr.bind_info;
	// this should never happen if the binder below is sane
	D_ASSERT(args.ColumnCount() == StructType::GetChildTypes(info.stype).size());
#endif
	bool all_const = true;
	auto &child_entries = StructVector::GetEntries(result);
	for (size_t i = 0; i < args.ColumnCount(); i++) {
		if (args.data[i].GetVectorType() != VectorType::CONSTANT_VECTOR) {
			all_const = false;
		}
		// same holds for this
		child_entries[i]->Reference(args.data[i]);
	}
	result.SetVectorType(all_const ? VectorType::CONSTANT_VECTOR : VectorType::FLAT_VECTOR);

	result.Verify(args.size());
}

static unique_ptr<FunctionData> StructPackBind(ClientContext &context, ScalarFunction &bound_function,
                                               vector<unique_ptr<Expression>> &arguments) {
	unordered_set<string> name_collision_set;

	// collect names and deconflict, construct return type
	if (arguments.empty()) {
		throw Exception("Can't pack nothing into a struct");
	}
	child_list_t<LogicalType> struct_children;
	for (idx_t i = 0; i < arguments.size(); i++) {
		auto &child = arguments[i];
		if (child->alias.empty() && bound_function.name == "struct_pack") {
			throw BinderException("Need named argument for struct pack, e.g. STRUCT_PACK(a := b)");
		}
		if (child->alias.empty() && bound_function.name == "row") {
			child->alias = "v" + std::to_string(i + 1);
		}
		if (name_collision_set.find(child->alias) != name_collision_set.end()) {
			throw BinderException("Duplicate struct entry name \"%s\"", child->alias);
		}
		ExpressionBinder::ResolveParameterType(arguments[i]);
		name_collision_set.insert(child->alias);
		struct_children.push_back(make_pair(child->alias, arguments[i]->return_type));
	}

	// this is more for completeness reasons
	bound_function.return_type = LogicalType::STRUCT(move(struct_children));
	return make_unique<VariableReturnBindData>(bound_function.return_type);
}

unique_ptr<BaseStatistics> StructPackStats(ClientContext &context, BoundFunctionExpression &expr,
                                           FunctionData *bind_data, vector<unique_ptr<BaseStatistics>> &child_stats) {
	auto struct_stats = make_unique<StructStatistics>(expr.return_type);
	D_ASSERT(child_stats.size() == struct_stats->child_stats.size());
	for (idx_t i = 0; i < struct_stats->child_stats.size(); i++) {
		struct_stats->child_stats[i] = child_stats[i] ? child_stats[i]->Copy() : nullptr;
	}
	return move(struct_stats);
}

void StructPackFun::RegisterFunction(BuiltinFunctions &set) {
	// the arguments and return types are actually set in the binder function
	ScalarFunction fun("struct_pack", {}, LogicalTypeId::STRUCT, StructPackFunction, false, StructPackBind, nullptr,
	                   StructPackStats);
	fun.varargs = LogicalType::ANY;
	set.AddFunction(fun);
	fun.name = "row";
	set.AddFunction(fun);
}

} // namespace duckdb