exduckdb

#include "duckdb/parser/expression/comparison_expression.hpp"
#include "duckdb/planner/expression/bound_cast_expression.hpp"
#include "duckdb/planner/expression/bound_constant_expression.hpp"
#include "duckdb/planner/expression/bound_comparison_expression.hpp"
#include "duckdb/planner/expression/bound_function_expression.hpp"
#include "duckdb/planner/expression_binder.hpp"
#include "duckdb/catalog/catalog_entry/collate_catalog_entry.hpp"
#include "duckdb/common/string_util.hpp"

#include "duckdb/function/scalar/string_functions.hpp"

#include "duckdb/common/types/decimal.hpp"

#include "duckdb/main/config.hpp"
#include "duckdb/catalog/catalog.hpp"

namespace duckdb {

unique_ptr<Expression> ExpressionBinder::PushCollation(ClientContext &context, unique_ptr<Expression> source,
                                                       const string &collation_p, bool equality_only) {
	// replace default collation with system collation
	string collation;
	if (collation_p.empty()) {
		collation = DBConfig::GetConfig(context).collation;
	} else {
		collation = collation_p;
	}
	// bind the collation
	if (collation.empty() || collation == "binary" || collation == "c" || collation == "posix") {
		// binary collation: just skip
		return source;
	}
	auto &catalog = Catalog::GetCatalog(context);
	auto splits = StringUtil::Split(StringUtil::Lower(collation), ".");
	vector<CollateCatalogEntry *> entries;
	for (auto &collation_argument : splits) {
		auto collation_entry = catalog.GetEntry<CollateCatalogEntry>(context, DEFAULT_SCHEMA, collation_argument);
		if (collation_entry->combinable) {
			entries.insert(entries.begin(), collation_entry);
		} else {
			if (!entries.empty() && !entries.back()->combinable) {
				throw BinderException("Cannot combine collation types \"%s\" and \"%s\"", entries.back()->name,
				                      collation_entry->name);
			}
			entries.push_back(collation_entry);
		}
	}
	for (auto &collation_entry : entries) {
		if (equality_only && collation_entry->not_required_for_equality) {
			continue;
		}
		vector<unique_ptr<Expression>> children;
		children.push_back(move(source));
		auto function = ScalarFunction::BindScalarFunction(context, collation_entry->function, move(children));
		source = move(function);
	}
	return source;
}

void ExpressionBinder::TestCollation(ClientContext &context, const string &collation) {
	PushCollation(context, make_unique<BoundConstantExpression>(Value("")), collation);
}

LogicalType BoundComparisonExpression::BindComparison(LogicalType left_type, LogicalType right_type) {
	auto result_type = LogicalType::MaxLogicalType(left_type, right_type);
	switch (result_type.id()) {
	case LogicalTypeId::DECIMAL: {
		// result is a decimal: we need the maximum width and the maximum scale over width
		vector<LogicalType> argument_types = {left_type, right_type};
		uint8_t max_width = 0, max_scale = 0, max_width_over_scale = 0;
		for (idx_t i = 0; i < argument_types.size(); i++) {
			uint8_t width, scale;
			auto can_convert = argument_types[i].GetDecimalProperties(width, scale);
			if (!can_convert) {
				return result_type;
			}
			max_width = MaxValue<uint8_t>(width, max_width);
			max_scale = MaxValue<uint8_t>(scale, max_scale);
			max_width_over_scale = MaxValue<uint8_t>(width - scale, max_width_over_scale);
		}
		max_width = MaxValue<uint8_t>(max_scale + max_width_over_scale, max_width);
		if (max_width > Decimal::MAX_WIDTH_DECIMAL) {
			// target width does not fit in decimal: truncate the scale (if possible) to try and make it fit
			max_width = Decimal::MAX_WIDTH_DECIMAL;
		}
		return LogicalType::DECIMAL(max_width, max_scale);
	}
	case LogicalTypeId::VARCHAR:
		// for comparison with strings, we prefer to bind to the numeric types
		if (left_type.IsNumeric() || left_type.id() == LogicalTypeId::BOOLEAN) {
			return left_type;
		} else if (right_type.IsNumeric() || right_type.id() == LogicalTypeId::BOOLEAN) {
			return right_type;
		} else {
			// else: check if collations are compatible
			auto left_collation = StringType::GetCollation(left_type);
			auto right_collation = StringType::GetCollation(right_type);
			if (!left_collation.empty() && !right_collation.empty() && left_collation != right_collation) {
				throw BinderException("Cannot combine types with different collation!");
			}
		}
		return result_type;
	case LogicalTypeId::UNKNOWN:
		// comparing two prepared statement parameters (e.g. SELECT ?=?)
		// default to VARCHAR
		return LogicalType::VARCHAR;
	default:
		return result_type;
	}
}

BindResult ExpressionBinder::BindExpression(ComparisonExpression &expr, idx_t depth) {
	// first try to bind the children of the case expression
	string error;
	BindChild(expr.left, depth, error);
	BindChild(expr.right, depth, error);
	if (!error.empty()) {
		return BindResult(error);
	}
	// the children have been successfully resolved
	auto &left = (BoundExpression &)*expr.left;
	auto &right = (BoundExpression &)*expr.right;
	auto left_sql_type = left.expr->return_type;
	auto right_sql_type = right.expr->return_type;
	// cast the input types to the same type
	// now obtain the result type of the input types
	auto input_type = BoundComparisonExpression::BindComparison(left_sql_type, right_sql_type);
	// add casts (if necessary)
	left.expr = BoundCastExpression::AddCastToType(move(left.expr), input_type);
	right.expr = BoundCastExpression::AddCastToType(move(right.expr), input_type);
	if (input_type.id() == LogicalTypeId::VARCHAR) {
		// handle collation
		auto collation = StringType::GetCollation(input_type);
		left.expr = PushCollation(context, move(left.expr), collation, expr.type == ExpressionType::COMPARE_EQUAL);
		right.expr = PushCollation(context, move(right.expr), collation, expr.type == ExpressionType::COMPARE_EQUAL);
	}
	// now create the bound comparison expression
	return BindResult(make_unique<BoundComparisonExpression>(expr.type, move(left.expr), move(right.expr)));
}

} // namespace duckdb