diff -r 532953173cd5 -r 9172bd97ae99 src/ScriptAttributeFinder.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/ScriptAttributeFinder.h	Mon Nov 11 14:42:13 2019 +0100
@@ -0,0 +1,123 @@
+/**
+ * Relational pipes
+ * Copyright © 2019 František Kučera (Frantovo.cz, GlobalCode.info)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 3 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+#pragma once
+
+#include <vector>
+#include <filesystem>
+
+#include <relpipe/writer/typedefs.h>
+#include <relpipe/writer/AttributeMetadata.h>
+#include <relpipe/writer/RelationalWriter.h>
+#include <regex>
+
+#include "RequestedField.h"
+#include "SystemProcess.h"
+#include "AttributeFinder.h"
+
+namespace relpipe {
+namespace in {
+namespace filesystem {
+
+namespace fs = std::filesystem;
+using namespace relpipe::writer;
+
+class ScriptAttributeFinder : public AttributeFinder {
+private:
+	std::wstring_convert<codecvt_utf8<wchar_t>> convertor; // TODO: support also other encodings.
+
+	std::string getScriptCommand(const RequestedField& field) {
+		return SCRIPT_PREFIX + convertor.to_bytes(field.name);
+	}
+
+	std::vector<std::string> toEnvironmentalVariables(const std::vector<string_t>& vector) {
+		std::vector<std::string> result;
+		for (int i = 0; i < vector.size();) {
+			string_t name = vector[i++];
+			string_t value = vector[i++];
+			if (name.rfind(L"env:" == 0)) {
+				result.push_back(convertor.to_bytes(name.substr(4)));
+				result.push_back(convertor.to_bytes(value));
+			}
+		}
+		return result;
+	}
+
+	TypeId getAttributeType(const RequestedField& field, const string_t& alias) {
+		// TODO: put latest supported version in the environmental variable
+		// TODO: put alias in the environmental variable
+		SystemProcess process({getScriptCommand(field)}, toEnvironmentalVariables(field.options));
+		std::string output = process.execute();
+		std::regex pattern("(.*)\\n(.*)\\n");
+		std::smatch match;
+		std::regex_match(output, match, pattern);
+		if (match.ready() && match[1] == "1") {
+			// TODO: move to a common library
+			if (match[2] == "boolean") return TypeId::BOOLEAN;
+			if (match[2] == "integer") return TypeId::INTEGER;
+			if (match[2] == "string") return TypeId::STRING;
+			throw RelpipeWriterException(L"Unsupported script data type – field: „" + field.name + L"“ type: „" + convertor.from_bytes(match[2]) + L"“");
+		} else {
+			throw RelpipeWriterException(L"Unsupported script version – field: „" + field.name + L"“ output: „" + convertor.from_bytes(output) + L"“");
+		}
+
+	}
+
+	string_t getScriptOutput(const fs::path& file, const RequestedField& field, const string_t& alias) {
+		try {
+			// TODO: put alias in the environmental variable
+			SystemProcess process({getScriptCommand(field), currentFileRaw}, toEnvironmentalVariables(field.options));
+			return convertor.from_bytes(process.execute());
+		} catch (relpipe::cli::RelpipeCLIException& e) {
+			// TODO: print warnings?
+			// TODO: do not fork/exec if the file is not readable
+			return L"";
+		}
+	}
+protected:
+
+	virtual void writeFieldOfExistingFile(RelationalWriter* writer, const RequestedField& field) override {
+		// TODO: paralelization?
+		if (field.group == RequestedField::GROUP_SCRIPT) {
+			for (string_t alias : field.getAliases()) {
+				writer->writeAttribute(getScriptOutput(currentFile, field, alias));
+			}
+		}
+	}
+
+public:
+
+	static const std::string SCRIPT_PREFIX;
+
+	virtual vector<AttributeMetadata> toMetadata(const RequestedField& field) override {
+		if (field.group == RequestedField::GROUP_SCRIPT) {
+			vector<AttributeMetadata> metadata;
+			for (string_t alias : field.getAliases()) metadata.push_back(AttributeMetadata{alias, getAttributeType(field, alias)});
+			return metadata;
+		} else {
+			return {};
+		}
+	}
+
+	virtual ~ScriptAttributeFinder() override {
+	}
+};
+
+const std::string ScriptAttributeFinder::SCRIPT_PREFIX = "__relpipe_in_filesystem_script_";
+
+}
+}
+}