#include "generator.h"

using namespace dsr;

static uint64_t checksum(const ReadableString& text) {
	uint64_t a = 0x8C2A03D4;
	uint64_t b = 0xF42B1583;
	uint64_t c = 0xA6815E74;
	uint64_t d = 0;
	for (int i = 0; i < string_length(text); i++) {
		a = (b * c + ((i * 3756 + 2654) & 58043)) & 0xFFFFFFFF;
		b = (231 + text[i] * (a & 154) + c * 867 + 28294061) & 0xFFFFFFFF;
		c = (a ^ b ^ (text[i] * 1543217521)) & 0xFFFFFFFF;
		d = d ^ (a << 32) ^ b ^ (c << 16);
	}
	return d;
}

static uint64_t checksum(const Buffer& buffer) {
	SafePointer<uint8_t> data = buffer_getSafeData<uint8_t>(buffer, "checksum input buffer");
	uint64_t a = 0x8C2A03D4;
	uint64_t b = 0xF42B1583;
	uint64_t c = 0xA6815E74;
	uint64_t d = 0;
	for (int i = 0; i < buffer_getSize(buffer); i++) {
		a = (b * c + ((i * 3756 + 2654) & 58043)) & 0xFFFFFFFF;
		b = (231 + data[i] * (a & 154) + c * 867 + 28294061) & 0xFFFFFFFF;
		c = (a ^ b ^ (data[i] * 1543217521)) & 0xFFFFFFFF;
		d = d ^ (a << 32) ^ b ^ (c << 16);
	}
	return d;
}

static int64_t findDependency(ProjectContext &context, const ReadableString& findPath);
static void resolveConnection(Connection &connection);
static void resolveDependency(Dependency &dependency);
static String findSourceFile(const ReadableString& headerPath, bool acceptC, bool acceptCpp);
static void flushToken(List<String> &target, String &currentToken);
static void tokenize(List<String> &target, const ReadableString& line);
static void interpretPreprocessing(ProjectContext &context, int64_t parentIndex, const List<String> &tokens, const ReadableString &parentFolder, int64_t lineNumber);
static void analyzeCode(ProjectContext &context, int64_t parentIndex, String content, const ReadableString &parentFolder);

static int64_t findDependency(ProjectContext &context, const ReadableString& findPath) {
	for (int d = 0; d < context.dependencies.length(); d++) {
		if (string_match(context.dependencies[d].path, findPath)) {
			return d;
		}
	}
	return -1;
}

static void resolveConnection(ProjectContext &context, Connection &connection) {
	connection.dependencyIndex = findDependency(context, connection.path);
}

static void resolveDependency(ProjectContext &context, Dependency &dependency) {
	for (int l = 0; l < dependency.links.length(); l++) {
		resolveConnection(context, dependency.links[l]);
	}
	for (int i = 0; i < dependency.includes.length(); i++) {
		resolveConnection(context, dependency.includes[i]);
	}
}

void resolveDependencies(ProjectContext &context) {
	for (int d = 0; d < context.dependencies.length(); d++) {
		resolveDependency(context, context.dependencies[d]);
	}
}

static String findSourceFile(const ReadableString& headerPath, bool acceptC, bool acceptCpp) {
	if (file_hasExtension(headerPath)) {
		ReadableString extensionlessPath = file_getExtensionless(headerPath);
		String cPath = extensionlessPath + U".c";
		String cppPath = extensionlessPath + U".cpp";
		if (acceptC && file_getEntryType(cPath) == EntryType::File) {
			return cPath;
		} else if (acceptCpp && file_getEntryType(cppPath) == EntryType::File) {
			return cppPath;
		}
	}
	return U"";
}

static void flushToken(List<String> &target, String &currentToken) {
	if (string_length(currentToken) > 0) {
		target.push(currentToken);
		currentToken = U"";
	}
}

static void tokenize(List<String> &target, const ReadableString& line) {
	String currentToken;
	for (int i = 0; i < string_length(line); i++) {
		DsrChar c = line[i];
		DsrChar nextC = line[i + 1];
		if (c == U'#' && nextC == U'#') {
			// Appending tokens using ##
			i++;
		} else if (c == U'#' || c == U'(' || c == U')' || c == U'[' || c == U']' || c == U'{' || c == U'}') {
			// Atomic token of a single character
			flushToken(target, currentToken);
			string_appendChar(currentToken, c);
			flushToken(target, currentToken);
		} else if (c == U' ' || c == U'\t') {
			// Whitespace
			flushToken(target, currentToken);
		} else {
			string_appendChar(currentToken, c);
		}
	}
	flushToken(target, currentToken);
}

static void interpretPreprocessing(ProjectContext &context, int64_t parentIndex, const List<String> &tokens, const ReadableString &parentFolder, int64_t lineNumber) {
	if (tokens.length() >= 3) {
		if (string_match(tokens[1], U"include")) {
			if (tokens[2][0] == U'\"') {
				String relativePath = string_unmangleQuote(tokens[2]);
				String absolutePath = file_getTheoreticalAbsolutePath(relativePath, parentFolder, LOCAL_PATH_SYNTAX);
				context.dependencies[parentIndex].includes.pushConstruct(absolutePath, lineNumber);
				analyzeFromFile(context, absolutePath);
			}
		}
	}
}

static void analyzeCode(ProjectContext &context, int64_t parentIndex, String content, const ReadableString &parentFolder) {
	List<String> tokens;
	bool continuingLine = false;
	int64_t lineNumber = 0;
	string_split_callback(content, U'\n', true, [&parentIndex, &parentFolder, &tokens, &continuingLine, &lineNumber, &context](ReadableString line) {
		lineNumber++;
		if (line[0] == U'#' || continuingLine) {
			tokenize(tokens, line);
			// Continuing pre-processing line using \ at the end.
			continuingLine = line[string_length(line) - 1] == U'\\';
		} else {
			continuingLine = false;
		}
		if (!continuingLine && tokens.length() > 0) {
			interpretPreprocessing(context, parentIndex, tokens, parentFolder, lineNumber);
			tokens.clear();
		}
	});
}

void analyzeFromFile(ProjectContext &context, const ReadableString& absolutePath) {
	if (findDependency(context, absolutePath) != -1) {
		// Already analyzed the current entry. Abort to prevent duplicate dependencies.
		return;
	}
	int lastDotIndex = string_findLast(absolutePath, U'.');
	if (lastDotIndex != -1) {
		Extension extension = extensionFromString(string_after(absolutePath, lastDotIndex));
		if (extension != Extension::Unknown) {
			// The old length will be the new dependency's index.
			int64_t parentIndex = context.dependencies.length();
			// Get the file's binary content.
			Buffer fileBuffer = file_loadBuffer(absolutePath);
			// Get the checksum
			uint64_t contentChecksum = checksum(fileBuffer);
			context.dependencies.pushConstruct(absolutePath, extension, contentChecksum);
			if (extension == Extension::H || extension == Extension::Hpp) {
				// The current file is a header, so look for an implementation with the corresponding name.
				String sourcePath = findSourceFile(absolutePath, extension == Extension::H, true);
				// If found:
				if (string_length(sourcePath) > 0) {
					// Remember that anything using the header will have to link with the implementation.
					context.dependencies[parentIndex].links.pushConstruct(sourcePath);
					// Look for included headers in the implementation file.
					analyzeFromFile(context, sourcePath);
				}
			}
			// Interpret the file's content.
			analyzeCode(context, parentIndex, string_loadFromMemory(fileBuffer), file_getRelativeParentFolder(absolutePath));
		}
	}
}

static void debugPrintDependencyList(const List<Connection> &connnections, const ReadableString verb) {
	for (int c = 0; c < connnections.length(); c++) {
		int64_t lineNumber = connnections[c].lineNumber;
		if (lineNumber != -1) {
			printText(U"  @", lineNumber, U"\t");
		} else {
			printText(U"    \t");
		}
		printText(U" ", verb, U" ", file_getPathlessName(connnections[c].path), U"\n");
	}
}

void printDependencies(ProjectContext &context) {
	for (int d = 0; d < context.dependencies.length(); d++) {
		printText(U"* ", file_getPathlessName(context.dependencies[d].path), U"\n");
		debugPrintDependencyList(context.dependencies[d].includes, U"including");
		debugPrintDependencyList(context.dependencies[d].links, U"linking");
	}
}

static void script_printMessage(ScriptTarget &output, const ReadableString message) {
	if (output.language == ScriptLanguage::Batch) {
		string_append(output.generatedCode, U"echo ", message, U"\n");
	} else if (output.language == ScriptLanguage::Bash) {
		string_append(output.generatedCode, U"echo ", message, U"\n");
	}
}

static void script_executeLocalBinary(ScriptTarget &output, const ReadableString fullPath) {
	if (output.language == ScriptLanguage::Batch) {
		string_append(output.generatedCode, fullPath, U"\n");
	} else if (output.language == ScriptLanguage::Bash) {
		string_append(output.generatedCode, fullPath, U";\n");
	}
}

static void traverserHeaderChecksums(ProjectContext &context, uint64_t &target, int64_t dependencyIndex) {
	// Use checksums from headers
	for (int h = 0; h < context.dependencies[dependencyIndex].includes.length(); h++) {
		int64_t includedIndex = context.dependencies[dependencyIndex].includes[h].dependencyIndex;
		if (!context.dependencies[includedIndex].visited) {
			//printText(U"	traverserHeaderChecksums(context, ", includedIndex, U") ", context.dependencies[includedIndex].path, "\n");
			// Bitwise exclusive or is both order independent and entropy preserving for non-repeated content.
			target = target ^ context.dependencies[includedIndex].contentChecksum;
			// Just have to make sure that the same checksum is not used twice.
			context.dependencies[includedIndex].visited = true;
			// Use checksums from headers recursively
			traverserHeaderChecksums(context, target, includedIndex);
		}
	}
}

static uint64_t getCombinedChecksum(ProjectContext &context, int64_t dependencyIndex) {
	//printText(U"getCombinedChecksum(context, ", dependencyIndex, U") ", context.dependencies[dependencyIndex].path, "\n");
	for (int d = 0; d < context.dependencies.length(); d++) {
		context.dependencies[d].visited = false;
	}
	context.dependencies[dependencyIndex].visited = true;
	uint64_t result = context.dependencies[dependencyIndex].contentChecksum;
	traverserHeaderChecksums(context, result, dependencyIndex);
	return result;
}

struct SourceObject {
	uint64_t identityChecksum = 0; // Identification number for the object's name.
	uint64_t combinedChecksum = 0; // Combined content of the source file and all included headers recursively.
	String sourcePath, objectPath;
	SourceObject(ProjectContext &context, const ReadableString& sourcePath, const ReadableString& tempFolder, const ReadableString& identity, int64_t dependencyIndex)
	: identityChecksum(checksum(identity)), combinedChecksum(getCombinedChecksum(context, dependencyIndex)), sourcePath(sourcePath) {
		// By making the content checksum a part of the name, one can switch back to an older version without having to recompile everything again.
		// Just need to clean the temporary folder once in a while because old versions can take a lot of space.
		this->objectPath = file_combinePaths(tempFolder, string_combine(U"dfpsr_", this->identityChecksum, U"_", this->combinedChecksum, U".o"));
	}
};

void generateCompilationScript(ScriptTarget &output, ProjectContext &context, const Machine &settings, ReadableString programPath) {
	// Convert lists of linker and compiler flags into strings.
	// TODO: Give a warning if two contradictory flags are used, such as optimization levels and language versions.
	// TODO: Make sure that no spaces are inside of the flags, because that can mess up detection of pre-existing and contradictory arguments.
	String compilerFlags;
	for (int i = 0; i < settings.compilerFlags.length(); i++) {
		string_append(compilerFlags, " ", settings.compilerFlags[i]);
	}
	String linkerFlags;
	for (int i = 0; i < settings.linkerFlags.length(); i++) {
		string_append(linkerFlags, " -l", settings.linkerFlags[i]);
	}
	printText(U"Generating build instructions for ", programPath, U" using settings:\n");
	printText(U"  Compiler flags:", compilerFlags, U"\n");
	printText(U"  Linker flags:", linkerFlags, U"\n");
	for (int v = 0; v < settings.variables.length(); v++) {
		printText(U"  * ", settings.variables[v].key, U" = ", settings.variables[v].value);
		if (settings.variables[v].inherited) {
			printText(U" (inherited input)");
		}
		printText(U"\n");
	}
	// The compiler is often a global alias, so the user must supply either an alias or an absolute path.
	ReadableString compilerName = getFlag(settings, U"Compiler", U"g++"); // Assume g++ as the compiler if not specified.
	ReadableString compileFrom = getFlag(settings, U"CompileFrom", U"");
	// Check if the build system was asked to run the compiler from a specific folder.
	bool changePath = (string_length(compileFrom) > 0);
	if (changePath) {
		printText(U"Using ", compilerName, " as the compiler executed from ", compileFrom, ".\n");
	} else {
		printText(U"Using ", compilerName, " as the compiler from the current directory.\n");
	}
	// TODO: Warn if -DNDEBUG, -DDEBUG, or optimization levels are given directly.
	//       Using the variables instead is both more flexible by accepting input arguments
	//       and keeping the same format to better reuse compiled objects.
	if (getFlagAsInteger(settings, U"Debug")) {
		printText(U"Building with debug mode.\n");
		string_append(compilerFlags, " -DDEBUG");
	} else {
		printText(U"Building with release mode.\n");
		string_append(compilerFlags, " -DNDEBUG");
	}
	if (getFlagAsInteger(settings, U"StaticRuntime")) {
		if (getFlagAsInteger(settings, U"Windows")) {
			printText(U"Building with static runtime. Your application's binary will be bigger but can run without needing any installer.\n");
			string_append(compilerFlags, " -static -static-libgcc -static-libstdc++");
			string_append(linkerFlags, " -static -static-libgcc -static-libstdc++");
		} else {
			printText(U"The target platform does not support static linking of runtime. But don't worry about bundling any runtimes, because it comes with most of the Posix compliant operating systems.\n");
		}
	} else {
		printText(U"Building with dynamic runtime. Don't forget to bundle the C and C++ runtimes for systems that don't have it pre-installed.\n");
	}
	ReadableString optimizationLevel = getFlag(settings, U"Optimization", U"2");
		printText(U"Building with optimization level ", optimizationLevel, U".\n");
	string_append(compilerFlags, " -O", optimizationLevel);

	List<SourceObject> sourceObjects;
	bool hasSourceCode = false;
	bool needCppCompiler = false;
	for (int d = 0; d < context.dependencies.length(); d++) {
		Extension extension = context.dependencies[d].extension;
		if (extension == Extension::Cpp) {
			needCppCompiler = true;
		}
		if (extension == Extension::C || extension == Extension::Cpp) {
			// Dependency paths are already absolute from the recursive search.
			String sourcePath = context.dependencies[d].path;
			String identity = string_combine(sourcePath, compilerFlags);
			sourceObjects.pushConstruct(context, sourcePath, output.tempPath, identity, d);
			if (file_getEntryType(sourcePath) != EntryType::File) {
				throwError(U"The source file ", sourcePath, U" could not be found!\n");
			} else {
				hasSourceCode = true;
			}
		}
	}
	if (hasSourceCode) {
		// TODO: Give a warning if a known C compiler incapable of handling C++ is given C++ source code when needCppCompiler is true.
		if (changePath) {
			// Go into the requested folder.
			if (output.language == ScriptLanguage::Batch) {
				string_append(output.generatedCode,  "pushd ", compileFrom, "\n");
			} else if (output.language == ScriptLanguage::Bash) {
				string_append(output.generatedCode, U"(cd ", compileFrom, ";\n");
			}
		}
		String allObjects;
		for (int i = 0; i < sourceObjects.length(); i++) {
			if (output.language == ScriptLanguage::Batch) {
				string_append(output.generatedCode,  U"if exist ", sourceObjects[i].objectPath, U" (\n");
			} else if (output.language == ScriptLanguage::Bash) {
				string_append(output.generatedCode, U"if [ -e \"", sourceObjects[i].objectPath, U"\" ]; then\n");
			}
			script_printMessage(output, string_combine(U"Reusing ", sourceObjects[i].sourcePath, U" ID:", sourceObjects[i].identityChecksum, U"."));
			if (output.language == ScriptLanguage::Batch) {
				string_append(output.generatedCode,  U") else (\n");
			} else if (output.language == ScriptLanguage::Bash) {
				string_append(output.generatedCode, U"else\n");
			}
			script_printMessage(output, string_combine(U"Compiling ", sourceObjects[i].sourcePath, U" ID:", sourceObjects[i].identityChecksum, U" with \"", compilerFlags, U"\"."));
			string_append(output.generatedCode, compilerName, compilerFlags, U" -c ", sourceObjects[i].sourcePath, U" -o ", sourceObjects[i].objectPath, U"\n");
			if (output.language == ScriptLanguage::Batch) {
				string_append(output.generatedCode,  ")\n");
			} else if (output.language == ScriptLanguage::Bash) {
				string_append(output.generatedCode, U"fi\n");
			}
			// Remember each object name for linking.
			string_append(allObjects, U" ", sourceObjects[i].objectPath);
		}
		script_printMessage(output, string_combine(U"Linking with \"", linkerFlags, U"\"."));
		string_append(output.generatedCode, compilerName, allObjects, linkerFlags, U" -o ", programPath, U"\n");
		if (changePath) {
			// Get back to the previous folder.
			if (output.language == ScriptLanguage::Batch) {
				string_append(output.generatedCode,  "popd\n");
			} else if (output.language == ScriptLanguage::Bash) {
				string_append(output.generatedCode, U")\n");
			}
		}
		script_printMessage(output, U"Done building.");
		if (getFlagAsInteger(settings, U"Supressed")) {
			script_printMessage(output, string_combine(U"Execution of ", programPath, U" was supressed using the Supressed flag."));
		} else {
			script_printMessage(output, string_combine(U"Starting ", programPath));
			script_executeLocalBinary(output, programPath);
			script_printMessage(output, U"The program terminated.");
		}
	} else {
		printText("Filed to find any source code to compile.\n");
	}
}