#include "lang/preprocessor.hpp"

namespace hex::lang {

    Preprocessor::Preprocessor() {

    }

    std::optional<std::string> Preprocessor::preprocess(const std::string& code, bool initialRun) {
        u32 offset = 0;
        u32 lineNumber = 1;

        if (initialRun) {
            this->m_defines.clear();
            this->m_pragmas.clear();
        }

        std::string output;
        output.reserve(code.length());

        try {
            while (offset < code.length()) {
                if (code[offset] == '#') {
                    offset += 1;

                    if (code.substr(offset, 7) == "include") {
                        offset += 7;

                        while (std::isblank(code[offset]) || std::isspace(code[offset]))
                            offset += 1;

                        if (code[offset] != '<' && code[offset] != '"')
                            throwPreprocessorError("expected '<' or '\"' before file name", lineNumber);

                        char endChar = code[offset];
                        if (endChar == '<') endChar = '>';

                        offset += 1;

                        std::string includeFile;
                        while (code[offset] != endChar) {
                            includeFile += code[offset];
                            offset += 1;

                            if (offset >= code.length())
                                throwPreprocessorError(hex::format("missing terminating '%c' character", endChar), lineNumber);
                        }
                        offset += 1;

                        if (includeFile[0] != '/')
                            includeFile = "include/" + includeFile;

                        FILE *file = fopen(includeFile.c_str(), "r");
                        if (file == nullptr)
                            throwPreprocessorError(hex::format("%s: No such file or directory", includeFile.c_str()), lineNumber);

                        fseek(file, 0, SEEK_END);
                        size_t size = ftell(file);
                        char *buffer = new char[size + 1];
                        rewind(file);

                        fread(buffer, size, 1, file);
                        buffer[size] = 0x00;

                        auto preprocessedInclude = this->preprocess(buffer, false);
                        if (!preprocessedInclude.has_value())
                            throw this->m_error;

                        output += preprocessedInclude.value();

                        delete[] buffer;

                        fclose(file);
                    } else if (code.substr(offset, 6) == "define") {
                        offset += 6;

                        while (std::isblank(code[offset])) {
                            offset += 1;
                        }

                        std::string defineName;
                        while (!std::isblank(code[offset])) {
                            defineName += code[offset];

                            if (offset >= code.length() || code[offset] == '\n' || code[offset] == '\r')
                                throwPreprocessorError("no value given in #define directive", lineNumber);
                            offset += 1;
                        }

                        while (std::isblank(code[offset])) {
                            offset += 1;
                            if (offset >= code.length())
                                throwPreprocessorError("no value given in #define directive", lineNumber);
                        }

                        std::string replaceValue;
                        while (code[offset] != '\n' && code[offset] != '\r') {
                            if (offset >= code.length())
                                throwPreprocessorError("missing new line after #define directive", lineNumber);

                            replaceValue += code[offset];
                            offset += 1;
                        }

                        if (replaceValue.empty())
                            throwPreprocessorError("no value given in #define directive", lineNumber);

                        this->m_defines.emplace(defineName, replaceValue);
                    } else if (code.substr(offset, 6) == "pragma") {
                        offset += 6;

                        while (std::isblank(code[offset]))
                            offset += 1;

                        std::string pragmaKey;
                        while (!std::isblank(code[offset])) {
                            pragmaKey += code[offset];

                            if (offset >= code.length() || code[offset] == '\n' || code[offset] == '\r')
                                throwPreprocessorError("no instruction given in #pragma directive", lineNumber);

                            offset += 1;
                        }

                        while (std::isblank(code[offset]))
                            offset += 1;

                        std::string pragmaValue;
                        while (code[offset] != '\n' && code[offset] != '\r') {
                            if (offset >= code.length())
                                throwPreprocessorError("missing new line after #pragma directive", lineNumber);

                            pragmaValue += code[offset];
                            offset += 1;
                        }

                        if (pragmaValue.empty())
                            throwPreprocessorError("missing value in #pragma directive", lineNumber);

                        this->m_pragmas.emplace(pragmaKey, pragmaValue);
                    } else
                        throwPreprocessorError("unknown preprocessor directive", lineNumber);
                } else if (code.substr(offset, 2) == "//") {
                    while (code[offset] != '\n' && offset < code.length())
                        offset += 1;
                } else if (code.substr(offset, 2) == "/*") {
                    while (code.substr(offset, 2) != "*/" && offset < code.length()) {
                        if (code[offset] == '\n')
                            lineNumber++;

                        offset += 1;
                    }

                    offset += 2;
                    if (offset >= code.length())
                        throwPreprocessorError("unterminated comment", lineNumber);
                }

                if (code[offset] == '\n')
                    lineNumber++;

                output += code[offset];
                offset += 1;
            }

            if (initialRun) {
                // Apply defines
                for (const auto &[define, value] : this->m_defines) {
                    s32 index = 0;
                    while((index = output.find(define, index)) != std::string::npos) {
                        output.replace(index, define.length(), value);
                        index += value.length();
                    }
                }

                // Handle pragmas
                for (const auto &[type, value] : this->m_pragmas) {
                    if (this->m_pragmaHandlers.contains(type)) {
                        if (!this->m_pragmaHandlers[type](value))
                            throwPreprocessorError(hex::format("invalid value provided to '%s' #pragma directive", type.c_str()), lineNumber);
                    } else
                        throwPreprocessorError(hex::format("no #pragma handler registered for type %s", type.c_str()), lineNumber);
                }
            }
        } catch (PreprocessorError &e) {
            this->m_error = e;
            return { };
        }

        return output;
    }

    void Preprocessor::addPragmaHandler(const std::string &pragmaType, const std::function<bool(const std::string&)> &function) {
        if (!this->m_pragmaHandlers.contains(pragmaType))
            this->m_pragmaHandlers.emplace(pragmaType, function);
    }

    void Preprocessor::addDefaultPragmaHandlers() {
        this->addPragmaHandler("MIME", [](const std::string &value) {
            return !std::all_of(value.begin(), value.end(), isspace) && !value.ends_with('\n') && !value.ends_with('\r');
        });
        this->addPragmaHandler("endian", [](const std::string &value) {
            return value == "big" || value == "little" || value == "native";
        });
    }

}