// SPDX-License-Identifier: MIT
#include "dbc_statement_handler.h"
#include <charconv>
#include <cmath>
#include <limits>
#include <set>

namespace {
    struct Token {
        std::string text;
        bool quoted = false;
    };

    std::vector<Token> Tokenize(const std::string &text) {
        std::vector<Token> tokens;
        std::size_t index = 0U;
        while (index < text.size()) {
            const char character = text[index++];
            if (character == ' ' || character == '\t')
                continue;
            Token token;
            if (character == '"') {
                token.quoted = true;
                bool closed = false;
                while (index < text.size()) {
                    char next = text[index++];
                    if (next == '"') {
                        closed = true;
                        break;
                    }
                    if (next == '\\') {
                        if (index == text.size())
                            throw std::runtime_error("Incomplete attribute escape.");
                        next = text[index++];
                        if (next != '"' && next != '\\')
                            throw std::runtime_error("Invalid attribute escape.");
                    }
                    token.text += next;
                }
                if (!closed)
                    throw std::runtime_error("Unterminated attribute string.");
                if (index < text.size() && text[index] != ' ' && text[index] != '\t' &&
                    text[index] != ',' && text[index] != ';')
                    throw std::runtime_error("Missing separator after attribute string.");
            } else if (character == ';' || character == ',') {
                token.text = character;
            } else {
                token.text = character;
                while (index < text.size() && text[index] != ' ' && text[index] != '\t' &&
                       text[index] != ';' && text[index] != ',') {
                    if (text[index] == '"')
                        throw std::runtime_error("Missing separator before attribute string.");
                    token.text += text[index++];
                }
            }
            tokens.push_back(token);
        }
        if (tokens.empty() || tokens.back().quoted || tokens.back().text != ";")
            throw std::runtime_error("Attribute statement requires a semicolon.");
        tokens.pop_back();
        return tokens;
    }

    class AttributeTokens {
    public:
        explicit AttributeTokens(const std::string &line) : tokens(Tokenize(line)) {}
        Token Take() {
            if (position == tokens.size())
                throw std::runtime_error("Incomplete attribute statement.");
            return tokens[position++];
        }
        std::string Word() {
            const Token token = Take();
            if (token.quoted || token.text == "," || token.text == ";")
                throw std::runtime_error("Expected an attribute keyword or number.");
            return token.text;
        }
        std::string Quoted() {
            const Token token = Take();
            if (!token.quoted)
                throw std::runtime_error("Expected a quoted attribute name or string.");
            return token.text;
        }
        bool Empty() const { return position == tokens.size(); }
        void End() const {
            if (!Empty())
                throw std::runtime_error("Unexpected trailing attribute fields.");
        }

    private:
        std::vector<Token> tokens;
        std::size_t position = 0U;
    };

    bool IsScope(const std::string &text) {
        return text == "BO_" || text == "SG_" || text == "BU_" || text == "EV_";
    }

    AttributeScope ParseScope(const std::string &text) {
        if (text == "BO_") return AttributeScope::Frame;
        if (text == "SG_") return AttributeScope::Signal;
        if (text == "BU_") return AttributeScope::Node;
        if (text == "EV_") return AttributeScope::Environment;
        throw std::runtime_error("Unsupported attribute scope: " + text);
    }

    std::int64_t Integer(const std::string &text) {
        const char *begin = text.data();
        const char *end = begin + text.size();
        if (begin != end && *begin == '+') {
            ++begin;
            if (begin != end && (*begin == '-' || *begin == '+'))
                throw std::runtime_error("Invalid attribute number: " + text);
        }
        std::int64_t value = 0;
        const std::from_chars_result parsed = std::from_chars(begin, end, value);
        if (begin == end || parsed.ec != std::errc() || parsed.ptr != end)
            throw std::runtime_error("Invalid attribute integer: " + text);
        return value;
    }

    double Number(const std::string &text) {
        const char *begin = text.data();
        const char *end = begin + text.size();
        if (begin != end && *begin == '+') {
            ++begin;
            if (begin != end && (*begin == '-' || *begin == '+'))
                throw std::runtime_error("Invalid attribute number: " + text);
        }
        double value = 0.0;
        const std::from_chars_result parsed = std::from_chars(begin, end, value);
        if (begin == end || parsed.ec != std::errc() || parsed.ptr != end || !std::isfinite(value))
            throw std::runtime_error("Invalid attribute number: " + text);
        return value;
    }

    AttributeValue Value(const Token &token, const AttributeDefinition &definition, bool isDefault) {
        if (definition.type == AttributeType::String) {
            if (!token.quoted) throw std::runtime_error("Attribute STRING requires quoted text.");
            return token.text;
        }
        if (definition.type == AttributeType::Enum && isDefault && token.quoted) {
            for (std::size_t index = 0U; index < definition.enumValues.size(); ++index) {
                if (definition.enumValues[index] == token.text)
                    return static_cast<std::int64_t>(index);
            }
            throw std::runtime_error("Unknown attribute ENUM default label.");
        }
        if (token.quoted) throw std::runtime_error("Numeric attribute requires an unquoted number.");
        if (definition.type == AttributeType::Float) {
            const double value = Number(token.text);
            if (value < definition.minimum || value > definition.maximum)
                throw std::runtime_error("Attribute FLOAT value outside definition range.");
            return value;
        }
        const std::int64_t value = Integer(token.text);
        if (value < definition.integerMinimum || value > definition.integerMaximum)
            throw std::runtime_error("Attribute integer/ENUM value outside definition range.");
        return value;
    }

    void Define(AttributeTokens &tokens, DbcDatabase &database) {
        AttributeDefinition definition;
        const Token first = tokens.Take();
        std::string name = first.text;
        if (!first.quoted) {
            definition.scope = ParseScope(first.text);
            name = tokens.Quoted();
        }
        if (name.empty()) throw std::runtime_error("Empty attribute name.");
        const std::string type = tokens.Word();
        if (type == "INT" || type == "HEX") {
            definition.type = type == "INT" ? AttributeType::Integer : AttributeType::Hex;
            definition.integerMinimum = Integer(tokens.Word());
            definition.integerMaximum = Integer(tokens.Word());
            if (definition.integerMinimum > definition.integerMaximum)
                throw std::runtime_error("Reversed attribute integer range.");
        } else if (type == "FLOAT") {
            definition.type = AttributeType::Float;
            definition.minimum = Number(tokens.Word());
            definition.maximum = Number(tokens.Word());
            if (definition.minimum > definition.maximum)
                throw std::runtime_error("Reversed attribute FLOAT range.");
        } else if (type == "STRING") {
            definition.type = AttributeType::String;
        } else if (type == "ENUM") {
            definition.type = AttributeType::Enum;
            std::set<std::string> labels;
            for (;;) {
                const std::string label = tokens.Quoted();
                if (!labels.insert(label).second)
                    throw std::runtime_error("Duplicate attribute ENUM label.");
                definition.enumValues.push_back(label);
                if (tokens.Empty()) break;
                const Token separator = tokens.Take();
                if (separator.quoted || separator.text != ",") throw std::runtime_error("Expected ENUM comma.");
            }
            definition.integerMaximum = static_cast<std::int64_t>(definition.enumValues.size() - 1U);
        } else {
            throw std::runtime_error("Unsupported attribute definition type: " + type);
        }
        tokens.End();
        if (name == "VFrameFormat" && (definition.scope != AttributeScope::Frame || definition.type != AttributeType::Enum))
            throw std::runtime_error("VFrameFormat requires a BO_ ENUM definition.");
        if (name == "GenMsgCycleTime" && (definition.scope != AttributeScope::Frame ||
                                          (definition.type != AttributeType::Integer && definition.type != AttributeType::Hex)))
            throw std::runtime_error("GenMsgCycleTime requires a BO_ integer definition.");
        if (!database.attributeDefinitions.emplace(name, definition).second)
            throw std::runtime_error("Duplicate attribute definition: " + name);
    }

    AttributeDefinition &FindDefinition(DbcDatabase &database, const std::string &name) {
        const std::map<std::string, AttributeDefinition>::iterator found = database.attributeDefinitions.find(name);
        if (found == database.attributeDefinitions.end())
            throw std::runtime_error("Undefined attribute: " + name);
        return found->second;
    }

    void ParseId(const std::string &text, AttributeAssignment &assignment) {
        const std::int64_t raw = Integer(text);
        if (raw < 0 || raw > std::numeric_limits<std::uint32_t>::max() || (raw & 0x60000000U) != 0)
            throw std::runtime_error("Invalid attribute CAN ID.");
        const std::uint32_t id = static_cast<std::uint32_t>(raw);
        assignment.canId = id & 0x1fffffffU;
        assignment.isExtended = (id & 0x80000000U) != 0U || id > 0x7ffU;
    }

    AttributeMap &Target(DbcDatabase &database, const AttributeAssignment &assignment) {
        if (assignment.scope == AttributeScope::Database) return database.attributes;
        for (FrameInfo &frame: database.frames) {
            if (frame.canId != assignment.canId || frame.isExtended != assignment.isExtended) continue;
            if (assignment.scope == AttributeScope::Frame) return frame.attributes;
            for (SignalInfo &signal: frame.signals) {
                if (signal.name == assignment.targetName) return signal.attributes;
            }
            throw std::runtime_error("Unresolved attribute signal: " + assignment.targetName);
        }
        throw std::runtime_error("Unresolved attribute frame.");
    }

    void ValidateCycleTime(const std::string &name, const AttributeValue &value) {
        if (name != "GenMsgCycleTime") return;
        const std::int64_t milliseconds = std::get<std::int64_t>(value);
        if (milliseconds < 0 || milliseconds > std::numeric_limits<std::uint32_t>::max())
            throw std::runtime_error("GenMsgCycleTime must fit unsigned 32-bit milliseconds.");
    }

    void ApplyDefault(DbcDatabase &database, const std::string &name, const AttributeDefinition &definition) {
        if (!definition.defaultValue) return;
        if (definition.scope == AttributeScope::Database) database.attributes[name] = *definition.defaultValue;
        for (FrameInfo &frame: database.frames) {
            if (definition.scope == AttributeScope::Frame) frame.attributes[name] = *definition.defaultValue;
            if (definition.scope == AttributeScope::Signal) {
                for (SignalInfo &signal: frame.signals) signal.attributes[name] = *definition.defaultValue;
            }
        }
    }
}// namespace

void DbcAttributeHandler::Handle(const std::string &line, DbcParseContext &context) const {
    context.pendingAttributes.push_back({line, context.lineNumber});
}

void DbcParseContext::ResolveAttributes(const std::string &filePath, std::vector<DbcDiagnostic> &diagnostics) {
    std::map<std::string, std::size_t> defaultLines;
    std::vector<std::size_t> assignmentLines;
    // Resolve each phase independently of source ordering.
    const char *keywords[] = {"BA_DEF_", "BA_DEF_DEF_", "BA_"};
    for (int phase = 0; phase < 3; ++phase) {
        for (const PendingAttribute &pending: pendingAttributes) {
            const std::string keyword = pending.statement.substr(0U, pending.statement.find_first_of(" \t"));
            if (keyword != keywords[phase]) continue;
            try {
                AttributeTokens tokens(pending.statement);
                tokens.Word();
                if (phase == 0) {
                    Define(tokens, database);
                    continue;
                }
                const std::string name = tokens.Quoted();
                AttributeDefinition &definition = FindDefinition(database, name);
                if (phase == 1) {
                    if (definition.defaultValue) throw std::runtime_error("Duplicate attribute default: " + name);
                    definition.defaultValue = Value(tokens.Take(), definition, true);
                    ValidateCycleTime(name, *definition.defaultValue);
                    tokens.End();
                    defaultLines[name] = pending.lineNumber;
                    ApplyDefault(database, name, definition);
                    continue;
                }
                AttributeAssignment assignment;
                assignment.name = name;
                Token value = tokens.Take();
                if (!value.quoted && IsScope(value.text)) {
                    assignment.scope = ParseScope(value.text);
                    if (assignment.scope == AttributeScope::Frame || assignment.scope == AttributeScope::Signal)
                        ParseId(tokens.Word(), assignment);
                    if (assignment.scope != AttributeScope::Frame)
                        assignment.targetName = tokens.Word();
                    value = tokens.Take();
                }
                if (assignment.scope != definition.scope) throw std::runtime_error("Attribute assignment scope differs from definition.");
                assignment.value = Value(value, definition, false);
                ValidateCycleTime(name, assignment.value);
                tokens.End();
                // Repeated explicit assignments use the last value, matching comments.
                if (assignment.scope != AttributeScope::Node && assignment.scope != AttributeScope::Environment)
                    Target(database, assignment)[name] = assignment.value;
                database.attributeAssignments.push_back(assignment);
                assignmentLines.push_back(pending.lineNumber);
            } catch (const std::exception &error) {
                throw DbcDiagnosticError(DbcDiagnosticCode::InvalidAttribute, filePath, pending.lineNumber, error.what());
            }
        }
    }
    for (FrameInfo &frame: database.frames) {
        for (const AttributeMap::value_type &attribute: frame.attributes) {
            if (attribute.first != "VFrameFormat" && attribute.first != "GenMsgCycleTime") continue;
            std::size_t line = defaultLines[attribute.first];
            for (std::size_t index = 0U; index < database.attributeAssignments.size(); ++index) {
                const AttributeAssignment &assignment = database.attributeAssignments[index];
                if (assignment.name == attribute.first && assignment.scope == AttributeScope::Frame &&
                    assignment.canId == frame.canId && assignment.isExtended == frame.isExtended)
                    line = assignmentLines[index];
            }
            const std::int64_t value = std::get<std::int64_t>(attribute.second);
            if (attribute.first == "GenMsgCycleTime") {
                frame.cycleTimeMs = static_cast<std::uint32_t>(value);
                continue;
            }
            frame.frameFormat = database.attributeDefinitions.at(attribute.first).enumValues[static_cast<std::size_t>(value)];
            const std::string &format = *frame.frameFormat;
            std::string warning;
            if (format != "StandardCAN" && format != "ExtendedCAN")
                warning = "Unsupported VFrameFormat '" + format + "' is preserved; decoding may be incomplete.";
            else if ((format == "ExtendedCAN") != frame.isExtended)
                warning = "VFrameFormat '" + format + "' conflicts with the BO_ CAN ID; ID interpretation is unchanged.";
            if (!warning.empty())
                diagnostics.push_back({DbcDiagnosticSeverity::Warning, DbcDiagnosticCode::UnsupportedAttribute, filePath, line, warning});
        }
    }
}