#include "software_logic_executor.h"

#include <map>
#include <type_traits>

namespace {

LogicScanResult success()
{
    return {true, LogicScanError::None, {}, {}, {}, {}};
}

LogicScanResult failure(
    LogicScanError error,
    const std::string &message,
    const std::string &logic_id = {},
    const std::string &rung_id = {},
    const std::string &node_id = {})
{
    return {false, error, message, logic_id, rung_id, node_id};
}

bool compareWord(
    std::int16_t actual,
    ComparisonOperator comparison,
    std::int16_t expected)
{
    switch (comparison)
    {
    case ComparisonOperator::Equal:
    {
        return actual == expected;
    }
    case ComparisonOperator::NotEqual:
    {
        return actual != expected;
    }
    case ComparisonOperator::LessThan:
    {
        return actual < expected;
    }
    case ComparisonOperator::LessThanOrEqual:
    {
        return actual <= expected;
    }
    case ComparisonOperator::GreaterThan:
    {
        return actual > expected;
    }
    case ComparisonOperator::GreaterThanOrEqual:
    {
        return actual >= expected;
    }
    default:
    {
        return false;
    }
    }
}

} // namespace

LogicScanResult SoftwareLogicExecutor::validate(
    const std::vector<ControlLogic> &logics) const
{
    std::map<int, CoilMode> output_modes;
    for (const ControlLogic &logic : logics)
    {
        std::string validation_error;
        if (!logic.validateForRunning(&validation_error))
        {
            return failure(
                LogicScanError::InvalidLogic,
                validation_error,
                logic.id);
        }
        if (!logic.enabled)
        {
            continue;
        }
        for (const LadderRung &rung : logic.rungs)
        {
            if (!rung.output.has_value())
            {
                continue;
            }
            const auto *output = std::get_if<CoilNodeConfig>(&rung.output->config);
            if (output == nullptr)
            {
                return failure(
                    LogicScanError::InvalidLogic,
                    "ladder output is not a coil",
                    logic.id,
                    rung.id,
                    rung.output->id);
            }
            const auto existing = output_modes.find(output->address.index());
            if (existing != output_modes.end() && existing->second != output->mode)
            {
                return failure(
                    LogicScanError::ConflictingOutput,
                    "mixed coil modes target " + output->address.toString(),
                    logic.id,
                    rung.id,
                    rung.output->id);
            }
            output_modes[output->address.index()] = output->mode;
        }
    }
    return success();
}

LogicScanResult SoftwareLogicExecutor::executeScan(
    const std::vector<ControlLogic> &logics,
    RegisterRepository &repository) const
{
    const LogicScanResult validation = validate(logics);
    if (!validation.succeeded)
    {
        return validation;
    }

    for (const ControlLogic &logic : logics)
    {
        if (!logic.enabled)
        {
            continue;
        }
        for (const LadderRung &rung : logic.rungs)
        {
            if (rung.stages.empty() && !rung.output.has_value())
            {
                continue;
            }

            bool rung_value = true;
            for (const LadderStage &stage : rung.stages)
            {
                bool stage_value = false;
                for (const LogicNode &node : stage.branches)
                {
                    bool condition_value = false;
                    LogicScanResult result = evaluateCondition(
                        node, repository, &condition_value);
                    if (!result.succeeded)
                    {
                        result.logicId = logic.id;
                        result.rungId = rung.id;
                        return result;
                    }
                    stage_value = stage_value || condition_value;
                }
                rung_value = rung_value && stage_value;
            }

            LogicScanResult result = writeOutput(
                *rung.output, rung_value, repository);
            if (!result.succeeded)
            {
                result.logicId = logic.id;
                result.rungId = rung.id;
                return result;
            }
        }
    }
    return success();
}

LogicScanResult SoftwareLogicExecutor::evaluateCondition(
    const LogicNode &node,
    RegisterRepository &repository,
    bool *value) const
{
    if (value == nullptr)
    {
        return failure(
            LogicScanError::InvalidLogic,
            "condition result target is missing",
            {},
            {},
            node.id);
    }

    return std::visit(
        [&repository, value, &node](const auto &config) -> LogicScanResult
        {
            using Config = std::decay_t<decltype(config)>;
            if constexpr (std::is_same_v<Config, ContactNodeConfig>)
            {
                const BitReadResult read = repository.readBit(config.address);
                if (!read.succeeded)
                {
                    return failure(
                        LogicScanError::RegisterReadFailed,
                        "failed to read " + config.address.toString(),
                        {},
                        {},
                        node.id);
                }
                *value = config.mode == ContactMode::NormallyOpen
                    ? read.value : !read.value;
                return success();
            }
            else if constexpr (std::is_same_v<Config, CompareNodeConfig>)
            {
                const WordReadResult read = repository.readWord(config.address);
                if (!read.succeeded)
                {
                    return failure(
                        LogicScanError::RegisterReadFailed,
                        "failed to read " + config.address.toString(),
                        {},
                        {},
                        node.id);
                }
                *value = compareWord(read.value, config.comparison, config.value);
                return success();
            }
            else
            {
                return failure(
                    LogicScanError::InvalidLogic,
                    "condition node contains an output coil",
                    {},
                    {},
                    node.id);
            }
        },
        node.config);
}

LogicScanResult SoftwareLogicExecutor::writeOutput(
    const LogicNode &node,
    bool rung_value,
    RegisterRepository &repository) const
{
    const auto *config = std::get_if<CoilNodeConfig>(&node.config);
    if (config == nullptr)
    {
        return failure(
            LogicScanError::InvalidLogic,
            "ladder output is not a coil",
            {},
            {},
            node.id);
    }

    bool should_write = true;
    bool output_value = rung_value;
    switch (config->mode)
    {
    case CoilMode::Normal:
    {
        break;
    }
    case CoilMode::Set:
    {
        should_write = rung_value;
        output_value = true;
        break;
    }
    case CoilMode::Reset:
    {
        should_write = rung_value;
        output_value = false;
        break;
    }
    default:
    {
        return failure(
            LogicScanError::InvalidLogic,
            "unsupported coil mode",
            {},
            {},
            node.id);
    }
    }

    if (!should_write)
    {
        return success();
    }
    const RegisterWriteResult write = repository.writeBit(
        config->address, output_value);
    if (!write.succeeded)
    {
        return failure(
            LogicScanError::RegisterWriteFailed,
            "failed to write " + config->address.toString(),
            {},
            {},
            node.id);
    }
    return success();
}