/**
 * @file device.cpp
 * @brief Contains code for device-related UI elements and logic.
 *
 * Copyright (C) 2021 Clyne Sullivan
 *
 * Distributed under the GNU GPL v3 or later. You should have received a copy of
 * the GNU General Public License along with this program.
 * If not, see <https://www.gnu.org/licenses/>.
 */

#include "stmdsp.hpp"

#include "circular.hpp"
#include "imgui.h"
#include "wav.hpp"

#include <array>
#include <cctype>
#include <charconv>
#include <cmath>
#include <deque>
#include <fstream>
#include <functional>
#include <iostream>
#include <memory>
#include <mutex>
#include <string>
#include <string_view>
#include <thread>
#include <vector>

extern void log(const std::string& str);
extern std::vector<stmdsp::dacsample_t> deviceGenLoadFormulaEval(const std::string&);
extern std::ifstream compileOpenBinaryFile();
extern void deviceRenderDisconnect();

std::shared_ptr<stmdsp::device> m_device;

static std::timed_mutex mutexDrawSamples;
static std::timed_mutex mutexDeviceLoad;
static std::ofstream logSamplesFile;
static wav::clip wavOutput;
static std::deque<stmdsp::dacsample_t> drawSamplesQueue;
static std::deque<stmdsp::dacsample_t> drawSamplesInputQueue;
static bool drawSamplesInput = false;
static unsigned int drawSamplesBufferSize = 1;

bool deviceConnect();

void deviceSetInputDrawing(bool enabled)
{
    drawSamplesInput = enabled;
    if (enabled) {
        drawSamplesQueue.clear();
        drawSamplesInputQueue.clear();
    }
}

static void measureCodeTask(std::shared_ptr<stmdsp::device> device)
{
    std::this_thread::sleep_for(std::chrono::seconds(1));

    if (device) {
        const auto cycles = device->measurement_read();
        log(std::string("Execution time: ") + std::to_string(cycles) + " cycles.");
    }
}

static std::vector<stmdsp::dacsample_t> tryReceiveChunk(
    std::shared_ptr<stmdsp::device> device,
    auto readFunc)
{
    for (int tries = 0; tries < 100; ++tries) {
        if (!device->is_running())
            break;

        const auto chunk = readFunc(device.get());
        if (!chunk.empty())
            return chunk;
        else
            std::this_thread::sleep_for(std::chrono::microseconds(20));
    }

    return {};
}

static std::chrono::duration<double> getBufferPeriod(
    std::shared_ptr<stmdsp::device> device,
    const double factor = 0.975)
{
    if (device) {
        const double bufferSize = device->get_buffer_size();
        const double sampleRate = device->get_sample_rate();
        return std::chrono::duration<double>(bufferSize / sampleRate * factor);
    } else {
        return {};
    }
}

static void drawSamplesTask(std::shared_ptr<stmdsp::device> device)
{
    if (!device)
        return;

    // This is the amount of time to wait between device reads.
    const auto bufferTime = getBufferPeriod(device, 1);

    // Adds the given chunk of samples to the given queue.
    const auto addToQueue = [](auto& queue, const auto& chunk) {
        std::scoped_lock lock (mutexDrawSamples);
        std::copy(chunk.cbegin(), chunk.cend(), std::back_inserter(queue));
    };

    std::unique_lock<std::timed_mutex> lockDevice (mutexDeviceLoad, std::defer_lock);

    while (device && device->is_running()) {
        const auto next = std::chrono::high_resolution_clock::now() + bufferTime;

        if (lockDevice.try_lock_until(next)) {
            std::vector<stmdsp::dacsample_t> chunk, chunk2;

            chunk = tryReceiveChunk(device,
                std::mem_fn(&stmdsp::device::continuous_read));
            if (drawSamplesInput) {
                chunk2 = tryReceiveChunk(device,
                    std::mem_fn(&stmdsp::device::continuous_read_input));
            }

            lockDevice.unlock();

            addToQueue(drawSamplesQueue, chunk);
            if (drawSamplesInput)
                addToQueue(drawSamplesInputQueue, chunk2);

            if (logSamplesFile.is_open()) {
                for (const auto& s : chunk)
                    logSamplesFile << s << '\n';
            }
        } else {
            // Device must be busy, back off for a bit.
            std::this_thread::sleep_for(std::chrono::milliseconds(50));
        }

        std::this_thread::sleep_until(next);
    }
}

static void feedSigGenTask(std::shared_ptr<stmdsp::device> device)
{
    if (!device)
        return;

    const auto delay = getBufferPeriod(device);
    const auto uploadDelay = getBufferPeriod(device, 0.001);

    std::vector<stmdsp::dacsample_t> wavBuf (device->get_buffer_size() * 2, 2048);

    {
        std::scoped_lock lock (mutexDeviceLoad);
        device->siggen_upload(wavBuf.data(), wavBuf.size());
        device->siggen_start();
        std::this_thread::sleep_for(std::chrono::milliseconds(1));
    }

    wavBuf.resize(wavBuf.size() / 2);
    std::vector<int16_t> wavIntBuf (wavBuf.size());

    while (device->is_siggening()) {
        const auto next = std::chrono::high_resolution_clock::now() + delay;

        wavOutput.next(wavIntBuf.data(), wavIntBuf.size());
        std::transform(wavIntBuf.cbegin(), wavIntBuf.cend(),
            wavBuf.begin(),
            [](auto i) { return static_cast<stmdsp::dacsample_t>(i / 16 + 2048); });

        {
            std::scoped_lock lock (mutexDeviceLoad);
            while (!device->siggen_upload(wavBuf.data(), wavBuf.size()))
                std::this_thread::sleep_for(uploadDelay);
        }

        std::this_thread::sleep_until(next);
    }
}

static void statusTask(std::shared_ptr<stmdsp::device> device)
{
    if (!device)
        return;

    while (device->connected()) {
        mutexDeviceLoad.lock();
        const auto [status, error] = device->get_status();
        mutexDeviceLoad.unlock();

        if (error != stmdsp::Error::None) {
            switch (error) {
            case stmdsp::Error::NotIdle:
                log("Error: Device already running...");
                break;
            case stmdsp::Error::ConversionAborted:
                log("Error: Algorithm unloaded, a fault occurred!");
                break;
            case stmdsp::Error::GUIDisconnect:
                // Do GUI events for disconnect if device was lost.
                deviceConnect();
                deviceRenderDisconnect();
                return;
                break;
            default:
                log("Error: Device had an issue...");
                break;
            }
        }

        std::this_thread::sleep_for(std::chrono::seconds(1));
    }
}

void deviceLoadAudioFile(const std::string& file)
{
    wavOutput = wav::clip(file);
    if (wavOutput.valid())
        log("Audio file loaded.");
    else
        log("Error: Bad WAV audio file.");
}

void deviceLoadLogFile(const std::string& file)
{
    logSamplesFile = std::ofstream(file);
    if (logSamplesFile.is_open())
        log("Log file ready.");
    else
        log("Error: Could not open log file.");
}

bool deviceGenStartToggle()
{
    if (m_device) {
        const bool running = m_device->is_siggening();

        if (!running) {
            if (wavOutput.valid()) {
                std::thread(feedSigGenTask, m_device).detach();
            } else {
                std::scoped_lock dlock (mutexDeviceLoad);
                m_device->siggen_start();
            }
            log("Generator started.");
        } else {
            {
                std::scoped_lock dlock (mutexDeviceLoad);
                m_device->siggen_stop();
            }
            log("Generator stopped.");
        }

        return !running;
    }

    return false;
}

void deviceUpdateDrawBufferSize(double timeframe)
{
    drawSamplesBufferSize = std::round(
        m_device->get_sample_rate() * timeframe);
}

void deviceSetSampleRate(unsigned int rate)
{
    do {
        m_device->set_sample_rate(rate);
        std::this_thread::sleep_for(std::chrono::milliseconds(10));
    } while (m_device->get_sample_rate() != rate);
}

bool deviceConnect()
{
    static std::thread statusThread;

    if (!m_device) {
        stmdsp::scanner scanner;
        if (const auto devices = scanner.scan(); !devices.empty()) {
            try {
                m_device.reset(new stmdsp::device(devices.front()));
            } catch (...) {
                log("Failed to connect (check permissions?).");
                m_device.reset();
            }

            if (m_device) {
                if (m_device->connected()) {
                    log("Connected!");
                    statusThread = std::thread(statusTask, m_device);
                    statusThread.detach();
                    return true;
                } else {
                    m_device.reset();
                    log("Failed to connect.");
                }
            }
        } else {
            log("No devices found.");
        }
    } else {
        m_device->disconnect();
        if (statusThread.joinable())
            statusThread.join();
        m_device.reset();
        log("Disconnected.");
    }

    return false;
}

void deviceStart(bool fetchSamples)
{
    if (!m_device) {
        log("No device connected.");
        return;
    }

    if (m_device->is_running()) {
        {
            std::scoped_lock lock (mutexDrawSamples, mutexDeviceLoad);
            std::this_thread::sleep_for(std::chrono::microseconds(150));
            m_device->continuous_stop();
        }
        if (logSamplesFile.is_open()) {
            logSamplesFile.close();
            log("Log file saved and closed.");
        }
        log("Ready.");
    } else {
        m_device->continuous_start();
        if (fetchSamples || wavOutput.valid())
            std::thread(drawSamplesTask, m_device).detach();

        log("Running.");
    }
}

void deviceStartMeasurement()
{
    if (m_device && m_device->is_running()) {
        m_device->measurement_start();
        std::thread(measureCodeTask, m_device).detach();
    }
}

void deviceAlgorithmUpload()
{
    if (!m_device) {
        log("No device connected.");
    } else if (m_device->is_running()) {
        log("Cannot upload algorithm while running.");
    } else if (auto algo = compileOpenBinaryFile(); algo.is_open()) {
        std::ostringstream sstr;
        sstr << algo.rdbuf();
        auto str = sstr.str();

        m_device->upload_filter(reinterpret_cast<unsigned char *>(&str[0]), str.size());
        log("Algorithm uploaded.");
    } else {
        log("Algorithm must be compiled first.");
    }
}

void deviceAlgorithmUnload()
{
    if (!m_device) {
        log("No device connected.");
    } else if (m_device->is_running()) {
        log("Cannot unload algorithm while running.");
    } else {
        m_device->unload_filter();
        log("Algorithm unloaded.");
    }
}

void deviceGenLoadList(const std::string_view list)
{
    std::vector<stmdsp::dacsample_t> samples;

    auto it = list.cbegin();
    while (it != list.cend()) {
        const auto itend = std::find_if(it, list.cend(),
            [](char c) { return !isdigit(c); });

        unsigned long n;
        const auto ec = std::from_chars(it, itend, n).ec;
        if (ec != std::errc()) {
            log("Error: Bad data in sample list.");
            break;
        } else if (n > 4095) {
            log("Error: Sample data value larger than max of 4095.");
            break;
        } else {
            samples.push_back(n & 4095);
            if (samples.size() >= stmdsp::SAMPLES_MAX * 2) {
                log("Error: Too many samples for signal generator.");
                break;
            }
        }

        it = std::find_if(itend, list.cend(), isdigit);
    }

    if (it == list.cend()) {
        // DAC buffer must be of even size
        if (samples.size() % 2 != 0)
            samples.push_back(samples.back());

        m_device->siggen_upload(samples.data(), samples.size());
        log("Generator ready.");
    }
}

void deviceGenLoadFormula(const std::string& formula)
{
    auto samples = deviceGenLoadFormulaEval(formula);

    if (!samples.empty()) {
        m_device->siggen_upload(samples.data(), samples.size());
        log("Generator ready.");
    } else {
        log("Error: Bad formula.");
    }
}

std::size_t pullFromQueue(
    std::deque<stmdsp::dacsample_t>& queue,
    CircularBuffer<std::vector, stmdsp::dacsample_t>& circ)
{
    // We know how big the circular buffer should be to hold enough samples to
    // fill the current draw samples view.
    // If the given buffer does not match this size, notify the caller.
    // TODO this could be done better... drawSamplesBufferSize should be a GUI-
    // only thing.
    if (circ.size() != drawSamplesBufferSize)
        return drawSamplesBufferSize;

    std::scoped_lock lock (mutexDrawSamples);

    // The render code will draw all of the new samples we add to the buffer.
    // So, we must provide a certain amount of samples at a time to make the
    // render appear smooth.
    // The 1.025 factor keeps us on top of the stream; don't want to fall
    // behind.
    const double FPS = ImGui::GetIO().Framerate;
    const auto desiredCount = m_device->get_sample_rate() / FPS;

    // Transfer from the queue to the render buffer.
    auto count = std::min(queue.size(), static_cast<std::size_t>(desiredCount));
    while (count--) {
        circ.put(queue.front());
        queue.pop_front();
    }

    return 0;
}

/**
 * Pulls a render frame's worth of samples from the draw samples queue, adding
 * the samples to the given buffer.
 */
std::size_t pullFromDrawQueue(
    CircularBuffer<std::vector, stmdsp::dacsample_t>& circ)
{
    return pullFromQueue(drawSamplesQueue, circ);
}

std::size_t pullFromInputDrawQueue(
    CircularBuffer<std::vector, stmdsp::dacsample_t>& circ)
{
    return pullFromQueue(drawSamplesInputQueue, circ);
}