#ifndef SIM_HAL_H
#define SIM_HAL_H

#include "hal.h"

#include <cstdio>
#include <cstring>
#include <functional>
#include <map>
#include <queue>
#include <string>
#include <vector>

/*
 * Simulated HAL for system tests.
 *
 * Unlike MockHal (which verifies call expectations), SimHal actually
 * maintains state: pin values, a virtual clock, serial output capture,
 * and pluggable I2C device simulators.
 *
 * This lets you write system tests that exercise full application logic
 * against simulated hardware:
 *
 *     SimHal sim;
 *     BlinkApp app(&sim);
 *     app.begin();
 *
 *     sim.setPin(2, LOW);          // simulate button press
 *     sim.advanceMillis(600);      // advance clock
 *     app.update();
 *
 *     EXPECT_EQ(sim.getPin(13), HIGH);  // check LED state
 */

// --------------------------------------------------------------------
// I2C device simulator interface
// --------------------------------------------------------------------
class I2cDeviceSim {
public:
    virtual ~I2cDeviceSim() = default;

    // Called when master writes bytes to this device
    virtual void onReceive(const uint8_t* data, size_t len) = 0;

    // Called when master requests bytes; fill response buffer
    virtual size_t onRequest(uint8_t* buf, size_t max_len) = 0;
};

// --------------------------------------------------------------------
// Simulated HAL
// --------------------------------------------------------------------
class SimHal : public Hal {
public:
    static const int NUM_PINS = 20;  // D0-D13 + A0-A5

    SimHal() : clock_ms_(0), clock_us_(0) {
        memset(pin_modes_, 0, sizeof(pin_modes_));
        memset(pin_values_, 0, sizeof(pin_values_));
    }

    // -- GPIO ---------------------------------------------------------------
    void pinMode(uint8_t pin, uint8_t mode) override {
        if (pin < NUM_PINS) {
            pin_modes_[pin] = mode;
            // INPUT_PULLUP defaults to HIGH
            if (mode == INPUT_PULLUP) {
                pin_values_[pin] = HIGH;
            }
        }
    }

    void digitalWrite(uint8_t pin, uint8_t value) override {
        if (pin < NUM_PINS) {
            pin_values_[pin] = value;
            gpio_log_.push_back({clock_ms_, pin, value});
        }
    }

    uint8_t digitalRead(uint8_t pin) override {
        if (pin < NUM_PINS) return pin_values_[pin];
        return LOW;
    }

    int analogRead(uint8_t pin) override {
        if (pin < NUM_PINS) return analog_values_[pin];
        return 0;
    }

    void analogWrite(uint8_t pin, int value) override {
        if (pin < NUM_PINS) pin_values_[pin] = (value > 0) ? HIGH : LOW;
    }

    // -- Timing -------------------------------------------------------------
    unsigned long millis() override { return clock_ms_; }
    unsigned long micros() override { return clock_us_; }
    void delay(unsigned long ms) override { advanceMillis(ms); }
    void delayMicroseconds(unsigned long us) override { clock_us_ += us; }

    // -- Serial -------------------------------------------------------------
    void serialBegin(unsigned long baud) override { (void)baud; }
    void serialPrint(const char* msg) override {
        serial_output_ += msg;
    }
    void serialPrintln(const char* msg) override {
        serial_output_ += msg;
        serial_output_ += "\n";
    }
    int serialAvailable() override {
        return static_cast<int>(serial_input_.size());
    }
    int serialRead() override {
        if (serial_input_.empty()) return -1;
        int c = serial_input_.front();
        serial_input_.erase(serial_input_.begin());
        return c;
    }

    // -- I2C ----------------------------------------------------------------
    void i2cBegin() override {}

    void i2cBeginTransmission(uint8_t addr) override {
        i2c_addr_ = addr;
        i2c_tx_buf_.clear();
    }

    size_t i2cWrite(uint8_t data) override {
        i2c_tx_buf_.push_back(data);
        return 1;
    }

    uint8_t i2cEndTransmission() override {
        auto it = i2c_devices_.find(i2c_addr_);
        if (it == i2c_devices_.end()) return 2;  // NACK on address
        it->second->onReceive(i2c_tx_buf_.data(), i2c_tx_buf_.size());
        return 0;  // success
    }

    uint8_t i2cRequestFrom(uint8_t addr, uint8_t count) override {
        i2c_rx_buf_.clear();
        auto it = i2c_devices_.find(addr);
        if (it == i2c_devices_.end()) return 0;
        uint8_t tmp[256];
        size_t n = it->second->onRequest(tmp, count);
        for (size_t i = 0; i < n; ++i) {
            i2c_rx_buf_.push_back(tmp[i]);
        }
        return static_cast<uint8_t>(n);
    }

    int i2cAvailable() override {
        return static_cast<int>(i2c_rx_buf_.size());
    }

    int i2cRead() override {
        if (i2c_rx_buf_.empty()) return -1;
        int val = i2c_rx_buf_.front();
        i2c_rx_buf_.erase(i2c_rx_buf_.begin());
        return val;
    }

    // ====================================================================
    // Test control API (not part of Hal interface)
    // ====================================================================

    // -- Clock control ------------------------------------------------------
    void advanceMillis(unsigned long ms) {
        clock_ms_ += ms;
        clock_us_ += ms * 1000;
    }

    void setMillis(unsigned long ms) {
        clock_ms_ = ms;
        clock_us_ = ms * 1000;
    }

    // -- GPIO control -------------------------------------------------------
    void setPin(uint8_t pin, uint8_t value) {
        if (pin < NUM_PINS) pin_values_[pin] = value;
    }

    uint8_t getPin(uint8_t pin) const {
        if (pin < NUM_PINS) return pin_values_[pin];
        return LOW;
    }

    uint8_t getPinMode(uint8_t pin) const {
        if (pin < NUM_PINS) return pin_modes_[pin];
        return 0;
    }

    void setAnalog(uint8_t pin, int value) {
        analog_values_[pin] = value;
    }

    // -- GPIO history -------------------------------------------------------
    struct GpioEvent {
        unsigned long timestamp_ms;
        uint8_t pin;
        uint8_t value;
    };

    const std::vector<GpioEvent>& gpioLog() const { return gpio_log_; }

    void clearGpioLog() { gpio_log_.clear(); }

    // Count how many times a pin was set to a specific value
    int countWrites(uint8_t pin, uint8_t value) const {
        int count = 0;
        for (const auto& e : gpio_log_) {
            if (e.pin == pin && e.value == value) ++count;
        }
        return count;
    }

    // -- Serial control -----------------------------------------------------
    const std::string& serialOutput() const { return serial_output_; }
    void clearSerialOutput() { serial_output_.clear(); }

    void injectSerialInput(const std::string& data) {
        for (char c : data) {
            serial_input_.push_back(static_cast<uint8_t>(c));
        }
    }

    // -- I2C device registration --------------------------------------------
    void attachI2cDevice(uint8_t addr, I2cDeviceSim* device) {
        i2c_devices_[addr] = device;
    }

    void detachI2cDevice(uint8_t addr) {
        i2c_devices_.erase(addr);
    }

private:
    // GPIO
    uint8_t pin_modes_[NUM_PINS];
    uint8_t pin_values_[NUM_PINS];
    std::map<uint8_t, int> analog_values_;
    std::vector<GpioEvent> gpio_log_;

    // Timing
    unsigned long clock_ms_;
    unsigned long clock_us_;

    // Serial
    std::string serial_output_;
    std::vector<uint8_t> serial_input_;

    // I2C
    uint8_t i2c_addr_ = 0;
    std::vector<uint8_t> i2c_tx_buf_;
    std::vector<uint8_t> i2c_rx_buf_;
    std::map<uint8_t, I2cDeviceSim*> i2c_devices_;
};

#endif // SIM_HAL_H