#include <gtest/gtest.h>

#include "hal.h"
#include "sim_hal.h"

// ============================================================================
// Example: I2C Temperature Sensor Simulator
//
// Demonstrates how to mock an I2C device. This simulates a simple
// temperature sensor at address 0x48 (like a TMP102 or LM75).
//
// Protocol (simplified):
//   Write register pointer (1 byte), then read 2 bytes back.
//   Register 0x00 = temperature (MSB:LSB, 12-bit, 0.0625 deg/LSB)
//   Register 0x01 = config register
// ============================================================================

class TempSensorSim : public I2cDeviceSim {
public:
    static const uint8_t ADDR = 0x48;
    static const uint8_t REG_TEMP   = 0x00;
    static const uint8_t REG_CONFIG = 0x01;

    TempSensorSim() : reg_pointer_(0), temp_raw_(0) {}

    // Set temperature in degrees C (converted to 12-bit raw)
    void setTemperature(float deg_c) {
        temp_raw_ = static_cast<int16_t>(deg_c / 0.0625f);
    }

    // I2cDeviceSim interface
    void onReceive(const uint8_t* data, size_t len) override {
        if (len >= 1) {
            reg_pointer_ = data[0];
        }
    }

    size_t onRequest(uint8_t* buf, size_t max_len) override {
        if (max_len < 2) return 0;

        if (reg_pointer_ == REG_TEMP) {
            // 12-bit left-aligned in 16 bits
            int16_t raw = temp_raw_ << 4;
            buf[0] = static_cast<uint8_t>((raw >> 8) & 0xFF);
            buf[1] = static_cast<uint8_t>(raw & 0xFF);
            return 2;
        }
        if (reg_pointer_ == REG_CONFIG) {
            buf[0] = 0x60;  // default config
            buf[1] = 0xA0;
            return 2;
        }
        return 0;
    }

private:
    uint8_t reg_pointer_;
    int16_t temp_raw_;
};

// -----------------------------------------------------------------------
// Helper: read temperature the way real Arduino code would
// -----------------------------------------------------------------------
static float readTemperature(Hal* hal, uint8_t addr) {
    // Set register pointer to 0x00 (temperature)
    hal->i2cBeginTransmission(addr);
    hal->i2cWrite(TempSensorSim::REG_TEMP);
    hal->i2cEndTransmission();

    // Read 2 bytes
    uint8_t count = hal->i2cRequestFrom(addr, 2);
    if (count < 2) return -999.0f;

    uint8_t msb = static_cast<uint8_t>(hal->i2cRead());
    uint8_t lsb = static_cast<uint8_t>(hal->i2cRead());

    // Convert 12-bit left-aligned to temperature
    int16_t raw = (static_cast<int16_t>(msb) << 8) | lsb;
    raw >>= 4;  // right-align the 12 bits
    return raw * 0.0625f;
}

// ============================================================================
// Tests
// ============================================================================

class I2cTempSensorTest : public ::testing::Test {
protected:
    void SetUp() override {
        sensor_.setTemperature(25.0f);
        sim_.attachI2cDevice(TempSensorSim::ADDR, &sensor_);
        sim_.i2cBegin();
    }

    SimHal sim_;
    TempSensorSim sensor_;
};

TEST_F(I2cTempSensorTest, ReadsRoomTemperature) {
    sensor_.setTemperature(25.0f);
    float temp = readTemperature(&sim_, TempSensorSim::ADDR);
    EXPECT_NEAR(temp, 25.0f, 0.1f);
}

TEST_F(I2cTempSensorTest, ReadsFreezing) {
    sensor_.setTemperature(0.0f);
    float temp = readTemperature(&sim_, TempSensorSim::ADDR);
    EXPECT_NEAR(temp, 0.0f, 0.1f);
}

TEST_F(I2cTempSensorTest, ReadsNegativeTemperature) {
    sensor_.setTemperature(-10.5f);
    float temp = readTemperature(&sim_, TempSensorSim::ADDR);
    EXPECT_NEAR(temp, -10.5f, 0.1f);
}

TEST_F(I2cTempSensorTest, ReadsHighTemperature) {
    sensor_.setTemperature(85.0f);
    float temp = readTemperature(&sim_, TempSensorSim::ADDR);
    EXPECT_NEAR(temp, 85.0f, 0.1f);
}

TEST_F(I2cTempSensorTest, UnregisteredDeviceReturnsNack) {
    // Try to talk to a device that does not exist
    sim_.i2cBeginTransmission(0x50);
    sim_.i2cWrite(0x00);
    uint8_t result = sim_.i2cEndTransmission();
    EXPECT_NE(result, 0);  // non-zero = error
}

TEST_F(I2cTempSensorTest, TemperatureUpdatesLive) {
    sensor_.setTemperature(20.0f);
    float t1 = readTemperature(&sim_, TempSensorSim::ADDR);

    sensor_.setTemperature(30.0f);
    float t2 = readTemperature(&sim_, TempSensorSim::ADDR);

    EXPECT_NEAR(t1, 20.0f, 0.1f);
    EXPECT_NEAR(t2, 30.0f, 0.1f);
}