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#include "n900lightsensor.h"
#include <QFile>
#include <QDebug>
#include <time.h>

const char *n900lightsensor::id("n900.ambientlight");
const char *n900lightsensor::filename("/sys/class/i2c-adapter/i2c-2/2-0029/lux");

n900lightsensor::n900lightsensor(QSensor *sensor)
    : n900filebasedsensor(sensor)
{
    setReading<QAmbientLightReading>(&m_reading);
    // Sensor takes 12-400ms to complete one reading and is triggered by
    // a read of the /sys file (no interrupt/timing loop/etc. is used).
    // Since no continuous operation is possible, don't set a data rate.
    addDataRate(2, 2); // Close enough to 2 Hz
    sensor->setDataRate(2);
    setDescription(QLatin1String("tsl2563"));
}

void n900lightsensor::start()
{
    if (!QFile::exists(QLatin1String(filename)))
        goto error;

    n900filebasedsensor::start();
    return;

error:
    sensorStopped();
}

struct lux_limit {
    int min;
    int max;
};

// Defines the min and max lux values that a given level has.
// These are used to add histeresis to the sensor.
// If the previous level is below a level, the lux must be at or above the minimum.
// If the previous level is above a level, the lux muyt be at or below the maximum.
static lux_limit limits[] = {
    { 0,    0    }, // Undefined (not used)
    { 0,    5    }, // Dark
    { 10,   50   }, // Twilight
    { 100,  200  }, // Light
    { 500,  2000 }, // Bright
    { 5000, 0    }  // Sunny
};

#if 0
// Used for debugging
static QString light_level(int level)
{
    switch (level) {
    case 1:
        return QLatin1String("Dark");
    case 2:
        return QLatin1String("Twilight");
    case 3:
        return QLatin1String("Light");
    case 4:
        return QLatin1String("Bright");
    case 5:
        return QLatin1String("Sunny");
    default:
        return QLatin1String("Undefined");
    }
}
#endif

void n900lightsensor::poll()
{
    FILE *fd = fopen(filename, "r");
    if (!fd) return;
    int lux;
    int rs = fscanf(fd, "%i", &lux);
    fclose(fd);
    if (rs != 1) return;

    // It's unweildly dealing with these constants so make some
    // local aliases that are shorter. This makes the code below
    // much easier to read.
    enum {
        Undefined = QAmbientLightReading::Undefined,
        Dark = QAmbientLightReading::Dark,
        Twilight = QAmbientLightReading::Twilight,
        Light = QAmbientLightReading::Light,
        Bright = QAmbientLightReading::Bright,
        Sunny = QAmbientLightReading::Sunny
    };

    int lightLevel = m_reading.lightLevel();
    // Check for change direction to allow for histeresis
    if      (lightLevel < Sunny    && lux >= limits[Sunny   ].min) lightLevel = Sunny;
    else if (lightLevel < Bright   && lux >= limits[Bright  ].min) lightLevel = Bright;
    else if (lightLevel < Light    && lux >= limits[Light   ].min) lightLevel = Light;
    else if (lightLevel < Twilight && lux >= limits[Twilight].min) lightLevel = Twilight;
    else if (lightLevel < Dark     && lux >= limits[Dark    ].min) lightLevel = Dark;
    else if (lightLevel > Dark     && lux <= limits[Dark    ].max) lightLevel = Dark;
    else if (lightLevel > Twilight && lux <= limits[Twilight].max) lightLevel = Twilight;
    else if (lightLevel > Light    && lux <= limits[Light   ].max) lightLevel = Light;
    else if (lightLevel > Bright   && lux <= limits[Bright  ].max) lightLevel = Bright;

    //qDebug() << "lightLevel" << light_level(lightLevel) << "lux" << lux;

    if (static_cast<int>(m_reading.lightLevel()) != lightLevel) {
        m_reading.setTimestamp(clock());
        m_reading.setLightLevel(static_cast<QAmbientLightReading::LightLevel>(lightLevel));

        newReadingAvailable();
    }
}