// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

use std::path::Path;
use std::{fs, io};

use anyhow::{format_err, Context as _, Error};
use async_trait::async_trait;
use byteorder::{ByteOrder, LittleEndian};
use fidl_fuchsia_hardware_input::{
    DeviceMarker as SensorMarker, DeviceProxy as SensorProxy, ReportType,
};
use fuchsia_syslog::fx_log_info;

/// Unique signature for the light sensor
const HID_SENSOR_DESCRIPTOR: [u8; 4] = [5, 32, 9, 65];

#[derive(Debug)]
pub struct AmbientLightInputRpt {
    pub rpt_id: u8,
    pub state: u8,
    pub event: u8,
    pub illuminance: u16,
    pub red: u16,
    pub green: u16,
    pub blue: u16,
}

/// Opens the sensor's device file.
/// Tries all the input devices until the one with the correct signature is found.
async fn open_sensor() -> Result<SensorProxy, Error> {
    let input_devices_directory = "/dev/class/input";
    let path = Path::new(input_devices_directory);
    let entries = fs::read_dir(path)?;
    for entry in entries {
        let entry = entry?;
        let device = open_input_device(entry.path().to_str().expect("Bad path"))?;
        if let Ok(device_descriptor) = device.get_report_desc().await {
            if device_descriptor.len() < 4 {
                return Err(format_err!("Short HID header"));
            }
            let device_header = &device_descriptor[0..4];
            if device_header == HID_SENSOR_DESCRIPTOR {
                return Ok(device);
            }
        }
    }
    Err(io::Error::new(io::ErrorKind::NotFound, "no sensor found").into())
}

/// Reads the sensor's HID record and decodes it.
async fn read_sensor(sensor: &SensorProxy) -> Result<AmbientLightInputRpt, Error> {
    let report = sensor.get_report(ReportType::Input, 1).await?;
    let report = report.1;
    if report.len() < 11 {
        return Err(format_err!("Sensor HID report too short"));
    }
    Ok(AmbientLightInputRpt {
        rpt_id: report[0],
        state: report[1],
        event: report[2],
        illuminance: LittleEndian::read_u16(&report[3..5]),
        red: LittleEndian::read_u16(&report[5..7]),
        blue: LittleEndian::read_u16(&report[7..9]),
        green: LittleEndian::read_u16(&report[9..11]),
    })
}

/// TODO(lingxueluo) Default and temporary report when sensor is not valid(fxbug.dev/42782).
fn default_report() -> Result<AmbientLightInputRpt, Error> {
    Ok(AmbientLightInputRpt {
        rpt_id: 0,
        state: 0,
        event: 0,
        illuminance: 200,
        red: 200,
        green: 200,
        blue: 200,
    })
}

fn open_input_device(path: &str) -> Result<SensorProxy, Error> {
    fx_log_info!("Opening sensor at {:?}", path);
    let (proxy, server) =
        fidl::endpoints::create_proxy::<SensorMarker>().context("Failed to create sensor proxy")?;
    fdio::service_connect(path, server.into_channel())
        .context("Failed to connect built-in service")?;
    Ok(proxy)
}

pub struct Sensor {
    proxy: Option<SensorProxy>,
}

impl Sensor {
    pub async fn new() -> Sensor {
        let proxy = open_sensor().await;
        match proxy {
            Ok(proxy) => return Sensor { proxy: Some(proxy) },
            Err(_e) => {
                println!("No valid sensor found.");
                return Sensor { proxy: None };
            }
        }
    }

    async fn read(&self) -> Result<AmbientLightInputRpt, Error> {
        if self.proxy.is_none() {
            default_report()
        } else {
            read_sensor(self.proxy.as_ref().unwrap()).await
        }
    }
}

#[async_trait]
pub trait SensorControl: Send {
    async fn read(&self) -> Result<AmbientLightInputRpt, Error>;
}

#[async_trait]
impl SensorControl for Sensor {
    async fn read(&self) -> Result<AmbientLightInputRpt, Error> {
        self.read().await
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use fuchsia_async as fasync;

    #[fasync::run_singlethreaded(test)]
    async fn test_open_sensor_error() {
        let sensor = Sensor { proxy: None };
        let ambient_light_input_rpt = sensor.read().await.unwrap();
        assert_eq!(ambient_light_input_rpt.rpt_id, 0);
        assert_eq!(ambient_light_input_rpt.state, 0);
        assert_eq!(ambient_light_input_rpt.event, 0);
        assert_eq!(ambient_light_input_rpt.illuminance, 200);
        assert_eq!(ambient_light_input_rpt.red, 200);
        assert_eq!(ambient_light_input_rpt.green, 200);
        assert_eq!(ambient_light_input_rpt.blue, 200);
    }
}