use crate::app_config::AppConfig;
use crate::devices::device::DeviceRelayID;
use crate::utils::files_utils;
use crate::utils::time_utils::day_number;

const TIME_INTERVAL: usize = 30;

#[derive(thiserror::Error, Debug)]
pub enum RelayStateHistoryError {
    #[error("Given time is out of file bounds!")]
    TimeOutOfFileBound,
}

/// # RelayStateHistory
///
/// This structures handles the manipulation of relay state history files
///
/// These file are binary file optimizing used space.
pub struct RelayStateHistory {
    id: DeviceRelayID,
    day: u64,
    buff: Vec<u8>,
}

impl RelayStateHistory {
    /// Open relay state history file, if it exists, or create an empty one
    pub fn open(id: DeviceRelayID, time: u64) -> anyhow::Result<Self> {
        let day = day_number(time);
        let path = AppConfig::get().relay_runtime_file_path(id, day);

        if path.exists() {
            Ok(Self {
                id,
                day,
                buff: std::fs::read(path)?,
            })
        } else {
            log::debug!(
                "Stats for relay {id:?} for day {day} does not exists yet, creating memory buffer"
            );
            Ok(Self::new_memory(id, day))
        }
    }

    /// Create a new in memory dev relay state history
    fn new_memory(id: DeviceRelayID, day: u64) -> Self {
        Self {
            id,
            day,
            buff: vec![0; 3600 * 24 / TIME_INTERVAL],
        }
    }

    /// Resolve time offset of a given time in buffer
    fn resolve_offset(&self, time: u64) -> anyhow::Result<(usize, u8)> {
        let start_of_day = self.day * 3600 * 24;

        if time < start_of_day || time >= start_of_day + 3600 * 24 {
            return Err(RelayStateHistoryError::TimeOutOfFileBound.into());
        }

        let relative_time = (time - start_of_day) / TIME_INTERVAL as u64;

        Ok(((relative_time / 8) as usize, (relative_time % 8) as u8))
    }

    /// Set new state of relay
    pub fn set_state(&mut self, time: u64, on: bool) -> anyhow::Result<()> {
        let (idx, offset) = self.resolve_offset(time)?;

        self.buff[idx] = if on {
            self.buff[idx] | (0x1 << offset)
        } else {
            self.buff[idx] & !(0x1 << offset)
        };

        Ok(())
    }

    /// Get the state of relay at a given time
    pub fn get_state(&self, time: u64) -> anyhow::Result<bool> {
        let (idx, offset) = self.resolve_offset(time)?;

        Ok(self.buff[idx] & (0x1 << offset) != 0)
    }

    /// Persist device relay state history
    pub fn save(&self) -> anyhow::Result<()> {
        let path = AppConfig::get().relay_runtime_file_path(self.id, self.day);
        files_utils::create_directory_if_missing(path.parent().unwrap())?;
        std::fs::write(path, &self.buff)?;
        Ok(())
    }
}

#[cfg(test)]
mod tests {
    use crate::devices::device::DeviceRelayID;
    use crate::energy::relay_state_history::RelayStateHistory;

    #[test]
    fn test_relay_state_history() {
        let mut history = RelayStateHistory::new_memory(DeviceRelayID::default(), 0);

        let val_1 = 5 * 30;
        let val_2 = 7 * 30;

        for i in 0..500 {
            assert!(!history.get_state(i).unwrap())
        }

        history.set_state(val_1, true).unwrap();

        for i in 0..500 {
            assert_eq!(history.get_state(i).unwrap(), (i / 30) * 30 == val_1);
        }

        history.set_state(val_2, true).unwrap();

        for i in 0..500 {
            assert_eq!(
                history.get_state(i).unwrap(),
                (i / 30) * 30 == val_1 || (i / 30) * 30 == val_2
            );
        }

        history.set_state(val_2, false).unwrap();

        for i in 0..500 {
            assert_eq!(history.get_state(i).unwrap(), (i / 30) * 30 == val_1);
        }

        history.set_state(val_1, false).unwrap();

        for i in 0..500 {
            assert!(!history.get_state(i).unwrap())
        }

        assert!(history.get_state(8989898).is_err());
    }
}