use futures::{TryStream, TryStreamExt as _};
use snafu::{OptionExt as _, ResultExt as _, Snafu};
use std::num::ParseIntError;

use super::{CreateListerSnafu, ListError, Month, RecordingManager, Year};

pub type Day = u8;

#[derive(Debug, Snafu)]
pub enum TakeError {
    /// days are supposed to be directories, but this wasn't (because it didn't end with `/`)
    NotADirectory,

    /// could not parse the day as an integer
    ParseIntegerError { source: ParseIntError },
}

pub fn take(s: &str) -> Result<(Day, &str), TakeError> {
    let (day, rest) = s.split_once('/').context(NotADirectorySnafu)?;

    let day = day.parse().context(ParseIntegerSnafu)?;

    Ok((day, rest))
}

#[derive(Debug, Snafu)]
pub enum DayEntryError {
    /// failed to get an entry from the storage operator's lister
    ReceiveEntryError { source: opendal::Error },

    /// failed to parse the entry as a day
    ParseError { source: TakeError },
}

impl RecordingManager {
    pub async fn days(
        &self,
        year: Year,
        month: Month,
    ) -> Result<impl TryStream<Ok = Day, Error = DayEntryError> + Unpin, ListError> {
        let lister = self
            .operator
            .lister(&format!("{year}/{month}/"))
            .await
            .context(CreateListerSnafu)?;

        Ok(lister
            .map_err(|error| DayEntryError::ReceiveEntryError { source: error })
            .and_then(|entry| {
                std::future::ready(
                    take(entry.name())
                        .map(|(day, _rest)| day)
                        .context(ParseSnafu),
                )
            }))
    }
}