use std::fs::{File, OpenOptions};
use std::io::{self, Seek, SeekFrom};
use std::os::unix::fs::OpenOptionsExt;

use crate::cli::CONFIG;

use anyhow::Context;

/// Get length of data stream.
/// Physical length of data stream in bytes
/// (multiple of sector_size, rather than actual).
///
/// This will attempt to return the stream to its current read position.
pub fn get_stream_length<S: Seek>(stream: &mut S) -> io::Result<u64> {
    let pos = stream.stream_position()?;
    let len = stream.seek(SeekFrom::End(0));

    stream.seek(SeekFrom::Start(pos))?;

    len
}

pub fn load_input() -> anyhow::Result<File> {
    OpenOptions::new()
        .read(true)
        .custom_flags(libc::O_DIRECT)
        .open(&CONFIG.input)
        .with_context(|| format!("Failed to open input file: {}", &CONFIG.input.display()))
}

pub fn load_output() -> anyhow::Result<File> {
    OpenOptions::new()
        .read(true)
        .write(true)
        .create(true)
        .open(crate::path::OUTPUT_PATH.clone())
        .with_context(|| {
            format!(
                "Failed to open/create output file at: {}",
                crate::path::OUTPUT_PATH.display()
            )
        })
}

pub fn load_map_read() -> std::io::Result<File> {
    OpenOptions::new()
        .read(true)
        .open(crate::path::MAP_PATH.clone())
}

pub fn load_map_write() -> anyhow::Result<File> {
    OpenOptions::new()
        .write(true)
        .create(true)
        .truncate(true) // Wipe old map. Should really make a backup first.
        .open(crate::path::MAP_PATH.clone())
        .with_context(|| {
            format!(
                "Failed to open map file at: {}",
                crate::path::MAP_PATH.display()
            )
        })
}

#[repr(C, align(512))]
pub struct DirectIOBuffer(pub [u8; crate::MAX_BUFFER_SIZE]);

impl Default for DirectIOBuffer {
    fn default() -> Self {
        Self([crate::FB_NULL_VALUE; _])
    }
}

impl From<[u8; crate::MAX_BUFFER_SIZE]> for DirectIOBuffer {
    fn from(value: [u8; crate::MAX_BUFFER_SIZE]) -> Self {
        Self(value)
    }
}