//! Utility functions and types.
use std::{
    borrow::Borrow,
    fmt,
    io::{BufReader, Read},
    sync::{Arc, Weak},
    time::SystemTime,
};

use bao_tree::{io::outboard::PreOrderOutboard, BaoTree, ChunkRanges};
use bytes::Bytes;
use derive_more::{Debug, Display, From, Into};
use range_collections::range_set::RangeSetRange;
use serde::{Deserialize, Serialize};

use crate::{BlobFormat, Hash, HashAndFormat, IROH_BLOCK_SIZE};

pub mod fs;
pub mod io;
mod mem_or_file;
pub mod progress;
pub use mem_or_file::MemOrFile;
mod sparse_mem_file;
pub use sparse_mem_file::SparseMemFile;
pub mod local_pool;

/// A tag
#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Serialize, Deserialize, From, Into)]
pub struct Tag(pub Bytes);

#[cfg(feature = "redb")]
mod redb_support {
    use bytes::Bytes;
    use redb::{Key as RedbKey, Value as RedbValue};

    use super::Tag;

    impl RedbValue for Tag {
        type SelfType<'a> = Self;

        type AsBytes<'a> = bytes::Bytes;

        fn fixed_width() -> Option<usize> {
            None
        }

        fn from_bytes<'a>(data: &'a [u8]) -> Self::SelfType<'a>
        where
            Self: 'a,
        {
            Self(Bytes::copy_from_slice(data))
        }

        fn as_bytes<'a, 'b: 'a>(value: &'a Self::SelfType<'b>) -> Self::AsBytes<'a>
        where
            Self: 'a,
            Self: 'b,
        {
            value.0.clone()
        }

        fn type_name() -> redb::TypeName {
            redb::TypeName::new("Tag")
        }
    }

    impl RedbKey for Tag {
        fn compare(data1: &[u8], data2: &[u8]) -> std::cmp::Ordering {
            data1.cmp(data2)
        }
    }
}

impl Borrow<[u8]> for Tag {
    fn borrow(&self) -> &[u8] {
        self.0.as_ref()
    }
}

impl From<String> for Tag {
    fn from(value: String) -> Self {
        Self(Bytes::from(value))
    }
}

impl From<&str> for Tag {
    fn from(value: &str) -> Self {
        Self(Bytes::from(value.to_owned()))
    }
}

impl Display for Tag {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let bytes = self.0.as_ref();
        match std::str::from_utf8(bytes) {
            Ok(s) => write!(f, "\"{}\"", s),
            Err(_) => write!(f, "{}", hex::encode(bytes)),
        }
    }
}

struct DD<T: fmt::Display>(T);

impl<T: fmt::Display> fmt::Debug for DD<T> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Display::fmt(&self.0, f)
    }
}

impl Debug for Tag {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_tuple("Tag").field(&DD(self)).finish()
    }
}

impl Tag {
    /// Create a new tag that does not exist yet.
    pub fn auto(time: SystemTime, exists: impl Fn(&[u8]) -> bool) -> Self {
        let now = chrono::DateTime::<chrono::Utc>::from(time);
        let mut i = 0;
        loop {
            let mut text = format!("auto-{}", now.format("%Y-%m-%dT%H:%M:%S%.3fZ"));
            if i != 0 {
                text.push_str(&format!("-{}", i));
            }
            if !exists(text.as_bytes()) {
                return Self::from(text);
            }
            i += 1;
        }
    }
}

/// Option for commands that allow setting a tag
#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Serialize, Deserialize)]
pub enum SetTagOption {
    /// A tag will be automatically generated
    Auto,
    /// The tag is explicitly named
    Named(Tag),
}

/// Trait used from temp tags to notify an abstract store that a temp tag is
/// being dropped.
pub trait TagDrop: std::fmt::Debug + Send + Sync + 'static {
    /// Called on drop
    fn on_drop(&self, inner: &HashAndFormat);
}

/// A trait for things that can track liveness of blobs and collections.
///
/// This trait works together with [TempTag] to keep track of the liveness of a
/// blob or collection.
///
/// It is important to include the format in the liveness tracking, since
/// protecting a collection means protecting the blob and all its children,
/// whereas protecting a raw blob only protects the blob itself.
pub trait TagCounter: TagDrop + Sized {
    /// Called on creation of a temp tag
    fn on_create(&self, inner: &HashAndFormat);

    /// Get this as a weak reference for use in temp tags
    fn as_weak(self: &Arc<Self>) -> Weak<dyn TagDrop> {
        let on_drop: Arc<dyn TagDrop> = self.clone();
        Arc::downgrade(&on_drop)
    }

    /// Create a new temp tag for the given hash and format
    fn temp_tag(self: &Arc<Self>, inner: HashAndFormat) -> TempTag {
        self.on_create(&inner);
        TempTag::new(inner, Some(self.as_weak()))
    }
}

/// A hash and format pair that is protected from garbage collection.
///
/// If format is raw, this will protect just the blob
/// If format is collection, this will protect the collection and all blobs in it
#[derive(Debug)]
pub struct TempTag {
    /// The hash and format we are pinning
    inner: HashAndFormat,
    /// optional callback to call on drop
    on_drop: Option<Weak<dyn TagDrop>>,
}

impl TempTag {
    /// Create a new temp tag for the given hash and format
    ///
    /// This should only be used by store implementations.
    ///
    /// The caller is responsible for increasing the refcount on creation and to
    /// make sure that temp tags that are created between a mark phase and a sweep
    /// phase are protected.
    pub fn new(inner: HashAndFormat, on_drop: Option<Weak<dyn TagDrop>>) -> Self {
        Self { inner, on_drop }
    }

    /// The hash of the pinned item
    pub fn inner(&self) -> &HashAndFormat {
        &self.inner
    }

    /// The hash of the pinned item
    pub fn hash(&self) -> &Hash {
        &self.inner.hash
    }

    /// The format of the pinned item
    pub fn format(&self) -> BlobFormat {
        self.inner.format
    }

    /// The hash and format of the pinned item
    pub fn hash_and_format(&self) -> HashAndFormat {
        self.inner
    }

    /// Keep the item alive until the end of the process
    pub fn leak(mut self) {
        // set the liveness tracker to None, so that the refcount is not decreased
        // during drop. This means that the refcount will never reach 0 and the
        // item will not be gced until the end of the process.
        self.on_drop = None;
    }
}

impl Drop for TempTag {
    fn drop(&mut self) {
        if let Some(on_drop) = self.on_drop.take() {
            if let Some(on_drop) = on_drop.upgrade() {
                on_drop.on_drop(&self.inner);
            }
        }
    }
}

/// Get the number of bytes given a set of chunk ranges and the total size.
///
/// If some ranges are out of bounds, they will be clamped to the size.
pub fn total_bytes(ranges: ChunkRanges, size: u64) -> u64 {
    ranges
        .iter()
        .map(|range| {
            let (start, end) = match range {
                RangeSetRange::Range(r) => {
                    (r.start.to_bytes().min(size), r.end.to_bytes().min(size))
                }
                RangeSetRange::RangeFrom(range) => (range.start.to_bytes().min(size), size),
            };
            end.saturating_sub(start)
        })
        .reduce(u64::saturating_add)
        .unwrap_or_default()
}

/// A non-sendable marker type
#[derive(Debug)]
pub(crate) struct NonSend {
    _marker: std::marker::PhantomData<std::rc::Rc<()>>,
}

impl NonSend {
    /// Create a new non-sendable marker.
    #[allow(dead_code)]
    pub const fn new() -> Self {
        Self {
            _marker: std::marker::PhantomData,
        }
    }
}

/// copy a limited slice from a slice as a `Bytes`.
pub(crate) fn copy_limited_slice(bytes: &[u8], offset: u64, len: usize) -> Bytes {
    bytes[limited_range(offset, len, bytes.len())]
        .to_vec()
        .into()
}

pub(crate) fn limited_range(offset: u64, len: usize, buf_len: usize) -> std::ops::Range<usize> {
    if offset < buf_len as u64 {
        let start = offset as usize;
        let end = start.saturating_add(len).min(buf_len);
        start..end
    } else {
        0..0
    }
}

/// zero copy get a limited slice from a `Bytes` as a `Bytes`.
#[allow(dead_code)]
pub(crate) fn get_limited_slice(bytes: &Bytes, offset: u64, len: usize) -> Bytes {
    bytes.slice(limited_range(offset, len, bytes.len()))
}

/// Compute raw outboard size, without the size header.
#[allow(dead_code)]
pub(crate) fn raw_outboard_size(size: u64) -> u64 {
    BaoTree::new(size, IROH_BLOCK_SIZE).outboard_size()
}

/// Synchronously compute the outboard of a file, and return hash and outboard.
///
/// It is assumed that the file is not modified while this is running.
///
/// If it is modified while or after this is running, the outboard will be
/// invalid, so any attempt to compute a slice from it will fail.
///
/// If the size of the file is changed while this is running, an error will be
/// returned.
///
/// The computed outboard is without length prefix.
pub(crate) fn compute_outboard(
    read: impl Read,
    size: u64,
    progress: impl Fn(u64) -> std::io::Result<()> + Send + Sync + 'static,
) -> std::io::Result<(Hash, Option<Vec<u8>>)> {
    use bao_tree::io::sync::CreateOutboard;

    // wrap the reader in a progress reader, so we can report progress.
    let reader = ProgressReader::new(read, progress);
    // wrap the reader in a buffered reader, so we read in large chunks
    // this reduces the number of io ops and also the number of progress reports
    let buf_size = usize::try_from(size).unwrap_or(usize::MAX).min(1024 * 1024);
    let reader = BufReader::with_capacity(buf_size, reader);

    let ob = PreOrderOutboard::<Vec<u8>>::create_sized(reader, size, IROH_BLOCK_SIZE)?;
    let root = ob.root.into();
    let data = ob.data;
    tracing::trace!(%root, "done");
    let data = if !data.is_empty() { Some(data) } else { None };
    Ok((root, data))
}

/// Compute raw outboard, without the size header.
#[cfg(test)]
#[allow(dead_code)]
pub(crate) fn raw_outboard(data: &[u8]) -> (Vec<u8>, Hash) {
    let res = bao_tree::io::outboard::PreOrderMemOutboard::create(data, IROH_BLOCK_SIZE);
    (res.data, res.root.into())
}

/// A reader that calls a callback with the number of bytes read after each read.
pub(crate) struct ProgressReader<R, F: Fn(u64) -> std::io::Result<()>> {
    inner: R,
    offset: u64,
    cb: F,
}

impl<R: std::io::Read, F: Fn(u64) -> std::io::Result<()>> ProgressReader<R, F> {
    pub fn new(inner: R, cb: F) -> Self {
        Self {
            inner,
            offset: 0,
            cb,
        }
    }
}

impl<R: std::io::Read, F: Fn(u64) -> std::io::Result<()>> std::io::Read for ProgressReader<R, F> {
    fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
        let read = self.inner.read(buf)?;
        self.offset += read as u64;
        (self.cb)(self.offset)?;
        Ok(read)
    }
}