use std::io;

use git_object::WriteTo;

/// Describe the capability to write git objects into an object store.
pub trait Write {
    /// The error type used for all trait methods.
    ///
    /// _Note_ the default implementations require the `From<io::Error>` bound.
    type Error: std::error::Error + From<io::Error>;

    /// Write objects using the given kind of [`hash`][git_hash::Kind] into the database,
    /// returning id to reference it in subsequent reads.
    fn write(&self, object: impl WriteTo, hash: git_hash::Kind) -> Result<git_hash::ObjectId, Self::Error> {
        let mut buf = Vec::with_capacity(2048);
        object.write_to(&mut buf)?;
        self.write_stream(object.kind(), buf.len() as u64, buf.as_slice(), hash)
    }
    /// As [`write`][Write::write], but takes an [`object` kind][git_object::Kind] along with its encoded bytes.
    fn write_buf(
        &self,
        object: git_object::Kind,
        from: &[u8],
        hash: git_hash::Kind,
    ) -> Result<git_hash::ObjectId, Self::Error> {
        self.write_stream(object, from.len() as u64, from, hash)
    }
    /// As [`write`][Write::write], but takes an input stream.
    /// This is commonly used for writing blobs directly without reading them to memory first.
    fn write_stream(
        &self,
        kind: git_object::Kind,
        size: u64,
        from: impl io::Read,
        hash: git_hash::Kind,
    ) -> Result<git_hash::ObjectId, Self::Error>;
}