use bstr::{BString, ByteSlice, ByteVec};
use git_object::Commit;

use crate::commit;

/// Generate a message typical for git commit logs based on the given `operation`
pub fn message(operation: &str, commit: &Commit) -> BString {
    let mut out = BString::from(operation);
    if let Some(commit_type) = commit_type_by_parents(commit.parents.len()) {
        out.push_str(b" (");
        out.extend_from_slice(commit_type.as_bytes());
        out.push_byte(b')');
    }
    out.push_str(b": ");
    out.extend_from_slice(&commit::summary(commit.message.as_bstr()));
    out
}

pub(crate) fn commit_type_by_parents(count: usize) -> Option<&'static str> {
    Some(match count {
        0 => "initial",
        1 => return None,
        _two_or_more => "merge",
    })
}