use serde::{Deserialize, Serialize};

/// The null OID representing "no object" in git protocol.
pub const ZERO_OID: &str = "0000000000000000000000000000000000000000";

#[derive(Deserialize, Serialize, Clone, Debug, PartialEq, Eq)]
pub struct ObjectId(pub String);

impl ObjectId {
    pub fn new(hex: impl AsRef<str>) -> Self {
        Self(hex.as_ref().to_lowercase())
    }
    pub fn as_str(&self) -> &str {
        &self.0
    }
}
impl std::fmt::Display for ObjectId {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.0)
    }
}

impl AsRef<str> for ObjectId {
    fn as_ref(&self) -> &str {
        &self.0
    }
}

pub fn hex_to_bytes(hex: &str) -> Result<Vec<u8>, crate::error::GitError> {
    let hex = hex.trim();
    if !hex.len().is_multiple_of(2) {
        return Err(crate::error::GitError::InvalidOid(
            "hex oid has odd length".into(),
        ));
    }

    hex.as_bytes()
        .chunks_exact(2)
        .map(|pair| {
            let part = std::str::from_utf8(pair)
                .map_err(|e| crate::error::GitError::InvalidOid(e.to_string()))?;
            u8::from_str_radix(part, 16)
                .map_err(|e| crate::error::GitError::InvalidOid(e.to_string()))
        })
        .collect()
}

impl TryFrom<&ObjectId> for gix::hash::ObjectId {
    type Error = crate::error::GitError;

    fn try_from(id: &ObjectId) -> Result<Self, Self::Error> {
        gix::hash::ObjectId::from_hex(id.as_str().as_bytes())
            .map_err(|e| crate::error::GitError::InvalidOid(format!("invalid hex oid: {e}")))
    }
}