//! Signal [`InlineIpld`] IPLD formatted [`Ipld`]

use ipld_core::{cid::Cid, ipld, ipld::Ipld};

/// [Inline IPLD][spec] formatted [`Ipld`]
///
/// This is helpful to indictate that spec-compliant inlining has already been performed.
///
/// [Recall][spec] that the shape of Inline IPLD is either:
///
/// ``` js
/// {"/": {".": Ipld}}
/// {"/": {".": Ipld, "&": Cid}}
/// ```
///
/// [`InlineIpld`] can also be used directly in place of [`Ipld`] in [`ipld!`] macros. For example:
///
/// ```
/// # use inline_ipld::{cid, ipld::inline::InlineIpld};
/// # use ipld_core::{ipld, ipld::Ipld};
/// #
/// let inlined = InlineIpld {cid: None, ipld: ipld!([1, 2, 3])};
/// let dag = ipld!({"a": 1, "b": inlined});
/// assert_eq!(dag, ipld!({"a": 1, "b": {"/": {".": [1, 2, 3]}}}));
/// ```
///
/// [spec]: https://github.com/ucan-wg/inline-ipld
#[must_use]
#[derive(Clone, Debug, PartialEq)]
#[cfg_attr(feature = "serde-codec", derive(serde::Deserialize, serde::Serialize))]
#[allow(clippy::module_name_repetitions)]
pub struct InlineIpld {
    /// The [Ipld] to inline
    pub ipld: Ipld,

    /// An optional [Cid] to reference the inlined [Ipld] by
    pub cid: Option<Cid>,
}

impl From<InlineIpld> for Ipld {
    fn from(inline: InlineIpld) -> Ipld {
        ipld!({
            "/": match inline.cid {
                Some(link) => ipld!({".": inline.ipld, "&": link}),
                None => ipld!({".": inline.ipld})
            }
        })
    }
}

impl TryFrom<InlineIpld> for Cid {
    type Error = ();

    fn try_from(inline: InlineIpld) -> Result<Cid, ()> {
        inline.cid.ok_or(())
    }
}

impl<'a> From<&'a InlineIpld> for &'a Ipld {
    fn from(inline: &'a InlineIpld) -> &'a Ipld {
        &inline.ipld
    }
}

impl InlineIpld {
    /// Tag some already-inlined [`Ipld`] to [`InlineIpld`]
    ///
    /// Use with caution: non-inlined [`Ipld`] can be maked as inlined with this function.
    ///
    /// This is used in place of [`from`][`From::from`] to highlight that no conversion or checks happen.
    /// If conversion is desired, use [`Self::new`] with the `cid` field set to [`None`].
    ///
    /// # Arguments
    ///
    /// * `ipld` - [`Ipld`] that is already correctly inlined
    ///
    /// # Examples
    ///
    /// ```
    /// # use inline_ipld::{cid, ipld::inline::InlineIpld};
    /// # use std::str::FromStr;
    /// # use multihash_codetable::Code::Sha2_256;
    /// # use serde_ipld_dagcbor::codec::DagCborCodec;
    /// # use ipld_core::{
    /// #     cid::Version,
    /// #     ipld,
    /// #     ipld::Ipld,
    /// #     cid::Cid
    /// # };
    /// #
    /// let ready = ipld!({"a": 1, "b": {"/": {".": [1, 2, 3]}}});
    /// let observed = InlineIpld::attest(ready.clone());
    /// assert_eq!(Ipld::from(observed), ipld!({"/": {".": ready}}));
    /// ```
    pub fn attest(ipld: Ipld) -> Self {
        InlineIpld { ipld, cid: None }
    }
}