// Copyright © 2021 The Radicle Link Contributors
//
// This file is part of radicle-link, distributed under the GPLv3 with Radicle
// Linking Exception. For full terms see the included LICENSE file.

use git_ext::Oid;

use crate::pruning_fold;

use super::HistoryType;

#[derive(Clone, Debug, PartialEq, Hash, Eq)]
pub enum Contents {
    Automerge(Vec<u8>),
}

impl Contents {
    pub fn automerge(bytes: &[u8]) -> Self {
        Self::Automerge(bytes.to_vec())
    }
}

impl From<&Contents> for HistoryType {
    fn from(c: &Contents) -> Self {
        match c {
            Contents::Automerge(..) => HistoryType::Automerge,
        }
    }
}

impl AsRef<[u8]> for Contents {
    fn as_ref(&self) -> &[u8] {
        match self {
            Self::Automerge(bytes) => bytes,
        }
    }
}

/// A unique identifier for a history entry.
#[derive(Clone, Copy, Debug, PartialEq, Hash, Eq, PartialOrd, Ord)]
pub struct EntryId(Oid);

impl From<git2::Oid> for EntryId {
    fn from(id: git2::Oid) -> Self {
        Self(id.into())
    }
}

impl From<Oid> for EntryId {
    fn from(id: Oid) -> Self {
        Self(id)
    }
}

impl From<EntryId> for Oid {
    fn from(EntryId(id): EntryId) -> Self {
        id
    }
}

/// One entry in the dependency graph for a change
#[derive(Clone, Debug, PartialEq, Eq, Hash)]
pub struct Entry {
    /// The identifier for this entry
    pub(super) id: EntryId,
    /// The content-address for this entry's author.
    pub(super) author: Option<Oid>,
    /// The content-address for the resource this entry lives under.
    pub(super) resource: Oid,
    /// The child entries for this entry.
    pub(super) children: Vec<EntryId>,
    /// The contents of this entry.
    pub(super) contents: Contents,
}

impl Entry {
    pub fn new<Id1, Id2, ChildIds>(
        id: Id1,
        author: Option<Oid>,
        resource: Oid,
        children: ChildIds,
        contents: Contents,
    ) -> Self
    where
        Id1: Into<EntryId>,
        Id2: Into<EntryId>,
        ChildIds: IntoIterator<Item = Id2>,
    {
        Self {
            id: id.into(),
            author,
            resource,
            children: children.into_iter().map(|id| id.into()).collect(),
            contents,
        }
    }

    /// The ids of the changes this change depends on
    pub fn children(&self) -> impl Iterator<Item = &EntryId> {
        self.children.iter()
    }

    /// The `Oid` of the resource this change lives under.
    pub fn resource(&self) -> Oid {
        self.resource
    }

    /// The `Oid` of the author that made this change.
    pub fn author(&self) -> &Option<Oid> {
        &self.author
    }

    /// The contents of this change
    pub fn contents(&self) -> &Contents {
        &self.contents
    }

    pub fn id(&self) -> &EntryId {
        &self.id
    }
}

impl pruning_fold::GraphNode for Entry {
    type Id = EntryId;

    fn id(&self) -> &Self::Id {
        &self.id
    }

    fn child_ids(&self) -> &[Self::Id] {
        &self.children
    }
}