// Copyright 2020 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use crate::commit::Commit;
use crate::store::CommitId;
use crate::transaction::Transaction;
use git2::Error;

#[derive(Debug, PartialEq, Eq)]
pub enum GitImportError {
    NotAGitRepo,
    InternalGitError(String),
}

impl From<git2::Error> for GitImportError {
    fn from(err: Error) -> Self {
        GitImportError::InternalGitError(format!("failed to read git refs: {}", err))
    }
}

// Reflect changes made in the underlying Git repo in the Jujube repo.
pub fn import_refs(tx: &mut Transaction) -> Result<(), GitImportError> {
    let store = tx.store().clone();
    let git_repo = store.git_repo().ok_or(GitImportError::NotAGitRepo)?;
    let git_refs = git_repo.references()?;
    for git_ref in git_refs {
        let git_ref = git_ref?;
        if !(git_ref.is_tag() || git_ref.is_branch() || git_ref.is_remote()) {
            // Skip other refs (such as notes) and symbolic refs.
            // TODO: Is it useful to import HEAD (especially if it's detached)?
            continue;
        }
        let git_commit = git_ref.peel_to_commit()?;
        let id = CommitId(git_commit.id().as_bytes().to_vec());
        let commit = store.get_commit(&id).unwrap();
        tx.add_head(&commit);
    }
    Ok(())
}

#[derive(Debug, PartialEq, Eq)]
pub enum GitPushError {
    NotAGitRepo,
    NoSuchRemote,
    NotFastForward,
    // TODO: I'm sure there are other errors possible, such as transport-level errors,
    // and errors caused by the remote rejecting the push.
    InternalGitError(String),
}

pub fn push_commit(
    commit: &Commit,
    remote_name: &str,
    remote_branch: &str,
) -> Result<(), GitPushError> {
    let git_repo = commit.store().git_repo().ok_or(GitPushError::NotAGitRepo)?;
    // Create a temporary ref to work around https://github.com/libgit2/libgit2/issues/3178
    let temp_ref_name = format!("refs/jj/git-push/{}", commit.id().hex());
    let mut temp_ref = git_repo
        .reference(
            &temp_ref_name,
            git2::Oid::from_bytes(&commit.id().0).unwrap(),
            true,
            "temporary reference for git push",
        )
        .map_err(|err| {
            GitPushError::InternalGitError(format!(
                "failed to create temporary git ref for push: {}",
                err
            ))
        })?;
    let mut remote =
        git_repo
            .find_remote(remote_name)
            .map_err(|err| match (err.class(), err.code()) {
                (git2::ErrorClass::Config, git2::ErrorCode::NotFound) => GitPushError::NoSuchRemote,
                (git2::ErrorClass::Config, git2::ErrorCode::InvalidSpec) => {
                    GitPushError::NoSuchRemote
                }
                _ => panic!("unhandled git error: {:?}", err),
            })?;
    // Need to add "refs/heads/" prefix due to https://github.com/libgit2/libgit2/issues/1125
    let refspec = format!("{}:refs/heads/{}", temp_ref_name, remote_branch);
    remote
        .push(&[refspec], None)
        .map_err(|err| match (err.class(), err.code()) {
            (git2::ErrorClass::Reference, git2::ErrorCode::NotFastForward) => {
                GitPushError::NotFastForward
            }
            _ => panic!("unhandled git error: {:?}", err),
        })?;
    temp_ref.delete().map_err(|err| {
        GitPushError::InternalGitError(format!(
            "failed to delete temporary git ref for push: {}",
            err
        ))
    })
}