package tk.antoine_roux.wiki.service;

import com.fasterxml.jackson.databind.ObjectMapper;
import org.eclipse.jgit.api.Git;
import org.eclipse.jgit.api.errors.GitAPIException;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.revwalk.RevWalk;
import org.eclipse.jgit.transport.UsernamePasswordCredentialsProvider;
import org.eclipse.jgit.treewalk.TreeWalk;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Service;
import tk.antoine_roux.wiki.model.internal.GitlabCI;
import tk.antoine_roux.wiki.model.request.HookEvent;
import tk.antoine_roux.wiki.model.request.secondary.Commit;

import java.io.IOException;
import java.nio.file.Files;
import java.util.Optional;

@Service
public class GitService {

    public static final String GITLAB_CI_FILE_PATH = ".gitlab-ci.yml";
    private static final String GITLAB_RUNNER_CLONE_PREFIX = "gitlab-runner-clone";
    public final UsernamePasswordCredentialsProvider credentialsProvider;
    private final ObjectMapper objectMapper;

    @Autowired
    public GitService(UsernamePasswordCredentialsProvider credentialsProvider, @Qualifier("YAMLObjectMapper") ObjectMapper objectMapper) {
        this.credentialsProvider = credentialsProvider;
        this.objectMapper = objectMapper;
    }

    /**
     * return .gitlab-ci.yml content for {@link HookEvent}
     */
    public Optional<GitlabCI> getYMLGitlabCI(HookEvent hookEvent) throws IOException, GitAPIException {
        Optional<GitlabCI> optJob;
        if (hookEvent.commits.isEmpty()) {
            optJob = Optional.empty();
        } else {
            // search for head commit or take first in event's list of commit
            Commit commit = hookEvent.commits.stream().filter(co -> co.id.equals(hookEvent.headCommit))
                    .findFirst().orElse(hookEvent.commits.get(0));

            optJob = Optional.of(this.getGitlabCIContent(hookEvent.repository.cloneUrl, commit));
        }
        return optJob;
    }

    /**
     * return .gitlab-ci.yml content for given commit into cloneUrl repository
     */
    private GitlabCI getGitlabCIContent(String cloneURL, Commit commit) throws IOException, GitAPIException {
        Git call = Git.cloneRepository()
                .setURI(cloneURL)
                .setCredentialsProvider(this.credentialsProvider)
                .setDirectory(Files.createTempDirectory(GITLAB_RUNNER_CLONE_PREFIX).toFile())
                .call();

        RevWalk revWalk = new RevWalk(call.getRepository());
        RevCommit revCommit = revWalk.parseCommit(ObjectId.fromString(commit.id));

        try (TreeWalk walk = TreeWalk.forPath(call.getRepository(), GITLAB_CI_FILE_PATH, revCommit.getTree())) {
            if (walk != null) {
                byte[] bytes = call.getRepository().open(walk.getObjectId(0)).getBytes();
                return this.objectMapper.readValue(bytes, GitlabCI.class);
            } else {
                throw new IllegalArgumentException("No path found.");
            }
        }
    }
}