use git2::{Cred, Error, FetchOptions, Index, IndexEntry, IndexTime, Oid, Progress, PushOptions, RemoteCallbacks, Repository, Signature};
use indicatif::{ProgressBar, ProgressStyle};
use log::{info, trace};
use std::collections::{HashMap, HashSet};
use std::path::{Path, PathBuf};
use std::string::String;
use std::str;
use walkdir::WalkDir;

pub struct Job
{
	pub id: u32,
	pub key: String,
	pub result_repository_path: PathBuf,
}

pub struct BenchmarkRepository
{
	base_path: PathBuf,
	repository: Repository,
	jobs: HashMap<u32, Job>,
	ssh_user: String,
	user_name: String,
	user_email: String,
}

pub struct TargetPath
{
	pub source: PathBuf,
	pub destination: PathBuf,
}

impl BenchmarkRepository
{
	fn progress_bar_style() -> ProgressStyle
	{
		ProgressStyle::default_bar()
			.template("{bar:74.on_black} {percent:>3} %")
			.progress_chars("█▉▊▋▌▍▎▏  ")
	}

	fn transfer_progress_callback(progress: Progress, progress_bar: &mut ProgressBar) -> bool
	{
		progress_bar.set_length(progress.total_objects() as u64);
		progress_bar.set_position(progress.received_objects() as u64);

		// continue the transfer
		true
	}

	fn push_update_reference_callback(reference: &str, status: Option<&str>) -> Result<(), Error>
	{
		match status
		{
			None => trace!("Reference “{}” pushed successfully to remote “origin”", reference),
			Some(error) => panic!("Couldn’t push reference “{}” to remote “origin”: {}", reference, error),
		};

		Ok(())
	}

	fn reset_origin(&self, remote_url: &str) -> &Self
	{
		if let Err(error) = self.repository.find_remote("origin")
			.or_else(|_| self.repository.remote("origin", remote_url))
		{
			panic!("Could not reset remote “origin”: {}", error);
		}

		info!("Reset origin to “{}”", remote_url);

		self
	}

	fn fetch_branch(&self, branch_name: &str) -> &Self
	{
		let mut progress_bar = ProgressBar::new(0);
		progress_bar.set_style(BenchmarkRepository::progress_bar_style());

		{
			let mut remote_callbacks = RemoteCallbacks::new();
			remote_callbacks.credentials(
				|_, _, _|
				{
					match Cred::ssh_key_from_agent(&self.ssh_user)
					{
						Ok(credentials) => Ok(credentials),
						Err(error) => panic!("could not retrieve key pair for SSH authentication as user “{}”: {}", self.ssh_user, error),
					}
				});

			remote_callbacks.transfer_progress(
				|progress| BenchmarkRepository::transfer_progress_callback(progress, &mut progress_bar));

			let mut fetch_options = FetchOptions::new();
			fetch_options.remote_callbacks(remote_callbacks);

			let mut origin = self.repository.find_remote("origin").expect("could not find remote “origin”");

			info!("Updating branch “{}”", branch_name);

			if let Err(error) = origin.fetch(&[branch_name], Some(&mut fetch_options), None)
			{
				panic!("failed to fetch branch “{}” from remote “origin”: {}", branch_name, error);
			}
		}

		progress_bar.finish_and_clear();

		trace!("Branch “{}” is up-to-date", branch_name);

		self
	}

	fn init(base_path: &Path) -> Repository
	{
		let repository_path = base_path.join("upstream");

		let repository = match Repository::init_bare(&repository_path)
		{
			Ok(repository) => repository,
			Err(error) => panic!("failed to initialize Git repository in “{}”: {}", repository_path.display(), error),
		};

		info!("Initialized Git repository in “{}”", repository_path.display());

		repository
	}

	pub fn new(remote_url: &str, base_path: PathBuf, ssh_user: &str, user_name: &str, user_email: &str) -> BenchmarkRepository
	{
		let repository = match Repository::open(&base_path)
		{
			Ok(repository) =>
			{
				info!("Using existing Git repository");

				repository
			},
			Err(_) => BenchmarkRepository::init(&base_path),
		};

		let benchmark_repository =
			BenchmarkRepository
			{
				base_path: base_path,
				repository: repository,
				jobs: HashMap::new(),
				ssh_user: ssh_user.to_string(),
				user_name: user_name.to_string(),
				user_email: user_email.to_string(),
			};

		benchmark_repository
			.reset_origin(remote_url)
			.fetch_branch("config")
			.fetch_branch("results")
			.fetch_branch("status");

		benchmark_repository
	}

	pub fn read_file_as_index_entry(&self, file_path: &Path, result_file_path: &Path) -> IndexEntry
	{
		// create a new blob with the file contents
		let object_id = match self.repository.blob_path(file_path)
		{
			Ok(object_id) => object_id,
			Err(error) => panic!("Could not write blob for “{}”: {}", file_path.display(), error),
		};

		info!("Created object “{}” from “{}”", object_id, file_path.display());

		IndexEntry
		{
			ctime: IndexTime::new(0, 0),
			mtime: IndexTime::new(0, 0),
			dev: 0,
			ino: 0,
			mode: 0o100644,
			uid: 0,
			gid: 0,
			file_size: 0,
			id: object_id,
			flags: 0,
			flags_extended: 0,
			path: result_file_path.to_string_lossy().as_bytes().to_owned(),
		}
	}

	pub fn commit_directory(&self, directory_path: &TargetPath, branch_name: &str)
	{
		let mut file_paths = vec![];

		for entry in WalkDir::new(&directory_path.source)
		{
			let entry = entry.unwrap();

			if entry.path().file_name().unwrap() == ".lock" || entry.file_type().is_dir()
			{
				continue;
			}

			let relative_path = entry.path().strip_prefix(&directory_path.source).unwrap();

			trace!("Adding “{}” (from “{}”) to autocommit list", relative_path.display(), entry.path().display());

			file_paths.push(TargetPath{source: entry.path().to_owned(), destination: directory_path.destination.join(&relative_path)});
		}

		self.commit_files(&file_paths, branch_name);
	}

	pub fn commit_files(&self, file_paths: &[TargetPath], branch_name: &str)
	{
		let tip_reference_name = format!("refs/remotes/origin/{}", branch_name);
		let tip_reference = match self.repository.find_reference(&tip_reference_name)
		{
			Ok(value) => value,
			Err(error) => panic!("Could not find reference “{}”: {}", tip_reference_name, error),
		};

		let parent_tree = match tip_reference.peel_to_tree()
		{
			Ok(value) => value,
			Err(error) => panic!("Could not peel reference to tree: {}", error),
		};

		let mut index = match Index::new()
		{
			Ok(value) => value,
			Err(error) => panic!("Could not create index: {}", error),
		};

		match index.read_tree(&parent_tree)
		{
			Ok(value) => value,
			Err(error) => panic!("Could not read parent tree into index: {}", error),
		};

		for target_path in file_paths
		{
			let index_entry = self.read_file_as_index_entry(&target_path.source, &target_path.destination);

			if let Err(error) = index.add(&index_entry)
			{
				panic!("Could not add index entry for “{}”: {}", target_path.destination.display(), error);
			}
		}

		let tree_object_id = match index.write_tree_to(&self.repository)
		{
			Ok(value) => value,
			Err(error) => panic!("Could not write index to tree: {}", error),
		};

		let tree = match self.repository.find_tree(tree_object_id)
		{
			Ok(value) => value,
			Err(error) => panic!("Could obtain tree: {}", error),
		};

		info!("Created tree object “{}”", tree_object_id);

		let signature = Signature::now(&self.user_name, &self.user_email).expect("Could not create signature");
		let message = format!("Add files");

		let parent = match tip_reference.peel_to_commit()
		{
			Ok(value) => value,
			Err(error) => panic!("Could not peel reference: {}", error),
		};

		let commit_id = match self.repository.commit(Some(&tip_reference_name), &signature, &signature, &message, &tree, &[&parent])
		{
			Ok(value) => value,
			Err(error) => panic!("Could not write commit: {}", error),
		};

		let push_refspec = format!("refs/remotes/origin/{}:refs/heads/{}", branch_name, branch_name);

		trace!("Created commit “{}”, using refspec “{}”", commit_id, push_refspec);

		let mut remote_callbacks = RemoteCallbacks::new();
		remote_callbacks.credentials(
			|_, _, _|
			{
				match Cred::ssh_key_from_agent(&self.ssh_user)
				{
					Ok(value) => Ok(value),
					Err(error) => panic!("could not retrieve key pair for SSH authentication as user “{}”: {}", self.ssh_user, error),
				}
			});

		remote_callbacks.push_update_reference(
			|reference, status| BenchmarkRepository::push_update_reference_callback(reference, status));

		let mut push_options = PushOptions::new();
		push_options.remote_callbacks(remote_callbacks);

		let mut remote = self.repository.find_remote("origin").expect("");
		remote.push(&[&push_refspec], Some(&mut push_options)).expect("couldn’t push");
	}

	pub fn file_exists(&self, file_path: &Path, branch_name: &str) -> bool
	{
		let tip_reference_name = format!("refs/remotes/origin/{}", branch_name);
		let tip_reference = match self.repository.find_reference(&tip_reference_name)
		{
			Ok(value) => value,
			Err(error) => panic!("Could not find reference “{}”: {}", tip_reference_name, error),
		};

		let tree = match tip_reference.peel_to_tree()
		{
			Ok(value) => value,
			Err(error) => panic!("Could not peel reference to tree: {}", error),
		};

		let object_id = match tree.get_path(file_path)
		{
			Ok(tree_entry) => tree_entry.id(),
			Err(_) => return false,
		};

		if let Err(_) = self.repository.find_blob(object_id)
		{
			return false;
		}

		true
	}

	pub fn read_file(&self, file_path: &Path, branch_name: &str) -> Option<String>
	{
		let tip_reference_name = format!("refs/remotes/origin/{}", branch_name);
		let tip_reference = match self.repository.find_reference(&tip_reference_name)
		{
			Ok(value) => value,
			Err(error) => panic!("Could not find reference “{}”: {}", tip_reference_name, error),
		};

		let tree = match tip_reference.peel_to_tree()
		{
			Ok(value) => value,
			Err(error) => panic!("Could not peel reference to tree: {}", error),
		};

		let object_id = match tree.get_path(file_path)
		{
			Ok(tree_entry) => tree_entry.id(),
			Err(_) => return None,
		};

		let blob = match self.repository.find_blob(object_id)
		{
			Ok(blob) => blob,
			Err(_) => return None,
		};

		let content = match std::str::from_utf8(blob.content())
		{
			Ok(content) => content,
			Err(error) => panic!("Could not interpret file “{}” as UTF-8: {}", file_path.display(), error),
		};

		Some(content.to_owned())
	}

	pub fn create_job(&mut self, key: String) -> &Job
	{
		let id = self.jobs.len() as u32;
		let result_repository_path = self.base_path.join(format!("job-{}", id));

		if result_repository_path.exists()
		{
			match std::fs::remove_dir_all(&result_repository_path)
			{
				Ok(_) => (),
				Err(error) => panic!("failed to initialize result Git repository for job {} in “{}”: {}", id, result_repository_path.display(), error),
			};
		}

		match Repository::init_bare(&result_repository_path)
		{
			Ok(repository) => repository,
			Err(error) => panic!("failed to initialize result Git repository for job {} in “{}”: {}", id, result_repository_path.display(), error),
		};

		info!("Initialized result Git repository for job {} in “{}”", id, result_repository_path.display());

		self.jobs.insert(id, Job{id, key, result_repository_path});
		self.jobs.get(&id).unwrap()
	}

	fn tip_commit<'repository>(repository: &'repository git2::Repository, from_remote: bool, branch_name: &str) -> Result<git2::Commit<'repository>, git2::Error>
	{
		let tip_reference_name = match from_remote
		{
			true => format!("refs/remotes/origin/{}", branch_name),
			false => format!("refs/heads/{}", branch_name),
		};

		repository.find_reference(&tip_reference_name).and_then(|tip_reference| tip_reference.peel_to_commit())
	}

	pub fn join(&self)
	{
		let mut active_job_ids = HashSet::new();

		for (job_id, _) in &self.jobs
		{
			active_job_ids.insert(job_id);
		}

		while !active_job_ids.is_empty()
		{
			active_job_ids.retain
			(
				|job_id|
				{
					let job = self.jobs.get(job_id).unwrap();
					let job_repository = match Repository::open(&job.result_repository_path)
					{
						Ok(value) => value,
						Err(error) => panic!("cannot access result repository for job {}: {}", job_id, error),
					};

					let job_commit = match Self::tip_commit(&job_repository, false, "master")
					{
						Ok(value) => value,
						// Job is not done yet, so skip it until it is
						Err(_) => return true,
					};

					info!("job {} finished", job_id);

					let remote_commit = match Self::tip_commit(&self.repository, true, "results")
					{
						Ok(value) => value,
						Err(error) => panic!("could not access tip commit of “results” branch: {}", error),
					};

					false
				}
			);

			println!("...");
			std::thread::sleep(std::time::Duration::from_secs(2));
		}
	}
}

#[cfg(test)]
mod tests
{
}