//! Defines of an iris [plugin][Plugin].

use crate::{error::error, path, Repository, Result};

use log::{debug, trace, warn};
use std::{borrow::Cow, cmp::Ordering, collections::HashSet, path::PathBuf};
use url::Url;

/// Returns the url to the fallback git server. If a repository url is provided
/// and it does not contain a git server (just author and repo), this url will
/// be used in its absence.
fn fallback_git_server() -> &'static Url {
	use std::sync::OnceLock;
	static FALLBACK: OnceLock<Url> = OnceLock::new();
	FALLBACK.get_or_init(|| {
		Url::parse("https://github.com")
			.expect("!! IRIS BUG !! invalid fallback git server url")
	})
}

/// # Plugin
///
/// A structure representing an iris plugin specification.
///
/// An iris plugin has two parts.
///
/// - [id], must be a unique identifier for this plugin and the plugins
///   module name
/// - [args], a set of arguments to configure this plugin
///
/// [id]: Self::id
/// [args]: Self::args
#[derive(Debug, Eq)]
pub struct Plugin {
	/// The plugins unique identifier. Used for the vim module name and
	/// repository checkout foler.
	pub id: String,
	/// The commit oid (if set) that the local repository will be forced to
	/// track. If not set then the repository will track the latest commit in
	/// the current tracking branch.
	pub commit: Option<String>,
	/// The branch name (if set) that the local repository will be forced to
	/// track. If not set then the repository will track the repositories
	/// default branch.
	pub branch: Option<String>,
	/// Set of plugin ids this plugin should load before
	pub run: Option<String>,
	/// Handle to the local plugin repository.
	pub before: HashSet<String>,
	/// Set of plugin ids this plugin should load after
	pub after: HashSet<String>,
	/// The command to run when vim starts up
	repo: Repository,
}

impl Plugin {
	/// Create a new iris plugin.
	///
	/// Creates a plugin from the git repo at `url` with the unique id `id`.
	/// The plugin will be unlocked meaning it will always track the latest
	/// commit until locked. A handle to a local repository will be created but
	/// not loaded until called upon.
	pub fn new(id: String, url: &str) -> Result<Self> {
		// resolve and parse url
		let url = {
			// try url as is
			Url::parse(url)
				// try url with fallback
				.or_else(|_| fallback_git_server().join(url))
				// invalid git url!
				.map_err(|_| error!("invalid git url {url}"))
		}?;

		// get the path to the local repository checkout
		let repo_path = path::plugin_dir().join(&id);

		// create repository handle
		let repo = Repository::new(url, repo_path);

		debug!("found plugin '{id}'");

		Ok(Self {
			id,
			commit: None,
			branch: None,
			run: None,
			before: HashSet::new(),
			after: HashSet::new(),
			repo,
		})
	}

	/// The url to the remote git repository.
	pub const fn url(&self) -> &Url {
		&self.repo.url
	}

	/// The path to the local repository
	pub const fn repo_path(&self) -> &PathBuf {
		&self.repo.path
	}

	/// The commit oid that the plugin repository is currently tracking
	fn commit(&self) -> Result<Cow<'_, str>> {
		// returned locked commit if set
		if let Some(commit) = &self.commit {
			return Ok(Cow::Borrowed(commit));
		}

		// get commit from repo
		let branch = self.branch()?;
		let commit = self.repo.latest_commit(&branch)?;
		Ok(Cow::Owned(commit))
	}

	/// The branch name that the plugin repository is currently tracking
	fn branch(&self) -> Result<Cow<'_, str>> {
		// return locked branch if set
		if let Some(branch) = &self.branch {
			return Ok(Cow::Borrowed(branch));
		}

		// get branch from repo
		let branch = self.repo.default_branch()?;
		Ok(Cow::Owned(branch))
	}

	/// Fetches latest changes in the local repository but does not update
	/// checkout.
	pub fn fetch(&self) -> Result<()> {
		trace!("fetching {}", self.id);
		let branch = self.branch()?;
		self.repo.fetch(&branch)?;
		Ok(())
	}

	/// Checkout plugin repository using their current refs
	pub fn switch(&self) -> Result<()> {
		trace!("switching {}", self.id);
		let commit = self.commit()?;
		self.repo.checkout(&commit)?;
		Ok(())
	}

	/// Update plugin ref to point to the latest commit
	pub fn lock(&mut self) -> Result<()> {
		trace!("locking {}", self.id);
		let branch = self.branch()?;
		self.repo.fetch(&branch)?;
		let commit = self.repo.latest_commit(&branch)?;
		self.commit = Some(commit);
		Ok(())
	}

	/// Runtime path
	///
	/// This this the plugins root directory, and is used by vim/neovim to
	/// find the vim/lua runtime scripts.
	///
	/// vim: set runtimepath+=<path>
	pub fn runtime_path(&self) -> &PathBuf {
		self.repo_path()
	}

	/// Lua package path
	///
	/// This is the path to the lua module if the plugin has one. If so
	/// it needs to be added to the lua package path. The path is located
	/// in the repos lua directory at /lua/<id>/init.lua or /lua/<id>.lua. If
	/// both exist the former takes priority.
	///
	/// lua: package.path = package.path .. ";<path>"
	pub fn lua_package_path(&self) -> Option<PathBuf> {
		let mut lua = self.repo_path().to_owned();
		lua.push("lua");
		lua.push(&self.id);
		// /lua/<id>/init.lua
		let module = lua.join("init.lua");
		if module.exists() {
			return Some(module.with_file_name("?.lua"));
		}
		// /lua/<id>/.lua
		let module = lua.with_extension("lua");
		if module.exists() {
			return Some(module.with_file_name("?.lua"));
		}
		// no lua package path found
		None
	}

	/// Vim source file
	///
	/// Path to a vim file in the /plugin directory that needs to be
	/// sourced. This is located at /plugin/<id>.vim
	///
	/// vim: source <path>
	pub fn vim_source_file(&self) -> Option<PathBuf> {
		let mut path = self.repo_path().to_owned();
		path.push("plugin");
		path.push(&self.id);
		path.set_extension("vim");
		Some(path).filter(|path| path.exists())
	}

	/// Lua source file
	///
	/// Path to a lua file in the /plugin directory that needs to be
	/// sourced. This is located at /plugin/<id>.lua
	///
	/// lua: dofile('<path>')
	pub fn lua_source_file(&self) -> Option<PathBuf> {
		let mut path = self.repo_path().to_owned();
		path.push("plugin");
		path.push(&self.id);
		path.set_extension("lua");
		Some(path).filter(|path| path.exists())
	}

	/// Vim source after file
	///
	/// Path to a vim file in the /after/plugin directory that needs to be
	/// sourced last. This is located at /after/plugin/<id>.vim
	///
	/// vim: source <path>
	pub fn vim_source_after_file(&self) -> Option<PathBuf> {
		let mut path = self.repo_path().to_owned();
		path.push("after/plugin");
		path.push(&self.id);
		path.set_extension("vim");
		Some(path).filter(|path| path.exists())
	}

	/// Lua source after file
	///
	/// Path to a lua file in the /after/plugin directory that needs to be
	/// sourced last. This is located at /after/plugin/<id>.lua
	///
	/// lua: dofile('<path>')
	pub fn lua_source_after_file(&self) -> Option<PathBuf> {
		let mut path = self.repo_path().to_owned();
		path.push("after/plugin");
		path.push(&self.id);
		path.set_extension("lua");
		Some(path).filter(|path| path.exists())
	}
}

impl PartialEq for Plugin {
	fn eq(&self, other: &Self) -> bool {
		self.id.eq(&other.id)
	}
}

impl PartialOrd for Plugin {
	fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
		let is_after =
			other.before.contains(&self.id) || self.after.contains(&other.id);
		let is_before =
			other.after.contains(&self.id) || self.before.contains(&other.id);
		match (is_before, is_after) {
			// equal, no ordering
			(false, false) => Some(Ordering::Equal),
			// before
			(true, false) => Some(Ordering::Less),
			// after
			(false, true) => Some(Ordering::Greater),
			// cycle detected
			(true, true) => {
				warn!(
					"plugin dependency cycle detected between '{}' and '{}'",
					&self.id, &other.id
				);
				None
			}
		}
	}
}

impl Ord for Plugin {
    fn cmp(&self, other: &Self) -> Ordering {
        self.partial_cmp(other).unwrap_or(Ordering::Equal)
    }
}