use std::borrow::Cow;

use camino::{Utf8Path, Utf8PathBuf};

use crate::{
	JournalName, Settings, WikError,
	error::FileOp,
	fs::{self, EitherPath, Open, WikFile, WikPath},
	git::GitContext,
	journal::{Journal, JournalLine},
	table::{SectionData, TableEntry, Tables, Tags},
};

pub enum CommitMessage<'a> {
	None,
	Borrow(&'a str),
	Owned(String),
}

impl<'a> Into<Option<Cow<'a, str>>> for CommitMessage<'a> {
	fn into(self) -> Option<Cow<'a, str>> {
		match self {
			Self::None => None,
			Self::Borrow(s) => Some(Cow::Borrowed(s)),
			Self::Owned(own) => Some(Cow::Owned(own)),
		}
	}
}

impl<'a, T: Into<CommitMessage<'a>>> From<Option<T>> for CommitMessage<'a> {
	fn from(opt: Option<T>) -> Self {
		match opt {
			None => Self::None,
			Some(msg) => msg.into(),
		}
	}
}

impl From<String> for CommitMessage<'static> {
	fn from(owned: String) -> Self {
		Self::Owned(owned)
	}
}

impl<'a> From<&'a str> for CommitMessage<'a> {
	fn from(s: &'a str) -> Self {
		Self::Borrow(s)
	}
}

pub struct Source {
	pub path: WikPath,
	pub data: String,
}

pub enum PathType {
	Page,
	Section,
}

pub struct Wikarden {
	root: Utf8PathBuf,
	journal: Journal,
	tables: Tables,

	settings: Settings,
}

impl Wikarden {
	const DRAFT_DIR: &'static str = ".wikarden/drafts";

	pub async fn new<Root: Into<Utf8PathBuf>>(
		root: Root,
		settings: Settings,
	) -> Result<Self, WikError> {
		let root = root.into();
		Self::init(&root)?;

		Ok(Self {
			root: root.clone(),
			journal: Journal::init(&root).await?,
			tables: Tables::new(&root).await?,

			settings,
		})
	}

	fn init(root: &Utf8Path) -> Result<(), WikError> {
		let draft_path = root.join(Self::DRAFT_DIR);

		if let Err(_e) = std::fs::create_dir_all(&draft_path) {
			Err(WikError::DirectoryCreation { path: draft_path })
		} else {
			Ok(())
		}
	}

	pub async fn refresh_sections(&self) -> Result<(), WikError> {
		let res = read_sections_from_fs(&self.root).await;
		match res {
			Err(e) => WikError::file_operation(FileOp::Read, self.root.clone(), e),
			Ok(sections) => {
				let entries = sections
					.into_iter()
					.map(|n| TableEntry::new(n, SectionData::default()))
					.collect();

				self.tables.replace_sections(entries).await
			}
		}
	}

	pub async fn sections(&self) -> Vec<String> {
		self.tables
			.get_sections()
			.await
			.into_iter()
			.map(|te| te.into_name())
			.collect()
	}

	pub async fn journal_tail(&self, kind: JournalName, count: usize) -> Vec<JournalLine> {
		self.journal.journal_tail(kind, count).await
	}

	pub async fn path_type<P: Into<WikPath>>(&self, path: P) -> Option<PathType> {
		let path = path.into();

		match self.page_exists(path.clone()).await {
			Ok(true) => return Some(PathType::Page),
			Ok(false) => match self.section_exists(path.clone()).await {
				false => None,
				true => Some(PathType::Section),
			},
			Err(WikError::SectionNoexist { .. }) => None,
			Err(_) => unreachable!(),
		}
	}

	// assumes the post stable stays up to date
	pub async fn page_exists<P: Into<WikPath>>(&self, path: P) -> Result<bool, WikError> {
		let path = path.into();
		self.check_parent_section(&path).await?;
		Ok(self.tables.has_page(path).await)
	}

	// assumes the section table stays up to date
	pub async fn section_exists<P: Into<WikPath>>(&self, path: P) -> bool {
		self.tables.has_section(path.into()).await
	}

	//MARK: Page Handling
	pub async fn source<P: Into<WikPath>>(&self, path: P) -> Result<Source, WikError> {
		let path = path.into();
		let file = self.file_from_path(path.clone(), Open::Read).await?;
		let content = file.read_to_string().await?;

		Ok(Source {
			path,
			data: content,
		})
	}

	pub async fn create<Path, Content, Message>(
		&self,
		path: Path,
		content: Content,
		commit: Message,
	) -> Result<(), WikError>
	where
		Path: Into<WikPath>,
		Content: AsRef<str>,
		Message: Into<CommitMessage<'static>>,
	{
		let path = path.into();

		if self.page_exists(path.clone()).await? {
			return Err(WikError::page_exists(path));
		}

		let mut file = self.file_from_path(path.clone(), Open::Create).await?;
		file.write_str(content.as_ref()).await?;
		file.done().await?;

		self.tables.add_page(path.as_ref(), Tags::default()).await?;

		self.journal
			.push(JournalName::Created, path.clone())
			.await?;

		self.git_commit_file(
			path.clone(),
			commit.into(),
			format!("created page '{path}'"),
		)
	}

	pub async fn move_page<FromPath: Into<WikPath>, ToPath: Into<WikPath>>(
		&self,
		from: FromPath,
		to: ToPath,
	) -> Result<(), WikError> {
		let from = from.into();
		let to = to.into();

		if !self.page_exists(from.clone()).await? {
			return Err(WikError::page_noexists(from));
		}

		if self.page_exists(to.clone()).await? {
			return Err(WikError::page_exists(to));
		}

		let safe_from = EitherPath::from(from.clone()).safe(&self.root)?;
		let safe_to = EitherPath::safe_nonexist(&self.root, &to)?;
		if let Err(e) = tokio::fs::rename(safe_from.0, &safe_to.0).await {
			return WikError::file_operation(FileOp::Write, safe_to.0, e);
		}

		self.journal
			.rename(JournalName::Created, from.clone(), to.clone())
			.await?;

		self.journal
			.rename(JournalName::Modified, from.clone(), to.clone())
			.await?;

		self.tables
			.posts()
			.modify_entry(from.as_ref(), |te| te.set_name(to.to_string()))
			.await?;

		Ok(())
	}

	pub async fn modify<Path, Content, Message>(
		&self,
		path: Path,
		new_content: Content,
		commit: Message,
	) -> Result<(), WikError>
	where
		Path: Into<WikPath>,
		Content: AsRef<str>,
		Message: Into<CommitMessage<'static>>,
	{
		let path = path.into();

		if !self.page_exists(path.clone()).await? {
			return Err(WikError::page_noexists(path));
		}

		let mut file = self.file_from_path(path.clone(), Open::Write).await?;
		file.write_str(new_content.as_ref()).await?;
		file.done().await?;

		self.journal
			.push(JournalName::Modified, path.clone())
			.await?;

		self.git_commit_file(path.clone(), commit.into(), format!("edited page '{path}'"))
	}

	pub async fn delete<P: Into<WikPath>>(&self, path: P) -> Result<(), WikError> {
		let path = path.into();

		if !self.page_exists(path.clone()).await? {
			return Err(WikError::page_noexists(path));
		}

		let safe = EitherPath::Wik(path.clone()).safe(&self.root)?;
		WikFile::remove(safe).await?;

		self.tables.del_page(&path).await?;

		self.journal.del(JournalName::Created, path.clone()).await?;
		self.journal
			.del(JournalName::Modified, path.clone())
			.await?;

		self.git_commit_file(
			path.clone(),
			CommitMessage::None,
			format!("deleted page '{path}'"),
		)
	}

	pub async fn create_section<P: Into<WikPath>>(
		&self,
		path: P,
		commit: Option<Cow<'static, str>>,
	) -> Result<(), WikError> {
		let path = path.into();
		self.check_parent_section(&path).await?;

		if self.tables.has_section(&path).await {
			return Err(WikError::section_exists(path));
		}

		let system_path = EitherPath::safe_nonexist(&self.root, &path)?;
		fs::create_dir(system_path).await?;

		self.tables
			.add_section(path.as_ref(), SectionData::default())
			.await?;

		let wikarden_message = format!("created section '{path}'");
		let message = Self::make_commit_message(commit, wikarden_message);
		let git = self.get_git();
		self.finish_git(git, message)
	}

	pub async fn get_section_data<P: Into<WikPath>>(
		&self,
		path: P,
	) -> Result<SectionData, WikError> {
		let path = path.into();

		match self.tables.sections().entry_data(path.as_ref()).await {
			None => Err(WikError::section_noexist(path)),
			Some(data) => Ok(data),
		}
	}

	pub async fn modify_section_data<P: Into<WikPath>, F>(
		&self,
		path: P,
		commit: Option<Cow<'static, str>>,
		f: F,
	) -> Result<(), WikError>
	where
		F: FnOnce(&mut SectionData),
	{
		let path = path.into();

		if !self.section_exists(path.clone()).await {
			return Err(WikError::section_noexist(path));
		}

		let sections = self.tables.sections();
		sections.modify_entry_data(path.as_ref(), f).await?;

		let wikarden_message = format!("modified section '{path}'");
		let message = Self::make_commit_message(commit, wikarden_message);
		let git = self.get_git();
		self.finish_git(git, message)
	}

	//MARK: Utilities
	async fn file_from_path<P: Into<WikPath>>(
		&self,
		path: P,
		flags: Open,
	) -> Result<WikFile, WikError> {
		let safe = EitherPath::safe_nonexist(&self.root, &path.into())?;
		WikFile::open(safe.0, flags).await
	}

	async fn check_parent_section(&self, path: &WikPath) -> Result<(), WikError> {
		if let Some(parent) = path.parent() {
			if !self.section_exists(parent.clone()).await {
				return Err(WikError::section_noexist(parent));
			}
		}

		Ok(())
	}

	/// Creates a new git commit, including the provided path. It also commits
	/// the tables and journals
	fn git_commit_file<P: Into<EitherPath>>(
		&self,
		path: P,
		user_message: CommitMessage<'static>,
		our_message: String,
	) -> Result<(), WikError> {
		let safe = path.into().safe(&self.root)?;
		let mut git = self.get_git();
		git.add(&safe)?;

		let message = Self::make_commit_message(user_message.into(), our_message.into());
		self.finish_git(git, message)
	}

	fn make_commit_message(
		user_message: Option<Cow<'static, str>>,
		our_message: String,
	) -> Cow<'static, str> {
		match user_message {
			None => Cow::Owned(our_message),
			Some(user) => Cow::Owned(format!("{user}\n\n{our_message}")),
		}
	}

	/// Creates a new [GitContext] with the Tables and Journal already added
	/// to the commit
	fn get_git(&self) -> GitContext {
		let mut git = GitContext::open(&self.root);
		Tables::git_add(&mut git);
		self.journal.git_add(&mut git);
		git
	}

	/// Writes the index and then makes a commit with the provided string
	fn finish_git(&self, mut git: GitContext, commit: Cow<'static, str>) -> Result<(), WikError> {
		git.write_index()?;
		git.commit(self.settings.signature(), commit)?;
		Ok(())
	}
}

/// Reads the filesystem looking for sections.
async fn read_sections_from_fs(root: &Utf8Path) -> Result<Vec<String>, std::io::Error> {
	let mut sections = vec![];

	let mut dirs = tokio::fs::read_dir(root).await?;
	while let Some(entry) = dirs.next_entry().await? {
		let name = entry.file_name();
		let path = entry.path();

		if !name.to_string_lossy().starts_with(".") {
			let meta = entry.metadata().await?;
			if meta.is_dir() {
				match path.to_str() {
					None => (),
					Some(s) => {
						let stripped = s.strip_prefix(&format!("{root}/")).unwrap();
						sections.push(stripped.to_owned());
						let subsec = Box::pin(read_sections_from_fs(s.into())).await?;
						sections.extend(subsec.iter().map(|s| format!("{stripped}/{s}")));
					}
				}
			}
		}
	}

	return Ok(sections);
}