use std::{str::FromStr, sync::Arc};

use axum::{Extension, body::Body, extract::Multipart, http::StatusCode, response::Response};
use somethings::auth::Session;
use wikarden::Wikarden;

use super::PageFrontmatter;

use crate::{
	Query, RuntimeError,
	config::Settings,
	extractor::Wrap,
	handler::{quark::open_template_path, see_other},
};

/// POST /quark/api/create
pub async fn create(
	Extension(wikarden): Extension<Arc<Wikarden>>,
	Extension(settings): Extension<Settings>,
	Wrap(_session): Wrap<Session>,
	mut multipart: Multipart,
) -> Result<Response, RuntimeError> {
	let data = MultipartFields::from_multipart(&mut multipart).await?;
	let operation = data.operation()?;

	match operation {
		Operation::Preview => match data.content {
			None => Err(RuntimeError::incomplete_form("content")),
			Some(content) => super::markup::preview(&content, &settings).await,
		},
		Operation::Create => {
			let CreateForm { name, content }: CreateForm = data.try_into()?;
			let redirect = api_redirect(&settings, &name, format!("../{name}"));

			let wikres = wikarden
				.create(&name, content, format!("Create page '{name}'"))
				.await;

			match wikres {
				Err(e) => api_error(&settings, e).await,
				Ok(_) => redirect.await,
			}
		}
		_ => Err(RuntimeError::bad_request("usupported operation")),
	}
}

/// POST /quark/api/create/section
pub async fn create_section(
	Extension(wikarden): Extension<Arc<Wikarden>>,
	Extension(settings): Extension<Settings>,
	Wrap(_session): Wrap<Session>,
	body: String,
) -> Result<Response, RuntimeError> {
	let query: Query = body.parse()?;

	match query.get_first_value("name") {
		None => Err(RuntimeError::incomplete_form("name")),
		Some(name) => match wikarden.create_section(name, None).await {
			Err(e) => return api_error(&settings, e).await,
			Ok(_) => super::markup::preview(&format!("created section {name}"), &settings).await,
		},
	}
}

/// POST /quark/api/edit
pub async fn edit(
	Extension(wikarden): Extension<Arc<Wikarden>>,
	Extension(settings): Extension<Settings>,
	Wrap(_session): Wrap<Session>,
	mut multipart: Multipart,
) -> Result<Response, RuntimeError> {
	let data = MultipartFields::from_multipart(&mut multipart).await?;
	let operation = data.operation()?;

	match operation {
		Operation::Preview => match data.content {
			None => Err(RuntimeError::incomplete_form("content")),
			Some(content) => super::markup::preview(&content, &settings).await,
		},
		Operation::Edit => {
			let EditForm {
				name,
				content,
				commit,
				frontmatter,
			}: EditForm = data.try_into()?;
			let redirect = api_redirect(&settings, &name, format!("../{name}"));

			let commit = match commit {
				Some(commit) => commit,
				None => {
					let time = timeparse::format::human_with_time(&timeparse::whichever_now());
					format!("edited '{name}' {time}")
				}
			};
			tracing::trace!("editing with commit='{commit}'");

			let source = format!("{frontmatter}\n{content}");

			match wikarden.modify(&name, source, commit).await {
				Err(e) => api_error(&settings, e).await,
				Ok(_) => redirect.await,
			}
		}
		_ => Err(RuntimeError::bad_request("usupported operation")),
	}
}

/// POST /quark/api/edit/section
pub async fn edit_section(
	Extension(wikarden): Extension<Arc<Wikarden>>,
	Extension(settings): Extension<Settings>,
	Wrap(_session): Wrap<Session>,
	body: String,
) -> Result<Response, RuntimeError> {
	let query: Query = body.parse()?;
	let name = query
		.get_first_value("name")
		.ok_or(RuntimeError::incomplete_form("name"))?;

	match query.get_first_value("home") {
		None => Err(RuntimeError::incomplete_form("home")),
		Some(home) => {
			if home.is_empty() {
				return Err(RuntimeError::incomplete_form("home"));
			}

			let full_path = format!("{name}/{home}");
			match wikarden.page_exists(&full_path).await {
				Ok(true) => (),
				_ => {
					return api_error(&settings, format!("page '{full_path}' does not exist"))
						.await;
				}
			}

			let res = wikarden
				.modify_section_data(name, None, |sd| sd.set_home(Some(&full_path)))
				.await;

			match res {
				Err(e) => api_error(&settings, e).await,
				Ok(_) => api_success(&settings, format!("set redirection to '{full_path}'")).await,
			}
		}
	}
}

/// POST /quark/api/move
pub async fn move_page(
	Extension(wikarden): Extension<Arc<Wikarden>>,
	Extension(settings): Extension<Settings>,
	Wrap(_session): Wrap<Session>,
	body: String,
) -> Result<Response, RuntimeError> {
	let query: Query = body.parse()?;
	let from = query
		.get_first_value("from")
		.ok_or(RuntimeError::incomplete_form("from"))?;

	let to = query
		.get_first_value("to")
		.ok_or(RuntimeError::incomplete_form("to"))?;

	match wikarden.move_page(from, to).await {
		Err(e) => api_error(&settings, e).await,
		Ok(()) => api_success(&settings, format!("moved '{from}' to '{to}'")).await,
	}
}

/// POST /quark/api/delete
pub async fn delete(
	Extension(wikarden): Extension<Arc<Wikarden>>,
	Extension(settings): Extension<Settings>,
	Wrap(_session): Wrap<Session>,
	body: String,
) -> Result<Response, RuntimeError> {
	let query = Query::from_str(&body)?;
	let page = query
		.get_first_value("name")
		.ok_or(RuntimeError::incomplete_form("name"))?;

	let page_path = format!("../{page}");

	if query.has("rejection") || !query.has("confirmation") {
		return see_other(page_path).await;
	}

	if page == settings.wikarden_index() {
		//FIXME: Return an error here explaining that the index cannot be deleted
		return see_other(page_path).await;
	}

	match wikarden.delete(page).await {
		Err(e) => api_error(&settings, e).await,
		Ok(_) => see_other(format!("../")).await,
	}
}

/// redirect for API paths
///
/// reads the `api_redirect.html` template and returns a constructed `Response`
///
/// The `api_redirct.html` template has javascript within it that allows
/// the `<iframe>` to navigate the top-level window (`window.top.location`)
async fn api_redirect(
	settings: &Settings,
	page_name: &str,
	page_location: String,
) -> Result<Response, RuntimeError> {
	let path = settings.quark_template_dir().join("api_redirect.html");
	let mut doc = open_template_path(path, settings).await?;

	doc.set("page-name", page_name);
	doc.set("page-location", page_location);

	Response::builder()
		.status(StatusCode::OK)
		.body(Body::from(doc.compile()))
		.map_err(|_| RuntimeError::Unknown)
}

async fn api_error<E: std::fmt::Display>(
	settings: &Settings,
	error: E,
) -> Result<Response, RuntimeError> {
	let content = format!("# |Error|%red\n{error}");
	super::markup::preview(&content, settings).await
}

async fn api_success<D: std::fmt::Display>(
	settings: &Settings,
	message: D,
) -> Result<Response, RuntimeError> {
	let content = format!("# |Success|%green\n{message}");
	super::markup::preview(&content, settings).await
}

/// page creation form
#[derive(Debug, PartialEq)]
struct CreateForm {
	name: String,
	content: String,
}

/// page editing form
#[derive(Debug)]
struct EditForm {
	name: String,
	content: String,
	commit: Option<String>,
	frontmatter: PageFrontmatter<'static>,
}

/// what an endpoint does; mutually exclusive
#[derive(Debug, PartialEq)]
enum Operation {
	Create,
	Edit,
	Preview,
}

/// data read from axum's `Multipart` structure
///
/// This struct is meant to be turned into forms, like [`CreateForm`] and
/// [`EditForm`], with the `TryInto` trait.
struct MultipartFields {
	name: Option<String>,
	content: Option<String>,
	commit: Option<String>,
	og_description: Option<String>,

	create: bool,
	edit: bool,
	preview: bool,
}

impl MultipartFields {
	pub async fn from_multipart(multipart: &mut Multipart) -> Result<Self, RuntimeError> {
		let mut name = None;
		let mut content = None;
		let mut commit = None;
		let mut og_description = None;

		let mut create = false;
		let mut edit = false;
		let mut preview = false;

		macro_rules! field_text {
			($field:ident $fieldname:literal) => {
				Some($field.text().await.map_err(|_| {
					RuntimeError::bad_request(format!("failed to decode field '{}'", $fieldname))
				})?)
				.map(|s| if s.is_empty() { None } else { Some(s) })
				.flatten()
			};
		}

		while let Some(field) = multipart
			.next_field()
			.await
			.map_err(|_| RuntimeError::bad_request("multipart decode failed"))?
		{
			match field.name() {
				Some("create") => create = true,
				Some("edit") => edit = true,
				Some("preview") => preview = true,
				Some("name") => name = field_text!(field "name"),
				Some("content") => content = field_text!(field "content"),
				Some("commit") => commit = field_text!(field "commit"),
				Some("og-description") => og_description = field_text!(field "og_description"),
				_ => (),
			}
		}

		Ok(MultipartFields {
			name,
			content,
			commit,
			og_description,
			create,
			edit,
			preview,
		})
	}

	fn operation(&self) -> Result<Operation, RuntimeError> {
		match (self.create, self.edit, self.preview) {
			(true, false, false) => Ok(Operation::Create),
			(false, true, false) => Ok(Operation::Edit),
			(false, false, true) => Ok(Operation::Preview),

			_ => Err(RuntimeError::bad_request("too many operations")),
		}
	}

	fn frontmatter(&mut self) -> PageFrontmatter<'static> {
		let mut pf = PageFrontmatter::default();

		if let Some(description) = self.og_description.take() {
			pf.set_description(description);
		}

		pf
	}
}

impl TryInto<CreateForm> for MultipartFields {
	type Error = RuntimeError;

	fn try_into(self) -> Result<CreateForm, RuntimeError> {
		match (self.name, self.content) {
			(Some(name), Some(content)) => Ok(CreateForm { name, content }),
			_ => Err(RuntimeError::bad_request("create request missing fields")),
		}
	}
}

impl TryInto<EditForm> for MultipartFields {
	type Error = RuntimeError;

	fn try_into(mut self) -> Result<EditForm, RuntimeError> {
		let pf = self.frontmatter();

		match (self.name, self.content) {
			(Some(name), Some(content)) => Ok(EditForm {
				name,
				content,
				commit: self.commit,
				frontmatter: pf,
			}),
			_ => Err(RuntimeError::bad_request("edit request missing fields")),
		}
	}
}