use crate::DesktopContext;
use dioxus_core::ScopeState;
use slab::Slab;
use std::{
    borrow::Cow,
    future::Future,
    ops::Deref,
    path::{Path, PathBuf},
    pin::Pin,
    rc::Rc,
    sync::Arc,
};
use tokio::{
    runtime::Handle,
    sync::{OnceCell, RwLock},
};
use wry::{
    http::{status::StatusCode, Request, Response},
    Result,
};

use crate::desktop_context::EditQueue;

static MINIFIED: &str = include_str!("./minified.js");

fn module_loader(root_name: &str, headless: bool) -> String {
    format!(
        r#"
<script type="module">
    {MINIFIED}
    // Wait for the page to load
    window.onload = function() {{
        let rootname = "{root_name}";
        let root_element = window.document.getElementById(rootname);
        if (root_element != null) {{
            window.interpreter.initialize(root_element);
            window.ipc.postMessage(window.interpreter.serializeIpcMessage("initialize"));
        }}
        window.interpreter.wait_for_request({headless});
    }}
</script>
"#
    )
}

/// An arbitrary asset is an HTTP response containing a binary body.
pub type AssetResponse = Response<Cow<'static, [u8]>>;

/// A future that returns an [`AssetResponse`]. This future may be spawned in a new thread,
/// so it must be [`Send`], [`Sync`], and `'static`.
pub trait AssetFuture: Future<Output = Option<AssetResponse>> + Send + Sync + 'static {}
impl<T: Future<Output = Option<AssetResponse>> + Send + Sync + 'static> AssetFuture for T {}

#[derive(Debug, Clone)]
/// A request for an asset. This is a wrapper around [`Request<Vec<u8>>`] that provides methods specific to asset requests.
pub struct AssetRequest {
    path: PathBuf,
    request: Arc<Request<Vec<u8>>>,
}

impl AssetRequest {
    /// Get the path the asset request is for
    pub fn path(&self) -> &Path {
        &self.path
    }
}

impl From<Request<Vec<u8>>> for AssetRequest {
    fn from(request: Request<Vec<u8>>) -> Self {
        let decoded = urlencoding::decode(request.uri().path().trim_start_matches('/'))
            .expect("expected URL to be UTF-8 encoded");
        let path = PathBuf::from(&*decoded);
        Self {
            request: Arc::new(request),
            path,
        }
    }
}

impl Deref for AssetRequest {
    type Target = Request<Vec<u8>>;

    fn deref(&self) -> &Self::Target {
        &self.request
    }
}

/// A handler that takes an [`AssetRequest`] and returns a future that either loads the asset, or returns `None`.
/// This handler is stashed indefinitely in a context object, so it must be `'static`.
pub trait AssetHandler<F: AssetFuture>: Send + Sync + 'static {
    /// Handle an asset request, returning a future that either loads the asset, or returns `None`
    fn handle_request(&self, request: &AssetRequest) -> F;
}

impl<F: AssetFuture, T: Fn(&AssetRequest) -> F + Send + Sync + 'static> AssetHandler<F> for T {
    fn handle_request(&self, request: &AssetRequest) -> F {
        self(request)
    }
}

type AssetHandlerRegistryInner =
    Slab<Box<dyn Fn(&AssetRequest) -> Pin<Box<dyn AssetFuture>> + Send + Sync + 'static>>;

#[derive(Clone)]
pub struct AssetHandlerRegistry(Arc<RwLock<AssetHandlerRegistryInner>>);

impl AssetHandlerRegistry {
    pub fn new() -> Self {
        AssetHandlerRegistry(Arc::new(RwLock::new(Slab::new())))
    }

    pub async fn register_handler<F: AssetFuture>(&self, f: impl AssetHandler<F>) -> usize {
        let mut registry = self.0.write().await;
        registry.insert(Box::new(move |req| Box::pin(f.handle_request(req))))
    }

    pub async fn remove_handler(&self, id: usize) -> Option<()> {
        let mut registry = self.0.write().await;
        registry.try_remove(id).map(|_| ())
    }

    pub async fn try_handlers(&self, req: &AssetRequest) -> Option<AssetResponse> {
        let registry = self.0.read().await;
        for (_, handler) in registry.iter() {
            if let Some(response) = handler(req).await {
                return Some(response);
            }
        }
        None
    }
}

/// A handle to a registered asset handler.
pub struct AssetHandlerHandle {
    desktop: DesktopContext,
    handler_id: Rc<OnceCell<usize>>,
}

impl AssetHandlerHandle {
    /// Returns the ID for this handle.
    ///
    /// Because registering an ID is asynchronous, this may return `None` if the
    /// registration has not completed yet.
    pub fn handler_id(&self) -> Option<usize> {
        self.handler_id.get().copied()
    }
}

impl Drop for AssetHandlerHandle {
    fn drop(&mut self) {
        let cell = Rc::clone(&self.handler_id);
        let desktop = Rc::clone(&self.desktop);
        tokio::task::block_in_place(move || {
            Handle::current().block_on(async move {
                if let Some(id) = cell.get() {
                    desktop.asset_handlers.remove_handler(*id).await;
                }
            })
        });
    }
}

/// Provide a callback to handle asset loading yourself.
///
/// The callback takes a path as requested by the web view, and it should return `Some(response)`
/// if you want to load the asset, and `None` if you want to fallback on the default behavior.
pub fn use_asset_handler<F: AssetFuture>(
    cx: &ScopeState,
    handler: impl AssetHandler<F>,
) -> &AssetHandlerHandle {
    cx.use_hook(|| {
        let desktop = crate::window();
        let handler_id = Rc::new(OnceCell::new());
        let handler_id_ref = Rc::clone(&handler_id);
        let desktop_ref = Rc::clone(&desktop);
        cx.push_future(async move {
            let id = desktop.asset_handlers.register_handler(handler).await;
            handler_id.set(id).unwrap();
        });
        AssetHandlerHandle {
            desktop: desktop_ref,
            handler_id: handler_id_ref,
        }
    })
}

pub(super) async fn desktop_handler(
    request: Request<Vec<u8>>,
    custom_head: Option<String>,
    custom_index: Option<String>,
    root_name: &str,
    asset_handlers: &AssetHandlerRegistry,
    edit_queue: &EditQueue,
    headless: bool,
    responder: wry::RequestAsyncResponder,
) {
    let request = AssetRequest::from(request);

    // If the request is for the root, we'll serve the index.html file.
    if request.uri().path() == "/" {
        // If a custom index is provided, just defer to that, expecting the user to know what they're doing.
        // we'll look for the closing </body> tag and insert our little module loader there.
        let body = match custom_index {
            Some(custom_index) => custom_index
                .replace(
                    "</body>",
                    &format!("{}</body>", module_loader(root_name, headless)),
                )
                .into_bytes(),

            None => {
                // Otherwise, we'll serve the default index.html and apply a custom head if that's specified.
                let mut template = include_str!("./index.html").to_string();

                if let Some(custom_head) = custom_head {
                    template = template.replace("<!-- CUSTOM HEAD -->", &custom_head);
                }

                template
                    .replace(
                        "<!-- MODULE LOADER -->",
                        &module_loader(root_name, headless),
                    )
                    .into_bytes()
            }
        };

        match Response::builder()
            .header("Content-Type", "text/html")
            .header("Access-Control-Allow-Origin", "*")
            .body(Cow::from(body))
        {
            Ok(response) => {
                return responder.respond(response);
            }
            Err(err) => tracing::error!("error building response: {}", err),
        }
    } else if request.uri().path().trim_matches('/') == "edits" {
        edit_queue.handle_request(responder);
        return;
    }

    // If the user provided a custom asset handler, then call it and return the response
    // if the request was handled.
    if let Some(response) = asset_handlers.try_handlers(&request).await {
        responder.respond(response);
        return;
    }

    // Else, try to serve a file from the filesystem.

    // If the path is relative, we'll try to serve it from the assets directory.
    let mut asset = get_asset_root()
        .unwrap_or_else(|| Path::new(".").to_path_buf())
        .join(&request.path);

    if !asset.exists() {
        asset = PathBuf::from("/").join(request.path);
    }

    if asset.exists() {
        let content_type = match get_mime_from_path(&asset) {
            Ok(content_type) => content_type,
            Err(err) => {
                tracing::error!("error getting mime type: {}", err);
                return;
            }
        };
        let asset = match std::fs::read(asset) {
            Ok(asset) => asset,
            Err(err) => {
                tracing::error!("error reading asset: {}", err);
                return;
            }
        };
        match Response::builder()
            .header("Content-Type", content_type)
            .body(Cow::from(asset))
        {
            Ok(response) => return responder.respond(response),
            Err(err) => tracing::error!("error building response: {}", err),
        }
    }

    match Response::builder()
        .status(StatusCode::NOT_FOUND)
        .body(Cow::from(String::from("Not Found").into_bytes()))
    {
        Ok(response) => {
            responder.respond(response);
        }
        Err(err) => tracing::error!("error building response: {}", err),
    }
}

#[allow(unreachable_code)]
fn get_asset_root() -> Option<PathBuf> {
    /*
    We're matching exactly how cargo-bundle works.

    - [x] macOS
    - [ ] Windows
    - [ ] Linux (rpm)
    - [ ] Linux (deb)
    - [ ] iOS
    - [ ] Android

    */

    if std::env::var_os("CARGO").is_some() {
        return None;
    }

    // TODO: support for other platforms
    #[cfg(target_os = "macos")]
    {
        let bundle = core_foundation::bundle::CFBundle::main_bundle();
        let bundle_path = bundle.path()?;
        let resources_path = bundle.resources_path()?;
        let absolute_resources_root = bundle_path.join(resources_path);
        let canonical_resources_root = dunce::canonicalize(absolute_resources_root).ok()?;

        return Some(canonical_resources_root);
    }

    None
}

/// Get the mime type from a path-like string
fn get_mime_from_path(trimmed: &Path) -> Result<&'static str> {
    if trimmed.extension().is_some_and(|ext| ext == "svg") {
        return Ok("image/svg+xml");
    }

    let res = match infer::get_from_path(trimmed)?.map(|f| f.mime_type()) {
        Some(f) => {
            if f == "text/plain" {
                get_mime_by_ext(trimmed)
            } else {
                f
            }
        }
        None => get_mime_by_ext(trimmed),
    };

    Ok(res)
}

/// Get the mime type from a URI using its extension
fn get_mime_by_ext(trimmed: &Path) -> &'static str {
    match trimmed.extension().and_then(|e| e.to_str()) {
        Some("bin") => "application/octet-stream",
        Some("css") => "text/css",
        Some("csv") => "text/csv",
        Some("html") => "text/html",
        Some("ico") => "image/vnd.microsoft.icon",
        Some("js") => "text/javascript",
        Some("json") => "application/json",
        Some("jsonld") => "application/ld+json",
        Some("mjs") => "text/javascript",
        Some("rtf") => "application/rtf",
        Some("svg") => "image/svg+xml",
        Some("mp4") => "video/mp4",
        // Assume HTML when a TLD is found for eg. `dioxus:://dioxuslabs.app` | `dioxus://hello.com`
        Some(_) => "text/html",
        // https://developer.mozilla.org/en-US/docs/Web/HTTP/Basics_of_HTTP/MIME_types/Common_types
        // using octet stream according to this:
        None => "application/octet-stream",
    }
}