use crate::{default_impl, fmt_impls, write_impls};
use crate::{
    read::Readable, write::Writable, CopyValue, GlobalMemo, GlobalSignal, ReactiveContext,
    ReadableRef,
};
use crate::{Memo, WritableRef};
use dioxus_core::IntoDynNode;
use dioxus_core::{prelude::IntoAttributeValue, ScopeId};
use generational_box::{AnyStorage, Storage, SyncStorage, UnsyncStorage};
use std::{
    any::Any,
    collections::HashSet,
    ops::{Deref, DerefMut},
    sync::Mutex,
};

/// Creates a new Signal. Signals are a Copy state management solution with automatic dependency tracking.
///
/// ```rust
/// use dioxus::prelude::*;
/// use dioxus_signals::*;
///
/// #[component]
/// fn App() -> Element {
///     let mut count = use_signal(|| 0);
///
///     // Because signals have automatic dependency tracking, if you never read them in a component, that component will not be re-rended when the signal is updated.
///     // The app component will never be rerendered in this example.
///     rsx! { Child { state: count } }
/// }
///
/// #[component]
/// fn Child(mut state: Signal<u32>) -> Element {
///     use_future(move || async move {
///         // Because the signal is a Copy type, we can use it in an async block without cloning it.
///         state += 1;
///     });
///
///     rsx! {
///         button {
///             onclick: move |_| state += 1,
///             "{state}"
///         }
///     }
/// }
/// ```
pub struct Signal<T: 'static, S: Storage<SignalData<T>> = UnsyncStorage> {
    pub(crate) inner: CopyValue<SignalData<T>, S>,
}

/// A signal that can safely shared between threads.
pub type SyncSignal<T> = Signal<T, SyncStorage>;

/// The data stored for tracking in a signal.
pub struct SignalData<T> {
    pub(crate) subscribers: Mutex<HashSet<ReactiveContext>>,
    pub(crate) value: T,
}

impl<T: 'static> Signal<T> {
    /// Creates a new Signal. Signals are a Copy state management solution with automatic dependency tracking.
    #[track_caller]
    pub fn new(value: T) -> Self {
        Self::new_maybe_sync(value)
    }

    /// Create a new signal with a custom owner scope. The signal will be dropped when the owner scope is dropped instead of the current scope.
    #[track_caller]
    pub fn new_in_scope(value: T, owner: ScopeId) -> Self {
        Self::new_maybe_sync_in_scope(value, owner)
    }

    /// Creates a new global Signal that can be used in a global static.
    #[track_caller]
    pub const fn global(constructor: fn() -> T) -> GlobalSignal<T> {
        GlobalSignal::new(constructor)
    }
}

impl<T: PartialEq + 'static> Signal<T> {
    /// Creates a new global Signal that can be used in a global static.
    #[track_caller]
    pub const fn global_memo(constructor: fn() -> T) -> GlobalMemo<T> {
        GlobalMemo::new(constructor)
    }

    /// Creates a new unsync Selector. The selector will be run immediately and whenever any signal it reads changes.
    ///
    /// Selectors can be used to efficiently compute derived data from signals.
    #[track_caller]
    pub fn memo(f: impl FnMut() -> T + 'static) -> Memo<T> {
        Memo::new(f)
    }

    /// Creates a new unsync Selector with an explicit location. The selector will be run immediately and whenever any signal it reads changes.
    ///
    /// Selectors can be used to efficiently compute derived data from signals.
    pub fn memo_with_location(
        f: impl FnMut() -> T + 'static,
        location: &'static std::panic::Location<'static>,
    ) -> Memo<T> {
        Memo::new_with_location(f, location)
    }
}

impl<T: 'static, S: Storage<SignalData<T>>> Signal<T, S> {
    /// Creates a new Signal. Signals are a Copy state management solution with automatic dependency tracking.
    #[track_caller]
    #[tracing::instrument(skip(value))]
    pub fn new_maybe_sync(value: T) -> Self {
        Self {
            inner: CopyValue::<SignalData<T>, S>::new_maybe_sync(SignalData {
                subscribers: Default::default(),
                value,
            }),
        }
    }

    /// Creates a new Signal. Signals are a Copy state management solution with automatic dependency tracking.
    pub fn new_with_caller(
        value: T,
        #[cfg(debug_assertions)] caller: &'static std::panic::Location<'static>,
    ) -> Self {
        Self {
            inner: CopyValue::new_with_caller(
                SignalData {
                    subscribers: Default::default(),
                    value,
                },
                #[cfg(debug_assertions)]
                caller,
            ),
        }
    }

    /// Create a new signal with a custom owner scope. The signal will be dropped when the owner scope is dropped instead of the current scope.
    #[track_caller]
    #[tracing::instrument(skip(value))]
    pub fn new_maybe_sync_in_scope(value: T, owner: ScopeId) -> Self {
        Self {
            inner: CopyValue::<SignalData<T>, S>::new_maybe_sync_in_scope(
                SignalData {
                    subscribers: Default::default(),
                    value,
                },
                owner,
            ),
        }
    }

    /// Drop the value out of the signal, invalidating the signal in the process.
    pub fn manually_drop(&self) -> Option<T> {
        self.inner.manually_drop().map(|i| i.value)
    }

    /// Get the scope the signal was created in.
    pub fn origin_scope(&self) -> ScopeId {
        self.inner.origin_scope()
    }

    fn update_subscribers(&self) {
        {
            let inner = self.inner.read();

            // We cannot hold the subscribers lock while calling mark_dirty, because mark_dirty can run user code which may cause a new subscriber to be added. If we hold the lock, we will deadlock.
            let mut subscribers = std::mem::take(&mut *inner.subscribers.lock().unwrap());
            subscribers.retain(|reactive_context| reactive_context.mark_dirty());
            // Extend the subscribers list instead of overwriting it in case a subscriber is added while reactive contexts are marked dirty
            inner.subscribers.lock().unwrap().extend(subscribers);
        }
    }

    /// Get the generational id of the signal.
    pub fn id(&self) -> generational_box::GenerationalBoxId {
        self.inner.id()
    }

    /// **This pattern is no longer recommended. Prefer [`peek`](Signal::peek) or creating new signals instead.**
    ///
    /// This function is the equivalent of the [write_silent](https://docs.rs/dioxus/latest/dioxus/prelude/struct.UseRef.html#method.write_silent) method on use_ref.
    ///
    /// ## What you should use instead
    ///
    /// ### Reading and Writing to data in the same scope
    ///
    /// Reading and writing to the same signal in the same scope will cause that scope to rerun forever:
    /// ```rust, no_run
    /// # use dioxus::prelude::*;
    /// let mut signal = use_signal(|| 0);
    /// // This makes the scope rerun whenever we write to the signal
    /// println!("{}", *signal.read());
    /// // This will rerun the scope because we read the signal earlier in the same scope
    /// *signal.write() += 1;
    /// ```
    ///
    /// You may have used the write_silent method to avoid this infinite loop with use_ref like this:
    /// ```rust, no_run
    /// # use dioxus::prelude::*;
    /// let signal = use_signal(|| 0);
    /// // This makes the scope rerun whenever we write to the signal
    /// println!("{}", *signal.read());
    /// // Write silent will not rerun any subscribers
    /// *signal.write_silent() += 1;
    /// ```
    ///
    /// Instead you can use the [`peek`](Signal::peek) and [`write`](Signal::write) methods instead. The peek method will not subscribe to the current scope which will avoid an infinite loop if you are reading and writing to the same signal in the same scope.
    /// ```rust, no_run
    /// # use dioxus::prelude::*;
    /// let mut signal = use_signal(|| 0);
    /// // Peek will read the value but not subscribe to the current scope
    /// println!("{}", *signal.peek());
    /// // Write will update any subscribers which does not include the current scope
    /// *signal.write() += 1;
    /// ```
    ///
    /// ### Reading and Writing to different data
    ///
    ///
    ///
    /// ## Why is this pattern no longer recommended?
    ///
    /// This pattern is no longer recommended because it is very easy to allow your state and UI to grow out of sync. `write_silent` globally opts out of automatic state updates which can be difficult to reason about.
    ///
    ///
    /// Lets take a look at an example:
    /// main.rs:
    /// ```rust, no_run
    /// # use dioxus::prelude::*;
    /// # fn Child() -> Element { todo!() }
    /// fn app() -> Element {
    ///     let signal = use_context_provider(|| Signal::new(0));
    ///     
    ///     // We want to log the value of the signal whenever the app component reruns
    ///     println!("{}", *signal.read());
    ///     
    ///     rsx! {
    ///         button {
    ///             // If we don't want to rerun the app component when the button is clicked, we can use write_silent
    ///             onclick: move |_| *signal.write_silent() += 1,
    ///             "Increment"
    ///         }
    ///         Child {}
    ///     }
    /// }
    /// ```
    /// child.rs:
    /// ```rust, no_run
    /// # use dioxus::prelude::*;
    /// fn Child() -> Element {
    ///     let signal: Signal<i32> = use_context();
    ///     
    ///     // It is difficult to tell that changing the button to use write_silent in the main.rs file will cause UI to be out of sync in a completely different file
    ///     rsx! {
    ///         "{signal}"
    ///     }
    /// }
    /// ```
    ///
    /// Instead [`peek`](Signal::peek) locally opts out of automatic state updates explicitly for a specific read which is easier to reason about.
    ///
    /// Here is the same example using peek:
    /// main.rs:
    /// ```rust, no_run
    /// # use dioxus::prelude::*;
    /// # fn Child() -> Element { todo!() }
    /// fn app() -> Element {
    ///     let mut signal = use_context_provider(|| Signal::new(0));
    ///     
    ///     // We want to log the value of the signal whenever the app component reruns, but we don't want to rerun the app component when the signal is updated so we use peek instead of read
    ///     println!("{}", *signal.peek());
    ///     
    ///     rsx! {
    ///         button {
    ///             // We can use write like normal and update the child component automatically
    ///             onclick: move |_| *signal.write() += 1,
    ///             "Increment"
    ///         }
    ///         Child {}
    ///     }
    /// }
    /// ```
    /// child.rs:
    /// ```rust, no_run
    /// # use dioxus::prelude::*;
    /// fn Child() -> Element {
    ///     let signal: Signal<i32> = use_context();
    ///     
    ///     rsx! {
    ///         "{signal}"
    ///     }
    /// }
    /// ```
    #[track_caller]
    #[deprecated = "This pattern is no longer recommended. Prefer `peek` or creating new signals instead."]
    pub fn write_silent(&self) -> S::Mut<'static, T> {
        S::map_mut(self.inner.write_unchecked(), |inner| &mut inner.value)
    }
}

impl<T, S: Storage<SignalData<T>>> Readable for Signal<T, S> {
    type Target = T;
    type Storage = S;

    #[track_caller]
    fn try_read_unchecked(
        &self,
    ) -> Result<ReadableRef<'static, Self>, generational_box::BorrowError> {
        let inner = self.inner.try_read_unchecked()?;

        if let Some(reactive_context) = ReactiveContext::current() {
            tracing::trace!("Subscribing to the reactive context {}", reactive_context);
            inner.subscribers.lock().unwrap().insert(reactive_context);
        }

        Ok(S::map(inner, |v| &v.value))
    }

    /// Get the current value of the signal. **Unlike read, this will not subscribe the current scope to the signal which can cause parts of your UI to not update.**
    ///
    /// If the signal has been dropped, this will panic.
    #[track_caller]
    fn peek_unchecked(&self) -> ReadableRef<'static, Self> {
        let inner = self.inner.try_read_unchecked().unwrap();
        S::map(inner, |v| &v.value)
    }
}

impl<T: 'static, S: Storage<SignalData<T>>> Writable for Signal<T, S> {
    type Mut<'a, R: ?Sized + 'static> = Write<'a, R, S>;

    fn map_mut<I: ?Sized, U: ?Sized + 'static, F: FnOnce(&mut I) -> &mut U>(
        ref_: Self::Mut<'_, I>,
        f: F,
    ) -> Self::Mut<'_, U> {
        Write::map(ref_, f)
    }

    fn try_map_mut<
        I: ?Sized + 'static,
        U: ?Sized + 'static,
        F: FnOnce(&mut I) -> Option<&mut U>,
    >(
        ref_: Self::Mut<'_, I>,
        f: F,
    ) -> Option<Self::Mut<'_, U>> {
        Write::filter_map(ref_, f)
    }

    fn downcast_lifetime_mut<'a: 'b, 'b, R: ?Sized + 'static>(
        mut_: Self::Mut<'a, R>,
    ) -> Self::Mut<'b, R> {
        Write::downcast_lifetime(mut_)
    }

    #[track_caller]
    fn try_write_unchecked(
        &self,
    ) -> Result<WritableRef<'static, Self>, generational_box::BorrowMutError> {
        #[cfg(debug_assertions)]
        let origin = std::panic::Location::caller();
        self.inner.try_write_unchecked().map(|inner| {
            let borrow = S::map_mut(inner, |v| &mut v.value);
            Write {
                write: borrow,
                drop_signal: Box::new(SignalSubscriberDrop {
                    signal: *self,
                    #[cfg(debug_assertions)]
                    origin,
                }),
            }
        })
    }
}

impl<T> IntoAttributeValue for Signal<T>
where
    T: Clone + IntoAttributeValue,
{
    fn into_value(self) -> dioxus_core::AttributeValue {
        self.with(|f| f.clone().into_value())
    }
}

impl<T> IntoDynNode for Signal<T>
where
    T: Clone + IntoDynNode,
{
    fn into_dyn_node(self) -> dioxus_core::DynamicNode {
        self().into_dyn_node()
    }
}

impl<T: 'static, S: Storage<SignalData<T>>> PartialEq for Signal<T, S> {
    fn eq(&self, other: &Self) -> bool {
        self.inner == other.inner
    }
}

impl<T: 'static, S: Storage<SignalData<T>>> Eq for Signal<T, S> {}

/// Allow calling a signal with signal() syntax
///
/// Currently only limited to copy types, though could probably specialize for string/arc/rc
impl<T: Clone, S: Storage<SignalData<T>> + 'static> Deref for Signal<T, S> {
    type Target = dyn Fn() -> T;

    fn deref(&self) -> &Self::Target {
        Readable::deref_impl(self)
    }
}

#[cfg(feature = "serde")]
impl<T: serde::Serialize + 'static, Store: Storage<SignalData<T>>> serde::Serialize
    for Signal<T, Store>
{
    fn serialize<S: serde::Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
        self.read().serialize(serializer)
    }
}

#[cfg(feature = "serde")]
impl<'de, T: serde::Deserialize<'de> + 'static, Store: Storage<SignalData<T>>>
    serde::Deserialize<'de> for Signal<T, Store>
{
    fn deserialize<D: serde::Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
        Ok(Self::new_maybe_sync(T::deserialize(deserializer)?))
    }
}

/// A mutable reference to a signal's value.
///
/// T is the current type of the write
/// S is the storage type of the signal
pub struct Write<'a, T: ?Sized + 'static, S: AnyStorage = UnsyncStorage> {
    write: S::Mut<'a, T>,
    drop_signal: Box<dyn Any>,
}

impl<'a, T: ?Sized + 'static, S: AnyStorage> Write<'a, T, S> {
    /// Map the mutable reference to the signal's value to a new type.
    pub fn map<O: ?Sized>(myself: Self, f: impl FnOnce(&mut T) -> &mut O) -> Write<'a, O, S> {
        let Self {
            write, drop_signal, ..
        } = myself;
        Write {
            write: S::map_mut(write, f),
            drop_signal,
        }
    }

    /// Try to map the mutable reference to the signal's value to a new type
    pub fn filter_map<O: ?Sized>(
        myself: Self,
        f: impl FnOnce(&mut T) -> Option<&mut O>,
    ) -> Option<Write<'a, O, S>> {
        let Self {
            write, drop_signal, ..
        } = myself;
        let write = S::try_map_mut(write, f);
        write.map(|write| Write { write, drop_signal })
    }

    /// Downcast the lifetime of the mutable reference to the signal's value.
    ///
    /// This function enforces the variance of the lifetime parameter `'a` in Mut.  Rust will typically infer this cast with a concrete type, but it cannot with a generic type.
    pub fn downcast_lifetime<'b>(mut_: Self) -> Write<'b, T, S>
    where
        'a: 'b,
    {
        Write {
            write: S::downcast_lifetime_mut(mut_.write),
            drop_signal: mut_.drop_signal,
        }
    }
}

impl<T: ?Sized + 'static, S: AnyStorage> Deref for Write<'_, T, S> {
    type Target = T;

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

impl<T: ?Sized, S: AnyStorage> DerefMut for Write<'_, T, S> {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.write
    }
}

#[allow(unused)]
const SIGNAL_READ_WRITE_SAME_SCOPE_HELP: &str = r#"This issue is caused by reading and writing to the same signal in a reactive scope. Components, effects, memos, and resources each have their own a reactive scopes. Reactive scopes rerun when any signal you read inside of them are changed. If you read and write to the same signal in the same scope, the write will cause the scope to rerun and trigger the write again. This can cause an infinite loop.

You can fix the issue by either:
1) Splitting up your state and Writing, reading to different signals:

For example, you could change this broken code:

#[derive(Clone, Copy)]
struct Counts {
    count1: i32,
    count2: i32,
}

fn app() -> Element {
    let mut counts = use_signal(|| Counts { count1: 0, count2: 0 });
    
    use_effect(move || {
        // This effect both reads and writes to counts
        counts.write().count1 = counts().count2;
    })
}

Into this working code:

fn app() -> Element {
    let mut count1 = use_signal(|| 0);
    let mut count2 = use_signal(|| 0);

    use_effect(move || {
        count1.write(count2());
    });
}
2) Reading and Writing to the same signal in different scopes:

For example, you could change this broken code:

fn app() -> Element {
    let mut count = use_signal(|| 0);

    use_effect(move || {
        // This effect both reads and writes to count
        println!("{}", count());
        count.write(count());
    });
}


To this working code:

fn app() -> Element {
    let mut count = use_signal(|| 0);

    use_effect(move || {
        count.write(count());
    });
    use_effect(move || {
        println!("{}", count());
    });
}
"#;

struct SignalSubscriberDrop<T: 'static, S: Storage<SignalData<T>>> {
    signal: Signal<T, S>,
    #[cfg(debug_assertions)]
    origin: &'static std::panic::Location<'static>,
}

impl<T: 'static, S: Storage<SignalData<T>>> Drop for SignalSubscriberDrop<T, S> {
    fn drop(&mut self) {
        #[cfg(debug_assertions)]
        {
            tracing::trace!(
                "Write on signal at {} finished, updating subscribers",
                self.origin
            );

            // Check if the write happened during a render. If it did, we should warn the user that this is generally a bad practice.
            if dioxus_core::vdom_is_rendering() {
                tracing::warn!(
                    "Write on signal at {} happened while a component was running. Writing to signals during a render can cause infinite rerenders when you read the same signal in the component. Consider writing to the signal in an effect, future, or event handler if possible.",
                    self.origin
                );
            }

            // Check if the write happened during a scope that the signal is also subscribed to. If it did, this will probably cause an infinite loop.
            if let Some(reactive_context) = ReactiveContext::current() {
                if let Ok(inner) = self.signal.inner.try_read() {
                    if let Ok(subscribers) = inner.subscribers.lock() {
                        for subscriber in subscribers.iter() {
                            if reactive_context == *subscriber {
                                let origin = self.origin;
                                tracing::warn!(
                                    "Write on signal at {origin} finished in {reactive_context} which is also subscribed to the signal. This will likely cause an infinite loop. When the write finishes, {reactive_context} will rerun which may cause the write to be rerun again.\nHINT:\n{SIGNAL_READ_WRITE_SAME_SCOPE_HELP}",
                                );
                            }
                        }
                    }
                }
            }
        }
        self.signal.update_subscribers();
    }
}

fmt_impls!(Signal<T, S: Storage<SignalData<T>>>);
default_impl!(Signal<T, S: Storage<SignalData<T>>>);
write_impls!(Signal<T, S: Storage<SignalData<T>>>);

impl<T: 'static, S: Storage<SignalData<T>>> Clone for Signal<T, S> {
    fn clone(&self) -> Self {
        *self
    }
}

impl<T: 'static, S: Storage<SignalData<T>>> Copy for Signal<T, S> {}