#![cfg_attr(feature = "ssr", allow(unused_variables, unused_imports, dead_code))]

use crate::core::MaybeRwSignal;
use crate::utils::{CloneableFn, CloneableFnWithArg, FilterOptions};
use crate::{
    filter_builder_methods, use_event_listener, watch_pausable_with_options, DebounceOptions,
    ThrottleOptions, WatchOptions, WatchPausableReturn,
};
use cfg_if::cfg_if;
use default_struct_builder::DefaultBuilder;
use js_sys::Reflect;
use leptos::*;
use serde::{Deserialize, Serialize};
use serde_json::Error;
use std::time::Duration;
use wasm_bindgen::{JsCast, JsValue};

pub use crate::core::StorageType;

const CUSTOM_STORAGE_EVENT_NAME: &str = "leptos-use-storage";

/// Reactive [LocalStorage](https://developer.mozilla.org/en-US/docs/Web/API/Window/localStorage) / [SessionStorage](https://developer.mozilla.org/en-US/docs/Web/API/Window/sessionStorage).
///
/// ## Demo
///
/// [Link to Demo](https://github.com/Synphonyte/leptos-use/tree/main/examples/use_storage)
///
/// ## Usage
///
/// It returns a triplet `(read_signal, write_signal, delete_from_storage_func)` of type `(ReadSignal<T>, WriteSignal<T>, Fn())`.
///
/// Values are (de-)serialized to/from JSON using [`serde`](https://serde.rs/).
///
/// ```
/// # use leptos::*;
/// # use leptos_use::storage::{StorageType, use_storage, use_storage_with_options, UseStorageOptions};
/// # use serde::{Deserialize, Serialize};
/// #
/// #[derive(Serialize, Deserialize, Clone)]
/// pub struct MyState {
///     pub hello: String,
///     pub greeting: String,
/// }
///
/// # pub fn Demo() -> impl IntoView {
/// // bind struct. Must be serializable.
/// let (state, set_state, _) = use_storage(
///     "my-state",
///     MyState {
///         hello: "hi".to_string(),
///         greeting: "Hello".to_string()
///     },
/// ); // returns Signal<MyState>
///
/// // bind bool.
/// let (flag, set_flag, remove_flag) = use_storage("my-flag", true); // returns Signal<bool>
///
/// // bind number
/// let (count, set_count, _) = use_storage("my-count", 0); // returns Signal<i32>
///
/// // bind string with SessionStorage
/// let (id, set_id, _) = use_storage_with_options(
///     "my-id",
///     "some_string_id".to_string(),
///     UseStorageOptions::default().storage_type(StorageType::Session),
/// );
/// #    view! { }
/// # }
/// ```
///
/// ## Merge Defaults
///
/// By default, [`use_storage`] will use the value from storage if it is present and ignores the default value.
/// Be aware that when you add more properties to the default value, the key might be `None`
/// (in the case of an `Option<T>` field) if client's storage does not have that key
/// or deserialization might fail altogether.
///
/// Let's say you had a struct `MyState` that has been saved to storage
///
/// ```ignore
/// #[derive(Serialize, Deserialize, Clone)]
/// struct MyState {
///     hello: String,
/// }
///
/// let (state, .. ) = use_storage("my-state", MyState { hello: "hello" });
/// ```
///
/// Now, in a newer version you added a field `greeting` to `MyState`.
///
/// ```ignore
/// #[derive(Serialize, Deserialize, Clone)]
/// struct MyState {
///     hello: String,
///     greeting: String,
/// }
///
/// let (state, .. ) = use_storage(
///     "my-state",
///     MyState { hello: "hi", greeting: "whatsup" },
/// ); // fails to deserialize -> default value
/// ```
///
/// This will fail to deserialize the stored string `{"hello": "hello"}` because it has no field `greeting`.
/// Hence it just uses the new default value provided and the previously saved value is lost.
///
/// To mitigate that you can provide a `merge_defaults` option. This is a pure function pointer
/// that takes the serialized (to json) stored value and the default value as arguments
/// and should return the serialized merged value.
///
/// ```
/// # use leptos::*;
/// # use leptos_use::storage::{use_storage_with_options, UseStorageOptions};
/// # use serde::{Deserialize, Serialize};
/// #
/// #[derive(Serialize, Deserialize, Clone)]
/// pub struct MyState {
///     pub hello: String,
///     pub greeting: String,
/// }
/// #
/// # pub fn Demo() -> impl IntoView {
/// let (state, set_state, _) = use_storage_with_options(
///     "my-state",
///     MyState {
///         hello: "hi".to_string(),
///         greeting: "Hello".to_string()
///     },
///     UseStorageOptions::<MyState>::default().merge_defaults(|stored_value, default_value| {
///         if stored_value.contains(r#""greeting":"#) {
///             stored_value.to_string()
///         } else {
///             // add "greeting": "Hello" to the string
///             stored_value.replace("}", &format!(r#""greeting": "{}"}}"#, default_value.greeting))
///         }
///     }),
/// );
/// #
/// #    view! { }
/// # }
/// ```
///
/// ## Filter Storage Write
///
/// You can specify `debounce` or `throttle` options for limiting writes to storage.
///
/// ## Server-Side Rendering
///
/// On the server this falls back to a `create_signal(default)` and an empty remove function.
///
/// ## See also
///
/// * [`use_local_storage`]
/// * [`use_session_storage`]
// #[doc(cfg(feature = "storage"))]
pub fn use_storage<T, D>(key: &str, defaults: D) -> (Signal<T>, WriteSignal<T>, impl Fn() + Clone)
where
    for<'de> T: Serialize + Deserialize<'de> + Clone + 'static,
    D: Into<MaybeRwSignal<T>>,
    T: Clone,
{
    use_storage_with_options(key, defaults, UseStorageOptions::default())
}

/// Version of [`use_storage`] that accepts [`UseStorageOptions`]. See [`use_storage`] for how to use.
// #[doc(cfg(feature = "storage"))]
pub fn use_storage_with_options<T, D>(
    key: &str,
    defaults: D,
    options: UseStorageOptions<T>,
) -> (Signal<T>, WriteSignal<T>, impl Fn() + Clone)
where
    for<'de> T: Serialize + Deserialize<'de> + Clone + 'static,
    D: Into<MaybeRwSignal<T>>,
    T: Clone,
{
    let defaults = defaults.into();

    let UseStorageOptions {
        storage_type,
        listen_to_storage_changes,
        write_defaults,
        merge_defaults,
        on_error,
        filter,
    } = options;

    let (data, set_data) = defaults.into_signal();

    let raw_init = data.get_untracked();

    cfg_if! { if #[cfg(feature = "ssr")] {
        let remove: Box<dyn CloneableFn> = Box::new(|| {});
    } else {
        let storage = storage_type.into_storage();

        let remove: Box<dyn CloneableFn> = match storage {
            Ok(Some(storage)) => {
                let write = {
                    let on_error = on_error.clone();
                    let storage = storage.clone();
                    let key = key.to_string();

                    move |v: &T| {
                        match serde_json::to_string(&v) {
                            Ok(ref serialized) => match storage.get_item(&key) {
                                Ok(old_value) => {
                                    if old_value.as_ref() != Some(serialized) {
                                        if let Err(e) = storage.set_item(&key, serialized) {
                                            on_error(UseStorageError::StorageAccessError(e));
                                        } else {
                                            let mut event_init = web_sys::CustomEventInit::new();
                                            event_init.detail(
                                                &StorageEventDetail {
                                                    key: Some(key.clone()),
                                                    old_value,
                                                    new_value: Some(serialized.clone()),
                                                    storage_area: Some(storage.clone()),
                                                }
                                                .into(),
                                            );

                                            // importantly this should _not_ be a StorageEvent since those cannot
                                            // be constructed with a non-built-in storage area
                                            let _ = window().dispatch_event(
                                                &web_sys::CustomEvent::new_with_event_init_dict(
                                                    CUSTOM_STORAGE_EVENT_NAME,
                                                    &event_init,
                                                )
                                                .expect("Failed to create CustomEvent"),
                                            );
                                        }
                                    }
                                }
                                Err(e) => {
                                    on_error.clone()(UseStorageError::StorageAccessError(e));
                                }
                            },
                            Err(e) => {
                                on_error.clone()(UseStorageError::SerializationError(e));
                            }
                        }
                    }
                };

                let read = {
                    let storage = storage.clone();
                    let on_error = on_error.clone();
                    let key = key.to_string();
                    let raw_init = raw_init.clone();

                    move |event_detail: Option<StorageEventDetail>| -> Option<T> {
                        let serialized_init = match serde_json::to_string(&raw_init) {
                            Ok(serialized) => Some(serialized),
                            Err(e) => {
                                on_error.clone()(UseStorageError::DefaultSerializationError(e));
                                None
                            }
                        };

                        let raw_value = if let Some(event_detail) = event_detail {
                            event_detail.new_value
                        } else {
                            match storage.get_item(&key) {
                                Ok(raw_value) => match raw_value {
                                    Some(raw_value) => Some(merge_defaults(&raw_value, &raw_init)),
                                    None => serialized_init.clone(),
                                },
                                Err(e) => {
                                    on_error.clone()(UseStorageError::StorageAccessError(e));
                                    None
                                }
                            }
                        };

                        match raw_value {
                            Some(raw_value) => match serde_json::from_str(&raw_value) {
                                Ok(v) => Some(v),
                                Err(e) => {
                                    on_error.clone()(UseStorageError::SerializationError(e));
                                    None
                                }
                            },
                            None => {
                                if let Some(serialized_init) = &serialized_init {
                                    if write_defaults {
                                        if let Err(e) = storage.set_item(&key, serialized_init) {
                                            on_error(UseStorageError::StorageAccessError(e));
                                        }
                                    }
                                }

                                Some(raw_init)
                            }
                        }
                    }
                };

                let WatchPausableReturn {
                    pause: pause_watch,
                    resume: resume_watch,
                    ..
                } = watch_pausable_with_options(
                    move || data.get(),
                    move |data, _, _| write.clone()(data),
                    WatchOptions::default().filter(filter),
                );

                let update = {
                    let key = key.to_string();
                    let storage = storage.clone();
                    let raw_init = raw_init.clone();

                    move |event_detail: Option<StorageEventDetail>| {
                        if let Some(event_detail) = &event_detail {
                            if event_detail.storage_area != Some(storage) {
                                return;
                            }

                            match &event_detail.key {
                                None => {
                                    set_data.set(raw_init);
                                    return;
                                }
                                Some(event_key) => {
                                    if event_key != &key {
                                        return;
                                    }
                                }
                            };
                        }

                        pause_watch();

                        if let Some(value) = read(event_detail.clone()) {
                            set_data.set(value);
                        }

                        if event_detail.is_some() {
                            // use timeout to avoid inifinite loop
                            let resume = resume_watch.clone();
                            let _ = set_timeout_with_handle(resume, Duration::ZERO);
                        } else {
                            resume_watch();
                        }
                    }
                };

                let upd = update.clone();
                let update_from_custom_event =
                    move |event: web_sys::CustomEvent| upd.clone()(Some(event.into()));

                let upd = update.clone();
                let update_from_storage_event =
                    move |event: web_sys::StorageEvent| upd.clone()(Some(event.into()));

                if listen_to_storage_changes {
                    let _ = use_event_listener(window(), ev::storage, update_from_storage_event);
                    let _ = use_event_listener(
                                                window(),
                        ev::Custom::new(CUSTOM_STORAGE_EVENT_NAME),
                        update_from_custom_event,
                    );
                }

                update(None);

                let k = key.to_string();

                Box::new(move || {
                    let _ = storage.remove_item(&k);
                })
            }
            Err(e) => {
                on_error(UseStorageError::NoStorage(e));
                Box::new(move || {})
            }
            _ => {
                // do nothing
                Box::new(move || {})
            }
        };
    }}

    (data, set_data, move || remove.clone()())
}

#[derive(Clone)]
pub struct StorageEventDetail {
    pub key: Option<String>,
    pub old_value: Option<String>,
    pub new_value: Option<String>,
    pub storage_area: Option<web_sys::Storage>,
}

impl From<web_sys::StorageEvent> for StorageEventDetail {
    fn from(event: web_sys::StorageEvent) -> Self {
        Self {
            key: event.key(),
            old_value: event.old_value(),
            new_value: event.new_value(),
            storage_area: event.storage_area(),
        }
    }
}

impl From<web_sys::CustomEvent> for StorageEventDetail {
    fn from(event: web_sys::CustomEvent) -> Self {
        let detail = event.detail();
        Self {
            key: get_optional_string(&detail, "key"),
            old_value: get_optional_string(&detail, "oldValue"),
            new_value: get_optional_string(&detail, "newValue"),
            storage_area: Reflect::get(&detail, &"storageArea".into())
                .map(|v| v.dyn_into::<web_sys::Storage>().ok())
                .unwrap_or_default(),
        }
    }
}

impl From<StorageEventDetail> for JsValue {
    fn from(event: StorageEventDetail) -> Self {
        let obj = js_sys::Object::new();

        let _ = Reflect::set(&obj, &"key".into(), &event.key.into());
        let _ = Reflect::set(&obj, &"oldValue".into(), &event.old_value.into());
        let _ = Reflect::set(&obj, &"newValue".into(), &event.new_value.into());
        let _ = Reflect::set(&obj, &"storageArea".into(), &event.storage_area.into());

        obj.into()
    }
}

fn get_optional_string(v: &JsValue, key: &str) -> Option<String> {
    Reflect::get(v, &key.into())
        .map(|v| v.as_string())
        .unwrap_or_default()
}

/// Error type for use_storage_with_options
// #[doc(cfg(feature = "storage"))]
pub enum UseStorageError<E = ()> {
    NoStorage(JsValue),
    StorageAccessError(JsValue),
    CustomStorageAccessError(E),
    SerializationError(Error),
    DefaultSerializationError(Error),
}

/// Options for [`use_storage_with_options`].
// #[doc(cfg(feature = "storage"))]
#[derive(DefaultBuilder)]
pub struct UseStorageOptions<T> {
    /// Type of storage. Can be `Local` (default), `Session` or `Custom(web_sys::Storage)`
    pub(crate) storage_type: StorageType,
    /// Listen to changes to this storage key from somewhere else. Defaults to true.
    pub(crate) listen_to_storage_changes: bool,
    /// If no value for the give key is found in the storage, write it. Defaults to true.
    pub(crate) write_defaults: bool,
    /// Takes the serialized (json) stored value and the default value and returns a merged version.
    /// Defaults to simply returning the stored value.
    pub(crate) merge_defaults: fn(&str, &T) -> String,
    /// Optional callback whenever an error occurs. The callback takes an argument of type [`UseStorageError`].
    pub(crate) on_error: Box<dyn CloneableFnWithArg<UseStorageError>>,

    /// Debounce or throttle the writing to storage whenever the value changes.
    pub(crate) filter: FilterOptions,
}

impl<T> Default for UseStorageOptions<T> {
    fn default() -> Self {
        Self {
            storage_type: Default::default(),
            listen_to_storage_changes: true,
            write_defaults: true,
            merge_defaults: |stored_value, _default_value| stored_value.to_string(),
            on_error: Box::new(|_| ()),
            filter: Default::default(),
        }
    }
}

impl<T> UseStorageOptions<T> {
    filter_builder_methods!(
        /// the serializing and storing into storage
        filter
    );
}