use std::{
    any::Any, borrow::Cow, fmt::Debug, hash::Hash, marker::PhantomData, ops::Deref, time::Duration,
    vec::IntoIter,
};

use async_trait::async_trait;

use super::DownloaderError;

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum DownloadSimpleState {
    Paused,
    Active,
    Completed,
    Error,
    Unknown,
}

pub trait DownloadStateTrait: Sized + Debug {
    fn to_download_state(&self) -> DownloadSimpleState;
}

pub trait DownloadIdTrait: Hash + Sized + Clone + Send + Debug {}

pub trait DownloadTaskTrait: Sized + Send + Debug {
    type State: DownloadStateTrait;
    type Id: DownloadIdTrait;

    fn id(&self) -> &Self::Id;
    fn into_id(self) -> Self::Id;
    fn name(&self) -> Cow<'_, str>;
    fn speed(&self) -> Option<u64>;
    fn state(&self) -> &Self::State;
    fn dl_bytes(&self) -> Option<u64>;
    fn total_bytes(&self) -> Option<u64>;
    fn left_bytes(&self) -> Option<u64> {
        if let (Some(tt), Some(dl)) = (self.total_bytes(), self.dl_bytes()) {
            tt.checked_sub(dl)
        } else {
            None
        }
    }
    fn et(&self) -> Option<Duration>;
    fn eta(&self) -> Option<Duration> {
        if let (Some(left_bytes), Some(speed)) = (self.left_bytes(), self.speed()) {
            if speed > 0 {
                Some(Duration::from_secs_f64(left_bytes as f64 / speed as f64))
            } else {
                None
            }
        } else {
            None
        }
    }
    fn average_speed(&self) -> Option<f64> {
        if let (Some(et), Some(dl_bytes)) = (self.et(), self.dl_bytes()) {
            let secs = et.as_secs_f64();

            if secs > 0.0 {
                Some(dl_bytes as f64 / secs)
            } else {
                None
            }
        } else {
            None
        }
    }
    fn progress(&self) -> Option<f32> {
        if let (Some(dl), Some(tt)) = (self.dl_bytes(), self.total_bytes()) {
            if dl > 0 {
                if tt > 0 {
                    Some(dl as f32 / tt as f32)
                } else {
                    None
                }
            } else {
                Some(0.0)
            }
        } else {
            None
        }
    }
}

pub trait DownloadCreationTrait: Sized {
    type Task: DownloadTaskTrait;
}

pub trait DownloadSelectorTrait: Sized + Any + Send {
    type Id: DownloadIdTrait;
    type Task: DownloadTaskTrait<Id = Self::Id>;

    fn try_into_ids_only(self) -> Result<Vec<Self::Id>, Self> {
        Err(self)
    }
}

pub trait DownloadIdSelectorTrait:
    DownloadSelectorTrait
    + IntoIterator<Item = Self::Id>
    + FromIterator<Self::Id>
    + Into<Vec<Self::Id>>
    + From<Vec<Self::Id>>
{
    fn try_into_ids_only(self) -> Result<Vec<Self::Id>, Self> {
        Ok(Vec::from_iter(self))
    }

    fn from_id(id: Self::Id) -> Self;
}

#[derive(Debug)]
pub struct DownloadIdSelector<Task>
where
    Task: DownloadTaskTrait,
{
    pub ids: Vec<Task::Id>,
    pub marker: PhantomData<Task>,
}

impl<Task> Deref for DownloadIdSelector<Task>
where
    Task: DownloadTaskTrait,
{
    type Target = Vec<Task::Id>;

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

impl<Task> IntoIterator for DownloadIdSelector<Task>
where
    Task: DownloadTaskTrait,
{
    type Item = Task::Id;
    type IntoIter = IntoIter<Task::Id>;

    fn into_iter(self) -> Self::IntoIter {
        self.ids.into_iter()
    }
}

impl<Task> FromIterator<Task::Id> for DownloadIdSelector<Task>
where
    Task: DownloadTaskTrait,
{
    fn from_iter<T: IntoIterator<Item = Task::Id>>(iter: T) -> Self {
        Self {
            ids: Vec::from_iter(iter),
            marker: PhantomData,
        }
    }
}

impl<Task> DownloadSelectorTrait for DownloadIdSelector<Task>
where
    Task: DownloadTaskTrait + 'static,
{
    type Id = Task::Id;
    type Task = Task;
}

impl<Task> From<Vec<Task::Id>> for DownloadIdSelector<Task>
where
    Task: DownloadTaskTrait + 'static,
{
    fn from(value: Vec<Task::Id>) -> Self {
        Self {
            ids: value,
            marker: PhantomData,
        }
    }
}

impl<Task> From<DownloadIdSelector<Task>> for Vec<Task::Id>
where
    Task: DownloadTaskTrait + 'static,
{
    fn from(value: DownloadIdSelector<Task>) -> Self {
        value.ids
    }
}

impl<Task> DownloadIdSelectorTrait for DownloadIdSelector<Task>
where
    Task: DownloadTaskTrait + 'static,
{
    fn try_into_ids_only(self) -> Result<Vec<Self::Id>, Self> {
        Ok(self.ids)
    }

    fn from_id(id: Self::Id) -> Self {
        Self {
            ids: vec![id],
            marker: PhantomData,
        }
    }
}

#[async_trait]
pub trait DownloaderTrait {
    type State: DownloadStateTrait;
    type Id: DownloadIdTrait;
    type Task: DownloadTaskTrait<State = Self::State, Id = Self::Id>;
    type Creation: DownloadCreationTrait<Task = Self::Task>;
    type Selector: DownloadSelectorTrait<Task = Self::Task>;

    async fn add_downloads(
        &self,
        creation: Self::Creation,
    ) -> Result<impl IntoIterator<Item = Self::Id>, DownloaderError>;
    async fn pause_downloads(
        &self,
        selector: Self::Selector,
    ) -> Result<impl IntoIterator<Item = Self::Id>, DownloaderError>;
    async fn resume_downloads(
        &self,
        selector: Self::Selector,
    ) -> Result<impl IntoIterator<Item = Self::Id>, DownloaderError>;
    async fn remove_downloads(
        &self,
        selector: Self::Selector,
    ) -> Result<impl IntoIterator<Item = Self::Id>, DownloaderError>;
    async fn query_downloads(
        &self,
        selector: Self::Selector,
    ) -> Result<impl IntoIterator<Item = Self::Task>, DownloaderError>;
}