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use core::ops::ControlFlow;

use crate::{
    effect::{Effective, ErasedEffective, Ss},
    never::Never,
    Flow, Status,
};

mod recoverable;
mod request_hint;
mod sequence;
mod tag;
mod value;

pub use recoverable::*;
pub use request_hint::*;
pub use sequence::*;
pub use tag::*;
pub use value::*;

#[derive(Copy, Clone)]
#[must_use]
pub enum VisitResult<S> {
    /// The protocol was not used.
    ///
    /// This either means the visitor doesn't support the protocol at all, or
    /// it didn't want to use the protocol right now.
    Skipped(S),

    /// How control flow should proceed.
    Control(Flow),
}

impl<S> VisitResult<S> {
    pub fn unit_skipped(self) -> VisitResult<()> {
        match self {
            VisitResult::Skipped(_) => VisitResult::Skipped(()),
            VisitResult::Control(flow) => VisitResult::Control(flow),
        }
    }

    pub fn to_status(self) -> Status {
        match self {
            VisitResult::Skipped(_) => Status::Ok,
            VisitResult::Control(flow) => flow.to_status(),
        }
    }

    pub fn to_flow(self) -> Option<Flow> {
        match self {
            VisitResult::Skipped(_) => None,
            VisitResult::Control(flow) => Some(flow),
        }
    }

    pub fn dont_break_if_skipped(self) -> Option<Status> {
        match self {
            VisitResult::Skipped(_) => None,
            VisitResult::Control(Flow::Continue) => Some(Status::Ok),
            VisitResult::Control(Flow::Done) => Some(Status::Ok),
            VisitResult::Control(Flow::Err) => Some(Status::Err),
        }
    }

    pub fn break_if_done_or_err(self) -> Option<Status> {
        match self {
            VisitResult::Skipped(_) => None,
            VisitResult::Control(Flow::Continue) => None,
            VisitResult::Control(Flow::Done) => Some(Status::Ok),
            VisitResult::Control(Flow::Err) => Some(Status::Err),
        }
    }

    pub fn break_if_err(self) -> Option<Status> {
        match self {
            VisitResult::Skipped(_) => None,
            VisitResult::Control(Flow::Continue) => None,
            VisitResult::Control(Flow::Done) => None,
            VisitResult::Control(Flow::Err) => Some(Status::Err),
        }
    }

    pub fn map_skipped<R, F>(self, f: F) -> VisitResult<R>
    where
        F: FnOnce(S) -> R,
    {
        match self {
            VisitResult::Skipped(s) => VisitResult::Skipped(f(s)),
            VisitResult::Control(flow) => VisitResult::Control(flow),
        }
    }
}

pub trait EffectiveVisitExt<'lt>: Effective<'lt> {
    fn if_skipped<'ctx, 'wrap, Ctx, F>(
        self,
        f: F,
    ) -> ErasedEffective<'wrap, (Ctx, VisitResult<()>), Self::Effect>
    where
        Self: Effective<'lt, Output = (Ctx, VisitResult<()>)>,
        F: 'wrap
            + Ss
            + for<'temp> FnOnce(
                &'temp mut Ctx,
            )
                -> ErasedEffective<'temp, VisitResult<()>, Self::Effect, &'ctx ()>,
        Ctx: Ss,
        'ctx: 'lt,
        'lt: 'wrap,
    {
        self.r#do(
            |(ctx, v)| {
                (
                    ctx,
                    match v {
                        VisitResult::Skipped(()) => ControlFlow::Continue(()),
                        v => ControlFlow::Break(v),
                    },
                )
            },
            |ctx, ()| f(ctx).cast(),
            |_, v| ControlFlow::<_, Never>::Break(v),
            |_, _| unreachable!(),
            |_, _, _: Never| unreachable!(),
            |ctx, _, v| (ctx, v),
        )
    }

    fn if_not_finished<'ctx, 'wrap, Ctx, F>(
        self,
        f: F,
    ) -> ErasedEffective<'wrap, (Ctx, VisitResult<()>), Self::Effect>
    where
        Self: Effective<'lt, Output = (Ctx, VisitResult<()>)>,
        F: 'wrap
            + for<'temp> FnOnce(
                &'temp mut Ctx,
            )
                -> ErasedEffective<'temp, VisitResult<()>, Self::Effect, &'ctx ()>,
        'ctx: 'lt,
        Ctx: Ss,
        F: Ss,
        'lt: 'wrap,
    {
        self.r#do(
            |(ctx, v)| {
                (
                    ctx,
                    match v {
                        VisitResult::Skipped(()) | VisitResult::Control(Flow::Continue) => {
                            ControlFlow::Continue(())
                        }
                        v => ControlFlow::Break(v),
                    },
                )
            },
            |ctx, ()| f(ctx).cast(),
            |_, v| ControlFlow::<_, Never>::Break(v),
            |_, _| unreachable!(),
            |_, _, _: Never| unreachable!(),
            |ctx, _, v| (ctx, v),
        )
    }
}

impl<'lt, T: Effective<'lt>> EffectiveVisitExt<'lt> for T {}

impl<S> PartialEq for VisitResult<S> {
    fn eq(&self, other: &Self) -> bool {
        match (self, other) {
            (Self::Skipped(_), Self::Skipped(_)) => true,
            (Self::Control(l0), Self::Control(r0)) => l0 == r0,
            _ => false,
        }
    }
}

impl<S> core::fmt::Debug for VisitResult<S> {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        match self {
            Self::Skipped(_) => f.debug_tuple("Skipped").finish(),
            Self::Control(arg0) => f.debug_tuple("Control").field(arg0).finish(),
        }
    }
}

impl<S> From<Flow> for VisitResult<S> {
    fn from(value: Flow) -> Self {
        Self::Control(value)
    }
}