use std::cell::{Cell, RefCell};
use std::collections::BTreeMap;
use std::rc::Rc;

use wip_host::{
    CallErrorKind, CallRequest, ExecutionContext, InterfaceRegistry, InterfaceTarget,
    ObjectProvider, ProviderResult, PublishedObject, RegisteredInterface, RegistrationError, Scope,
    ScopeObservation, Target, Validator, WipObject,
};
use wip_interface::{OperationResult, interface};
use wip_protocol::{InterfaceReference, ProtocolErrorCode, Value};

#[interface]
pub trait Read {
    fn read(&self, value: String) -> OperationResult<String>;
}

#[interface]
pub trait Count {
    fn read(&self, value: i64) -> OperationResult<i64>;
}

#[derive(Clone)]
struct Metadata {
    name: String,
    reference: Option<String>,
    validator: Option<Validator>,
}
impl WipObject for Metadata {
    fn name(&self) -> &str {
        &self.name
    }
    fn reference(&self) -> Option<&str> {
        self.reference.as_deref()
    }
    fn validator(&self) -> Option<&Validator> {
        self.validator.as_ref()
    }
}

type OnStart = Rc<RefCell<Option<Box<dyn Fn()>>>>;

struct Implementation {
    metadata: Metadata,
    calls: Rc<Cell<usize>>,
    on_start: OnStart,
}
impl WipObject for Implementation {
    fn name(&self) -> &str {
        self.metadata.name()
    }
    fn reference(&self) -> Option<&str> {
        self.metadata.reference()
    }
    fn validator(&self) -> Option<&Validator> {
        self.metadata.validator()
    }
}
impl Read for Implementation {
    fn read(&self, value: String) -> OperationResult<String> {
        self.calls.set(self.calls.get() + 1);
        if let Some(action) = self.on_start.borrow_mut().take() {
            action();
        }
        Ok(value)
    }
}

struct Provider {
    interface: RegisteredInterface<ReadDefinition>,
    current: Rc<RefCell<Option<(Scope, Metadata)>>>,
    target_path: String,
    target_exists: Cell<bool>,
    member: Cell<bool>,
    calls: Rc<Cell<usize>>,
    resolutions: Cell<usize>,
    on_start: OnStart,
}
impl Provider {
    fn new(
        scope: &Scope,
        interface: RegisteredInterface<ReadDefinition>,
        target: &str,
        reference: Option<&str>,
    ) -> Self {
        Self {
            interface,
            current: Rc::new(RefCell::new(Some((
                scope.clone(),
                Metadata {
                    name: scope.path().rsplit('/').next().unwrap().into(),
                    reference: reference.map(str::to_owned),
                    validator: Some(Validator::new(b"scope-state-v1")),
                },
            )))),
            target_path: target.into(),
            target_exists: Cell::new(true),
            member: Cell::new(true),
            calls: Rc::new(Cell::new(0)),
            resolutions: Cell::new(0),
            on_start: Rc::new(RefCell::new(None)),
        }
    }
    fn request(&self, scope_ref: Option<&str>) -> CallRequest {
        CallRequest {
            target: Target {
                path: self.target_path.clone(),
                validator: None,
            },
            interface: InterfaceTarget {
                reference: self.interface.reference().protocol_reference(),
                scope_ref: scope_ref.map(str::to_owned),
                validator: Some(b"descriptor-v1".to_vec()),
            },
            operation: "read".into(),
            arguments: BTreeMap::from([("value".into(), Value::String("original backend".into()))]),
        }
    }
}
impl ObjectProvider for Provider {
    type Object = Implementation;
    fn with_object<R>(
        &self,
        _: &ExecutionContext,
        path: &str,
        callback: impl FnOnce(&PublishedObject<Self::Object>) -> R,
    ) -> ProviderResult<R> {
        self.resolutions.set(self.resolutions.get() + 1);
        // A single boundary captures both the target and the live scope association.
        let current = self.current.borrow().clone();
        let target = path == self.target_path;
        let metadata = if target {
            if !self.target_exists.get() {
                return ProviderResult::NotFound;
            }
            if let Some((scope, object)) = &current
                && scope.path() == path
            {
                object.clone()
            } else {
                Metadata {
                    name: path.rsplit('/').next().unwrap().into(),
                    reference: None,
                    validator: Some(Validator::new(b"target-v1")),
                }
            }
        } else if let Some((scope, object)) = &current {
            if path != scope.path() {
                return ProviderResult::NotFound;
            }
            object.clone()
        } else {
            return ProviderResult::NotFound;
        };
        let mut publication = PublishedObject::new(Implementation {
            metadata,
            calls: self.calls.clone(),
            on_start: self.on_start.clone(),
        });
        if target && self.member.get() {
            publication = publication.expose(&self.interface).unwrap();
        }
        if let Some((scope, object)) = current {
            publication = publication.bind_scope(ScopeObservation::new(&scope, &object));
        }
        ProviderResult::Found(callback(&publication))
    }
}
fn setup(
    scope: &str,
    target: &str,
    reference: Option<&str>,
) -> (InterfaceRegistry, Scope, Provider) {
    let scope = Scope::new(scope).unwrap();
    let mut registry = InterfaceRegistry::new();
    let interface = registry
        .register(
            &scope,
            "read::#日本語",
            ReadDefinition,
            Some(Validator::new(b"descriptor-v1")),
        )
        .unwrap();
    let provider = Provider::new(&scope, interface, target, reference);
    (registry, scope, provider)
}

#[test]
fn registrations_use_scope_name_not_definition_type_or_delimiters() {
    let mut registry = InterfaceRegistry::new();
    let left = Scope::new("/left").unwrap();
    let right = Scope::new("/right").unwrap();
    let a = registry
        .register(&left, "read::#日本語", ReadDefinition, None)
        .unwrap();
    let b = registry
        .register(&right, "read::#日本語", ReadDefinition, None)
        .unwrap();
    assert_ne!(a.reference(), b.reference());
    assert_eq!(
        a.reference().protocol_reference(),
        InterfaceReference {
            scope: "/left".into(),
            name: "read::#日本語".into(),
        }
    );
    assert!(matches!(
        registry.register(&left, "read::#日本語", CountDefinition, None),
        Err(RegistrationError::AlreadyRegistered)
    ));
    assert!(matches!(
        registry.register(&left, "", ReadDefinition, None),
        Err(RegistrationError::InvalidReference(_))
    ));
    assert!(Scope::new("/invalid/").is_err());
    registry
        .register(&left, "another", ReadDefinition, None)
        .unwrap();
}

#[test]
fn self_root_ancestor_and_membership_are_independent() {
    for (scope, target) in [
        ("/", "/"),
        ("/", "/target"),
        ("/scope", "/scope"),
        ("/scope", "/scope/target"),
    ] {
        let (registry, _, provider) = setup(scope, target, Some("scope-id"));
        assert_eq!(
            provider
                .call_operation(provider.request(Some("scope-id")))
                .unwrap()
                .result,
            Value::String("original backend".into())
        );
        assert_eq!(
            provider
                .fetch_interface(&registry, &provider.request(None).interface.reference)
                .unwrap()
                .scope_ref
                .as_deref(),
            Some("scope-id")
        );
        provider.member.set(false);
        assert_eq!(
            provider
                .call_operation(provider.request(None))
                .unwrap_err()
                .kind(),
            CallErrorKind::InterfaceMismatch
        );
    }
    // Non-self scope Objects need not implement or expose any Interface.
    let (registry, _, provider) = setup("/scope", "/scope/target", None);
    assert!(
        provider
            .observe_object("/scope")
            .unwrap()
            .interfaces
            .is_empty()
    );
    provider
        .fetch_interface(&registry, &provider.request(None).interface.reference)
        .unwrap();
    for target in ["/sibling/target", "/scopelong", "/"] {
        let (_, _, provider) = setup("/scope", target, None);
        assert_eq!(
            provider
                .call_operation(provider.request(None))
                .unwrap_err()
                .kind(),
            CallErrorKind::InterfaceMismatch
        );
        assert_eq!(provider.calls.get(), 0);
        assert_eq!(
            provider.observe_object(target).unwrap_err().kind(),
            CallErrorKind::Internal
        );
    }
}

#[test]
fn optional_scope_ref_and_state_validator_have_distinct_responsibilities() {
    for current in [Some("scope-id"), None, Some("")] {
        let (registry, _, provider) = setup("/scope", "/scope/target", current);
        let observation = provider
            .fetch_interface(&registry, &provider.request(None).interface.reference)
            .unwrap();
        assert_eq!(
            observation
                .protocol_response()
                .unwrap()
                .scope_ref
                .as_deref(),
            current
        );
        assert_eq!(
            observation.validator,
            Some(Validator::new(b"descriptor-v1"))
        );
        provider.call_operation(provider.request(None)).unwrap();
        if let Some(reference) = current {
            provider
                .call_operation(provider.request(Some(reference)))
                .unwrap();
        }
        let before = provider.calls.get();
        for supplied in ["other", "missing"] {
            let mut call = provider.request(Some(supplied));
            call.interface.validator = None;
            call.operation = "missing".into();
            assert_eq!(
                provider.call_operation(call).unwrap_err().kind(),
                CallErrorKind::InterfaceMismatch
            );
        }
        assert_eq!(provider.calls.get(), before);
        provider.current.borrow_mut().as_mut().unwrap().1.validator =
            Some(Validator::new(b"scope-state-v2"));
        provider.call_operation(provider.request(current)).unwrap();
        assert_eq!(
            provider
                .fetch_interface(&registry, &provider.request(None).interface.reference)
                .unwrap(),
            observation
        );
    }
}

#[test]
fn scope_precondition_is_membership_stage_in_both_dispatch_paths() {
    let (_, _, provider) = setup("/scope", "/scope/target", Some("current"));
    let mut call = provider.request(Some("stale"));
    call.target.validator = Some(b"wrong".to_vec());
    assert_eq!(
        provider.call_operation(call.clone()).unwrap_err().kind(),
        CallErrorKind::ValidatorMismatch
    );
    provider.target_exists.set(false);
    assert_eq!(
        provider.call_operation(call).unwrap_err().kind(),
        CallErrorKind::NotFound
    );
    provider.target_exists.set(true);
    let call = provider.request(Some("stale"));
    assert_eq!(
        provider
            .call_operation_with_context_and_decoder(
                &ExecutionContext::new(),
                call.target,
                call.interface,
                call.operation,
                |_| -> Result<BTreeMap<String, Value>, ()> { panic!("decoder must not run") }
            )
            .unwrap_err()
            .kind(),
        CallErrorKind::InterfaceMismatch
    );
    assert_eq!(provider.calls.get(), 0);
}

#[test]
fn deletion_republication_and_movement_never_inherit_retained_artifacts() {
    let (mut registry, scope, provider) = setup("/scope", "/scope/target", Some("old"));
    let reference = provider.request(None).interface.reference;
    provider.fetch_interface(&registry, &reference).unwrap();
    *provider.current.borrow_mut() = None;
    provider.target_exists.set(false);
    assert_eq!(
        provider
            .fetch_interface(&registry, &reference)
            .unwrap_err()
            .code,
        ProtocolErrorCode::InterfaceNotFound
    );
    assert_eq!(
        provider
            .call_operation(provider.request(None))
            .unwrap_err()
            .kind(),
        CallErrorKind::NotFound
    );
    provider.target_exists.set(true);
    // Even the same ref is not proof that a replacement inherits registration.
    let replacement = Scope::new("/scope").unwrap();
    *provider.current.borrow_mut() = Some((
        replacement.clone(),
        Metadata {
            name: "scope".into(),
            reference: Some("old".into()),
            validator: None,
        },
    ));
    assert_eq!(
        provider
            .fetch_interface(&registry, &reference)
            .unwrap_err()
            .code,
        ProtocolErrorCode::InterfaceNotFound
    );
    assert_eq!(
        provider
            .call_operation(provider.request(Some("old")))
            .unwrap_err()
            .kind(),
        CallErrorKind::InterfaceMismatch
    );
    registry.remove_scope(&scope);
    assert!(matches!(
        registry.register(&scope, "new", ReadDefinition, None),
        Err(RegistrationError::RetiredScope)
    ));
    let fresh = registry
        .register(&replacement, reference.name.clone(), ReadDefinition, None)
        .unwrap();
    provider.fetch_interface(&registry, &reference).unwrap();
    // Old target membership still binds the old lifetime, even after new publication.
    assert_eq!(
        provider
            .call_operation(provider.request(None))
            .unwrap_err()
            .kind(),
        CallErrorKind::InterfaceMismatch
    );
    let new_provider = Provider::new(&replacement, fresh, "/scope/target", Some("new"));
    let mut new_call = new_provider.request(Some("new"));
    new_call.interface.validator = None;
    new_provider.call_operation(new_call).unwrap();
    let moved = Scope::new("/moved").unwrap();
    new_provider.target_exists.set(false);
    *new_provider.current.borrow_mut() = Some((
        moved.clone(),
        Metadata {
            name: "moved".into(),
            reference: Some("new".into()),
            validator: None,
        },
    ));
    assert_eq!(
        new_provider
            .fetch_interface(&registry, &reference)
            .unwrap_err()
            .code,
        ProtocolErrorCode::InterfaceNotFound
    );
    assert_eq!(
        new_provider
            .call_operation(new_provider.request(None))
            .unwrap_err()
            .kind(),
        CallErrorKind::NotFound
    );
    let moved_interface = registry
        .register(&moved, reference.name, ReadDefinition, None)
        .unwrap();
    assert_eq!(
        moved_interface.reference().protocol_reference().scope,
        "/moved"
    );
    assert_eq!(provider.calls.get(), 0);
}

#[test]
fn replacement_after_fetch_rejects_old_ref_but_omission_and_refless_are_allowed() {
    for previous_ref in [Some("old"), None] {
        let (mut registry, old_scope, old_provider) =
            setup("/scope", "/scope/target", previous_ref);
        let observed = old_provider
            .fetch_interface(&registry, &old_provider.request(None).interface.reference)
            .unwrap();
        registry.remove_scope(&old_scope);
        let new_scope = Scope::new("/scope").unwrap();
        let token = registry
            .register(
                &new_scope,
                "read::#日本語",
                ReadDefinition,
                Some(Validator::new(b"descriptor-v1")),
            )
            .unwrap();
        let new_provider = Provider::new(&new_scope, token, "/scope/target", None);
        if let Some(reference) = observed.scope_ref {
            assert_eq!(
                new_provider
                    .call_operation(new_provider.request(Some(&reference)))
                    .unwrap_err()
                    .kind(),
                CallErrorKind::InterfaceMismatch
            );
            assert_eq!(new_provider.calls.get(), 0);
        }
        new_provider
            .call_operation(new_provider.request(None))
            .unwrap();
    }
}

#[test]
fn started_execution_retains_target_and_same_descriptor_through_replacement() {
    let (registry, old_scope, provider) = setup("/scope", "/scope/target", Some("old"));
    let registry = Rc::new(RefCell::new(registry));
    let current = provider.current.clone();
    let replacement = Scope::new("/scope").unwrap();
    let registry_for_action = registry.clone();
    let replacement_for_action = replacement.clone();
    *provider.on_start.borrow_mut() = Some(Box::new(move || {
        let mut registry = registry_for_action.borrow_mut();
        registry.remove_scope(&old_scope);
        registry
            .register(
                &replacement_for_action,
                "read::#日本語",
                CountDefinition,
                Some(Validator::new(b"descriptor-v2")),
            )
            .unwrap();
        *current.borrow_mut() = Some((
            replacement_for_action.clone(),
            Metadata {
                name: "scope".into(),
                reference: Some("new".into()),
                validator: None,
            },
        ));
    }));
    let call = provider.request(Some("old"));
    let result = provider
        .call_operation_with_context_and_decoder(
            &ExecutionContext::new(),
            call.target,
            call.interface,
            call.operation,
            |descriptor| {
                assert_eq!(descriptor, &ReadDefinition::descriptor());
                Ok::<_, ()>(call.arguments)
            },
        )
        .unwrap();
    assert_eq!(result.result, Value::String("original backend".into()));
    assert_eq!(provider.calls.get(), 1);
    assert_eq!(provider.resolutions.get(), 1);
    let new = provider
        .fetch_interface(
            &registry.borrow(),
            &provider.request(None).interface.reference,
        )
        .unwrap();
    assert_eq!(new.descriptor, CountDefinition::descriptor());
    assert_eq!(new.scope_ref.as_deref(), Some("new"));
    // The old bound target can no longer start a call against the new descriptor.
    assert_eq!(
        provider
            .call_operation(provider.request(None))
            .unwrap_err()
            .kind(),
        CallErrorKind::InterfaceMismatch
    );
    assert_eq!(provider.calls.get(), 1);
}