use crate::validation::context::ValidatorContext;
use graphql_parser::query::{
    Definition, Directive, Document, Field, FragmentDefinition, FragmentSpread, InlineFragment,
    Name, OperationDefinition, Selection, SelectionSet, TypeCondition, Value, VariableDefinition,
};

pub trait Visitor<'a> {
    fn enter_document(&mut self, _ctx: &mut ValidatorContext<'a>, _doc: &'a Document) {}
    fn exit_document(&mut self, _ctx: &mut ValidatorContext<'a>, _doc: &'a Document) {}

    fn enter_operation_definition(
        &mut self,
        _ctx: &mut ValidatorContext<'a>,
        _operation_definition: &'a OperationDefinition,
    ) {
    }
    fn exit_operation_definition(
        &mut self,
        _ctx: &mut ValidatorContext<'a>,
        _operation_definition: &'a OperationDefinition,
    ) {
    }

    fn enter_fragment_definition(
        &mut self,
        _ctx: &mut ValidatorContext<'a>,
        _fragment_definition: &'a FragmentDefinition,
    ) {
    }
    fn exit_fragment_definition(
        &mut self,
        _ctx: &mut ValidatorContext<'a>,
        _fragment_definition: &'a FragmentDefinition,
    ) {
    }

    fn enter_variable_definition(
        &mut self,
        _ctx: &mut ValidatorContext<'a>,
        _variable_definition: &'a VariableDefinition,
    ) {
    }
    fn exit_variable_definition(
        &mut self,
        _ctx: &mut ValidatorContext<'a>,
        _variable_definition: &'a VariableDefinition,
    ) {
    }

    fn enter_directive(&mut self, _ctx: &mut ValidatorContext<'a>, _directive: &'a Directive) {}
    fn exit_directive(&mut self, _ctx: &mut ValidatorContext<'a>, _directive: &'a Directive) {}

    fn enter_argument(&mut self, _ctx: &mut ValidatorContext<'a>, _name: &str, _value: &'a Value) {}
    fn exit_argument(&mut self, _ctx: &mut ValidatorContext<'a>, _name: &str, _value: &'a Value) {}

    fn enter_selection(&mut self, _ctx: &mut ValidatorContext<'a>, _selection: &'a Selection) {}
    fn exit_selection(&mut self, _ctx: &mut ValidatorContext<'a>, _selection: &'a Selection) {}

    fn enter_field(&mut self, _ctx: &mut ValidatorContext<'a>, _field: &'a Field) {}
    fn exit_field(&mut self, _ctx: &mut ValidatorContext<'a>, _field: &'a Field) {}

    fn enter_fragment_spread(
        &mut self,
        _ctx: &mut ValidatorContext<'a>,
        _fragment_spread: &'a FragmentSpread,
    ) {
    }
    fn exit_fragment_spread(
        &mut self,
        _ctx: &mut ValidatorContext<'a>,
        _fragment_spread: &'a FragmentSpread,
    ) {
    }

    fn enter_inline_fragment(
        &mut self,
        _ctx: &mut ValidatorContext<'a>,
        _inline_fragment: &'a InlineFragment,
    ) {
    }
    fn exit_inline_fragment(
        &mut self,
        _ctx: &mut ValidatorContext<'a>,
        _inline_fragment: &'a InlineFragment,
    ) {
    }
}

pub struct VisitorNil;

impl VisitorNil {
    pub fn with<V>(self, visitor: V) -> VisitorCons<V, Self> {
        VisitorCons(visitor, self)
    }
}

pub struct VisitorCons<A, B>(A, B);

impl<A, B> VisitorCons<A, B> {
    pub fn with<V>(self, visitor: V) -> VisitorCons<V, Self> {
        VisitorCons(visitor, self)
    }
}

impl<'a> Visitor<'a> for VisitorNil {}

impl<'a, A, B> Visitor<'a> for VisitorCons<A, B>
where
    A: Visitor<'a> + 'a,
    B: Visitor<'a> + 'a,
{
    fn enter_document(&mut self, ctx: &mut ValidatorContext<'a>, doc: &'a Document) {
        self.0.enter_document(ctx, doc);
        self.1.enter_document(ctx, doc);
    }

    fn exit_document(&mut self, ctx: &mut ValidatorContext<'a>, doc: &'a Document) {
        self.0.exit_document(ctx, doc);
        self.1.exit_document(ctx, doc);
    }

    fn enter_operation_definition(
        &mut self,
        ctx: &mut ValidatorContext<'a>,
        operation_definition: &'a OperationDefinition,
    ) {
        self.0.enter_operation_definition(ctx, operation_definition);
        self.1.enter_operation_definition(ctx, operation_definition);
    }

    fn exit_operation_definition(
        &mut self,
        ctx: &mut ValidatorContext<'a>,
        operation_definition: &'a OperationDefinition,
    ) {
        self.0.exit_operation_definition(ctx, operation_definition);
        self.1.exit_operation_definition(ctx, operation_definition);
    }

    fn enter_fragment_definition(
        &mut self,
        ctx: &mut ValidatorContext<'a>,
        fragment_definition: &'a FragmentDefinition,
    ) {
        self.0.enter_fragment_definition(ctx, fragment_definition);
        self.1.enter_fragment_definition(ctx, fragment_definition);
    }

    fn exit_fragment_definition(
        &mut self,
        ctx: &mut ValidatorContext<'a>,
        fragment_definition: &'a FragmentDefinition,
    ) {
        self.0.exit_fragment_definition(ctx, fragment_definition);
        self.1.exit_fragment_definition(ctx, fragment_definition);
    }

    fn enter_variable_definition(
        &mut self,
        ctx: &mut ValidatorContext<'a>,
        variable_definition: &'a VariableDefinition,
    ) {
        self.0.enter_variable_definition(ctx, variable_definition);
        self.1.enter_variable_definition(ctx, variable_definition);
    }

    fn exit_variable_definition(
        &mut self,
        ctx: &mut ValidatorContext<'a>,
        variable_definition: &'a VariableDefinition,
    ) {
        self.0.exit_variable_definition(ctx, variable_definition);
        self.1.exit_variable_definition(ctx, variable_definition);
    }

    fn enter_directive(&mut self, ctx: &mut ValidatorContext<'a>, directive: &'a Directive) {
        self.0.enter_directive(ctx, directive);
        self.1.enter_directive(ctx, directive);
    }

    fn exit_directive(&mut self, ctx: &mut ValidatorContext<'a>, directive: &'a Directive) {
        self.0.exit_directive(ctx, directive);
        self.1.exit_directive(ctx, directive);
    }

    fn enter_argument(&mut self, ctx: &mut ValidatorContext<'a>, name: &str, value: &'a Value) {
        self.0.enter_argument(ctx, name, value);
        self.1.enter_argument(ctx, name, value);
    }

    fn exit_argument(&mut self, ctx: &mut ValidatorContext<'a>, name: &str, value: &'a Value) {
        self.0.exit_argument(ctx, name, value);
        self.1.exit_argument(ctx, name, value);
    }

    fn enter_selection(&mut self, ctx: &mut ValidatorContext<'a>, selection: &'a Selection) {
        self.0.enter_selection(ctx, selection);
        self.1.enter_selection(ctx, selection);
    }

    fn exit_selection(&mut self, ctx: &mut ValidatorContext<'a>, selection: &'a Selection) {
        self.0.exit_selection(ctx, selection);
        self.1.exit_selection(ctx, selection);
    }

    fn enter_field(&mut self, ctx: &mut ValidatorContext<'a>, field: &'a Field) {
        self.0.enter_field(ctx, field);
        self.1.enter_field(ctx, field);
    }

    fn exit_field(&mut self, ctx: &mut ValidatorContext<'a>, field: &'a Field) {
        self.0.exit_field(ctx, field);
        self.1.exit_field(ctx, field);
    }

    fn enter_fragment_spread(
        &mut self,
        ctx: &mut ValidatorContext<'a>,
        fragment_spread: &'a FragmentSpread,
    ) {
        self.0.enter_fragment_spread(ctx, fragment_spread);
        self.1.enter_fragment_spread(ctx, fragment_spread);
    }

    fn exit_fragment_spread(
        &mut self,
        ctx: &mut ValidatorContext<'a>,
        fragment_spread: &'a FragmentSpread,
    ) {
        self.0.exit_fragment_spread(ctx, fragment_spread);
        self.1.exit_fragment_spread(ctx, fragment_spread);
    }

    fn enter_inline_fragment(
        &mut self,
        ctx: &mut ValidatorContext<'a>,
        inline_fragment: &'a InlineFragment,
    ) {
        self.0.enter_inline_fragment(ctx, inline_fragment);
        self.1.enter_inline_fragment(ctx, inline_fragment);
    }

    fn exit_inline_fragment(
        &mut self,
        ctx: &mut ValidatorContext<'a>,
        inline_fragment: &'a InlineFragment,
    ) {
        self.0.exit_inline_fragment(ctx, inline_fragment);
        self.1.exit_inline_fragment(ctx, inline_fragment);
    }
}

pub fn visit<'a, V: Visitor<'a>>(v: &mut V, ctx: &mut ValidatorContext<'a>, doc: &'a Document) {
    v.enter_document(ctx, doc);
    visit_definitions(v, ctx, doc);
    v.exit_document(ctx, doc);
}

fn visit_definitions<'a, V: Visitor<'a>>(
    v: &mut V,
    ctx: &mut ValidatorContext<'a>,
    doc: &'a Document,
) {
    for d in &doc.definitions {
        match d {
            Definition::Operation(operation) => {
                visit_operation_definition(v, ctx, operation);
            }
            Definition::Fragment(fragment) => {
                let TypeCondition::On(name) = &fragment.type_condition;
                if let Some(ty) = ctx.registry.types.get(name) {
                    ctx.with_type(ty, |ctx| visit_fragment_definition(v, ctx, fragment));
                } else {
                    ctx.report_error(
                        vec![fragment.position],
                        format!("Unknown type \"{}\".", name),
                    );
                }
            }
        }
    }
}

fn visit_operation_definition<'a, V: Visitor<'a>>(
    v: &mut V,
    ctx: &mut ValidatorContext<'a>,
    operation: &'a OperationDefinition,
) {
    v.enter_operation_definition(ctx, operation);
    match operation {
        OperationDefinition::SelectionSet(selection_set) => {
            ctx.with_type(&ctx.registry.types[&ctx.registry.query_type], |ctx| {
                visit_selection_set(v, ctx, selection_set)
            });
        }
        OperationDefinition::Query(query) => {
            ctx.with_type(&ctx.registry.types[&ctx.registry.query_type], |ctx| {
                visit_variable_definitions(v, ctx, &query.variable_definitions);
                visit_directives(v, ctx, &query.directives);
                visit_selection_set(v, ctx, &query.selection_set);
            });
        }
        OperationDefinition::Mutation(mutation) => {
            if let Some(mutation_type) = &ctx.registry.mutation_type {
                ctx.with_type(&ctx.registry.types[mutation_type], |ctx| {
                    visit_variable_definitions(v, ctx, &mutation.variable_definitions);
                    visit_directives(v, ctx, &mutation.directives);
                    visit_selection_set(v, ctx, &mutation.selection_set);
                });
            } else {
                ctx.report_error(
                    vec![mutation.position],
                    "Schema is not configured for mutations.",
                );
            }
        }
        OperationDefinition::Subscription(subscription) => {
            ctx.report_error(vec![subscription.position], "Not supported.");
            // visit_variable_definitions(v, ctx, &subscription.variable_definitions);
            // visit_directives(v, ctx, &subscription.directives);
            // visit_selection_set(v, ctx, &subscription.selection_set);
        }
    }
    v.exit_operation_definition(ctx, operation);
}

fn visit_selection_set<'a, V: Visitor<'a>>(
    v: &mut V,
    ctx: &mut ValidatorContext<'a>,
    selection_set: &'a SelectionSet,
) {
    for selection in &selection_set.items {
        visit_selection(v, ctx, selection);
    }
}

fn visit_selection<'a, V: Visitor<'a>>(
    v: &mut V,
    ctx: &mut ValidatorContext<'a>,
    selection: &'a Selection,
) {
    v.enter_selection(ctx, selection);
    match selection {
        Selection::Field(field) => visit_field(v, ctx, field),
        Selection::FragmentSpread(fragment_spread) => {
            visit_fragment_spread(v, ctx, fragment_spread)
        }
        Selection::InlineFragment(inline_fragment) => {
            visit_inline_fragment(v, ctx, inline_fragment)
        }
    }
    v.exit_selection(ctx, selection);
}

fn visit_field<'a, V: Visitor<'a>>(v: &mut V, ctx: &mut ValidatorContext<'a>, field: &'a Field) {
    v.enter_field(ctx, field);
    visit_arguments(v, ctx, &field.arguments);
    visit_directives(v, ctx, &field.directives);

    if let Some(schema_field) = ctx.parent_type().field_by_name(&field.name) {
        ctx.with_type(
            ctx.registry.get_basic_type(&schema_field.ty).unwrap(),
            |ctx| {
                visit_selection_set(v, ctx, &field.selection_set);
            },
        );
    } else {
        ctx.report_error(
            vec![field.position],
            format!(
                "Cannot query field \"{}\" on type \"{}\".",
                field.name,
                ctx.parent_type().name()
            ),
        );
    }

    v.exit_field(ctx, field);
}

fn visit_arguments<'a, V: Visitor<'a>>(
    v: &mut V,
    ctx: &mut ValidatorContext<'a>,
    arguments: &'a Vec<(Name, Value)>,
) {
    for (name, value) in arguments {
        v.enter_argument(ctx, name, value);
        v.exit_argument(ctx, name, value);
    }
}

fn visit_variable_definitions<'a, V: Visitor<'a>>(
    v: &mut V,
    ctx: &mut ValidatorContext<'a>,
    variable_definitions: &'a Vec<VariableDefinition>,
) {
    for d in variable_definitions {
        v.enter_variable_definition(ctx, d);
        v.exit_variable_definition(ctx, d);
    }
}

fn visit_directives<'a, V: Visitor<'a>>(
    v: &mut V,
    ctx: &mut ValidatorContext<'a>,
    directives: &'a Vec<Directive>,
) {
    for d in directives {
        v.enter_directive(ctx, d);
        visit_arguments(v, ctx, &d.arguments);
        v.exit_directive(ctx, d);
    }
}

fn visit_fragment_definition<'a, V: Visitor<'a>>(
    v: &mut V,
    ctx: &mut ValidatorContext<'a>,
    fragment: &'a FragmentDefinition,
) {
    v.enter_fragment_definition(ctx, fragment);
    visit_directives(v, ctx, &fragment.directives);
    visit_selection_set(v, ctx, &fragment.selection_set);
    v.exit_fragment_definition(ctx, fragment);
}

fn visit_fragment_spread<'a, V: Visitor<'a>>(
    v: &mut V,
    ctx: &mut ValidatorContext<'a>,
    fragment_spread: &'a FragmentSpread,
) {
    v.enter_fragment_spread(ctx, fragment_spread);
    visit_directives(v, ctx, &fragment_spread.directives);
    v.exit_fragment_spread(ctx, fragment_spread);
}

fn visit_inline_fragment<'a, V: Visitor<'a>>(
    v: &mut V,
    ctx: &mut ValidatorContext<'a>,
    inline_fragment: &'a InlineFragment,
) {
    v.enter_inline_fragment(ctx, inline_fragment);
    visit_directives(v, ctx, &inline_fragment.directives);
    visit_selection_set(v, ctx, &inline_fragment.selection_set);
    v.exit_inline_fragment(ctx, inline_fragment);
}