use std::{borrow::Cow, collections::BTreeMap};

use async_graphql_derive::SimpleObject;
use async_graphql_parser::{Positioned, types::Field};
use indexmap::IndexMap;

use crate::{
    Context, ContextSelectionSet, Error, IntrospectionMode, Name, SDLExportOptions, ServerError,
    ServerResult, Value,
    dynamic::{
        FieldFuture, FieldValue, Object, ObjectAccessor, ResolverContext, Schema, Type, TypeRef,
        field::FieldValueInner,
    },
    extensions::ResolveInfo,
    parser::types::Selection,
    resolver_utils::create_value_object,
    sendable::{FutureMaybeSendExt, MaybeBoxFuture},
};

/// Federation service
#[derive(SimpleObject)]
#[graphql(internal, name = "_Service")]
struct Service {
    sdl: Option<String>,
}

type BoxFieldFuture<'a> = MaybeBoxFuture<'a, ServerResult<(Name, Value)>>;

pub(crate) async fn resolve_container(
    schema: &Schema,
    object: &Object,
    ctx: &ContextSelectionSet<'_>,
    parent_value: &FieldValue<'_>,
    serial: bool,
) -> ServerResult<Option<Value>> {
    let mut fields = Vec::new();
    collect_fields(&mut fields, schema, object, ctx, parent_value)?;

    let res = if !serial {
        futures_util::future::try_join_all(fields).await?
    } else {
        let mut results = Vec::with_capacity(fields.len());
        for field in fields {
            results.push(field.await?);
        }
        results
    };

    Ok(Some(create_value_object(res)))
}

fn collect_typename_field<'a>(
    fields: &mut Vec<BoxFieldFuture<'a>>,
    object: &'a Object,
    field: &'a Positioned<Field>,
) {
    fields.push(
        async move {
            Ok((
                field.node.response_key().node.clone(),
                Value::from(object.name.as_str()),
            ))
        }
        .boxed_maybe_send(),
    )
}

fn collect_schema_field<'a>(
    fields: &mut Vec<BoxFieldFuture<'a>>,
    ctx: &ContextSelectionSet<'a>,
    field: &'a Positioned<Field>,
) {
    let ctx = ctx.clone();
    fields.push(
        async move {
            let ctx_field = ctx.with_field(field);
            let mut ctx_obj = ctx.with_selection_set(&ctx_field.item.node.selection_set);
            ctx_obj.is_for_introspection = true;
            let visible_types = ctx.schema_env.registry.find_visible_types(&ctx_field);
            let value = crate::OutputType::resolve(
                &crate::model::__Schema::new(&ctx.schema_env.registry, &visible_types),
                &ctx_obj,
                ctx_field.item,
            )
            .await?;
            Ok((field.node.response_key().node.clone(), value))
        }
        .boxed_maybe_send(),
    );
}

fn collect_type_field<'a>(
    fields: &mut Vec<BoxFieldFuture<'a>>,
    ctx: &ContextSelectionSet<'a>,
    field: &'a Positioned<Field>,
) {
    let ctx = ctx.clone();
    fields.push(
        async move {
            let ctx_field = ctx.with_field(field);
            let (_, type_name) = ctx_field.param_value::<String>("name", None)?;
            let mut ctx_obj = ctx.with_selection_set(&ctx_field.item.node.selection_set);
            ctx_obj.is_for_introspection = true;
            let visible_types = ctx.schema_env.registry.find_visible_types(&ctx_field);
            let value = crate::OutputType::resolve(
                &ctx.schema_env
                    .registry
                    .types
                    .get(&type_name)
                    .filter(|_| visible_types.contains(type_name.as_str()))
                    .map(|ty| {
                        crate::model::__Type::new_simple(
                            &ctx.schema_env.registry,
                            &visible_types,
                            ty,
                        )
                    }),
                &ctx_obj,
                ctx_field.item,
            )
            .await?;
            Ok((field.node.response_key().node.clone(), value))
        }
        .boxed_maybe_send(),
    );
}

fn collect_service_field<'a>(
    fields: &mut Vec<BoxFieldFuture<'a>>,
    ctx: &ContextSelectionSet<'a>,
    field: &'a Positioned<Field>,
) {
    let ctx = ctx.clone();
    fields.push(
        async move {
            let ctx_field = ctx.with_field(field);
            let mut ctx_obj = ctx.with_selection_set(&ctx_field.item.node.selection_set);
            ctx_obj.is_for_introspection = true;

            let output_type = crate::OutputType::resolve(
                &Service {
                    sdl: Some(
                        ctx.schema_env
                            .registry
                            .export_sdl(SDLExportOptions::new().federation().compose_directive()),
                    ),
                },
                &ctx_obj,
                ctx_field.item,
            )
            .await?;

            Ok((field.node.response_key().node.clone(), output_type))
        }
        .boxed_maybe_send(),
    );
}

fn collect_entities_field<'a>(
    fields: &mut Vec<BoxFieldFuture<'a>>,
    schema: &'a Schema,
    ctx: &ContextSelectionSet<'a>,
    parent_value: &'a FieldValue,
    field: &'a Positioned<Field>,
) {
    let ctx = ctx.clone();
    fields.push(
        async move {
            let ctx_field = ctx.with_field(field);
            let entity_resolver = schema.0.entity_resolver.as_ref().ok_or_else(|| {
                ctx_field.set_error_path(
                    Error::new("internal: missing entity resolver")
                        .into_server_error(ctx_field.item.pos),
                )
            })?;
            let entity_type = TypeRef::named_list_nn("_Entity");

            let arguments = ObjectAccessor(Cow::Owned(
                field
                    .node
                    .arguments
                    .iter()
                    .map(|(name, value)| {
                        // Drop omitted variable-backed arguments instead of materializing them as
                        // `null`.
                        ctx_field
                            .resolve_input_value(value.clone())
                            .map(|value| value.map(|value| (name.node.clone(), value)))
                    })
                    .collect::<ServerResult<Vec<_>>>()?
                    .into_iter()
                    .flatten()
                    .collect::<IndexMap<_, _>>(),
            ));

            let field_future = (entity_resolver)(ResolverContext {
                ctx: &ctx_field,
                args: arguments,
                parent_value,
            });

            let field_value = match field_future {
                FieldFuture::Future(fut) => {
                    fut.await.map_err(|err| err.into_server_error(field.pos))?
                }
                FieldFuture::Value(value) => value,
            };
            let value = resolve(schema, &ctx_field, &entity_type, field_value.as_ref())
                .await?
                .unwrap_or_default();
            Ok((field.node.response_key().node.clone(), value))
        }
        .boxed_maybe_send(),
    );
}

fn collect_field<'a>(
    fields: &mut Vec<BoxFieldFuture<'a>>,
    schema: &'a Schema,
    object: &'a Object,
    ctx: &ContextSelectionSet<'a>,
    parent_value: &'a FieldValue,
    field_def: &'a crate::dynamic::Field,
    field: &'a Positioned<Field>,
) {
    let ctx = ctx.clone();
    fields.push(
        async move {
            let ctx_field = ctx.with_field(field);
            let arguments = ObjectAccessor(Cow::Owned({
                let mut args = field
                    .node
                    .arguments
                    .iter()
                    .map(|(name, value)| {
                        // Drop omitted variable-backed arguments instead of materializing them as
                        // `null`.
                        ctx_field
                            .resolve_input_value(value.clone())
                            .map(|value| value.map(|value| (name.node.clone(), value)))
                    })
                    .collect::<ServerResult<Vec<_>>>()?
                    .into_iter()
                    .flatten()
                    .collect::<IndexMap<_, _>>();
                field_def.arguments.iter().for_each(|(name, arg)| {
                    if let Some(def) = &arg.default_value
                        && !args.contains_key(name.as_str())
                    {
                        args.insert(Name::new(name), def.clone());
                    }
                });
                args
            }));

            let resolve_info = ResolveInfo {
                path_node: ctx_field.path_node.as_ref().unwrap(),
                parent_type: &object.name,
                return_type: &field_def.ty_str,
                name: &field.node.name.node,
                alias: field.node.alias.as_ref().map(|alias| &*alias.node),
                is_for_introspection: ctx_field.is_for_introspection,
                field: &field.node,
            };
            let resolve_fut = async {
                let field_future = (field_def.resolver_fn)(ResolverContext {
                    ctx: &ctx_field,
                    args: arguments,
                    parent_value,
                });

                let field_value = match field_future {
                    FieldFuture::Value(field_value) => field_value,
                    FieldFuture::Future(future) => future
                        .await
                        .map_err(|err| err.into_server_error(field.pos))?,
                };

                let value =
                    resolve(schema, &ctx_field, &field_def.ty, field_value.as_ref()).await?;

                Ok(value)
            };
            futures_util::pin_mut!(resolve_fut);

            let res_value = ctx_field
                .query_env
                .extensions
                .resolve(resolve_info, &mut resolve_fut)
                .await?
                .unwrap_or_default();
            Ok((field.node.response_key().node.clone(), res_value))
        }
        .boxed_maybe_send(),
    );
}

/// Checks if a fragment type condition applies to an object type.
///
/// This handles:
/// - Direct object type matches
/// - Interface type conditions (checks if object implements the interface)
/// - Union type conditions (checks if object is a member of the union)
fn does_fragment_type_apply(
    types: &BTreeMap<String, crate::registry::MetaType>,
    type_condition: &str,
    object_name: &str,
) -> bool {
    types
        .get(type_condition)
        .is_some_and(|ty| ty.is_possible_type(object_name))
}

fn collect_fields<'a>(
    fields: &mut Vec<BoxFieldFuture<'a>>,
    schema: &'a Schema,
    object: &'a Object,
    ctx: &ContextSelectionSet<'a>,
    parent_value: &'a FieldValue,
) -> ServerResult<()> {
    for selection in &ctx.item.node.items {
        match &selection.node {
            Selection::Field(field) => {
                if field.node.name.node == "__typename" {
                    collect_typename_field(fields, object, field);
                    continue;
                }

                if object.name == schema.0.env.registry.query_type
                    && matches!(
                        ctx.schema_env.registry.introspection_mode,
                        IntrospectionMode::Enabled | IntrospectionMode::IntrospectionOnly
                    )
                    && matches!(
                        ctx.query_env.introspection_mode,
                        IntrospectionMode::Enabled | IntrospectionMode::IntrospectionOnly,
                    )
                {
                    // is query root
                    if field.node.name.node == "__schema" {
                        collect_schema_field(fields, ctx, field);
                        continue;
                    } else if field.node.name.node == "__type" {
                        collect_type_field(fields, ctx, field);
                        continue;
                    } else if ctx.schema_env.registry.enable_federation
                        && field.node.name.node == "_service"
                    {
                        collect_service_field(fields, ctx, field);
                        continue;
                    } else if ctx.schema_env.registry.enable_federation
                        && field.node.name.node == "_entities"
                    {
                        collect_entities_field(fields, schema, ctx, parent_value, field);
                        continue;
                    }
                }

                if ctx.schema_env.registry.introspection_mode
                    == IntrospectionMode::IntrospectionOnly
                    || ctx.query_env.introspection_mode == IntrospectionMode::IntrospectionOnly
                {
                    fields.push(
                        async move { Ok((field.node.response_key().node.clone(), Value::Null)) }
                            .boxed_maybe_send(),
                    );
                    continue;
                }

                if let Some(field_def) = object.fields.get(field.node.name.node.as_str()) {
                    collect_field(fields, schema, object, ctx, parent_value, field_def, field);
                }
            }
            selection => {
                let (type_condition, selection_set) = match selection {
                    Selection::Field(_) => unreachable!(),
                    Selection::FragmentSpread(spread) => {
                        let fragment = ctx.query_env.fragments.get(&spread.node.fragment_name.node);
                        let fragment = match fragment {
                            Some(fragment) => fragment,
                            None => {
                                return Err(ServerError::new(
                                    format!(
                                        "Unknown fragment \"{}\".",
                                        spread.node.fragment_name.node
                                    ),
                                    Some(spread.pos),
                                ));
                            }
                        };
                        (
                            Some(&fragment.node.type_condition),
                            &fragment.node.selection_set,
                        )
                    }
                    Selection::InlineFragment(fragment) => (
                        fragment.node.type_condition.as_ref(),
                        &fragment.node.selection_set,
                    ),
                };

                let type_condition =
                    type_condition.map(|condition| condition.node.on.node.as_str());

                let type_condition_matched = match type_condition {
                    None => true,
                    Some(type_condition) => does_fragment_type_apply(
                        &schema.0.env.registry.types,
                        type_condition,
                        &object.name,
                    ),
                };
                if type_condition_matched {
                    collect_fields(
                        fields,
                        schema,
                        object,
                        &ctx.with_selection_set(selection_set),
                        parent_value,
                    )?;
                }
            }
        }
    }

    Ok(())
}

pub(crate) fn resolve<'a>(
    schema: &'a Schema,
    ctx: &'a Context<'a>,
    type_ref: &'a TypeRef,
    value: Option<&'a FieldValue>,
) -> MaybeBoxFuture<'a, ServerResult<Option<Value>>> {
    async move {
        match (type_ref, value) {
            (TypeRef::Named(type_name), Some(value)) => {
                resolve_value(schema, ctx, &schema.0.types[type_name.as_ref()], value).await
            }
            (TypeRef::Named(_), None) => Ok(None),

            (TypeRef::NonNull(type_ref), Some(value)) => {
                match resolve(schema, ctx, type_ref, Some(value)).await? {
                    Some(value) => Ok(Some(value)),
                    None => Err(ctx.set_error_path(
                        Error::new("internal: non-null types require a return value")
                            .into_server_error(ctx.item.pos),
                    )),
                }
            }
            (TypeRef::NonNull(_), None) => Err(ctx.set_error_path(
                Error::new("internal: non-null types require a return value")
                    .into_server_error(ctx.item.pos),
            )),

            (TypeRef::List(_), Some(FieldValue(FieldValueInner::Value(Value::Null)))) => Ok(None),
            (TypeRef::List(type_ref), Some(FieldValue(FieldValueInner::List(values)))) => {
                resolve_list(schema, ctx, type_ref, values).await
            }
            (
                TypeRef::List(type_ref),
                Some(FieldValue(FieldValueInner::Value(Value::List(values)))),
            ) => {
                let values = values
                    .iter()
                    .cloned()
                    .map(FieldValue::value)
                    .collect::<Vec<_>>();
                resolve_list(schema, ctx, type_ref, &values).await
            }
            (TypeRef::List(_), Some(_)) => Err(ctx.set_error_path(
                Error::new("internal: expects an array").into_server_error(ctx.item.pos),
            )),
            (TypeRef::List(_), None) => Ok(None),
        }
    }
    .boxed_maybe_send()
}

async fn resolve_list<'a>(
    schema: &'a Schema,
    ctx: &'a Context<'a>,
    type_ref: &'a TypeRef,
    values: &[FieldValue<'_>],
) -> ServerResult<Option<Value>> {
    let mut futures = Vec::with_capacity(values.len());
    for (idx, value) in values.iter().enumerate() {
        let ctx_item = ctx.with_index(idx);

        futures.push(async move {
            let parent_type = format!("[{}]", type_ref);
            let return_type = type_ref.to_string();
            let resolve_info = ResolveInfo {
                path_node: ctx_item.path_node.as_ref().unwrap(),
                parent_type: &parent_type,
                return_type: &return_type,
                name: ctx.item.node.name.node.as_str(),
                alias: ctx
                    .item
                    .node
                    .alias
                    .as_ref()
                    .map(|alias| alias.node.as_str()),
                is_for_introspection: ctx_item.is_for_introspection,
                field: &ctx_item.item.node,
            };

            let resolve_fut = async { resolve(schema, &ctx_item, type_ref, Some(value)).await };
            futures_util::pin_mut!(resolve_fut);

            let res_value = ctx_item
                .query_env
                .extensions
                .resolve(resolve_info, &mut resolve_fut)
                .await?;
            Ok::<_, ServerError>(res_value.unwrap_or_default())
        });
    }
    let values = futures_util::future::try_join_all(futures).await?;
    Ok(Some(Value::List(values)))
}

async fn resolve_value(
    schema: &Schema,
    ctx: &Context<'_>,
    field_type: &Type,
    value: &FieldValue<'_>,
) -> ServerResult<Option<Value>> {
    match (field_type, &value.0) {
        (Type::Scalar(_), FieldValueInner::Value(Value::Null)) => Ok(None),
        (Type::Scalar(scalar), FieldValueInner::Value(value)) if scalar.validate(value) => {
            Ok(Some(value.clone()))
        }
        (Type::Scalar(scalar), _) => Err(ctx.set_error_path(
            Error::new(format!(
                "internal: invalid value for scalar \"{}\", expected \"FieldValue::Value\"",
                scalar.name
            ))
            .into_server_error(ctx.item.pos),
        )),

        (Type::Object(object), _) => {
            resolve_container(
                schema,
                object,
                &ctx.with_selection_set(&ctx.item.node.selection_set),
                value,
                true,
            )
            .await
        }

        (Type::InputObject(obj), _) => Err(ctx.set_error_path(
            Error::new(format!(
                "internal: cannot use input object \"{}\" as output value",
                obj.name
            ))
            .into_server_error(ctx.item.pos),
        )),

        (Type::Enum(_), FieldValueInner::Value(Value::Null)) => Ok(None),
        (Type::Enum(e), FieldValueInner::Value(Value::Enum(name))) => {
            if !e.enum_values.contains_key(name.as_str()) {
                return Err(ctx.set_error_path(
                    Error::new(format!("internal: invalid item for enum \"{}\"", e.name))
                        .into_server_error(ctx.item.pos),
                ));
            }
            Ok(Some(Value::Enum(name.clone())))
        }
        (Type::Enum(e), FieldValueInner::Value(Value::String(name))) => {
            if !e.enum_values.contains_key(name) {
                return Err(ctx.set_error_path(
                    Error::new(format!("internal: invalid item for enum \"{}\"", e.name))
                        .into_server_error(ctx.item.pos),
                ));
            }
            Ok(Some(Value::Enum(Name::new(name))))
        }
        (Type::Enum(e), _) => Err(ctx.set_error_path(
            Error::new(format!("internal: invalid item for enum \"{}\"", e.name))
                .into_server_error(ctx.item.pos),
        )),

        (Type::Interface(interface), FieldValueInner::WithType { value, ty }) => {
            let is_contains_obj = schema
                .0
                .env
                .registry
                .types
                .get(&interface.name)
                .and_then(|meta_type| {
                    meta_type
                        .possible_types()
                        .map(|possible_types| possible_types.contains(ty.as_ref()))
                })
                .unwrap_or_default();
            if !is_contains_obj {
                return Err(ctx.set_error_path(
                    Error::new(format!(
                        "internal: object \"{}\" does not implement interface \"{}\"",
                        ty, interface.name,
                    ))
                    .into_server_error(ctx.item.pos),
                ));
            }

            let object_type = schema
                .0
                .types
                .get(ty.as_ref())
                .ok_or_else(|| {
                    ctx.set_error_path(
                        Error::new(format!("internal: object \"{}\" does not registered", ty))
                            .into_server_error(ctx.item.pos),
                    )
                })?
                .as_object()
                .ok_or_else(|| {
                    ctx.set_error_path(
                        Error::new(format!("internal: type \"{}\" is not object", ty))
                            .into_server_error(ctx.item.pos),
                    )
                })?;

            resolve_container(
                schema,
                object_type,
                &ctx.with_selection_set(&ctx.item.node.selection_set),
                value,
                true,
            )
            .await
        }
        (Type::Interface(interface), _) => Err(ctx.set_error_path(
            Error::new(format!(
                "internal: invalid value for interface \"{}\", expected \"FieldValue::WithType\"",
                interface.name
            ))
            .into_server_error(ctx.item.pos),
        )),

        (Type::Union(union), FieldValueInner::WithType { value, ty }) => {
            if !union.possible_types.contains(ty.as_ref()) {
                return Err(ctx.set_error_path(
                    Error::new(format!(
                        "internal: union \"{}\" does not contain object \"{}\"",
                        union.name, ty,
                    ))
                    .into_server_error(ctx.item.pos),
                ));
            }

            let object_type = schema
                .0
                .types
                .get(ty.as_ref())
                .ok_or_else(|| {
                    ctx.set_error_path(
                        Error::new(format!("internal: object \"{}\" does not registered", ty))
                            .into_server_error(ctx.item.pos),
                    )
                })?
                .as_object()
                .ok_or_else(|| {
                    ctx.set_error_path(
                        Error::new(format!("internal: type \"{}\" is not object", ty))
                            .into_server_error(ctx.item.pos),
                    )
                })?;

            resolve_container(
                schema,
                object_type,
                &ctx.with_selection_set(&ctx.item.node.selection_set),
                value,
                true,
            )
            .await
        }
        (Type::Union(union), _) => Err(ctx.set_error_path(
            Error::new(format!(
                "internal: invalid value for union \"{}\", expected \"FieldValue::WithType\"",
                union.name
            ))
            .into_server_error(ctx.item.pos),
        )),
        (Type::Subscription(subscription), _) => Err(ctx.set_error_path(
            Error::new(format!(
                "internal: cannot use subscription \"{}\" as output value",
                subscription.name
            ))
            .into_server_error(ctx.item.pos),
        )),
        (Type::Upload, _) => Err(ctx.set_error_path(
            Error::new("internal: cannot use upload as output value")
                .into_server_error(ctx.item.pos),
        )),
    }
}
