//! Extensions for schema

mod apollo_tracing;
mod tracing;

pub use self::tracing::Tracing;
use crate::context::{QueryPathNode, ResolveId};
pub use apollo_tracing::ApolloTracing;

pub(crate) type BoxExtension = Box<dyn Extension>;

/// Parameters for `Extension::resolve_field_start`
pub struct ResolveInfo<'a> {
    /// Because resolver is concurrent, `Extension::resolve_field_start` and `Extension::resolve_field_end` are
    /// not strictly ordered, so each pair is identified by an id.
    pub resolve_id: ResolveId,

    /// Current path node, You can go through the entire path.
    pub path_node: &'a QueryPathNode<'a>,

    /// Parent type
    pub parent_type: &'a str,

    /// Current return type, is qualified name.
    pub return_type: &'a str,
}

/// Represents a GraphQL extension
#[allow(unused_variables)]
pub trait Extension: Sync + Send + 'static {
    /// If this extension needs to output data to query results, you need to specify a name.
    fn name(&self) -> Option<&'static str> {
        None
    }

    /// Called at the begin of the parse.
    fn parse_start(&self, query_source: &str) {}

    /// Called at the end of the parse.
    fn parse_end(&self) {}

    /// Called at the begin of the validation.
    fn validation_start(&self) {}

    /// Called at the end of the validation.
    fn validation_end(&self) {}

    /// Called at the begin of the execution.
    fn execution_start(&self) {}

    /// Called at the end of the execution.
    fn execution_end(&self) {}

    /// Called at the begin of the resolve field.
    fn resolve_field_start(&self, info: &ResolveInfo<'_>) {}

    /// Called at the end of the resolve field.
    fn resolve_field_end(&self, resolve_id: ResolveId) {}

    /// Get the results
    fn result(&self) -> Option<serde_json::Value> {
        None
    }
}