grust-core 0.2.0

use std::{
    collections::{BTreeMap, BTreeSet},
    fmt,
};

use async_trait::async_trait;
use serde::{Deserialize, Serialize};

pub type Result<T> = std::result::Result<T, GrustError>;
pub type Props = BTreeMap<String, Value>;

#[derive(Debug, thiserror::Error)]
pub enum GrustError {
    #[error("backend error: {0}")]
    Backend(String),
    #[error("schema error: {0}")]
    Schema(String),
    #[error("unsupported graph feature: {0}")]
    Unsupported(String),
    #[error("serialization error: {0}")]
    Serialization(String),
}

#[derive(Clone, Debug, Eq, PartialEq, Ord, PartialOrd, Hash, Serialize, Deserialize)]
pub struct NodeId(String);

impl NodeId {
    pub fn new(value: impl Into<String>) -> Self {
        Self(value.into())
    }

    pub fn as_str(&self) -> &str {
        &self.0
    }

    pub fn into_string(self) -> String {
        self.0
    }
}

impl fmt::Display for NodeId {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str(&self.0)
    }
}

impl From<String> for NodeId {
    fn from(value: String) -> Self {
        Self::new(value)
    }
}

impl From<&str> for NodeId {
    fn from(value: &str) -> Self {
        Self::new(value)
    }
}

impl From<&String> for NodeId {
    fn from(value: &String) -> Self {
        Self::new(value.clone())
    }
}

impl From<&NodeId> for NodeId {
    fn from(value: &NodeId) -> Self {
        value.clone()
    }
}

#[derive(Clone, Debug, Eq, PartialEq, Ord, PartialOrd, Hash, Serialize, Deserialize)]
pub struct EdgeId(String);

impl EdgeId {
    pub fn new(value: impl Into<String>) -> Self {
        Self(value.into())
    }

    pub fn as_str(&self) -> &str {
        &self.0
    }

    pub fn into_string(self) -> String {
        self.0
    }
}

impl fmt::Display for EdgeId {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str(&self.0)
    }
}

impl From<String> for EdgeId {
    fn from(value: String) -> Self {
        Self::new(value)
    }
}

impl From<&str> for EdgeId {
    fn from(value: &str) -> Self {
        Self::new(value)
    }
}

impl From<&String> for EdgeId {
    fn from(value: &String) -> Self {
        Self::new(value.clone())
    }
}

impl From<&EdgeId> for EdgeId {
    fn from(value: &EdgeId) -> Self {
        value.clone()
    }
}

#[derive(Clone, Debug, Eq, PartialEq, Ord, PartialOrd, Hash, Serialize, Deserialize)]
pub struct Label(String);

impl Label {
    pub fn new(value: impl Into<String>) -> Self {
        Self(value.into())
    }

    pub fn as_str(&self) -> &str {
        &self.0
    }

    pub fn into_string(self) -> String {
        self.0
    }
}

impl fmt::Display for Label {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str(&self.0)
    }
}

impl From<String> for Label {
    fn from(value: String) -> Self {
        Self::new(value)
    }
}

impl From<&str> for Label {
    fn from(value: &str) -> Self {
        Self::new(value)
    }
}

impl From<&String> for Label {
    fn from(value: &String) -> Self {
        Self::new(value.clone())
    }
}

impl From<&Label> for Label {
    fn from(value: &Label) -> Self {
        value.clone()
    }
}

#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
#[serde(tag = "type", content = "value", rename_all = "snake_case")]
pub enum Value {
    Null,
    Bool(bool),
    Int(i64),
    Float(f64),
    String(String),
    StringArray(Vec<String>),
    Json(serde_json::Value),
}

impl Value {
    pub fn as_str(&self) -> Option<&str> {
        match self {
            Self::String(value) => Some(value),
            _ => None,
        }
    }

    pub fn as_string_array(&self) -> Option<&[String]> {
        match self {
            Self::StringArray(values) => Some(values),
            _ => None,
        }
    }
}

impl From<String> for Value {
    fn from(value: String) -> Self {
        Self::String(value)
    }
}

impl From<&str> for Value {
    fn from(value: &str) -> Self {
        Self::String(value.to_string())
    }
}

impl From<&String> for Value {
    fn from(value: &String) -> Self {
        Self::String(value.clone())
    }
}

impl From<Vec<String>> for Value {
    fn from(value: Vec<String>) -> Self {
        Self::StringArray(value)
    }
}

impl From<bool> for Value {
    fn from(value: bool) -> Self {
        Self::Bool(value)
    }
}

impl From<i64> for Value {
    fn from(value: i64) -> Self {
        Self::Int(value)
    }
}

impl From<i32> for Value {
    fn from(value: i32) -> Self {
        Self::Int(i64::from(value))
    }
}

impl From<usize> for Value {
    fn from(value: usize) -> Self {
        Self::Int(value as i64)
    }
}

impl From<f64> for Value {
    fn from(value: f64) -> Self {
        Self::Float(value)
    }
}

impl From<serde_json::Value> for Value {
    fn from(value: serde_json::Value) -> Self {
        match value {
            serde_json::Value::Null => Self::Null,
            serde_json::Value::Bool(value) => Self::Bool(value),
            serde_json::Value::Number(value) => {
                if let Some(value) = value.as_i64() {
                    Self::Int(value)
                } else if let Some(value) = value.as_f64() {
                    Self::Float(value)
                } else {
                    Self::Json(serde_json::Value::Number(value))
                }
            }
            serde_json::Value::String(value) => Self::String(value),
            serde_json::Value::Array(values) => {
                let strings = values
                    .iter()
                    .filter_map(|value| value.as_str().map(ToString::to_string))
                    .collect::<Vec<_>>();
                if strings.len() == values.len() {
                    Self::StringArray(strings)
                } else {
                    Self::Json(serde_json::Value::Array(values))
                }
            }
            serde_json::Value::Object(value) => Self::Json(serde_json::Value::Object(value)),
        }
    }
}

#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
pub struct Node {
    pub id: NodeId,
    pub label: Label,
    pub props: Props,
}

impl Node {
    pub fn new(label: impl Into<Label>, id: impl Into<NodeId>, props: impl Into<Props>) -> Self {
        let id = id.into();
        let mut props = props.into();
        props
            .entry("id".to_string())
            .or_insert_with(|| Value::from(id.as_str()));
        Self {
            id,
            label: label.into(),
            props,
        }
    }
}

#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
pub struct Edge {
    pub id: Option<EdgeId>,
    pub from: NodeId,
    pub to: NodeId,
    pub label: Label,
    pub props: Props,
}

impl Edge {
    pub fn new(
        label: impl Into<Label>,
        from: impl Into<NodeId>,
        to: impl Into<NodeId>,
        props: impl Into<Props>,
    ) -> Self {
        Self {
            id: None,
            from: from.into(),
            to: to.into(),
            label: label.into(),
            props: props.into(),
        }
    }

    pub fn with_id(mut self, id: impl Into<EdgeId>) -> Self {
        self.id = Some(id.into());
        self
    }
}

#[derive(Clone, Debug, Default, PartialEq, Serialize, Deserialize)]
pub struct Graph {
    pub nodes: Vec<Node>,
    pub edges: Vec<Edge>,
}

impl Graph {
    pub fn new(nodes: Vec<Node>, edges: Vec<Edge>) -> Self {
        Self { nodes, edges }
    }

    pub fn from_yaml(yaml: &str) -> Result<Self> {
        yaml::graph_from_yaml(yaml)
    }

    pub fn to_yaml(&self) -> Result<String> {
        yaml::graph_to_yaml(self)
    }

    pub fn from_json(json: &str) -> Result<Self> {
        json::graph_from_json(json)
    }

    pub fn to_json(&self) -> Result<String> {
        json::graph_to_json(self)
    }

    pub fn from_xml(xml: &str) -> Result<Self> {
        xml::graph_from_xml(xml)
    }

    pub fn to_xml(&self) -> Result<String> {
        xml::graph_to_xml(self)
    }

    pub fn builder() -> GraphBuilder {
        GraphBuilder::new()
    }
}

mod graph_doc {
    use std::collections::{BTreeMap, BTreeSet};

    use serde::{Deserialize, Serialize};

    use crate::{Edge, EdgeId, Graph, GrustError, Label, Node, NodeId, Props, Value};

    #[derive(Debug, Serialize, Deserialize)]
    pub(super) struct GraphDoc {
        #[serde(default)]
        pub(super) nodes: Vec<NodeDoc>,
        #[serde(default)]
        pub(super) edges: Vec<EdgeDoc>,
    }

    #[derive(Debug, Serialize, Deserialize)]
    pub(super) struct NodeDoc {
        pub(super) id: NodeId,
        pub(super) label: Label,
        #[serde(default, deserialize_with = "deserialize_props")]
        pub(super) props: Props,
    }

    #[derive(Debug, Serialize, Deserialize)]
    pub(super) struct NodeDocOut {
        pub(super) id: NodeId,
        pub(super) label: Label,
        #[serde(default)]
        pub(super) props: Props,
    }

    #[derive(Debug, Serialize, Deserialize)]
    pub(super) struct EdgeDoc {
        #[serde(default)]
        pub(super) id: Option<EdgeId>,
        pub(super) label: Label,
        pub(super) from: NodeId,
        pub(super) to: NodeId,
        #[serde(default, deserialize_with = "deserialize_props")]
        pub(super) props: Props,
    }

    #[derive(Debug, Serialize, Deserialize)]
    pub(super) struct EdgeDocOut {
        #[serde(default)]
        pub(super) id: Option<EdgeId>,
        pub(super) label: Label,
        pub(super) from: NodeId,
        pub(super) to: NodeId,
        #[serde(default)]
        pub(super) props: Props,
    }

    pub(super) fn graph_from_doc(doc: GraphDoc) -> super::Result<Graph> {
        let mut ids = BTreeSet::new();
        for node in &doc.nodes {
            if !ids.insert(node.id.clone()) {
                return Err(GrustError::Schema(format!(
                    "duplicate node id '{}'",
                    node.id
                )));
            }
        }

        let mut edges = Vec::with_capacity(doc.edges.len());
        for edge in doc.edges {
            if !ids.contains(&edge.from) {
                return Err(GrustError::Schema(format!(
                    "edge '{}' references unknown from node '{}'",
                    edge.label, edge.from
                )));
            }
            if !ids.contains(&edge.to) {
                return Err(GrustError::Schema(format!(
                    "edge '{}' references unknown to node '{}'",
                    edge.label, edge.to
                )));
            }

            let mut graph_edge = Edge::new(edge.label, edge.from, edge.to, edge.props);
            graph_edge.id = edge.id;
            edges.push(graph_edge);
        }

        let nodes = doc
            .nodes
            .into_iter()
            .map(|node| Node::new(node.label, node.id, node.props))
            .collect();

        Ok(Graph::new(nodes, edges))
    }

    pub(super) fn graph_to_doc(graph: &Graph) -> GraphDocOut {
        GraphDocOut {
            nodes: graph
                .nodes
                .iter()
                .map(|node| NodeDocOut {
                    id: node.id.clone(),
                    label: node.label.clone(),
                    props: without_generated_id(&node.props, &node.id),
                })
                .collect(),
            edges: graph
                .edges
                .iter()
                .map(|edge| EdgeDocOut {
                    id: edge.id.clone(),
                    label: edge.label.clone(),
                    from: edge.from.clone(),
                    to: edge.to.clone(),
                    props: edge.props.clone(),
                })
                .collect(),
        }
    }

    fn without_generated_id(props: &Props, id: &NodeId) -> Props {
        let mut props = props.clone();
        if props.get("id") == Some(&Value::from(id.as_str())) {
            props.remove("id");
        }
        props
    }

    fn deserialize_props<'de, D>(deserializer: D) -> std::result::Result<Props, D::Error>
    where
        D: serde::Deserializer<'de>,
    {
        let raw = BTreeMap::<String, serde_json::Value>::deserialize(deserializer)?;
        raw.into_iter()
            .map(|(key, value)| {
                value_from_json(value)
                    .map(|value| (key, value))
                    .map_err(serde::de::Error::custom)
            })
            .collect()
    }

    fn value_from_json(value: serde_json::Value) -> std::result::Result<Value, String> {
        if let serde_json::Value::Object(mapping) = &value
            && mapping.contains_key("type")
            && mapping.contains_key("value")
        {
            return serde_json::from_value(value)
                .map_err(|err| format!("invalid tagged Grust value: {err}"));
        }

        Ok(Value::from(value))
    }

    #[derive(Debug, Serialize, Deserialize)]
    pub(super) struct GraphDocOut {
        pub(super) nodes: Vec<NodeDocOut>,
        pub(super) edges: Vec<EdgeDocOut>,
    }
}

mod yaml {
    use crate::{Graph, GrustError};

    pub(super) fn graph_from_yaml(yaml: &str) -> super::Result<Graph> {
        let doc: super::graph_doc::GraphDoc = serde_yaml::from_str(yaml)
            .map_err(|err| GrustError::Serialization(format!("YAML parse error: {err}")))?;
        super::graph_doc::graph_from_doc(doc)
    }

    pub(super) fn graph_to_yaml(graph: &Graph) -> super::Result<String> {
        serde_yaml::to_string(&super::graph_doc::graph_to_doc(graph))
            .map_err(|err| GrustError::Serialization(format!("YAML serialization error: {err}")))
    }
}

mod json {
    use crate::{Graph, GrustError};

    pub(super) fn graph_from_json(json: &str) -> super::Result<Graph> {
        let doc: super::graph_doc::GraphDoc = serde_json::from_str(json)
            .map_err(|err| GrustError::Serialization(format!("JSON parse error: {err}")))?;
        super::graph_doc::graph_from_doc(doc)
    }

    pub(super) fn graph_to_json(graph: &Graph) -> super::Result<String> {
        serde_json::to_string_pretty(&super::graph_doc::graph_to_doc(graph))
            .map_err(|err| GrustError::Serialization(format!("JSON serialization error: {err}")))
    }
}

mod xml {
    use serde::{Deserialize, Serialize};

    use crate::{Edge, EdgeId, Graph, GrustError, Label, Node, NodeId, Props, Value};

    #[derive(Debug, Serialize, Deserialize)]
    #[serde(rename = "graph")]
    struct GraphXml {
        #[serde(default)]
        nodes: NodesXml,
        #[serde(default)]
        edges: EdgesXml,
    }

    #[derive(Debug, Default, Serialize, Deserialize)]
    struct NodesXml {
        #[serde(rename = "node", default)]
        items: Vec<NodeXml>,
    }

    #[derive(Debug, Default, Serialize, Deserialize)]
    struct EdgesXml {
        #[serde(rename = "edge", default)]
        items: Vec<EdgeXml>,
    }

    #[derive(Debug, Serialize, Deserialize)]
    struct NodeXml {
        id: NodeId,
        label: Label,
        #[serde(default)]
        props: PropsXml,
    }

    #[derive(Debug, Serialize, Deserialize)]
    struct EdgeXml {
        #[serde(default, skip_serializing_if = "Option::is_none")]
        id: Option<EdgeId>,
        label: Label,
        from: NodeId,
        to: NodeId,
        #[serde(default)]
        props: PropsXml,
    }

    #[derive(Debug, Default, Serialize, Deserialize)]
    struct PropsXml {
        #[serde(rename = "prop", default)]
        items: Vec<PropXml>,
    }

    #[derive(Debug, Serialize, Deserialize)]
    struct PropXml {
        key: String,
        value: Value,
    }

    pub(super) fn graph_from_xml(xml: &str) -> super::Result<Graph> {
        let doc: GraphXml = quick_xml::de::from_str(xml)
            .map_err(|err| GrustError::Serialization(format!("XML parse error: {err}")))?;
        super::graph_doc::graph_from_doc(doc.into())
    }

    pub(super) fn graph_to_xml(graph: &Graph) -> super::Result<String> {
        quick_xml::se::to_string(&GraphXml::from(graph))
            .map_err(|err| GrustError::Serialization(format!("XML serialization error: {err}")))
    }

    impl From<GraphXml> for super::graph_doc::GraphDoc {
        fn from(value: GraphXml) -> Self {
            Self {
                nodes: value.nodes.items.into_iter().map(Into::into).collect(),
                edges: value.edges.items.into_iter().map(Into::into).collect(),
            }
        }
    }

    impl From<NodeXml> for super::graph_doc::NodeDoc {
        fn from(value: NodeXml) -> Self {
            Self {
                id: value.id,
                label: value.label,
                props: value.props.into(),
            }
        }
    }

    impl From<EdgeXml> for super::graph_doc::EdgeDoc {
        fn from(value: EdgeXml) -> Self {
            Self {
                id: value.id,
                label: value.label,
                from: value.from,
                to: value.to,
                props: value.props.into(),
            }
        }
    }

    impl From<PropsXml> for Props {
        fn from(value: PropsXml) -> Self {
            value
                .items
                .into_iter()
                .map(|prop| (prop.key, prop.value))
                .collect()
        }
    }

    impl From<&Graph> for GraphXml {
        fn from(graph: &Graph) -> Self {
            Self {
                nodes: NodesXml {
                    items: graph.nodes.iter().map(NodeXml::from).collect(),
                },
                edges: EdgesXml {
                    items: graph.edges.iter().map(EdgeXml::from).collect(),
                },
            }
        }
    }

    impl From<&Node> for NodeXml {
        fn from(node: &Node) -> Self {
            let props = super::graph_doc::graph_to_doc(&Graph::new(vec![node.clone()], Vec::new()))
                .nodes
                .into_iter()
                .next()
                .expect("node exists")
                .props;
            Self {
                id: node.id.clone(),
                label: node.label.clone(),
                props: props.into(),
            }
        }
    }

    impl From<&Edge> for EdgeXml {
        fn from(edge: &Edge) -> Self {
            Self {
                id: edge.id.clone(),
                label: edge.label.clone(),
                from: edge.from.clone(),
                to: edge.to.clone(),
                props: edge.props.clone().into(),
            }
        }
    }

    impl From<Props> for PropsXml {
        fn from(value: Props) -> Self {
            Self {
                items: value
                    .into_iter()
                    .map(|(key, value)| PropXml { key, value })
                    .collect(),
            }
        }
    }
}

#[derive(Clone, Debug, Eq, PartialEq)]
pub enum EdgePolicy {
    AllowDuplicates,
    DedupeByFromLabelTo,
}

impl Default for EdgePolicy {
    fn default() -> Self {
        Self::DedupeByFromLabelTo
    }
}

#[derive(Clone, Debug, Default)]
pub struct GraphBuilder {
    nodes: BTreeMap<NodeId, Node>,
    edges: Vec<Edge>,
    edge_keys: BTreeSet<(NodeId, Label, NodeId)>,
    edge_policy: EdgePolicy,
}

impl GraphBuilder {
    pub fn new() -> Self {
        Self::default()
    }

    pub fn edge_policy(mut self, edge_policy: EdgePolicy) -> Self {
        self.edge_policy = edge_policy;
        self
    }

    pub fn node<'a>(
        &'a mut self,
        label: impl Into<Label>,
        id: impl Into<NodeId>,
    ) -> NodeBuilder<'a> {
        NodeBuilder {
            builder: self,
            label: label.into(),
            id: id.into(),
            props: Props::new(),
        }
    }

    pub fn edge<'a>(
        &'a mut self,
        label: impl Into<Label>,
        from: impl Into<NodeId>,
        to: impl Into<NodeId>,
    ) -> EdgeBuilder<'a> {
        EdgeBuilder {
            builder: self,
            id: None,
            label: label.into(),
            from: from.into(),
            to: to.into(),
            props: Props::new(),
        }
    }

    pub fn add_node(&mut self, node: Node) -> NodeId {
        let id = node.id.clone();
        self.nodes
            .entry(id.clone())
            .and_modify(|existing| {
                if existing.label == node.label {
                    existing.props.extend(node.props.clone());
                }
            })
            .or_insert(node);
        id
    }

    pub fn add_edge(&mut self, edge: Edge) -> Option<EdgeId> {
        let id = edge.id.clone();
        match self.edge_policy {
            EdgePolicy::AllowDuplicates => self.edges.push(edge),
            EdgePolicy::DedupeByFromLabelTo => {
                let key = (edge.from.clone(), edge.label.clone(), edge.to.clone());
                if self.edge_keys.insert(key) {
                    self.edges.push(edge);
                }
            }
        }
        id
    }

    pub fn build(self) -> Graph {
        Graph {
            nodes: self.nodes.into_values().collect(),
            edges: self.edges,
        }
    }
}

pub struct NodeBuilder<'a> {
    builder: &'a mut GraphBuilder,
    label: Label,
    id: NodeId,
    props: Props,
}

impl<'a> NodeBuilder<'a> {
    pub fn prop(mut self, key: impl Into<String>, value: impl Into<Value>) -> Self {
        self.props.insert(key.into(), value.into());
        self
    }

    pub fn props(mut self, props: Props) -> Self {
        self.props.extend(props);
        self
    }

    pub fn finish(self) -> NodeId {
        let node = Node::new(self.label, self.id, self.props);
        self.builder.add_node(node)
    }
}

pub struct EdgeBuilder<'a> {
    builder: &'a mut GraphBuilder,
    id: Option<EdgeId>,
    label: Label,
    from: NodeId,
    to: NodeId,
    props: Props,
}

impl<'a> EdgeBuilder<'a> {
    pub fn id(mut self, id: impl Into<EdgeId>) -> Self {
        self.id = Some(id.into());
        self
    }

    pub fn prop(mut self, key: impl Into<String>, value: impl Into<Value>) -> Self {
        self.props.insert(key.into(), value.into());
        self
    }

    pub fn props(mut self, props: Props) -> Self {
        self.props.extend(props);
        self
    }

    pub fn finish(self) -> Option<EdgeId> {
        let mut edge = Edge::new(self.label, self.from, self.to, self.props);
        edge.id = self.id;
        self.builder.add_edge(edge)
    }
}

#[derive(Clone, Debug, Default, PartialEq, Serialize, Deserialize)]
pub struct GraphSchema {
    pub nodes: Vec<NodeType>,
    pub edges: Vec<EdgeType>,
}

#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
pub struct NodeType {
    pub label: Label,
    pub fields: Vec<Field>,
}

#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
pub struct EdgeType {
    pub label: Label,
    pub from: Vec<Label>,
    pub to: Vec<Label>,
    pub fields: Vec<Field>,
    pub directed: bool,
    pub uniqueness: EdgeUniqueness,
}

#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
pub struct Field {
    pub name: String,
    pub ty: FieldType,
    pub required: bool,
}

#[derive(Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]
pub enum FieldType {
    String,
    Int,
    Float,
    Bool,
    DateTime,
    StringArray,
    Json,
}

#[derive(Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]
pub enum EdgeUniqueness {
    None,
    FromTo,
    FromLabelTo,
}

#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
pub struct Traversal {
    pub start: Start,
    pub steps: Vec<Step>,
    pub limit: Option<u32>,
}

impl Traversal {
    pub fn from_node(id: impl Into<NodeId>) -> Self {
        Self {
            start: Start::Node(id.into()),
            steps: Vec::new(),
            limit: None,
        }
    }

    pub fn out(mut self, edge: impl Into<Label>) -> Self {
        self.steps.push(Step {
            direction: Direction::Out,
            edge: Some(edge.into()),
            node: None,
        });
        self
    }

    pub fn in_(mut self, edge: impl Into<Label>) -> Self {
        self.steps.push(Step {
            direction: Direction::In,
            edge: Some(edge.into()),
            node: None,
        });
        self
    }

    pub fn both(mut self, edge: impl Into<Label>) -> Self {
        self.steps.push(Step {
            direction: Direction::Both,
            edge: Some(edge.into()),
            node: None,
        });
        self
    }

    pub fn to(mut self, node: impl Into<Label>) -> Self {
        if let Some(step) = self.steps.last_mut() {
            step.node = Some(node.into());
        }
        self
    }

    pub fn limit(mut self, limit: u32) -> Self {
        self.limit = Some(limit);
        self
    }
}

#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
pub enum Start {
    Node(NodeId),
    NodesByLabel(Label),
    NodesByProperty {
        label: Label,
        key: String,
        value: Value,
    },
}

#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
pub struct Step {
    pub direction: Direction,
    pub edge: Option<Label>,
    pub node: Option<Label>,
}

#[derive(Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]
pub enum Direction {
    Out,
    In,
    Both,
}

#[derive(Clone, Debug, Default, PartialEq)]
pub struct EdgeQuery {
    pub from: Option<NodeId>,
    pub to: Option<NodeId>,
    pub label: Option<Label>,
}

#[derive(Clone, Debug, Default, Eq, PartialEq)]
pub struct LoadReport {
    pub nodes: usize,
    pub edges: usize,
}

#[async_trait]
pub trait GraphStore: Send + Sync {
    async fn apply_schema(&self, _schema: &GraphSchema) -> Result<()> {
        Ok(())
    }

    async fn put_node(&self, node: &Node) -> Result<NodeId>;
    async fn put_edge(&self, edge: &Edge) -> Result<Option<EdgeId>>;

    async fn put_graph(&self, graph: &Graph) -> Result<LoadReport> {
        let mut report = LoadReport::default();
        for node in &graph.nodes {
            self.put_node(node).await?;
            report.nodes += 1;
        }
        for edge in &graph.edges {
            self.put_edge(edge).await?;
            report.edges += 1;
        }
        Ok(report)
    }

    async fn get_node(&self, id: &NodeId) -> Result<Option<Node>>;
    async fn get_edges(&self, query: EdgeQuery) -> Result<Vec<Edge>>;
    async fn traverse(&self, traversal: Traversal) -> Result<Vec<Node>>;
}

#[async_trait]
pub trait GraphAdminStore: GraphStore {
    async fn bootstrap(&self) -> Result<()> {
        Ok(())
    }

    async fn clear(&self) -> Result<()>;
}

pub mod prelude {
    pub use crate::{
        Direction, Edge, EdgeId, EdgePolicy, EdgeQuery, EdgeType, Field, FieldType, Graph,
        GraphAdminStore, GraphBuilder, GraphSchema, GraphStore, GrustError, Label, LoadReport,
        Node, NodeId, NodeType, Props, Result, Start, Step, Traversal, Value,
    };
}

#[cfg(test)]
mod tests;