//! RDFS (RDF Schema) reasoning
//!
//! Implements basic RDFS entailment rules for inference.

use super::{RdfStore, Triple};
use thiserror::Error;

/// Reasoning errors
#[derive(Error, Debug)]
pub enum ReasoningError {
    /// Invalid rule
    #[error("Invalid rule: {0}")]
    InvalidRule(String),

    /// Inference error
    #[error("Inference error: {0}")]
    InferenceError(String),
}

pub type ReasoningResult<T> = Result<T, ReasoningError>;

/// RDFS inference rule
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum InferenceRule {
    /// rdfs:subClassOf transitivity
    SubClassOfTransitive,

    /// rdfs:subPropertyOf transitivity
    SubPropertyOfTransitive,

    /// rdfs:domain inference
    DomainInference,

    /// rdfs:range inference
    RangeInference,

    /// rdf:type inheritance via rdfs:subClassOf
    TypeInheritance,
}

/// RDFS reasoner with forward chaining
pub struct RdfsReasoner {
    /// Enable specific rules
    enabled_rules: Vec<InferenceRule>,
}

impl RdfsReasoner {
    /// Create a new reasoner with all rules enabled
    pub fn new() -> Self {
        Self {
            enabled_rules: vec![
                InferenceRule::SubClassOfTransitive,
                InferenceRule::SubPropertyOfTransitive,
                InferenceRule::DomainInference,
                InferenceRule::RangeInference,
                InferenceRule::TypeInheritance,
            ],
        }
    }

    /// Create a reasoner with specific rules
    pub fn with_rules(rules: Vec<InferenceRule>) -> Self {
        Self {
            enabled_rules: rules,
        }
    }

    /// Materialize all inferences
    ///
    /// TODO: Implement RDFS entailment rules
    /// - rdfs:subClassOf transitivity: (A subClassOf B) ∧ (B subClassOf C) → (A subClassOf C)
    /// - rdfs:subPropertyOf transitivity
    /// - rdfs:domain: (P domain C) ∧ (X P Y) → (X type C)
    /// - rdfs:range: (P range C) ∧ (X P Y) → (Y type C)
    /// - Type inheritance: (X type A) ∧ (A subClassOf B) → (X type B)
    pub fn materialize(&self, _store: &RdfStore) -> ReasoningResult<Vec<Triple>> {
        // TODO: Implement materialization
        Ok(Vec::new())
    }

    /// Apply reasoning and add inferred triples to store
    pub fn reason(&self, _store: &mut RdfStore) -> ReasoningResult<usize> {
        // TODO: Implement reasoning
        Ok(0)
    }
}

impl Default for RdfsReasoner {
    fn default() -> Self {
        Self::new()
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_reasoner_creation() {
        let reasoner = RdfsReasoner::new();
        assert_eq!(reasoner.enabled_rules.len(), 5);
    }

    #[test]
    fn test_custom_rules() {
        let reasoner = RdfsReasoner::with_rules(vec![InferenceRule::SubClassOfTransitive]);
        assert_eq!(reasoner.enabled_rules.len(), 1);
    }

    #[test]
    fn test_materialization_stub() {
        let reasoner = RdfsReasoner::new();
        let store = RdfStore::new();

        let inferred = reasoner.materialize(&store).unwrap();
        assert!(inferred.is_empty()); // Stub returns empty
    }
}
