use serde::Serialize;
use serde::de::DeserializeOwned;

use crate::error::Result;
use crate::schema::SchemaType;

/// The `Instructor` trait combines JSON schema generation, serialization, and validation.
///
/// This trait is automatically implemented for any type that implements the required traits
/// (SchemaType, DeserializeOwned, and Serialize), but you can also provide a custom
/// implementation to add your own validation logic.
///
/// # Nested Types and Schema Embedding
///
/// When you have nested structs or enums, they should also derive `Instructor` to ensure
/// their full schema is embedded in the parent type. This produces complete JSON schemas
/// that help LLMs generate correct structured output.
///
/// ```rust
/// # use rstructor::Instructor;
/// # use serde::{Serialize, Deserialize};
/// // Parent type derives Instructor
/// #[derive(Instructor, Serialize, Deserialize)]
/// struct Parent {
///     child: Child,  // Child's schema will be embedded
/// }
///
/// // Nested types should also derive Instructor for complete schema
/// #[derive(Instructor, Serialize, Deserialize)]
/// struct Child {
///     name: String,
/// }
/// ```
///
/// This ensures the generated schema includes all nested properties.
///
/// # Validation
///
/// The `validate` method is called automatically when an LLM generates a structured response,
/// allowing you to apply domain-specific validation logic beyond what type checking provides.
///
/// To add custom validation, use the `validate` attribute with a function path:
///
/// ```
/// use rstructor::{Instructor, RStructorError};
/// use serde::{Serialize, Deserialize};
///
/// #[derive(Instructor, Serialize, Deserialize)]
/// #[llm(validate = "validate_product")]
/// struct Product {
///     name: String,
///     price: f64,
///     quantity: u32,
/// }
///
/// fn validate_product(product: &Product) -> rstructor::Result<()> {
///     // Price must be positive
///     if product.price <= 0.0 {
///         return Err(RStructorError::ValidationError(
///             format!("Product price must be positive, got {}", product.price)
///         ));
///     }
///
///     // Name can't be empty
///     if product.name.trim().is_empty() {
///         return Err(RStructorError::ValidationError(
///             "Product name cannot be empty".to_string()
///         ));
///     }
///
///     Ok(())
/// }
/// ```
///
/// # Example: Using with LLM clients
///
/// ```no_run
/// # async fn example() -> Result<(), Box<dyn std::error::Error>> {
/// use rstructor::{LLMClient, OpenAIClient, OpenAIModel, Instructor};
/// use serde::{Serialize, Deserialize};
///
/// // Define a product model
/// #[derive(Instructor, Serialize, Deserialize, Debug)]
/// struct ProductInfo {
///     name: String,
///     price: f64,
/// }
///
/// // Create a client
/// let client = OpenAIClient::new("your-api-key")?
///     .model(OpenAIModel::Gpt55);
///
/// // Get structured data with automatic validation
/// let product = client.materialize::<ProductInfo>("Describe a laptop").await?;
/// # Ok(())
/// # }
/// ```
pub trait Instructor: SchemaType + DeserializeOwned + Serialize {
    /// Optional validation logic beyond type checking
    ///
    /// This method is called automatically by `materialize` to validate
    /// the data returned by the LLM. The default implementation does nothing
    /// and returns Ok(()), but you can override it to add your own validation logic.
    ///
    /// # Example
    ///
    /// ```
    /// # use rstructor::{Instructor, RStructorError};
    /// # use serde::{Serialize, Deserialize};
    /// #
    /// # #[derive(Instructor, Serialize, Deserialize, Debug)]
    /// # struct Product {
    /// #     name: String,
    /// #     price: f64,
    /// # }
    /// #
    /// // Just implement validate directly on the struct
    /// // No need to manually implement the Instructor trait
    /// impl Product {
    ///     fn validate(&self) -> rstructor::Result<()> {
    ///         // Price must be positive
    ///         if self.price < 0.0 {
    ///             return Err(RStructorError::ValidationError(
    ///                 format!("Price must be positive, got {}", self.price)
    ///             ));
    ///         }
    ///         Ok(())
    ///     }
    /// }
    /// ```
    fn validate(&self) -> Result<()> {
        Ok(())
    }
}

// The blanket implementation is removed
// Instead, the derive macro will handle implementing Instructor for each type
// This avoids the conflicting implementation errors

/// Helper trait to mark a type as implementing custom validation.
///
/// This is a marker trait only used for documentation purposes to indicate
/// that a type provides a custom validation implementation beyond the default.
/// You don't need to implement this trait directly - it's only for clarity
/// in documentation.
pub trait Validatable {}
