use std::cell::RefCell;

use std::collections::HashSet;

use std::fmt::Debug;

use std::sync::{Arc, RwLock};

use derivative::Derivative;

use serde::{Deserialize, Serialize};

use serde_with::serde_as;

use crate::ast::{DecisionVariable, Domain, Expression, Name, SymbolTable};

use crate::context::Context;

use crate::metadata::Metadata;

/// Represents a computational model containing variables, constraints, and a shared context.

///

/// The `Model` struct holds a set of variables and constraints for manipulating and evaluating symbolic expressions.

///

/// # Fields

/// - `variables`:

///   - Type: `SymbolTable`

///   - A table that links each variable's name to its corresponding `DecisionVariable`.

///   - For example, the name `x` might be linked to a `DecisionVariable` that says `x` can only take values between 1 and 10.

///

/// - `constraints`:

///   - Type: `Expression`

///   - Represents the logical constraints applied to the model's variables.

///   - Can be a single constraint or a combination of various expressions, such as logical operations (e.g., `AND`, `OR`),

///     arithmetic operations (e.g., `SafeDiv`, `UnsafeDiv`), or specialized constraints like `SumEq`.

///

/// - `context`:

///   - Type: `Arc<RwLock<Context<'static>>>`

///   - A shared object that stores global settings and state for the model.

///   - Can be safely read or changed by multiple parts of the program at the same time, making it good for multi-threaded use.

///

/// - `next_var`:

///   - Type: `RefCell<i32>`

///   - A counter used to create new, unique variable names.

///   - Allows updating the counter inside the model without making the whole model mutable.

///

/// # Usage

/// This struct is typically used to:

/// - Define a set of variables and constraints for rule-based evaluation.

/// - Have transformations, optimizations, and simplifications applied to it using a set of rules.

#[serde_as]

#[derivative(PartialEq, Eq)]

pub struct Model {

    #[serde_as(as = "Vec<(_, _)>")]

    pub variables: SymbolTable,

    pub constraints: Vec<Expression>,

    #[serde(skip)]

    #[derivative(PartialEq = "ignore")]

    pub context: Arc<RwLock<Context<'static>>>,

    next_var: RefCell<i32>,

}

impl Model {

    // Function to update a DecisionVariable based on its Name

    // Function to add a new DecisionVariable to the Model

    /// Returns an arbitrary variable name that is not in the model.

    /// Extends the models symbol table with the given symbol table, updating the gensym counter if

    /// necessary.

    ///

                    }

                }

            }

}