use serde::{Deserialize, Serialize};
use std::cmp::Ordering;

/// Represents any piece of data that can be stored on the VM stack or in globals.
/// 
/// The PVM is "dynamically typed" at the bytecode level, meaning a single 
/// `Value` enum can hold different primitive types. The VM performs 
/// automatic type promotion (e.g., adding an Int32 to a Float64 results 
/// in a Float64) to ensure mathematical correctness.
#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(untagged)]
pub enum Value {
    /// 32-bit signed integer. Used for most loop counters and indices.
    Int32(i32),
    /// 64-bit signed integer. Used for large numbers and timestamps.
    Int64(i64),
    /// 64-bit double precision float. Used for physics and complex math.
    Float(f64),
    /// Boolean value (true/false).
    Boolean(bool),
    /// UTF-8 string. Strings are immutable and usually come from the Constant Pool.
    String(String),
    /// Bounded 16-bit-ish integer.
    Bounded(u32),
    /// A pointer to an object on the heap.
    Gate(usize),
    /// Represents the absence of a value (equivalent to `null` or `undefined`).
    Null,
}

impl PartialEq for Value {
    fn eq(&self, other: &Self) -> bool {
        match (self, other) {
            (Value::Int32(a), Value::Int32(b)) => a == b,
            (Value::Int64(a), Value::Int64(b)) => a == b,
            (Value::Int32(a), Value::Int64(b)) => *a as i64 == *b,
            (Value::Int64(a), Value::Int32(b)) => *a == *b as i64,
            (Value::Float(a), Value::Float(b)) => a == b,
            (Value::Int32(a), Value::Float(b)) => *a as f64 == *b,
            (Value::Float(a), Value::Int32(b)) => *a == *b as f64,
            (Value::Int64(a), Value::Float(b)) => *a as f64 == *b,
            (Value::Float(a), Value::Int64(b)) => *a == *b as f64,
            (Value::Boolean(a), Value::Boolean(b)) => a == b,
            (Value::String(a), Value::String(b)) => a == b,
            (Value::Bounded(a), Value::Bounded(b)) => a == b,
            (Value::Gate(a), Value::Gate(b)) => a == b,
            (Value::Null, Value::Null) => true,
            _ => false,
        }
    }
}

impl PartialOrd for Value {
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        match (self, other) {
            (Value::Int32(a), Value::Int32(b)) => a.partial_cmp(b),
            (Value::Int64(a), Value::Int64(b)) => a.partial_cmp(b),
            (Value::Int32(a), Value::Int64(b)) => (*a as i64).partial_cmp(b),
            (Value::Int64(a), Value::Int32(b)) => a.partial_cmp(&(*b as i64)),
            (Value::Float(a), Value::Float(b)) => a.partial_cmp(b),
            (Value::Bounded(a), Value::Bounded(b)) => a.partial_cmp(b),
            (Value::Int32(a), Value::Float(b)) => (*a as f64).partial_cmp(b),
            (Value::Float(a), Value::Int32(b)) => a.partial_cmp(&(*b as f64)),
            (Value::Int64(a), Value::Float(b)) => (*a as f64).partial_cmp(b),
            (Value::Float(a), Value::Int64(b)) => a.partial_cmp(&(*b as f64)),
            (Value::Boolean(a), Value::Boolean(b)) => a.partial_cmp(b),
            (Value::String(a), Value::String(b)) => a.partial_cmp(b),
            _ => None,
        }
    }
}

impl Value {
    pub fn as_float(&self) -> Option<f64> {
        match self {
            Value::Int32(i) => Some(*i as f64),
            Value::Int64(i) => Some(*i as f64),
            Value::Float(f) => Some(*f),
            Value::Bounded(b) => Some(*b as f64),
            _ => None,
        }
    }

    pub fn as_integer(&self) -> Option<i64> {
        match self {
            Value::Int32(i) => Some(*i as i64),
            Value::Int64(i) => Some(*i),
            Value::Float(f) => Some(*f as i64),
            Value::Bounded(b) => Some(*b as i64),
            _ => None,
        }
    }

    pub fn to_string(&self) -> String {
        match self {
            Value::Int32(i) => i.to_string(),
            Value::Int64(i) => i.to_string(),
            Value::Float(f) => f.to_string(),
            Value::Bounded(b) => format!("{}b", b),
            Value::Boolean(b) => b.to_string(),
            Value::String(s) => s.clone(),
            Value::Gate(r) => format!("[Gate {}]", r),
            Value::Null => "null".to_string(),
        }
    }
}

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

    #[test]
    fn test_value_equality() {
        assert_eq!(Value::Int32(10), Value::Int32(10));
        assert_eq!(Value::Int64(10), Value::Int64(10));
        assert_eq!(Value::Int32(10), Value::Int64(10));
        assert_eq!(Value::Int64(10), Value::Int32(10));
        assert_eq!(Value::Float(10.5), Value::Float(10.5));
        assert_eq!(Value::Int32(10), Value::Float(10.0));
        assert_eq!(Value::Float(10.0), Value::Int32(10));
        assert_eq!(Value::Int64(10), Value::Float(10.0));
        assert_eq!(Value::Float(10.0), Value::Int64(10));
        assert_ne!(Value::Int32(10), Value::Int32(11));
        assert_ne!(Value::Int64(10), Value::Int64(11));
        assert_ne!(Value::Int32(10), Value::Int64(11));
        assert_ne!(Value::Int32(10), Value::Float(10.1));
        assert_eq!(Value::Boolean(true), Value::Boolean(true));
        assert_ne!(Value::Boolean(true), Value::Boolean(false));
        assert_eq!(Value::String("oi".into()), Value::String("oi".into()));
        assert_eq!(Value::Null, Value::Null);
    }

    #[test]
    fn test_value_conversions() {
        let v_int32 = Value::Int32(42);
        assert_eq!(v_int32.as_float(), Some(42.0));
        assert_eq!(v_int32.as_integer(), Some(42));

        let v_int64 = Value::Int64(42);
        assert_eq!(v_int64.as_float(), Some(42.0));
        assert_eq!(v_int64.as_integer(), Some(42));

        let v_float = Value::Float(42.7);
        assert_eq!(v_float.as_float(), Some(42.7));
        assert_eq!(v_float.as_integer(), Some(42));

        let v_bool = Value::Boolean(true);
        assert_eq!(v_bool.as_float(), None);
        assert_eq!(v_bool.as_integer(), None);
    }
}