use std::fmt::{Debug, Formatter, Error};

pub struct Model {
    pub name: String,
    pub variables: Vec<Component>,
    pub equations: Vec<SimpleEquation>,
    pub connections: Vec<Connection>,
    pub extends: Vec<String>,
}

#[derive(Copy, Clone)]
pub enum ComponentPrefix {
    // incomplete: eg, can be parameter and input
    Flow,
    Stream,
    Input,
    Output,
    Discrete,
    Parameter,
    Constant,
}

pub struct Component {
    pub prefix: Option<ComponentPrefix>,
    pub specifier: String,
    pub name: String,
}

#[derive(Clone)]
pub struct Connection {
    pub a: String,
    pub b: String,
}

pub struct SimpleEquation {
    pub lhs: Expr,
    pub rhs: Expr,
}

pub enum Expr {
    Integer(i64),
    Float(f64),
    Ident(String),
    Der(Box<Expr>),
    Abs(Box<Expr>),
    BinExpr(BinOperator, Box<Expr>, Box<Expr>),
}

#[derive(Copy, Clone)]
pub enum BinOperator {
    Multiply,
    Divide,
    Add,
    Subtract,
}

//// Debug Implementations

impl Debug for Model {
    fn fmt(&self, fmt: &mut Formatter) -> Result<(), Error> {
        try!(write!(fmt, "model {}\n", self.name));
        for e in self.extends.iter() {
            try!(write!(fmt, "  extends {};\n", e));
        }
        for v in self.variables.iter() {
            try!(write!(fmt, "  {:?};\n", v));
        }
        try!(write!(fmt, "equation\n"));
        for e in self.equations.iter() {
            try!(write!(fmt, "  {:?};\n", e));
        }
        for c in self.connections.iter() {
            try!(write!(fmt, "  {:?};\n", c));
        }
        write!(fmt, "end {};\n", self.name)
    }
}

impl Debug for ComponentPrefix {
    fn fmt(&self, fmt: &mut Formatter) -> Result<(), Error> {
        use self::ComponentPrefix::*;
        write!(fmt, "{:?}", 
            match *self {
                Flow => "flow",
                Stream => "stream",
                Input => "input",
                Output => "output",
                Discrete => "discrete",
                Parameter => "parameter",
                Constant => "constant",
            })
    }
}

impl Debug for Component {
    fn fmt(&self, fmt: &mut Formatter) -> Result<(), Error> {
        write!(fmt, "{:?}{}",
            self.prefix.unwrap(),
            self.name,
        )
    }
}

impl Debug for Connection {
    fn fmt(&self, fmt: &mut Formatter) -> Result<(), Error> {
        write!(fmt, "connect({:?}, {:?});", self.a, self.b)
    }
}

impl Debug for SimpleEquation {
    fn fmt(&self, fmt: &mut Formatter) -> Result<(), Error> {
        write!(fmt, "{:?} = {:?}", self.lhs, self.rhs)
    }
}

impl Debug for Expr {
    fn fmt(&self, fmt: &mut Formatter) -> Result<(), Error> {
        use self::Expr::*;
        match *self {
            Integer(e) => write!(fmt, "{}", e),
            Float(e) => write!(fmt, "{}", e),
            Ident(ref e) => write!(fmt, "{}", e),
            Der(ref e) => write!(fmt, "der({:?})", e),
            Abs(ref e) => write!(fmt, "abs({:?})", e),
            BinExpr(op, ref l, ref r) => write!(fmt, "({:?} {:?} {:?})", l, op, r),
        }
    }
}

impl Debug for BinOperator {
    fn fmt(&self, fmt: &mut Formatter) -> Result<(), Error> {
        use self::BinOperator::*;
        match *self {
            Multiply => write!(fmt, "*"),
            Divide => write!(fmt, "/"),
            Add => write!(fmt, "+"),
            Subtract => write!(fmt, "-"),
        }
    }
}