pub fn model_from_json(str: &str, context: Arc<RwLock<Context<'static>>>) -> Result<Model> {

    let mut m = Model::new_empty(context);

    let v: JsonValue = serde_json::from_str(str)?;

    let statements = v["mStatements"]

        .as_array()

        .ok_or(Error::Parse("mStatements is not an array".to_owned()))?;

    for statement in statements {

        let entry = statement

            .as_object()

            .ok_or(Error::Parse("mStatements contains a non-object".to_owned()))?

            .iter()

            .next()

            .ok_or(Error::Parse(

                "mStatements contains an empty object".to_owned(),

            ))?;

        match entry.0.as_str() {

            "Declaration" => {

                let (name, var) = parse_variable(entry.1)?;

                m.add_variable(name, var);

            "SuchThat" => {

                let constraints_arr = match entry.1.as_array() {

                    Some(x) => x,

                let constraints: Vec<Expression> =

                    constraints_arr.iter().flat_map(parse_expression).collect();

                m.add_constraints(constraints);

    Ok(m)

}

fn parse_variable(v: &JsonValue) -> Result<(Name, DecisionVariable)> {

    let arr = v

        .as_object()

        .ok_or(Error::Parse("Declaration is not an object".to_owned()))?["FindOrGiven"]

        .as_array()

        .ok_or(Error::Parse("FindOrGiven is not an array".to_owned()))?;

    let name = arr[1]

        .as_object()

        .ok_or(Error::Parse("FindOrGiven[1] is not an object".to_owned()))?["Name"]

        .as_str()

        .ok_or(Error::Parse(

            "FindOrGiven[1].Name is not a string".to_owned(),

        ))?;

    let name = Name::UserName(name.to_owned());

    let domain = arr[2]

        .as_object()

        .ok_or(Error::Parse("FindOrGiven[2] is not an object".to_owned()))?

        .iter()

        .next()

        .ok_or(Error::Parse("FindOrGiven[2] is an empty object".to_owned()))?;

    let domain = match domain.0.as_str() {

        "DomainInt" => Ok(parse_int_domain(domain.1)?),

        "DomainBool" => Ok(Domain::BoolDomain),

    Ok((name, DecisionVariable { domain }))

}

fn parse_int_domain(v: &JsonValue) -> Result<Domain> {

    let mut ranges = Vec::new();

    let arr = v

        .as_array()

        .ok_or(Error::Parse("DomainInt is not an array".to_owned()))?[1]

        .as_array()

        .ok_or(Error::Parse("DomainInt[1] is not an array".to_owned()))?;

    for range in arr {

        let range = range

            .as_object()

            .ok_or(Error::Parse(

                "DomainInt[1] contains a non-object".to_owned(),

            ))?

            .iter()

            .next()

            .ok_or(Error::Parse(

                "DomainInt[1] contains an empty object".to_owned(),

            ))?;

        match range.0.as_str() {

            "RangeBounded" => {

                let arr = range

                    .1

                    .as_array()

                    .ok_or(Error::Parse("RangeBounded is not an array".to_owned()))?;

                let mut nums = Vec::new();

                for item in arr.iter() {

                    let num = parse_domain_value_int(item).ok_or(Error::Parse(

                        "Could not parse int domain constant".to_owned(),

                    ))?;

                    nums.push(num);

                ranges.push(Range::Bounded(nums[0], nums[1]));

            "RangeSingle" => {

                let num = parse_domain_value_int(range.1).ok_or(Error::Parse(

                    "Could not parse int domain constant".to_owned(),

                ))?;

                ranges.push(Range::Single(num));

    Ok(Domain::IntDomain(ranges))

}

fn parse_domain_value_int(obj: &JsonValue) -> Option<i32> {

    parser_trace!("trying to parse domain value: {}", obj);

    fn try_parse_positive_int(obj: &JsonValue) -> Option<i32> {

        parser_trace!(".. trying as a positive domain value: {}", obj);

        let leaf_node = obj.pointer("/Constant/ConstantInt/1")?;

        match leaf_node.as_i64()?.try_into() {

            Ok(x) => {

                parser_trace!(".. success!");

                Some(x)

    }

    fn try_parse_negative_int(obj: &JsonValue) -> Option<i32> {

        // Negative number: Op/MkOpNegate/Constant/ConstantInt/1

        // Unwrap negation operator, giving us a Constant/ConstantInt/1

        //

        // This is just a positive constant, so try to parse it as such

        parser_trace!(".. trying as a negative domain value: {}", obj);

        let inner_constant_node = obj.pointer("/Op/MkOpNegate")?;

        let inner_num = try_parse_positive_int(inner_constant_node)?;

        parser_trace!(".. success!");

        Some(-inner_num)

    }

    try_parse_positive_int(obj).or_else(|| try_parse_negative_int(obj))

}

fn parse_expression(obj: &JsonValue) -> Option<Expression> {

    let binary_operators: HashMap<&str, BinOp> = [

        (

            "MkOpEq",

            Box::new(Expression::Eq) as Box<dyn Fn(_, _, _) -> _>,

        ),

        (

            "MkOpNeq",

            Box::new(Expression::Neq) as Box<dyn Fn(_, _, _) -> _>,

        ),

        (

            "MkOpGeq",

            Box::new(Expression::Geq) as Box<dyn Fn(_, _, _) -> _>,

        ),

        (

            "MkOpLeq",

            Box::new(Expression::Leq) as Box<dyn Fn(_, _, _) -> _>,

        ),

        (

            "MkOpGt",

            Box::new(Expression::Gt) as Box<dyn Fn(_, _, _) -> _>,

        ),

        (

            "MkOpLt",

            Box::new(Expression::Lt) as Box<dyn Fn(_, _, _) -> _>,

        ),

        (

            "MkOpGt",

            Box::new(Expression::Gt) as Box<dyn Fn(_, _, _) -> _>,

        ),

        (

            "MkOpLt",

            Box::new(Expression::Lt) as Box<dyn Fn(_, _, _) -> _>,

        ),

        (

            "MkOpDiv",

            Box::new(Expression::UnsafeDiv) as Box<dyn Fn(_, _, _) -> _>,

        ),

        (

            "MkOpMod",

            Box::new(Expression::UnsafeMod) as Box<dyn Fn(_, _, _) -> _>,

        ),

        (

            "MkOpMinus",

            Box::new(Expression::Minus) as Box<dyn Fn(_, _, _) -> _>,

        ),

        (

            "MkOpImply",

            Box::new(Expression::Imply) as Box<dyn Fn(_, _, _) -> _>,

        ),

        (

            "MkOpPow",

            Box::new(Expression::UnsafePow) as Box<dyn Fn(_, _, _) -> _>,

        ),

    ]

    .into_iter()

    .collect();

    let unary_operators: HashMap<&str, UnaryOp> = [

        (

            "MkOpNot",

            Box::new(Expression::Not) as Box<dyn Fn(_, _) -> _>,

        ),

        (

            "MkOpNegate",

            Box::new(Expression::Neg) as Box<dyn Fn(_, _) -> _>,

        ),

        (

            "MkOpTwoBars",

            Box::new(Expression::Abs) as Box<dyn Fn(_, _) -> _>,

        ),

    ]

    .into_iter()

    .collect();

    let vec_operators: HashMap<&str, VecOp> = [

        (

            "MkOpSum",

            Box::new(Expression::Sum) as Box<dyn Fn(_, _) -> _>,

        ),

        (

            "MkOpProduct",

            Box::new(Expression::Product) as Box<dyn Fn(_, _) -> _>,

        ),

        (

            "MkOpAnd",

            Box::new(Expression::And) as Box<dyn Fn(_, _) -> _>,

        ),

        ("MkOpOr", Box::new(Expression::Or) as Box<dyn Fn(_, _) -> _>),

        (

            "MkOpMin",

            Box::new(Expression::Min) as Box<dyn Fn(_, _) -> _>,

        ),

        (

            "MkOpMax",

            Box::new(Expression::Max) as Box<dyn Fn(_, _) -> _>,

        ),

        (

            "MkOpAllDiff",

            Box::new(Expression::AllDiff) as Box<dyn Fn(_, _) -> _>,

        ),

    ]

    .into_iter()

    .collect();

    let mut binary_operator_names = binary_operators.iter().map(|x| x.0);

    let mut unary_operator_names = unary_operators.iter().map(|x| x.0);

    let mut vec_operator_names = vec_operators.iter().map(|x| x.0);

        Value::Object(op) if op.contains_key("Op") => match &op["Op"] {

            Value::Object(bin_op) if binary_operator_names.any(|key| bin_op.contains_key(*key)) => {

                parse_bin_op(bin_op, binary_operators)

            Value::Object(un_op) if unary_operator_names.any(|key| un_op.contains_key(*key)) => {

                parse_unary_op(un_op, unary_operators)

            Value::Object(vec_op) if vec_operator_names.any(|key| vec_op.contains_key(*key)) => {

                parse_vec_op(vec_op, vec_operators)

        Value::Object(refe) if refe.contains_key("Reference") => {

            let name = refe["Reference"].as_array()?[0].as_object()?["Name"].as_str()?;

            Some(Expression::Atomic(

                Metadata::new(),

                Atom::Reference(Name::UserName(name.to_string())),

            ))

        Value::Object(constant) if constant.contains_key("Constant") => parse_constant(constant),

        Value::Object(constant) if constant.contains_key("ConstantInt") => parse_constant(constant),

}

fn parse_bin_op(

    bin_op: &serde_json::Map<String, Value>,

    binary_operators: HashMap<&str, BinOp>,

) -> Option<Expression> {

    let (key, value) = bin_op.into_iter().next()?;

    let constructor = binary_operators.get(key.as_str())?;

    match &value {

        Value::Array(bin_op_args) if bin_op_args.len() == 2 => {

            let arg1 = parse_expression(&bin_op_args[0])?;

            let arg2 = parse_expression(&bin_op_args[1])?;

            Some(constructor(Metadata::new(), Box::new(arg1), Box::new(arg2)))

}

fn parse_unary_op(

    un_op: &serde_json::Map<String, Value>,

    unary_operators: HashMap<&str, UnaryOp>,

) -> Option<Expression> {

    let (key, value) = un_op.into_iter().next()?;

    let constructor = unary_operators.get(key.as_str())?;

    let arg = parse_expression(value)?;

    Some(constructor(Metadata::new(), Box::new(arg)))

}

fn parse_vec_op(

    vec_op: &serde_json::Map<String, Value>,

    vec_operators: HashMap<&str, VecOp>,

) -> Option<Expression> {

    let (key, value) = vec_op.into_iter().next()?;

    let constructor = vec_operators.get(key.as_str())?;

    let mut args_parsed: Option<Vec<Option<Expression>>> = None;

    if let Some(abs_lit_matrix) = value.pointer("/AbstractLiteral/AbsLitMatrix/1") {

        parser_trace!("... containing a matrix of literals");

        args_parsed = abs_lit_matrix.as_array().map(|x| {

            x.iter()

                .map(parse_expression)

                .collect::<Vec<Option<Expression>>>()

        });

    }

    else if let Some(const_abs_lit_matrix) =

        value.pointer("/Constant/ConstantAbstract/AbsLitMatrix/1")

        parser_trace!("... containing a matrix of constants");

        args_parsed = const_abs_lit_matrix.as_array().map(|x| {

            x.iter()

                .map(parse_expression)

                .collect::<Vec<Option<Expression>>>()

        });

    }

    let args_parsed = args_parsed?;

    let number_of_args = args_parsed.len();

    let valid_args: Vec<Expression> = args_parsed.into_iter().flatten().collect();

    if number_of_args != valid_args.len() {

        Some(constructor(Metadata::new(), valid_args))

}

fn parse_constant(constant: &serde_json::Map<String, Value>) -> Option<Expression> {

    match &constant.get("Constant") {

        Some(Value::Object(int)) if int.contains_key("ConstantInt") => {

            let int_32: i32 = match int["ConstantInt"].as_array()?[1].as_i64()?.try_into() {

                Ok(x) => x,

            Some(Expression::Atomic(

                Metadata::new(),

                Atom::Literal(Literal::Int(int_32)),

            ))

        Some(Value::Object(b)) if b.contains_key("ConstantBool") => {

            let b: bool = b["ConstantBool"].as_bool()?;

            Some(Expression::Atomic(

                Metadata::new(),

                Atom::Literal(Literal::Bool(b)),

            ))

            let int_expr = constant["ConstantInt"]

                .as_array()

                .and_then(|x| x[1].as_i64())

                .and_then(|x| x.try_into().ok())

                .map(|x| Expression::Atomic(Metadata::new(), Atom::Literal(Literal::Int(x))));

            if let e @ Some(_) = int_expr {

                return e;

}