use serde::{Deserialize, Serialize};
use tree_sitter::Node;

use crate::{AbstractTree, BuiltInFunction, Error, Map, Result, Value};

use super::expression::Expression;

#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
pub enum FunctionCall {
    BuiltIn(Box<BuiltInFunction>),
    ContextDefined {
        name: Expression,
        arguments: Vec<Expression>,
    },
}

impl AbstractTree for FunctionCall {
    fn from_syntax_node(source: &str, node: Node) -> Result<Self> {
        debug_assert_eq!("function_call", node.kind());

        let function_node = node.child(1).unwrap();
        let mut arguments = Vec::new();

        for index in 2..node.child_count() - 1 {
            let node = node.child(index).unwrap();

            if node.is_named() {
                let expression = Expression::from_syntax_node(source, node)?;

                arguments.push(expression);
            }
        }

        let function_call = if function_node.kind() == "built_in_function" {
            let function = BuiltInFunction::from_syntax_node(source, function_node)?;

            FunctionCall::BuiltIn(Box::new(function))
        } else {
            let name = Expression::from_syntax_node(source, function_node)?;

            FunctionCall::ContextDefined { name, arguments }
        };

        Ok(function_call)
    }

    fn run(&self, source: &str, context: &mut Map) -> Result<Value> {
        let (name, arguments) = match self {
            FunctionCall::BuiltIn(function) => return function.run(source, context),
            FunctionCall::ContextDefined { name, arguments } => (name, arguments),
        };

        let function = if let Expression::Identifier(identifier) = name {
            if let Some(value) = context.variables()?.get(identifier.inner()) {
                value.as_function().cloned()
            } else {
                return Err(Error::FunctionIdentifierNotFound(identifier.clone()));
            }
        } else {
            let name_run = name.run(source, context)?;

            name_run.as_function().cloned()
        }?;

        let mut function_context = Map::clone_from(context)?;
        let parameter_expression_pairs = function.parameters().iter().zip(arguments.iter());

        for ((identifier, r#type), expression) in parameter_expression_pairs {
            let key = identifier.clone().take_inner();
            let value = expression.run(source, context)?;

            r#type.check(&value)?;

            function_context.variables_mut()?.insert(key, value);
        }

        function.run(source, &mut function_context)
    }
}