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

use crate::{AbstractTree, Error, Identifier, Map, Result, Statement, Type, TypeDefinition, Value};

#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
pub struct Assignment {
    identifier: Identifier,
    type_definition: Option<TypeDefinition>,
    operator: AssignmentOperator,
    statement: Statement,
}

#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
pub enum AssignmentOperator {
    Equal,
    PlusEqual,
    MinusEqual,
}

impl AbstractTree for Assignment {
    fn from_syntax_node(source: &str, node: Node, context: &Map) -> Result<Self> {
        Error::expect_syntax_node(source, "assignment", node)?;

        let child_count = node.child_count();

        let identifier_node = node.child(0).unwrap();
        let identifier = Identifier::from_syntax_node(source, identifier_node, context)?;

        let type_node = node.child(1);
        let type_definition = if let Some(type_node) = type_node {
            if type_node.kind() == "type_definition" {
                Some(TypeDefinition::from_syntax_node(
                    source, type_node, context,
                )?)
            } else {
                None
            }
        } else {
            None
        };

        let operator_node = node.child(child_count - 2).unwrap().child(0).unwrap();
        let operator = match operator_node.kind() {
            "=" => AssignmentOperator::Equal,
            "+=" => AssignmentOperator::PlusEqual,
            "-=" => AssignmentOperator::MinusEqual,
            _ => {
                return Err(Error::UnexpectedSyntaxNode {
                    expected: "=, += or -=",
                    actual: operator_node.kind(),
                    location: operator_node.start_position(),
                    relevant_source: source[operator_node.byte_range()].to_string(),
                })
            }
        };

        let statement_node = node.child(child_count - 1).unwrap();
        let statement = Statement::from_syntax_node(source, statement_node, context)?;

        if let Some(type_definition) = &type_definition {
            let statement_type = statement.expected_type(context)?;

            match operator {
                AssignmentOperator::Equal => {
                    type_definition.inner().check(&statement_type)?;
                }
                AssignmentOperator::PlusEqual => {
                    let identifier_type = identifier.expected_type(context)?;

                    if let Type::List(item_type) = type_definition.inner() {
                        item_type.check(&identifier_type)?;
                        item_type.check(&statement_type)?;
                    } else {
                        type_definition.inner().check(&identifier_type)?;
                        type_definition.inner().check(&statement_type)?;
                    }
                }
                AssignmentOperator::MinusEqual => todo!(),
            }
        } else if let Some((_previous_value, previous_type)) =
            context.variables()?.get(identifier.inner())
        {
            let statement_type = statement.expected_type(context)?;
            let type_check = if let Type::List(item_type) = previous_type {
                item_type.check(&statement_type)
            } else {
                previous_type.check(&statement_type)
            };

            if let Err(error) = type_check {
                return Err(error.with_context(
                    statement_node.start_position(),
                    source[statement_node.byte_range()].to_string(),
                ));
            }
        }

        Ok(Assignment {
            identifier,
            type_definition,
            operator,
            statement,
        })
    }

    fn run(&self, source: &str, context: &Map) -> Result<Value> {
        let key = self.identifier.inner();
        let value = self.statement.run(source, context)?;

        let new_value = match self.operator {
            AssignmentOperator::PlusEqual => {
                if let Some((mut previous_value, _)) = context.variables()?.get(key).cloned() {
                    previous_value += value;
                    previous_value
                } else {
                    return Err(Error::VariableIdentifierNotFound(key.clone()));
                }
            }
            AssignmentOperator::MinusEqual => {
                if let Some((mut previous_value, _)) = context.variables()?.get(key).cloned() {
                    previous_value -= value;
                    previous_value
                } else {
                    return Err(Error::VariableIdentifierNotFound(key.clone()));
                }
            }
            AssignmentOperator::Equal => value,
        };

        if let Some(type_defintion) = &self.type_definition {
            context.set(key.clone(), new_value, Some(type_defintion.inner().clone()))?;
        } else {
            context.set(key.clone(), new_value, None)?;
        }

        Ok(Value::Empty)
    }

    fn expected_type(&self, _context: &Map) -> Result<Type> {
        Ok(Type::Empty)
    }
}

#[cfg(test)]
mod tests {
    use crate::{evaluate, Error, List, Value};

    #[test]
    fn simple_assignment() {
        let test = evaluate("x = 1 x").unwrap();

        assert_eq!(Value::Integer(1), test);
    }

    #[test]
    fn simple_assignment_with_type() {
        let test = evaluate("x <int> = 1 x").unwrap();

        assert_eq!(Value::Integer(1), test);
    }

    #[test]
    fn list_add_assign() {
        let test = evaluate(
            "
            x <[int]> = []
            x += 1
            x
            ",
        )
        .unwrap();

        assert_eq!(Value::List(List::with_items(vec![Value::Integer(1)])), test);
    }

    #[test]
    fn list_add_wrong_type() {
        let test = evaluate(
            "
            x <[str]> = []
            x += 1
            ",
        )
        .unwrap_err();

        match test {
            Error::WithContext { .. } => {}
            Error::TypeCheck { .. } => {}
            _ => panic!(),
        }
    }
}