use rayon::prelude::*;
use serde::{Deserialize, Serialize};
use tree_sitter::Node;

use crate::{AbstractTree, Error, Expression, Identifier, Item, Map, Result, Value};

#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
pub struct For {
    is_async: bool,
    identifier: Identifier,
    expression: Expression,
    item: Item,
}

impl AbstractTree for For {
    fn from_syntax_node(source: &str, node: Node) -> Result<Self> {
        let for_node = node.child(0).unwrap();
        let is_async = match for_node.kind() {
            "for" => false,
            "async for" => true,
            _ => {
                return Err(Error::UnexpectedSyntaxNode {
                    expected: "\"for\" or \"async for\"",
                    actual: for_node.kind(),
                    location: for_node.start_position(),
                    relevant_source: source[for_node.byte_range()].to_string(),
                })
            }
        };

        let identifier_node = node.child(1).unwrap();
        let identifier = Identifier::from_syntax_node(source, identifier_node)?;

        let expression_node = node.child(3).unwrap();
        let expression = Expression::from_syntax_node(source, expression_node)?;

        let item_node = node.child(5).unwrap();
        let item = Item::from_syntax_node(source, item_node)?;

        Ok(For {
            is_async,
            identifier,
            expression,
            item,
        })
    }

    fn run(&self, source: &str, context: &mut Map) -> Result<Value> {
        let expression_run = self.expression.run(source, context)?;
        let values = expression_run.as_list()?.items();
        let key = self.identifier.inner();

        if self.is_async {
            values.par_iter().try_for_each(|value| {
                let mut iter_context = Map::clone_from(context);

                iter_context.set_value(key.clone(), value.clone())?;

                self.item.run(source, &mut iter_context).map(|_value| ())
            })?;
        } else {
            let original_value = context.get_value(key)?;

            for value in values.iter() {
                context.set_value(key.clone(), value.clone())?;

                self.item.run(source, context)?;
            }

            if let Some(original_value) = original_value {
                context.set_value(key.clone(), original_value)?;
            } else {
                context.set_value(key.clone(), Value::Empty)?;
            }
        }

        Ok(Value::Empty)
    }
}