use std::fmt::{self, Display, Formatter};

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

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

/// A string by which a variable is known to a context.
///
/// Every variable is a key-value pair. An identifier holds the key part of that
/// pair. Its inner value can be used to retrieve a Value instance from a Map.
#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
pub struct Identifier(String);

impl Identifier {
    pub fn new(inner: String) -> Self {
        Identifier(inner)
    }

    pub fn take_inner(self) -> String {
        self.0
    }

    pub fn inner(&self) -> &String {
        &self.0
    }
}

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

        let text = &source[node.byte_range()];

        debug_assert!(!text.is_empty());

        Ok(Identifier(text.to_string()))
    }

    fn run(&self, _source: &str, context: &Map) -> Result<Value> {
        if let Some((value, _)) = context.variables()?.get(&self.0) {
            if !value.is_none() {
                return Ok(value.clone());
            }
        }

        Err(Error::VariableIdentifierNotFound(self.0.clone()))
    }

    fn expected_type(&self, context: &Map) -> Result<Type> {
        if let Some((_value, r#type)) = context.variables()?.get(&self.0) {
            Ok(r#type.clone())
        } else {
            Ok(Type::None)
        }
    }
}

impl Display for Identifier {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        write!(f, "{}", self.0)
    }
}