use crate::object::base::Block;
use crate::parser::{
    hir::{self, Expression, RawExpression},
    CommandRegistry, Spanned, Text,
};
use crate::prelude::*;
use derive_new::new;
use indexmap::IndexMap;

#[derive(new)]
crate struct Scope {
    it: Value,
    #[new(default)]
    vars: IndexMap<String, Value>,
}

impl Scope {
    crate fn empty() -> Scope {
        Scope {
            it: Value::nothing(),
            vars: IndexMap::new(),
        }
    }
}

crate fn evaluate_baseline_expr(
    expr: &Expression,
    registry: &dyn CommandRegistry,
    scope: &Scope,
    source: &str,
) -> Result<Spanned<Value>, ShellError> {
    match &expr.item {
        RawExpression::Literal(literal) => Ok(evaluate_literal(expr.copy_span(*literal), source)),
        RawExpression::Variable(var) => evaluate_reference(var, scope, source),
        RawExpression::Binary(binary) => {
            let left = evaluate_baseline_expr(binary.left(), registry, scope, source)?;
            let right = evaluate_baseline_expr(binary.right(), registry, scope, source)?;

            match left.compare(binary.op(), &*right) {
                Some(result) => Ok(Spanned::from_item(Value::boolean(result), *expr.span())),
                None => Err(ShellError::unimplemented(&format!(
                    "Comparison failure {:?}",
                    binary
                ))),
            }
        }
        RawExpression::Block(block) => Ok(Spanned::from_item(
            Value::Block(Block::new(*block.clone(), Text::from(source))), // TODO: Pass Text around
            block.span(),
        )),
        RawExpression::Path(path) => {
            let value = evaluate_baseline_expr(path.head(), registry, scope, source)?;
            let mut value = value.item();

            for name in path.tail() {
                let next = value.get_data_by_key(name);

                match next {
                    None => return Err(ShellError::unimplemented("Invalid property from path")),
                    Some(next) => value = next,
                };
            }

            Ok(Spanned::from_item(value.clone(), expr.span()))
        }
        RawExpression::Boolean(_boolean) => unimplemented!(),
    }
}

fn evaluate_literal(literal: Spanned<hir::Literal>, source: &str) -> Spanned<Value> {
    let result = match literal.item {
        hir::Literal::Integer(int) => Value::int(int),
        hir::Literal::Size(_int, _unit) => unimplemented!(),
        hir::Literal::String(span) => Value::string(span.slice(source)),
        hir::Literal::Bare => Value::string(literal.span().slice(source)),
    };

    literal.map(|_| result)
}

fn evaluate_reference(
    name: &hir::Variable,
    scope: &Scope,
    source: &str,
) -> Result<Spanned<Value>, ShellError> {
    match name {
        hir::Variable::It(span) => Ok(Spanned::from_item(scope.it.copy(), span)),
        hir::Variable::Other(span) => Ok(Spanned::from_item(
            scope
                .vars
                .get(span.slice(source))
                .map(|v| v.copy())
                .unwrap_or_else(|| Value::nothing()),
            span,
        )),
    }
}