use std::collections::BTreeMap;

use super::{Builtin, GLOBAL_FUNCTIONS};
use crate::common::QuoteKind;
use crate::units::Unit;
use crate::value::Value;

pub(crate) fn register(f: &mut BTreeMap<String, Builtin>) {
    decl!(f "if", |args, _| {
        max_args!(args, 3);
        if arg!(args, 0, "condition").is_true()? {
            Ok(arg!(args, 1, "if-true"))
        } else {
            Ok(arg!(args, 2, "if-false"))
        }
    });
    decl!(f "feature-exists", |args, _| {
        max_args!(args, 1);
        match arg!(args, 0, "feature").unquote().to_string().as_str() {
            // A local variable will shadow a global variable unless
            // `!global` is used.
            "global-variable-shadowing" => Ok(Value::False),
            // the @extend rule will affect selectors nested in pseudo-classes
            // like :not()
            "extend-selector-pseudoclass" => Ok(Value::False),
            // Full support for unit arithmetic using units defined in the
            // [Values and Units Level 3][] spec.
            "units-level-3" => Ok(Value::False),
            // The Sass `@error` directive is supported.
            "at-error" => Ok(Value::True),
            // The "Custom Properties Level 1" spec is supported. This means
            // that custom properties are parsed statically, with only
            // interpolation treated as SassScript.
            "custom-property" => Ok(Value::False),
            _ => Ok(Value::False),
        }
    });
    decl!(f "unit", |args, _| {
        max_args!(args, 1);
        let unit = match arg!(args, 0, "number") {
            Value::Dimension(_, u) => u.to_string(),
            _ => String::new()
        };
        Ok(Value::Ident(unit, QuoteKind::Double))
    });
    decl!(f "type-of", |args, _| {
        max_args!(args, 1);
        let value = arg!(args, 0, "value");
        Ok(Value::Ident(value.kind()?.to_owned(), QuoteKind::None))
    });
    decl!(f "unitless", |args, _| {
        max_args!(args, 1);
        match arg!(args, 0, "number") {
            Value::Dimension(_, Unit::None) => Ok(Value::True),
            Value::Dimension(_, _) => Ok(Value::False),
            _ => Ok(Value::True)
        }
    });
    decl!(f "inspect", |args, _| {
        max_args!(args, 1);
        let value = arg!(args, 0, "value");
        Ok(Value::Ident(value.to_string(), QuoteKind::None))
    });
    decl!(f "variable-exists", |args, scope| {
        max_args!(args, 1);
        let value = arg!(args, 0, "name");
        Ok(Value::bool(scope.var_exists(&value.to_string())))
    });
    decl!(f "mixin-exists", |args, scope| {
        max_args!(args, 1);
        let value = arg!(args, 0, "name");
        Ok(Value::bool(scope.mixin_exists(&value.to_string())))
    });
    decl!(f "function-exists", |args, scope| {
        max_args!(args, 1);
        let value = arg!(args, 0, "name");
        let s = value.unquote().to_string();
        Ok(Value::bool(scope.fn_exists(&s) || GLOBAL_FUNCTIONS.contains_key(&s)))
    });
    decl!(f "call", |_args, _scope| {
        todo!("builtin function `call()` is blocked on refactoring how call args are stored and parsed")
        // let func = arg!(args, 0, "function").to_string();
        // let func = match scope.get_fn(&func) {
        //     Ok(f) => f,
        //     Err(_) => match GLOBAL_FUNCTIONS.get(&func) {
        //         Some(f) => return f(&args, scope),
        //         None => todo!("called undefined function"),
        //     },
        // };
        // Some(func.clone().args(&args).call())
    });
}