//! An 'asm' block represents an opaque set of Fuel VM assembly instructions, embedded in place and
//! intended to be inserted as is into the assembly code generation.
//!
//! An [`AsmBlock`] has symbols for arguments and an optional return name and contains a list of
//! [`AsmInstruction`].
//!
//! The syntax in Sway for asm blocks is shown by this example, and [`AsmBlock`] represents it
//! symbolically:
//!
//! ```text
//! asm(r1: self, r2: other, r3) {
//!     add r3 r2 r1;
//!     r3: u64
//! }
//! ```

use sway_types::ident::Ident;

use crate::{context::Context, irtype::Type, metadata::MetadataIndex, value::Value};

/// A wrapper around an [ECS](https://github.com/fitzgen/generational-arena) handle into the
/// [`Context`].
#[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]
pub struct AsmBlock(pub generational_arena::Index);

#[doc(hidden)]
#[derive(Clone, Debug)]
pub struct AsmBlockContent {
    pub args_names: Vec<Ident>,
    pub body: Vec<AsmInstruction>,
    pub return_name: Option<Ident>,
}

#[derive(Clone, Debug)]
pub struct AsmArg {
    pub name: Ident,
    pub initializer: Option<Value>,
}

#[derive(Clone, Debug)]
pub struct AsmInstruction {
    pub name: Ident,
    pub args: Vec<Ident>,
    pub immediate: Option<Ident>,
    pub span_md_idx: Option<MetadataIndex>,
}

impl AsmBlock {
    /// Create a new [`AsmBlock`] in the passed context and return its handle.
    pub fn new(
        context: &mut Context,
        args_names: Vec<Ident>,
        body: Vec<AsmInstruction>,
        return_name: Option<Ident>,
    ) -> Self {
        let content = AsmBlockContent {
            args_names,
            body,
            return_name,
        };
        AsmBlock(context.asm_blocks.insert(content))
    }

    /// Return the [`AsmBlock`] return type.
    ///
    /// Currently this always returns either `None` or `Some(Type::Uint(64))` depending on whether
    /// the block returns a value at all.
    pub fn get_type(&self, context: &Context) -> Option<Type> {
        // The type is a named register, which will be a u64.
        context.asm_blocks[self.0]
            .return_name
            .as_ref()
            .map(|_| Type::Uint(64))
    }
}