use crate::component::Component;

use crate::core::{Module, ModuleField, ModuleKind};

use crate::kw;

use crate::parser::{Parse, Parser, Result};

use crate::token::Span;

/// A `*.wat` file parser, or a parser for one parenthesized module.

///

/// This is the top-level type which you'll frequently parse when working with

/// this crate. A `*.wat` file is either one `module` s-expression or a sequence

/// of s-expressions that are module fields.

#[derive(Debug)]

#[allow(missing_docs)]

pub enum Wat<'a> {

    Module(Module<'a>),

    Component(Component<'a>),

}

impl Wat<'_> {

    /// Encodes this `Wat` to binary form. This calls either [`Module::encode`]

    /// or [`Component::encode`].

    pub fn encode(&mut self) -> std::result::Result<Vec<u8>, crate::Error> {

        crate::core::EncodeOptions::default().encode_wat(self)

    }

    /// Returns the defining span of this file.

    pub fn span(&self) -> Span {

        match self {

            Wat::Module(m) => m.span,

            Wat::Component(c) => c.span,

        }

    }

}

impl<'a> Parse<'a> for Wat<'a> {

    fn parse(parser: Parser<'a>) -> Result<Self> {

        if !parser.has_meaningful_tokens() {

            return Err(parser.error("expected at least one module field"));

        }

        parser.with_standard_annotations_registered(|parser| {

            let wat = if parser.peek2::<kw::module>()? {

                Wat::Module(parser.parens(|parser| parser.parse())?)

            } else if parser.peek2::<kw::component>()? {

                Wat::Component(parser.parens(|parser| parser.parse())?)

            } else {

                let fields = ModuleField::parse_remaining(parser)?;

                Wat::Module(Module {

                    span: Span { offset: 0 },

                    id: None,

                    name: None,

                    kind: ModuleKind::Text(fields),

                })

            };

            Ok(wat)

        })

    }

}