use syn::{
    braced, parenthesized,
    parse::{Parse, ParseBuffer, ParseStream},
    token, Ident, Result, Token,
};

use crate::util;
use crate::widgets::{Widget, WidgetFunc};

impl Parse for Widget {
    fn parse(input: ParseStream) -> Result<Self> {
        let mut name_opt: Option<Ident> = None;

        // Check if first token is `mut`
        let mutable = input.parse().ok();

        // Look for name = Widget syntax
        if input.peek2(Token![=]) {
            name_opt = Some(input.parse()?);
            let _token: Token![=] = input.parse()?;
        };

        let inner_input: Option<ParseBuffer>;

        let upcomming_some = {
            let forked_input = input.fork();
            if forked_input.peek(Ident) {
                let ident: Ident = forked_input.parse()?;
                ident == "Some"
            } else {
                false
            }
        };

        let wrapper = if upcomming_some && input.peek2(token::Paren) {
            let ident = input.parse()?;
            let paren_input;
            parenthesized!(paren_input in input);
            inner_input = Some(paren_input);
            Some(ident)
        } else {
            inner_input = None;
            None
        };

        // get the inner input as func_input
        let func_input = if let Some(paren_input) = &inner_input {
            paren_input
        } else {
            input
        };

        // Look for &
        let ref_token = func_input.parse().ok();

        // Look for *
        let deref_token = func_input.parse().ok();

        let func: WidgetFunc = func_input.parse()?;

        let inner;
        let _token = braced!(inner in input);
        let properties = inner.parse()?;

        // Generat a name if no name was given.
        let name = if let Some(name) = name_opt {
            name
        } else {
            util::idents_to_snake_case(&func.path_segments, func.span)
        };

        let returned_widget = if input.peek(Token![->]) {
            let _arrow: Token![->] = input.parse()?;
            Some(input.parse()?)
        } else {
            None
        };

        Ok(Widget {
            mutable,
            name,
            func,
            properties,
            wrapper,
            ref_token,
            deref_token,
            returned_widget,
        })
    }
}