#![allow(dead_code)]

use proc_macro2::TokenStream;
use quote::quote;
use syn::parse::{Parse, ParseStream};
use syn::punctuated::Punctuated;
use syn::spanned::Spanned;
use syn::{Data, DeriveInput, Fields, Ident, LitStr, Variant};

const AT_ATTR_IDENT: &str = "at";
const NOT_FOUND_ATTR_IDENT: &str = "not_found";

pub struct Routable {
    ident: Ident,
    ats: Vec<LitStr>,
    variants: Punctuated<Variant, syn::token::Comma>,
    not_found_route: Option<Ident>,
}

impl Parse for Routable {
    fn parse(input: ParseStream) -> syn::Result<Self> {
        let DeriveInput { ident, data, .. } = input.parse()?;

        let data = match data {
            Data::Enum(data) => data,
            Data::Struct(s) => {
                return Err(syn::Error::new(
                    s.struct_token.span(),
                    "expected enum, found struct",
                ))
            }
            Data::Union(u) => {
                return Err(syn::Error::new(
                    u.union_token.span(),
                    "expected enum, found union",
                ))
            }
        };

        let (not_found_route, ats) = parse_variants_attributes(&data.variants)?;

        Ok(Self {
            ident,
            variants: data.variants,
            ats,
            not_found_route,
        })
    }
}

fn parse_variants_attributes(
    variants: &Punctuated<Variant, syn::token::Comma>,
) -> syn::Result<(Option<Ident>, Vec<LitStr>)> {
    let mut not_founds = vec![];
    let mut ats: Vec<LitStr> = vec![];

    let mut not_found_attrs = vec![];

    for variant in variants.iter() {
        if let Fields::Unnamed(ref field) = variant.fields {
            return Err(syn::Error::new(
                field.span(),
                "only named fields are supported",
            ));
        }

        let attrs = &variant.attrs;
        let at_attrs = attrs
            .iter()
            .filter(|attr| attr.path.is_ident(AT_ATTR_IDENT))
            .collect::<Vec<_>>();

        let attr = match at_attrs.len() {
            1 => *at_attrs.first().unwrap(),
            0 => {
                return Err(syn::Error::new(
                    variant.span(),
                    format!(
                        "{} attribute must be present on every variant",
                        AT_ATTR_IDENT
                    ),
                ))
            }
            _ => {
                return Err(syn::Error::new_spanned(
                    quote! { #(#at_attrs)* },
                    format!("only one {} attribute must be present", AT_ATTR_IDENT),
                ))
            }
        };

        let lit = attr.parse_args::<LitStr>()?;
        ats.push(lit);

        for attr in attrs.iter() {
            if attr.path.is_ident(NOT_FOUND_ATTR_IDENT) {
                not_found_attrs.push(attr);
                not_founds.push(variant.ident.clone())
            }
        }
    }

    if not_founds.len() > 1 {
        return Err(syn::Error::new_spanned(
            quote! { #(#not_found_attrs)* },
            format!("there can only be one {}", NOT_FOUND_ATTR_IDENT),
        ));
    }

    Ok((not_founds.into_iter().next(), ats))
}

impl Routable {
    // fn build_from_path(&self) -> TokenStream {
    //     let from_path_matches = self.variants.iter().enumerate().map(|(i, variant)| {
    //         let ident = &variant.ident;
    //         let right = match &variant.fields {
    //             Fields::Unit => quote! { Self::#ident },
    //             Fields::Named(field) => {
    //                 let fields = field.named.iter().map(|it| {
    //                     //named fields have idents
    //                     it.ident.as_ref().unwrap()
    //                 });
    //                 quote! { Self::#ident { #(#fields: params.get(stringify!(#fields))?.parse().ok()?,)* } }
    //             }
    //             Fields::Unnamed(_) => unreachable!(), // already checked
    //         };

    //         let left = self.ats.get(i).unwrap();
    //         quote! {
    //             #left => ::std::option::Option::Some(#right)
    //         }
    //     });

    //     quote! {
    //         fn from_path(path: &str, params: &::std::collections::HashMap<&str, &str>) -> ::std::option::Option<Self> {
    //             match path {
    //                 #(#from_path_matches),*,
    //                 _ => ::std::option::Option::None,
    //             }
    //         }
    //     }
    // }

    // fn build_to_path(&self) -> TokenStream {
    //     let to_path_matches = self.variants.iter().enumerate().map(|(i, variant)| {
    //         let ident = &variant.ident;
    //         let mut right = self.ats.get(i).unwrap().value();

    //         match &variant.fields {
    //             Fields::Unit => quote! { Self::#ident => ::std::string::ToString::to_string(#right) },
    //             Fields::Named(field) => {
    //                 let fields = field
    //                     .named
    //                     .iter()
    //                     .map(|it| it.ident.as_ref().unwrap())
    //                     .collect::<Vec<_>>();

    //                 for field in fields.iter() {
    //                     // :param -> {param}
    //                     // so we can pass it to `format!("...", param)`
    //                     right = right.replace(&format!(":{}", field), &format!("{{{}}}", field))
    //                 }

    //                 quote! {
    //                     Self::#ident { #(#fields),* } => ::std::format!(#right, #(#fields = #fields),*)
    //                 }
    //             }
    //             Fields::Unnamed(_) => unreachable!(), // already checked
    //         }
    //     });

    //     quote! {
    //         fn to_path(&self) -> ::std::string::String {
    //             match self {
    //                 #(#to_path_matches),*,
    //             }
    //         }
    //     }
    // }
}

pub fn routable_derive_impl(input: Routable) -> TokenStream {
    let Routable {
        // ats,
        // not_found_route,
        // ident,
        ..
    } = &input;

    // let from_path = input.build_from_path();
    // let to_path = input.build_to_path();

    quote! {
        // #[automatically_derived]
        // impl ::dioxus::router::Routable for #ident {

        //     fn recognize(pathname: &str) -> ::std::option::Option<Self> {
        //         todo!()
        //         // ::std::thread_local! {
        //         //     static ROUTER: ::dioxus::router::__macro::Router = ::dioxus::router::__macro::build_router::<#ident>();
        //         // }
        //         // let route = ROUTER.with(|router| ::dioxus::router::__macro::recognize_with_router(router, pathname));
        //         // {
        //         //     let route = ::std::clone::Clone::clone(&route);
        //         //     #cache_thread_local_ident.with(move |val| {
        //         //         *val.borrow_mut() = route;
        //         //     });
        //         // }
        //         // route
        //     }
        // }
    }
}