use std::{collections::BTreeMap, str::FromStr};

use proc_macro2::TokenStream;
use quote::quote;
use syn::{Data, DeriveInput, Generics, Meta};

use super::{
    super::TraitHandler,
    models::{FieldAttributeBuilder, TypeAttributeBuilder},
};
use crate::{panic, Trait};

pub struct PartialOrdStructHandler;

impl TraitHandler for PartialOrdStructHandler {
    fn trait_meta_handler(
        ast: &DeriveInput,
        tokens: &mut TokenStream,
        traits: &[Trait],
        meta: &Meta,
    ) {
        let type_attribute = TypeAttributeBuilder {
            enable_flag:  true,
            enable_bound: true,
            rank:         0,
            enable_rank:  false,
        }
        .from_partial_ord_meta(meta);

        let bound = type_attribute
            .bound
            .into_punctuated_where_predicates_by_generic_parameters(&ast.generics.params);

        let mut comparer_tokens = TokenStream::new();

        if let Data::Struct(data) = &ast.data {
            let mut field_attributes = BTreeMap::new();
            let mut field_names = BTreeMap::new();

            for (index, field) in data.fields.iter().enumerate() {
                let field_attribute = FieldAttributeBuilder {
                    enable_ignore: true,
                    enable_impl:   true,
                    rank:          isize::MIN + index as isize,
                    enable_rank:   true,
                }
                .from_attributes(&field.attrs, traits);

                if field_attribute.ignore {
                    continue;
                }

                let rank = field_attribute.rank;

                if field_attributes.contains_key(&rank) {
                    panic::reuse_a_rank(rank);
                }

                let field_name = if let Some(ident) = field.ident.as_ref() {
                    ident.to_string()
                } else {
                    format!("{}", index)
                };

                field_attributes.insert(rank, field_attribute);
                field_names.insert(rank, field_name);
            }

            for (index, field_attribute) in field_attributes {
                let field_name = field_names.get(&index).unwrap();

                let compare_trait = field_attribute.compare_trait;
                let compare_method = field_attribute.compare_method;

                match compare_trait {
                    Some(compare_trait) => {
                        let compare_method = compare_method.unwrap();

                        let statement = format!(
                            "match {compare_trait}::{compare_method}(&self.{field_name}, \
                             &other.{field_name}) {{ Some(core::cmp::Ordering::Equal) => (), \
                             Some(core::cmp::Ordering::Greater) => {{ return \
                             Some(core::cmp::Ordering::Greater); }}, \
                             Some(core::cmp::Ordering::Less) => {{ return \
                             Some(core::cmp::Ordering::Less); }}, None => {{ return None; }} }}",
                            compare_trait = compare_trait,
                            compare_method = compare_method,
                            field_name = field_name
                        );

                        comparer_tokens.extend(TokenStream::from_str(&statement).unwrap());
                    },
                    None => match compare_method {
                        Some(compare_method) => {
                            let statement = format!(
                                "match {compare_method}(&self.{field_name}, &other.{field_name}) \
                                 {{ Some(core::cmp::Ordering::Equal) => (), \
                                 Some(core::cmp::Ordering::Greater) => {{ return \
                                 Some(core::cmp::Ordering::Greater); }}, \
                                 Some(core::cmp::Ordering::Less) => {{ return \
                                 Some(core::cmp::Ordering::Less); }}, None => {{ return None; }} \
                                 }}",
                                compare_method = compare_method,
                                field_name = field_name
                            );

                            comparer_tokens.extend(TokenStream::from_str(&statement).unwrap());
                        },
                        None => {
                            let statement = format!(
                                "match core::cmp::PartialOrd::partial_cmp(&self.{field_name}, \
                                 &other.{field_name}) {{ Some(core::cmp::Ordering::Equal) => (), \
                                 Some(core::cmp::Ordering::Greater) => {{ return \
                                 Some(core::cmp::Ordering::Greater); }}, \
                                 Some(core::cmp::Ordering::Less) => {{ return \
                                 Some(core::cmp::Ordering::Less); }}, None => {{ return None; }} \
                                 }}",
                                field_name = field_name
                            );

                            comparer_tokens.extend(TokenStream::from_str(&statement).unwrap());
                        },
                    },
                }
            }
        }

        let ident = &ast.ident;

        let mut generics_cloned: Generics = ast.generics.clone();

        let where_clause = generics_cloned.make_where_clause();

        for where_predicate in bound {
            where_clause.predicates.push(where_predicate);
        }

        let (impl_generics, ty_generics, where_clause) = generics_cloned.split_for_impl();

        let compare_impl = quote! {
            impl #impl_generics core::cmp::PartialOrd for #ident #ty_generics #where_clause {
                #[inline]
                fn partial_cmp(&self, other: &Self) -> Option<core::cmp::Ordering> {
                    #comparer_tokens

                    Some(core::cmp::Ordering::Equal)
                }
            }
        };

        tokens.extend(compare_impl);
    }
}
