// SPDX-License-Identifier: LGPL-3.0-or-later
// See Notices.txt for copyright information
use indexmap::IndexMap;
use proc_macro2::{Span, TokenStream};
use quote::{IdentFragment, ToTokens, TokenStreamExt};
use serde::{Deserialize, Serialize};
use std::{
    fmt::{self, Write},
    iter::FusedIterator,
    str::FromStr,
};
use thiserror::Error;

macro_rules! impl_try_from_str {
    ($ty:ty) => {
        impl TryFrom<&'_ str> for $ty {
            type Error = <Self as FromStr>::Err;

            fn try_from(v: &str) -> Result<Self, Self::Error> {
                v.parse()
            }
        }

        impl TryFrom<String> for $ty {
            type Error = <Self as FromStr>::Err;

            fn try_from(v: String) -> Result<Self, Self::Error> {
                v.parse()
            }
        }
    };
}

#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Serialize, Deserialize, Hash)]
#[serde(into = "String", try_from = "String")]
pub struct Ident(pub String);

impl ToTokens for Ident {
    fn to_tokens(&self, tokens: &mut TokenStream) {
        syn::Ident::from(self).to_tokens(tokens);
    }
}

impl IdentFragment for Ident {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.write_str(&self.0)
    }
}

impl Ident {
    pub fn is_start_char(ch: char) -> bool {
        ch == '_' || ch.is_ascii_alphabetic()
    }
    pub fn is_continue_char(ch: char) -> bool {
        ch == '_' || ch.is_ascii_alphanumeric()
    }
    pub fn is_ident(v: &str) -> bool {
        !v.is_empty()
            && v.starts_with(Self::is_start_char)
            && v.trim_start_matches(Self::is_continue_char).is_empty()
    }
}

impl From<Ident> for Path {
    fn from(value: Ident) -> Self {
        Path(value.0)
    }
}

impl From<Ident> for String {
    fn from(value: Ident) -> Self {
        value.0
    }
}

impl From<Ident> for syn::Ident {
    fn from(value: Ident) -> Self {
        From::from(&value)
    }
}

impl From<&'_ Ident> for syn::Ident {
    fn from(value: &Ident) -> Self {
        syn::Ident::new(&value.0, Span::call_site())
    }
}

#[derive(Clone, Debug, Error)]
#[error("invalid identifier")]
pub struct IdentParseError;

impl_try_from_str!(Ident);

impl FromStr for Ident {
    type Err = IdentParseError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        if Self::is_ident(s) {
            Ok(Self(s.into()))
        } else {
            Err(IdentParseError)
        }
    }
}

#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Serialize, Deserialize, Hash)]
#[serde(into = "String", try_from = "String")]

pub struct Path(String);

impl Path {
    pub fn iter(&self) -> PathIter<'_> {
        PathIter(&self.0)
    }
    pub fn last(&self) -> Ident {
        self.iter().next_back().unwrap()
    }
    pub fn is_path(s: &str) -> bool {
        if s.is_empty() {
            false
        } else {
            s.split("::").all(Ident::is_ident)
        }
    }
}

#[derive(Debug, Clone)]
pub struct PathIter<'a>(&'a str);

impl Iterator for PathIter<'_> {
    type Item = Ident;

    fn next(&mut self) -> Option<Self::Item> {
        if self.0.is_empty() {
            None
        } else if let Some((first, rest)) = self.0.split_once("::") {
            self.0 = rest;
            Some(Ident(first.into()))
        } else {
            let retval = self.0;
            self.0 = &self.0[..0];
            Some(Ident(retval.into()))
        }
    }

    fn last(mut self) -> Option<Self::Item> {
        self.next_back()
    }
}

impl FusedIterator for PathIter<'_> {}

impl DoubleEndedIterator for PathIter<'_> {
    fn next_back(&mut self) -> Option<Self::Item> {
        if self.0.is_empty() {
            None
        } else if let Some((rest, last)) = self.0.rsplit_once("::") {
            self.0 = rest;
            Some(Ident(last.into()))
        } else {
            let retval = self.0;
            self.0 = &self.0[..0];
            Some(Ident(retval.into()))
        }
    }
}

impl ToTokens for Path {
    fn to_tokens(&self, tokens: &mut TokenStream) {
        tokens.append_separated(self.iter(), <syn::Token![::]>::default());
    }
}

#[derive(Clone, Debug, Error)]
#[error("invalid path")]
pub struct PathParseError;

impl From<Path> for String {
    fn from(value: Path) -> Self {
        value.0
    }
}

impl_try_from_str!(Path);

impl FromStr for Path {
    type Err = PathParseError;

    fn from_str(value: &str) -> Result<Self, Self::Err> {
        if value.is_empty() {
            Err(PathParseError)
        } else if value.split("::").all(Ident::is_ident) {
            Ok(Self(value.into()))
        } else {
            Err(PathParseError)
        }
    }
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub struct Definitions {
    pub types: std::collections::BTreeMap<Path, Definition>,
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub struct Definition {
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub fn_name_suffix: Option<Ident>,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub generics: Option<Generics>,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub fold_where: Option<WherePredicates>,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub visit_where: Option<WherePredicates>,
    pub data: Data,
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
#[serde(tag = "$kind")]
pub enum Data {
    ManualImpl,
    Opaque,
    Enum(Variants),
    Struct(Fields),
}

#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Serialize, Deserialize, Hash)]
#[serde(into = "String", try_from = "String")]
pub struct FieldNameIdent {
    pub ident: Ident,
    pub is_getter: bool,
}

impl FieldNameIdent {
    pub fn to_member(&self) -> Option<syn::Member> {
        let Self {
            ref ident,
            is_getter,
        } = *self;
        if is_getter {
            None
        } else {
            Some(syn::Ident::from(ident).into())
        }
    }
}

impl ToTokens for FieldNameIdent {
    fn to_tokens(&self, tokens: &mut TokenStream) {
        let Self {
            ref ident,
            is_getter,
        } = *self;
        ident.to_tokens(tokens);
        if is_getter {
            syn::token::Paren::default().surround(tokens, |_| {});
        }
    }
}

impl From<FieldNameIdent> for String {
    fn from(value: FieldNameIdent) -> Self {
        let mut retval = value.ident.0;
        if value.is_getter {
            retval.push_str("()");
        }
        retval
    }
}

#[derive(Clone, Debug, Error)]
#[error("invalid field name")]
pub struct FieldNameParseError;

impl_try_from_str!(FieldNameIdent);

impl FromStr for FieldNameIdent {
    type Err = FieldNameParseError;

    fn from_str(value: &str) -> Result<Self, Self::Err> {
        let ident = value.strip_suffix("()");
        let is_getter = ident.is_some();
        let ident = ident.unwrap_or(value);
        if let Ok(ident) = ident.parse() {
            Ok(Self { ident, is_getter })
        } else {
            Err(FieldNameParseError)
        }
    }
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize, Default, Hash)]
#[serde(into = "String", try_from = "String")]
pub struct WherePredicates(pub syn::punctuated::Punctuated<syn::WherePredicate, syn::Token![,]>);

#[derive(Debug, Error)]
#[error("invalid `where` predicates")]
pub struct WherePredicatesParseError;

impl_try_from_str!(WherePredicates);

impl FromStr for WherePredicates {
    type Err = WherePredicatesParseError;

    fn from_str(value: &str) -> Result<Self, Self::Err> {
        Ok(Self(
            syn::parse::Parser::parse_str(syn::punctuated::Punctuated::parse_terminated, value)
                .map_err(|_| WherePredicatesParseError)?,
        ))
    }
}

impl From<WherePredicates> for String {
    fn from(value: WherePredicates) -> Self {
        value.0.into_token_stream().to_string()
    }
}

impl From<WherePredicates> for syn::WhereClause {
    fn from(value: WherePredicates) -> Self {
        syn::WhereClause {
            where_token: Default::default(),
            predicates: value.0,
        }
    }
}

impl From<syn::WhereClause> for WherePredicates {
    fn from(value: syn::WhereClause) -> Self {
        Self(value.predicates)
    }
}

impl ToTokens for WherePredicates {
    fn to_tokens(&self, tokens: &mut TokenStream) {
        self.0.to_tokens(tokens);
    }
}

#[derive(Serialize, Deserialize)]
#[serde(untagged)]
enum SerializedGenerics {
    Where {
        generics: String,
        #[serde(rename = "where")]
        where_predicates: WherePredicates,
    },
    NoWhere(String),
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize, Default, Hash)]
#[serde(into = "SerializedGenerics", try_from = "SerializedGenerics")]
pub struct Generics(pub syn::Generics);

impl ToTokens for Generics {
    fn to_tokens(&self, tokens: &mut TokenStream) {
        self.0.to_tokens(tokens);
    }
}

impl From<Generics> for SerializedGenerics {
    fn from(mut value: Generics) -> Self {
        match value.0.where_clause.take() {
            Some(where_clause) => Self::Where {
                generics: value.0.into_token_stream().to_string(),
                where_predicates: where_clause.into(),
            },
            None => Self::NoWhere(value.0.into_token_stream().to_string()),
        }
    }
}

#[derive(Debug, Error)]
#[error("invalid generics")]
pub struct GenericsParseError;

impl TryFrom<SerializedGenerics> for Generics {
    type Error = GenericsParseError;

    fn try_from(value: SerializedGenerics) -> Result<Self, Self::Error> {
        let (generics, where_clause) = match value {
            SerializedGenerics::Where {
                generics,
                where_predicates,
            } => (generics, Some(where_predicates.into())),
            SerializedGenerics::NoWhere(generics) => (generics, None),
        };
        let Ok(mut generics) = syn::parse_str::<syn::Generics>(&generics) else {
            return Err(GenericsParseError);
        };
        generics.where_clause = where_clause;
        Ok(Self(generics))
    }
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize, Hash)]
#[serde(into = "String", try_from = "String")]
pub struct PathWithGenerics {
    pub path: Path,
    pub generics: Option<syn::AngleBracketedGenericArguments>,
}

impl ToTokens for PathWithGenerics {
    fn to_tokens(&self, tokens: &mut TokenStream) {
        let Self { path, generics } = self;
        path.to_tokens(tokens);
        if let Some(generics) = generics {
            <syn::Token![::]>::default().to_tokens(tokens);
            generics.to_tokens(tokens);
        }
    }
}

impl From<PathWithGenerics> for String {
    fn from(value: PathWithGenerics) -> Self {
        let PathWithGenerics { path, generics } = value;
        let mut retval = String::from(path);
        if let Some(generics) = generics {
            write!(retval, "{}", generics.to_token_stream()).unwrap();
        }
        retval
    }
}

#[derive(Clone, Debug, Error)]
#[error("invalid path with optional generics")]
pub struct PathWithGenericsParseError;

impl_try_from_str!(PathWithGenerics);

impl FromStr for PathWithGenerics {
    type Err = PathWithGenericsParseError;

    fn from_str(value: &str) -> Result<Self, Self::Err> {
        let (path, generics) = if let Some(lt_pos) = value.find('<') {
            let (path, generics) = value.split_at(lt_pos);
            let path = path.strip_suffix("::").unwrap_or(path);
            match syn::parse_str(generics) {
                Ok(generics) => (path, Some(generics)),
                Err(_) => return Err(PathWithGenericsParseError),
            }
        } else {
            (value, None)
        };
        if let Ok(path) = path.parse() {
            Ok(Self { path, generics })
        } else {
            Err(PathWithGenericsParseError)
        }
    }
}

#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Serialize, Deserialize, Hash)]
#[serde(into = "String", try_from = "String")]
pub enum FieldName {
    Index(usize),
    Ident(FieldNameIdent),
}

impl FieldName {
    pub fn to_member(&self) -> Option<syn::Member> {
        match self {
            &FieldName::Index(index) => Some(index.into()),
            FieldName::Ident(ident) => ident.to_member(),
        }
    }
}

impl ToTokens for FieldName {
    fn to_tokens(&self, tokens: &mut TokenStream) {
        match self {
            &FieldName::Index(index) => syn::Index::from(index).to_tokens(tokens),
            FieldName::Ident(ident) => ident.to_tokens(tokens),
        }
    }
}

impl From<FieldName> for String {
    fn from(value: FieldName) -> Self {
        match value {
            FieldName::Index(index) => index.to_string(),
            FieldName::Ident(ident) => ident.into(),
        }
    }
}

impl_try_from_str!(FieldName);

impl FromStr for FieldName {
    type Err = FieldNameParseError;

    fn from_str(value: &str) -> Result<Self, Self::Err> {
        if !value.is_empty()
            && value
                .trim_start_matches(|ch: char| ch.is_ascii_digit())
                .is_empty()
        {
            if let Ok(index) = value.parse() {
                Ok(Self::Index(index))
            } else {
                Err(FieldNameParseError)
            }
        } else {
            value.parse().map(Self::Ident)
        }
    }
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub struct Fields {
    #[serde(
        default,
        rename = "$constructor",
        skip_serializing_if = "Option::is_none"
    )]
    pub constructor: Option<PathWithGenerics>,
    #[serde(flatten)]
    pub fields: IndexMap<FieldName, Field>,
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
#[serde(transparent)]
pub struct Variants {
    pub variants: IndexMap<Ident, Option<Field>>,
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize, Hash)]
pub enum Field {
    Opaque,
    Visible,
    RefVisible,
}

#[cfg(test)]
mod tests {
    use crate::ast;

    #[test]
    fn test_serialize() {
        let definitions = ast::Definitions {
            types: FromIterator::from_iter([
                (
                    ast::Path("Module".into()),
                    ast::Definition {
                        fn_name_suffix: None,
                        generics: Some(
                            ast::SerializedGenerics::Where {
                                generics: "<T: BundleValue>".into(),
                                where_predicates: "T::Type: BundleType<Value = T>,"
                                    .parse()
                                    .unwrap(),
                            }
                            .try_into()
                            .unwrap(),
                        ),
                        fold_where: None,
                        visit_where: None,
                        data: ast::Data::Struct(ast::Fields {
                            constructor: Some("Module::new_unchecked".parse().unwrap()),
                            fields: FromIterator::from_iter([(
                                "name_id()".parse().unwrap(),
                                ast::Field::Visible,
                            )]),
                        }),
                    },
                ),
                (
                    ast::Path("NameId".into()),
                    ast::Definition {
                        fn_name_suffix: None,
                        generics: None,
                        fold_where: None,
                        visit_where: None,
                        data: ast::Data::Struct(ast::Fields {
                            constructor: None,
                            fields: FromIterator::from_iter([
                                ("0".try_into().unwrap(), ast::Field::Opaque),
                                ("1".try_into().unwrap(), ast::Field::Opaque),
                            ]),
                        }),
                    },
                ),
            ]),
        };
        let definitions_str = serde_json::to_string_pretty(&definitions).unwrap();
        println!("{definitions_str}");
        assert_eq!(
            definitions_str,
            r#"{
  "types": {
    "Module": {
      "generics": {
        "generics": "< T : BundleValue >",
        "where": "T :: Type : BundleType < Value = T > ,"
      },
      "data": {
        "$kind": "Struct",
        "$constructor": "Module::new_unchecked",
        "name_id()": "Visible"
      }
    },
    "NameId": {
      "data": {
        "$kind": "Struct",
        "0": "Opaque",
        "1": "Opaque"
      }
    }
  }
}"#
        );
    }
}