use proc_macro::{Ident, TokenStream, TokenTree};

#[path = "../../../../guests_macro/src/parse_fn.rs"]
mod parse_fn;
use crate::parse_fn::FunctionDefinition;
use toml::Table;

/// Extends an out TokenStream with `let` directives for all patterns (and
/// types). readfn specifies wether the input is public or private.
///
/// Each `let` binding calls the read! macro (defined in zkWasm wrapper_macro
/// crate), feeding it an autogenerated "type note", which is then used to
/// "deserialize" the input.
fn insert_reads(
    out: &mut TokenStream,
    patterns: &Vec<TokenStream>,
    types: &Vec<TokenStream>,
    readfn: &str,
) {
    for i in 0..patterns.len() {
        let type_note: String = format!("{}", types[i]).replace('<', "[").replace('>', "]");
        out.extend(
            format!(
                "let {} : {} = read!({} {});",
                patterns[i], types[i], readfn, type_note
            )
            .parse::<TokenStream>(),
        );
    }
}

/// Creates a body, which reads all inputs, stores them in variables, then
/// executes the entrypoint function with those arguments and writes the
/// result.
///
/// Inputs are read via the read! macro (defined in the zkWasm wrapper_macro
/// crate). Their public status is dependent on `default_public_input.toml`.
///
/// # Usage
///
/// Inside zkWasm's guest (excluding the `entrypoint_expr` call):
///
/// ```rust
/// make_wrapper!{fn main(...) -> ...}
/// ```
///
/// # Example output
///
/// ```rust
/// {
///     let ... : ... = read!(... ...);
///     let ... : ... = read!(... ...);
///     ...
///     let result = zkp::main(..., ..., ...);
///     write(result as u64);
/// }
/// ```
#[proc_macro]
pub fn make_wrapper(item: TokenStream) -> TokenStream {
    let fd = FunctionDefinition::new(&item);

    let mut out = TokenStream::new();

    insert_reads(&mut out, fd.public_patterns(), fd.public_types(), "read_public");
    insert_reads(&mut out, fd.private_patterns(), fd.private_types(), "read_private");

    out.extend(
        format!(
            "
        let result = zkp::{}({});
        let bytes = tobytes::to_bytes!(result);
        for val in bytes.into_iter() {{
            write(val);
        }}
    ",
            fd.name, fd.grouped_patterns()
        )
        .parse::<TokenStream>(),
    );

    let mut block = TokenStream::new();
    block.extend(format!("{{ {} }}", out).parse::<TokenStream>());
    block
}

fn return_primitive(readfn: &TokenTree, typ: &Ident) -> TokenStream {
    format!(
        "
        ({readfn}() as {typ})
    "
    )
    .parse()
    .unwrap()
}

fn return_bool(readfn: &TokenTree) -> TokenStream {
    format!(
        "
        ({readfn}() != 0)
    "
    )
    .parse()
    .unwrap()
}

fn return_char(readfn: &TokenTree) -> TokenStream {
    format!(
        "
        (({readfn}() as u8) as char)
    "
    )
    .parse()
    .unwrap()
}

fn return_string(readfn: &TokenTree) -> TokenStream {
    format!(
        "
        {{
             let mut ret = Vec::new();
             let size = read!({readfn} usize);
             for _ in 0..size {{
                 ret.push(read!({readfn} char));
             }}
             ret.into_iter().collect()
        }}
    "
    )
    .parse()
    .unwrap()
}

fn return_array(readfn: &TokenTree, inner: &TokenStream) -> TokenStream {
    format!(
        "
        {{
             let mut ret = Vec::new();
             let size = read!({readfn} usize);
             for _ in 0..size {{
                 ret.push(read!({readfn} {inner}));
             }}
             ret.try_into().unwrap()
        }}
    "
    )
    .parse()
    .unwrap()
}

fn return_cont(
    readfn: &TokenTree,
    container: &Ident,
    pushfn: &str,
    inner: &TokenStream,
) -> TokenStream {
    format!(
        "
        {{
             let mut ret = {container}::new();
             let size = read!({readfn} usize);
             for _ in 0..size {{
                 ret.{pushfn}(read!({readfn} {inner}));
             }}
             ret
        }}
    "
    )
    .parse()
    .unwrap()
}

fn return_hashmap(readfn: &TokenTree, container: &Ident, inner: &TokenStream) -> TokenStream {
    let mut inner = inner.clone().into_iter();
    let key_type = inner.next().unwrap();
    inner.next().unwrap();
    let value_type = inner.next().unwrap();
    format!(
        r#"
        {{
             let mut ret = {container}::new();
             let size = read!({readfn} usize);
             for _ in 0..size {{
                 ret.insert(read!({readfn} {key_type}), read!({readfn} {value_type}));
             }}
             ret
        }}
    "#
    )
    .parse()
    .unwrap()
}

fn return_tuple(readfn: &TokenTree, inner: &TokenStream) -> TokenStream {
    let mut value = String::new();
    for subtype in inner.clone().into_iter() {
        value += &format!("read!({readfn} {subtype}), ");
    }
    format!(
        "
        {{
             let _ = read!({readfn} usize);
             ( {value} )
        }}
    "
    )
    .parse()
    .unwrap()
}

/// Creates a body which returns a value of the type, defined as a "type note"
/// argument.
///
/// The host "serializes" all input data by flattening it as a series of
/// integers. This function, in turn, unflattens the input, by reading integers
/// multiple times and combining them in the appropriate structures.
///
/// It takes two arguments, separated by a space. The first is a string "type
/// note" and the second is the name of the read function (either read_private
/// or read_public).
///
/// The type note is similar to a print!("{:?}") output, however angled braces
/// are square.
#[proc_macro]
pub fn read(item: TokenStream) -> TokenStream {
    let mut parts = item.clone().into_iter();
    let readfn = parts.next().unwrap();
    match parts.next().unwrap() {
        // Primitive or STD Container
        TokenTree::Ident(ident) => {
            match ident.to_string().as_str() {
                "u8" | "u16" | "u32" | "u64" | "u128" | "usize" | "i8" | "i16" | "i32" | "i64"
                | "i128" | "isize" | "f32" | "f64" => return return_primitive(&readfn, &ident),
                "char" => return return_char(&readfn),
                "bool" => return return_bool(&readfn),
                "String" => return return_string(&readfn),
                _ => {}
            }

            let mut group = parts
                .next()
                .expect(format!("No group after \"{ident}\" while parsing \"{item}\"!").as_str());
            if let TokenTree::Group(inner_group) = group {
                let rest = inner_group.stream();

                match ident.to_string().as_str() {
                    // https://doc.rust-lang.org/std/collections/
                    "Vec" | "BinaryHeap" => return_cont(&readfn, &ident, "push", &rest),
                    "VecDeque" | "LinkedList" => return_cont(&readfn, &ident, "push_back", &rest),
                    "HashSet" | "BTreeSet" => return_cont(&readfn, &ident, "insert", &rest),
                    "HashMap" | "BTreeMap" => return_hashmap(&readfn, &ident, &rest),
                    _ => todo!("Unsupported container {ident}"),
                }
            } else {
                unreachable!("{group} is not a TokenTree::Group!");
            }
        }
        // Array or tuple
        TokenTree::Group(group) => {
            let mut group = group.stream().into_iter();
            let mut inner = TokenStream::new();
            while let Some(current) = group.next() {
                match current {
                    TokenTree::Punct(punct) => match punct.as_char() {
                        // Array
                        ';' => return return_array(&readfn, &inner),
                        // Tuple
                        ',' => continue,
                        _ => unreachable!("Group contains unexpected \"{punct}\""),
                    },
                    TokenTree::Ident(_) | TokenTree::Group(_) => {
                        inner.extend([current].into_iter())
                    }
                    _ => unreachable!(),
                }
            }
            return_tuple(&readfn, &inner)
        }
        _ => unreachable!(),
    }
}