#![deny(missing_docs)]
//! Macros for the `aisdk` library.

use proc_macro::TokenStream;
use quote::quote;
use syn::parse::Parser;
use syn::{
    Expr, ExprLit, FnArg, ItemFn, Lit, Meta, MetaNameValue, Pat, Token, parse_macro_input,
    punctuated::Punctuated,
};

#[proc_macro_attribute]
/// Constructs a tool from a function defnition. A tool has a name, a description,
/// an input and a body. all three components are infered from a standard rust
/// function. The name is the defined name of the function,
/// The description is infered from the doc comments of the function, The input
/// infered from the function arguments.
///
/// # Example
///
/// ```rust,no_run
/// use aisdk::macros::tool;
/// use aisdk::core::tools::Tool;
///
/// #[tool]
/// /// Returns the username
/// fn get_username(id: String) -> Tool {
///     // Your code here
///     Ok(format!("user_{}", id))
/// }
/// ```
///
/// - `get_username` becomes the name of the tool
/// - `"Returns the username"` becomes the description of the tool
/// - `id: String` becomes the input of the tool. converted to `{"id": "string"}`
///   as json schema
///
/// The function should return a `Result<String, String>` eventhough the return statement
/// returns a `Tool` object. This is because the macro will automatically convert the
/// function into a `Tool` object and return it. You should return what the model can
/// understand as a `String`.
///
/// In the event that the model refuses to send an argument, the default implementation
/// will be used. this works perfectly for arguments that are `Option`s. Make sure to
/// use `Option` types for arguments that are optional or implement a default for those
/// that are not and handle those defaults accordingly in the tool body.
///
/// You can override name and description using the macro arguments `name` and `desc`.
///
/// # Example with overrides
/// ```rust,no_run
/// use aisdk::macros::tool;
/// use aisdk::core::tools::Tool;
///
///     #[tool(
///         name = "the-name-for-this-tool",
///         desc = "the-description-for-this-tool"
///     )]
///     fn get_username(id: String) -> Tool {
///         // Your code here
///         Ok(format!("user_{}", id))
///     }
/// ```
pub fn tool(_attr: TokenStream, item: TokenStream) -> TokenStream {
    let input_fn = parse_macro_input!(item as ItemFn);
    let fn_name = &input_fn.sig.ident;
    let vis = &input_fn.vis;
    let return_type = &input_fn.sig.output;
    let block = &input_fn.block;
    let inputs = &input_fn.sig.inputs;
    let attrs = &input_fn.attrs;
    let args_parser = Punctuated::<MetaNameValue, Token![,]>::parse_terminated;
    let args = args_parser.parse(_attr);

    let (name_arg, description_arg) = if let Ok(args) = args {
        let mut name: Option<String> = None;
        let mut description: Option<String> = None;

        for arg in args {
            if arg.path.is_ident("desc")
                && let Expr::Lit(lit) = &arg.value
                && let Lit::Str(str_lit) = &lit.lit
            {
                description = Some(str_lit.value());
            } else if arg.path.is_ident("name")
                && let Expr::Lit(lit) = &arg.value
                && let Lit::Str(str_lit) = &lit.lit
            {
                name = Some(str_lit.value());
            }
        }

        (name, description)
    } else {
        (None, None)
    };

    let description = if let Some(desc) = description_arg {
        desc
    } else {
        // Extract doc comments
        let doc_comments: Vec<String> = attrs
            .iter()
            .filter_map(|attr| {
                if attr.path().is_ident("doc") {
                    if let Meta::NameValue(meta_name_value) = &attr.meta {
                        if let Expr::Lit(ExprLit {
                            lit: Lit::Str(lit_str),
                            ..
                        }) = &meta_name_value.value
                        {
                            let doc = lit_str.value();
                            Some(doc)
                        } else {
                            None
                        }
                    } else {
                        None
                    }
                } else {
                    None
                }
            })
            .collect();

        doc_comments.join("\n")
    };

    let name = if let Some(name) = name_arg {
        name
    } else {
        fn_name.to_string()
    };

    let binding_tokens: Vec<_> = inputs
        .iter()
        .filter_map(|arg| {
            if let FnArg::Typed(pat_type) = arg {
                if let Pat::Ident(pat_ident) = &*pat_type.pat {
                    let ident = &pat_ident.ident;
                    let ty = &*pat_type.ty;
                    let ident_str = ident.to_string();
                    Some(quote! {
                        let #ident: #ty = ::aisdk::__private::serde_json::from_value(
                            inp.as_object()
                                .unwrap()
                                .get(#ident_str)
                                .unwrap()
                                .clone()
                        ).unwrap_or_default();  // use default value if model doesn't send arg
                    })
                } else {
                    None
                }
            } else {
                None
            }
        })
        .collect();

    // Generate the struct definition
    let struct_fields = inputs.iter().filter_map(|arg| {
        if let FnArg::Typed(pat_type) = arg {
            if let Pat::Ident(pat_ident) = &*pat_type.pat {
                let ident = &pat_ident.ident;
                let ty = &*pat_type.ty;
                Some(quote! { #ident: #ty })
            } else {
                None
            }
        } else {
            None
        }
    });

    let expanded = quote! {
        #vis fn #fn_name() #return_type  {
            // use schemars::{schema_for, JsonSchema, Schema};
            use std::collections::HashMap;
            use ::aisdk::__private::schemars::{schema_for, JsonSchema, Schema};

            #[derive(::aisdk::__private::schemars::JsonSchema, Debug)]
            #[schemars(crate = "::aisdk::__private::schemars")]
            #[allow(dead_code)]
            //#[schemars(deny_unknown_fields)]
            struct Function {
                // Please add struct fields here
                #(#struct_fields),*
            }

            let input_schema = schema_for!(Function);
            // End

            let mut tool = ::aisdk::core::tools::Tool::builder()
                .name(#name.to_string())
                .description(#description.to_string())
                .input_schema(input_schema)
                .execute(::aisdk::core::tools::ToolExecute::new(Box::new(|inp| -> std::result::Result<String, String> {
                    #(#binding_tokens)*
                    #block
                })));

            tool.build().expect("Failed to build tool")
        }
    };

    TokenStream::from(expanded)
}
