use proc_macro::TokenStream;
use quote::quote;
use syn::{parse_macro_input, ItemEnum, Lit, DeriveInput, Fields, Data};

#[proc_macro_derive(HttpRequest, attributes(http_get))]
pub fn derive_http_get_request(input: TokenStream) -> TokenStream {
    let input = parse_macro_input!(input as DeriveInput);
    let name = &input.ident;

    // Parse #[http_get(url = "...")] attribute
    let mut base_url = None;
    for attr in &input.attrs {
        if attr.path().is_ident("http_get") {
            let _ = attr.parse_nested_meta(|meta| {
                if meta.path.is_ident("url") {
                    let value: Lit = meta.value()?.parse()?;
                    if let Lit::Str(litstr) = value {
                        base_url = Some(litstr.value());
                    }
                }
                Ok(())
            });
        }
    }

    let base_url = base_url.expect("Missing #[http_get(url = \"...\")] attribute");

    let expanded = match &input.data {
        Data::Struct(data_struct) => {
            let fields = match &data_struct.fields {
                Fields::Named(named) => &named.named,
                _ => panic!("#[derive(HttpRequest)] only supports structs with named fields"),
            };

            let mut query_param_code = Vec::new();
            for field in fields {
                let ident = field.ident.clone().unwrap();
                let field_name = ident.to_string();
                if field_name.starts_with("lnk_p_") {
                    let key = &field_name["lnk_p_".len()..];
                    query_param_code.push(quote! {
                        query_params.push((#key.to_string(), self.#ident.to_string()));
                    });
                }
            }

            quote! {
                impl #name {
                    pub async fn send(
                        &self,
                        client: std::sync::Arc<awc::Client>,
                        headers: Option<Vec<(&str, &str)>>,
                        api_key: Option<&str>,
                    ) -> Result<awc::ClientResponse, awc::error::SendRequestError> {
                        use urlencoding::encode;

                        let mut query_params: Vec<(String, String)> = Vec::new();
                        #(#query_param_code)*

                        if let Some(key) = api_key {
                            query_params.push(("api_key".to_string(), key.to_string()));
                        }

                        let mut url = #base_url.to_string();
                        if !query_params.is_empty() {
                            let query_parts: Vec<String> = query_params.iter()
                                .map(|(k, v)| format!("{}={}", k, encode(v)))
                                .collect();
                            url.push('?');
                            url.push_str(&query_parts.join("&"));
                        }

                        let mut request = client.get(url);

                        if let Some(hdrs) = headers {
                            for (k, v) in hdrs {
                                request = request.append_header((k, v));
                            }
                        }

                        let response = request.send().await?;
                        Ok(response)
                    }
                }
            }
        }

        Data::Enum(data_enum) => {
            let mut variant_arms = Vec::new();
            for variant in &data_enum.variants {
                let vname = &variant.ident;
                match &variant.fields {
                    Fields::Unnamed(fields) if fields.unnamed.len() == 1 => {
                        variant_arms.push(quote! {
                            #name::#vname(inner) => inner.send(client.clone(), headers.clone(), api_key).await,
                        });
                    }
                    _ => panic!("#[derive(HttpRequest)] enum variants must have a single unnamed field"),
                }
            }

            quote! {
                impl #name {
                    pub async fn send(
                        &self,
                        client: std::sync::Arc<awc::Client>,
                        headers: Option<Vec<(&str, &str)>>,
                        api_key: Option<&str>,
                    ) -> Result<awc::ClientResponse, awc::error::SendRequestError> {
                        match self {
                            #(#variant_arms)*
                        }
                    }
                }
            }
        }

        _ => panic!("#[derive(HttpRequest)] only supports structs and enums"),
    };

    TokenStream::from(expanded)
}

#[proc_macro_derive(HttpResponse)]
pub fn derive_http_response(input: TokenStream) -> TokenStream {
    let input = parse_macro_input!(input as DeriveInput);
    let name = &input.ident;

    let expanded = quote! {
        impl #name {
            pub async fn receive(resp: awc::ClientResponse) -> Result<Self, awc::error::JsonPayloadError> {
                resp.json().await
            }
        }
    };

    TokenStream::from(expanded)
}

#[proc_macro_derive(SendVec)]
pub fn derive_send_vec(input: TokenStream) -> TokenStream {
    let input = parse_macro_input!(input as DeriveInput);
    let name = &input.ident;

    let expanded = quote! {
        impl #name {
            /// Sends all items in the vec sequentially, awaiting each.
            pub async fn send_vec(
                items: Vec<Self>,
                client: std::sync::Arc<awc::Client>,
                headers: Option<Vec<(&str, &str)>>,
                api_key: Option<&str>,
            ) -> Result<Vec<awc::ClientResponse>, awc::error::SendRequestError> {
                let mut responses = Vec::with_capacity(items.len());
                for item in items {
                    let resp = item.send(client.clone(), headers.clone(), api_key).await?;
                    responses.push(resp);
                }
                Ok(responses)
            }
        }
    };

    TokenStream::from(expanded)
}

#[proc_macro_derive(ResponseVec)]
pub fn derive_response_vec(input: TokenStream) -> TokenStream {
    let input = parse_macro_input!(input as DeriveInput);
    let name = &input.ident;

    let expanded = quote! {
        impl #name {
            /// Deserializes all responses sequentially into a Vec<Self>.
            /// Assumes `Self` implements `DeserializeOwned`.
            pub async fn response_vec(
                responses: Vec<awc::ClientResponse>,
            ) -> Result<Vec<Self>, awc::error::JsonPayloadError>
            where
                Self: Sized + serde::de::DeserializeOwned,
            {
                let mut results = Vec::with_capacity(responses.len());
                for resp in responses {
                    let item = resp.json::<Self>().await?;
                    results.push(item);
                }
                Ok(results)
            }
        }
    };

    TokenStream::from(expanded)
}

#[proc_macro_attribute]
pub fn alpaca_cli(_attr: TokenStream, item: TokenStream) -> TokenStream {
    let input_enum = parse_macro_input!(item as ItemEnum);
    let enum_name = &input_enum.ident;
    let variants = &input_enum.variants;

    // Match arms for regular command variants (Single, Asset, etc.)
    let regular_arms = variants.iter().filter_map(|v| {
        let v_name = &v.ident;

        // Skip Bulk variant — we handle it separately
        if v_name == "Bulk" {
            return None;
        }

        Some(quote! {
            #enum_name::#v_name(req) => {
                let res = req.send(client.clone(), &api_key).await?;
                let body = res.body().await?;
                println!("{}", std::str::from_utf8(&body)?);
            }
        })
    });

    let expanded = quote! {
        #[derive(structopt::StructOpt, Debug)]
        #input_enum

        #[tokio::main]
        async fn main() -> Result<(), Box<dyn std::error::Error>> {
            use structopt::StructOpt;
            use std::fs::File;
            use std::io::{BufReader, Read};
            use std::sync::Arc;
            use std::thread;

            const THREADS: usize = 4;

            // Initialize shared HTTP client and API key
            let client = Arc::new(awc::Client::default());
            let api_key = std::env::var("APCA_API_KEY_ID")?;
            let cmd = #enum_name::from_args();

            match cmd {
                #(#regular_arms)*

                #enum_name::Bulk { input } => {
                    // Choose input source: file or stdin
                    let mut reader: Box<dyn Read> = match input {
                        Some(path) => Box::new(File::open(path)?),
                        None => Box::new(std::io::stdin()),
                    };

                    // Read input JSON into buffer
                    let mut buf = String::new();
                    reader.read_to_string(&mut buf)?;

                    // Deserialize into Vec<Query>
                    let queries: Vec<Query> = serde_json::from_str(&buf)?;
                    let total = queries.len();

                    if total == 0 {
                        eprintln!("No queries provided.");
                        return Ok(());
                    }

                    let shared_queries = Arc::new(queries);
                    let shared_key = Arc::new(api_key);

                    let per_thread = total / THREADS;

                    let mut handles = Vec::with_capacity(THREADS);
                    for i in 0..THREADS {
                        let queries_clone = Arc::clone(&shared_queries);
                        let client_clone = Arc::clone(&client);
                        let key_clone = Arc::clone(&shared_key);

                        let start_index = i * per_thread;
                        let end_index = if i == THREADS - 1 {
                            total // Last thread gets the remainder
                        } else {
                            start_index + per_thread
                        };

                        let handle = thread::spawn(move || {
                            let rt = tokio::runtime::Runtime::new().expect("Failed to create runtime");
                            for idx in start_index..end_index {
                                let query = &queries_clone[idx];
                                let send_result = rt.block_on(query.send(client_clone.clone(), &key_clone));

                                match send_result {
                                    Ok(response) => {
                                        let body_result = rt.block_on(response.body());
                                        match body_result {
                                            Ok(body) => println!("{}", String::from_utf8_lossy(&body)),
                                            Err(e) => eprintln!("Error reading response body: {:?}", e),
                                        }
                                    }
                                    Err(e) => {
                                        eprintln!("Request failed: {:?}", e);
                                    }
                                }
                            }
                        });

                        handles.push(handle);
                    }

                    // Wait for all threads to complete
                    for handle in handles {
                        handle.join().expect("A thread panicked");
                    }
                }
            }

            Ok(())
        }
    };

    TokenStream::from(expanded)
}