use tauri::{AppHandle, Emitter};
use serde::{Deserialize, Serialize};
use futures_util::StreamExt;
use reqwest::Client;

#[derive(Serialize, Deserialize, Clone)]
struct Message {
    role: String,
    content: String,
}

#[derive(Serialize, Deserialize, Clone)]
struct TranslationPayload {
    model: String,
    messages: Vec<Message>,
    stream: bool,
}

#[derive(Deserialize)]
struct OpenAIResponse {
    choices: Vec<Choice>,
}

#[derive(Deserialize)]
struct Choice {
    message: Option<Message>,
    delta: Option<Delta>,
}

#[derive(Deserialize)]
struct Delta {
    content: Option<String>,
}

#[tauri::command]
async fn translate(
    app: AppHandle,
    api_address: String,
    api_key: String,
    payload: TranslationPayload,
) -> Result<String, String> {
    let client = Client::new();
    // Ensure URL doesn't have double slashes if api_address ends with /
    let base_url = api_address.trim_end_matches('/');
    let url = format!("{}/chat/completions", base_url);

    let mut request = client.post(&url).json(&payload);

    if !api_key.is_empty() {
        request = request.header("Authorization", format!("Bearer {}", api_key));
    }

    let res = request
        .send()
        .await
        .map_err(|e| e.to_string())?;

    if !payload.stream {
        let data = res.json::<OpenAIResponse>().await.map_err(|e| e.to_string())?;
        return Ok(data.choices.get(0).and_then(|c| c.message.as_ref()).map(|m| m.content.clone()).unwrap_or_default());
    }

    let mut stream = res.bytes_stream();
    let mut full_response = String::new();

    while let Some(item) = stream.next().await {
        let chunk = item.map_err(|e| e.to_string())?;
        let text = String::from_utf8_lossy(&chunk);
        
        for line in text.lines() {
            let line = line.trim();
            if line.is_empty() { continue; }
            if line == "data: [DONE]" { break; }
            
            if let Some(data_str) = line.strip_prefix("data: ") {
                if let Ok(json) = serde_json::from_str::<OpenAIResponse>(data_str) {
                    if let Some(choice) = json.choices.get(0) {
                        if let Some(delta) = &choice.delta {
                            if let Some(content) = &delta.content {
                                full_response.push_str(content);
                                app.emit("translation-chunk", content).map_err(|e| e.to_string())?;
                            }
                        }
                    }
                }
            }
        }
    }

    Ok(full_response)
}

#[cfg_attr(mobile, tauri::mobile_entry_point)]
pub fn run() {
    tauri::Builder::default()
        .plugin(tauri_plugin_opener::init())
        .plugin(tauri_plugin_http::init())
        .invoke_handler(tauri::generate_handler![translate])
        .run(tauri::generate_context!())
        .expect("error while running tauri application");
}