use futures::AsyncBufReadExt;
use gio::prelude::SettingsExtManual;
use soup::prelude::*;
use adw::prelude::*;
use gettextrs::*;
use relm4::{gtk, prelude::{Component, ComponentParts}, ComponentSender};

// All of this is incredibly minimalist.
// This should be expanded later.
#[derive(Debug, serde::Serialize)]
pub(crate) struct OllamaRequest {
    model: String,
    prompt: String,
    system: String,
}

#[derive(Debug, serde::Deserialize)]
pub(crate) struct OllamaChunk {
    response: String,
    done: bool,
}

#[derive(Debug, serde::Deserialize)]
pub(crate) struct OllamaError {
    error: String
}
impl std::error::Error for OllamaError {}
impl std::fmt::Display for OllamaError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        self.error.fmt(f)
    }
}

#[derive(serde::Deserialize)]
#[serde(untagged)]
pub(crate) enum OllamaResult {
    Ok(OllamaChunk),
    Err(OllamaError),
}

impl From<OllamaResult> for Result<OllamaChunk, OllamaError> {
    fn from(val: OllamaResult) -> Self {
        match val {
            OllamaResult::Ok(chunk) => Ok(chunk),
            OllamaResult::Err(err) => Err(err)
        }
    }
}


#[derive(Debug, Default)]
pub(crate) struct SmartSummaryButton {
    task: Option<relm4::JoinHandle<()>>,
    waiting: bool,

    http: soup::Session,
}

impl SmartSummaryButton {
    async fn summarize(
        sender: relm4::Sender<Result<String, Error>>,
        http: soup::Session,
        text: String,
    ) {
        let settings = gio::Settings::new(crate::APPLICATION_ID);
        // We shouldn't let the user record a bad setting anyway.
        let endpoint = glib::Uri::parse(
            &settings.string("llm-endpoint"),
            glib::UriFlags::NONE,
        ).unwrap();
        let model = settings.get::<String>("smart-summary-model");
        let system_prompt = settings.get::<String>("smart-summary-system-prompt");
        let prompt_prefix = settings.get::<String>("smart-summary-prompt-prefix");
        let mut prompt_suffix = settings.get::<String>("smart-summary-prompt-suffix");

        let endpoint = endpoint.parse_relative("./api/generate", glib::UriFlags::NONE).unwrap();
        log::debug!("endpoint: {}, model: {}", endpoint, model);
        log::debug!("system prompt: {}", system_prompt);

        let msg = soup::Message::from_uri(
            "POST",
            &endpoint
        );

        if !prompt_suffix.is_empty() {
            prompt_suffix = String::from("\n\n") + &prompt_suffix;
        }
        msg.set_request_body_from_bytes(Some("application/json"),
            Some(&glib::Bytes::from_owned(serde_json::to_vec(&OllamaRequest {
                model, system: system_prompt, prompt: format!("{}\n\n{}{}", prompt_prefix, text, prompt_suffix),
            }).unwrap()))
        );

        let mut stream = match http.send_future(&msg, glib::Priority::DEFAULT).await {
            Ok(stream) => stream.into_async_buf_read(128),
            Err(err) => {
                let _ = sender.send(Err(err.into()));
                return
            }
        };
        log::debug!("response: {:?} ({})", msg.status(), msg.reason_phrase().unwrap_or_default());
        let mut buffer = Vec::with_capacity(2048);
        const DELIM: u8 = b'\n';
        loop {
            let len = match stream.read_until(DELIM, &mut buffer).await {
                Ok(len) => len,
                Err(err) => {
                    let _ = sender.send(Err(err.into()));
                    return
                }
            };
            log::debug!("Got chunk ({} bytes): {}", len, String::from_utf8_lossy(&buffer));
            let response: Result<OllamaResult, serde_json::Error> = serde_json::from_slice(&buffer[..len]);
            match response.map(Result::from) {
                Ok(Ok(OllamaChunk { response: chunk, done })) => {
                    if !chunk.is_empty() {
                        sender.emit(Ok(chunk));
                    }
                    if done {
                        sender.emit(Ok(String::new()));
                        return
                    }
                },
                Ok(Err(err)) => {
                    sender.emit(Err(err.into()));
                    return
                }
                Err(err) => {
                    sender.emit(Err(err.into()));
                    return
                }
            }
            buffer.truncate(0);
        }
    }
}

#[derive(Debug, thiserror::Error)]
pub(crate) enum Error {
    #[error("glib error: {0}")]
    Glib(#[from] glib::Error),
    #[error("json error: {0}")]
    Json(#[from] serde_json::Error),
    #[error("ollama error: {0}")]
    #[allow(private_interfaces)]
    Ollama(#[from] OllamaError),
    #[error("i/o error: {0}")]
    Io(#[from] std::io::Error)
}

#[derive(Debug)]
pub(crate) enum Input {
    #[doc(hidden)] ButtonPressed,
    Text(String),
    Cancel,
}

#[derive(Debug)]
pub(crate) enum Output {
    Start,
    Chunk(String),
    Done,

    Error(Error)
}

#[relm4::component(pub(crate))]
impl Component for SmartSummaryButton {
    type Input = Input;
    type Output = Output;

    type Init = soup::Session;
    type CommandOutput = Result<String, Error>;

    view! {
        #[root]
        #[name = "button"]
        gtk::Button {
            connect_clicked => Input::ButtonPressed,
            #[watch]
            set_sensitive: !(model.task.is_some() || model.waiting),
            // TRANSLATORS: please keep the newline and `<b>` tags
            set_tooltip_markup: Some(gettext("<b>Smart Summary</b>\nAsk a language model for a single-sentence summary.")).as_deref(),

            if model.task.is_some() || model.waiting {
                gtk::Spinner { set_spinning: true }
            } else {
                gtk::Label { set_markup: "✨" }
            }

        }
    }

    fn init(
        init: Self::Init,
        root: Self::Root,
        sender: ComponentSender<Self>
    ) -> ComponentParts<Self> {
        let model = Self {
            http: init,
            ..Self::default()
        };
        let widgets = view_output!();

        ComponentParts { model, widgets }
    }

    fn update(
        &mut self,
        msg: Self::Input,
        sender: ComponentSender<Self>,
        _root: &Self::Root
    ) {
        match msg {
            Input::Cancel => {
                self.waiting = false;
                if let Some(task) = self.task.take() {
                    log::debug!("Parent component asked us to cancel.");
                    task.abort();
                } else {
                    log::warn!("Parent component asked us to cancel, but we're not running a task.");
                }
            },
            Input::ButtonPressed => if let Ok(()) = sender.output(Output::Start) {
                self.waiting = true;
                log::debug!("Requesting text to summarize from parent component...");
                // TODO: set timeout in case parent component never replies
                // This shouldn't happen, but I feel like we should handle this case.
            },
            Input::Text(text) => {
                log::debug!("Would generate summary for the following text:\n{}", text);

                log::debug!("XDG_DATA_DIRS={:?}", std::env::var("XDG_DATA_DIRS"));
                let sender = sender.command_sender().clone();
                relm4::spawn_local(Self::summarize(
                    sender, self.http.clone(), text
                ));
            }
        }
    }

    fn update_cmd(&mut self, msg: Self::CommandOutput, sender: ComponentSender<Self>, _root: &Self::Root) {
        match msg {
            Ok(chunk) if chunk.is_empty() => {
                self.task = None;
                self.waiting = false;
                let _ = sender.output(Output::Done);
            },
            Err(err) => {
                self.task = None;
                self.waiting = false;
                let _ = sender.output(Output::Error(err));
            }
            Ok(chunk) => {
                let _ = sender.output(Output::Chunk(chunk));
            },
        }
    }
}