use std::{
    sync::{Arc, Mutex},
    thread,
};

use anyhow::Result;
use tokio::{select, sync::mpsc};

use crate::emulator::{
    EmulatorClient, EmulatorCommand, GameInfo, InlineStack, ProfileEvent, SimEvent, SimId,
};
use recording::Recording;
use state::ProgramState;

mod recording;
mod state;

pub struct Profiler {
    sim_id: SimId,
    client: EmulatorClient,
    status: Arc<Mutex<ProfilerStatus>>,
    action: Option<mpsc::UnboundedSender<RecordingAction>>,
    killer: Option<oneshot::Sender<()>>,
}

impl Profiler {
    pub fn new(sim_id: SimId, client: EmulatorClient) -> Self {
        Self {
            sim_id,
            client,
            status: Arc::new(Mutex::new(ProfilerStatus::Disabled)),
            action: None,
            killer: None,
        }
    }

    pub fn status(&self) -> ProfilerStatus {
        self.status.lock().unwrap().clone()
    }

    pub fn enable(&mut self) {
        let sim_id = self.sim_id;
        let client = self.client.clone();
        let status = self.status.clone();
        let (action_tx, action_rx) = mpsc::unbounded_channel();
        self.action = Some(action_tx);
        let (killer_tx, killer_rx) = oneshot::channel();
        self.killer = Some(killer_tx);
        thread::spawn(move || {
            tokio::runtime::Builder::new_current_thread()
                .enable_all()
                .build()
                .unwrap()
                .block_on(async move {
                    select! {
                        _ = run_profile(sim_id, client, status.clone(), action_rx) => {}
                        _ = killer_rx => {
                            *status.lock().unwrap() = ProfilerStatus::Disabled;
                        }
                    }
                })
        });
    }

    pub fn disable(&mut self) {
        if let Some(killer) = self.killer.take() {
            let _ = killer.send(());
        }
    }

    pub fn start_recording(&mut self) {
        if let Some(action) = &self.action {
            let _ = action.send(RecordingAction::Start);
        }
    }

    pub fn finish_recording(&mut self) -> oneshot::Receiver<Vec<u8>> {
        let (tx, rx) = oneshot::channel();
        if let Some(action) = &self.action {
            let _ = action.send(RecordingAction::Finish(tx));
        }
        rx
    }

    pub fn cancel_recording(&mut self) {
        if let Some(action) = &self.action {
            let _ = action.send(RecordingAction::Cancel);
        }
    }
}

impl Drop for Profiler {
    fn drop(&mut self) {
        self.disable();
    }
}

async fn run_profile(
    sim_id: SimId,
    client: EmulatorClient,
    status: Arc<Mutex<ProfilerStatus>>,
    mut action_source: mpsc::UnboundedReceiver<RecordingAction>,
) {
    let (profile_sync, mut profile_source) = mpsc::unbounded_channel();
    client.send_command(EmulatorCommand::StartProfiling(sim_id, profile_sync));

    *status.lock().unwrap() = ProfilerStatus::Enabled;

    let mut session = ProfilerSession::new();
    loop {
        select! {
            maybe_event = profile_source.recv() => {
                let Some(event) = maybe_event else {
                    break; // emulator thread disconnected
                };
                if let Err(error) = handle_event(event, &mut session).await {
                    *status.lock().unwrap() = ProfilerStatus::Error(error.to_string());
                    return;
                }
            }
            maybe_action = action_source.recv() => {
                let Some(action) = maybe_action else {
                    break; // ui thread disconnected
                };
                handle_action(action, &mut session, &status);
            }
        }
    }

    *status.lock().unwrap() = ProfilerStatus::Disabled;
}

async fn handle_event(event: ProfileEvent, session: &mut ProfilerSession) -> Result<()> {
    match event {
        ProfileEvent::Start { info } => session.start_profiling(info).await,
        ProfileEvent::Update {
            cycles,
            event,
            inline_stack,
        } => {
            session.track_elapsed_cycles(cycles);
            if let Some(event) = event {
                session.track_event(event)?;
            }
            if let Some(stack) = inline_stack {
                session.track_inline_stack(stack);
            }
        }
    }
    Ok(())
}

fn handle_action(
    action: RecordingAction,
    session: &mut ProfilerSession,
    status: &Mutex<ProfilerStatus>,
) {
    match action {
        RecordingAction::Start => {
            session.start_recording();
            *status.lock().unwrap() = ProfilerStatus::Recording;
        }
        RecordingAction::Finish(rx) => {
            if let Some(bytes) = session.finish_recording() {
                let _ = rx.send(bytes);
            }
            *status.lock().unwrap() = ProfilerStatus::Enabled;
        }
        RecordingAction::Cancel => {
            session.cancel_recording();
            *status.lock().unwrap() = ProfilerStatus::Enabled;
        }
    }
}

#[derive(Clone)]
pub enum ProfilerStatus {
    Disabled,
    Enabled,
    Recording,
    Error(String),
}

impl ProfilerStatus {
    pub fn enabled(&self) -> bool {
        matches!(self, Self::Enabled | Self::Recording)
    }
}

enum RecordingAction {
    Start,
    Finish(oneshot::Sender<Vec<u8>>),
    Cancel,
}

struct ProfilerSession {
    program: Option<ProgramState>,
    recording: Option<Recording>,
}

impl ProfilerSession {
    fn new() -> Self {
        Self {
            program: None,
            recording: None,
        }
    }

    async fn start_profiling(&mut self, info: Arc<GameInfo>) {
        let program = ProgramState::new(info).await;
        let recording = if self.recording.is_some() {
            Some(Recording::new(&program))
        } else {
            None
        };
        self.program = Some(program);
        self.recording = recording;
    }

    fn track_elapsed_cycles(&mut self, cycles: u32) {
        if let (Some(state), Some(recording)) = (&self.program, &mut self.recording) {
            recording.track_elapsed_cycles(state, cycles);
        }
    }

    fn track_event(&mut self, event: SimEvent) -> Result<()> {
        let Some(program) = &mut self.program else {
            return Ok(());
        };
        match event {
            SimEvent::Call(address) => program.track_call(address),
            SimEvent::Return => program.track_return(),
            SimEvent::Halt => program.track_halt(),
            SimEvent::Interrupt(code, address) => program.track_interrupt(code, address),
            SimEvent::Reti => program.track_reti(),
            SimEvent::Marker(name) => {
                if let Some(recording) = &mut self.recording {
                    recording.track_marker(name);
                };
                Ok(())
            }
        }
    }

    fn track_inline_stack(&mut self, inline_stack: InlineStack) {
        if let Some(program) = &mut self.program {
            program.track_inline_stack(inline_stack);
        }
    }

    fn start_recording(&mut self) {
        if let Some(program) = &self.program {
            self.recording = Some(Recording::new(program));
        }
    }

    fn finish_recording(&mut self) -> Option<Vec<u8>> {
        self.recording.take().map(|r| r.finish())
    }

    fn cancel_recording(&mut self) {
        self.recording.take();
    }
}