use crate::{Supermaven, SupermavenCompletionStateId};
use anyhow::Result;
use editor::{Direction, InlineCompletionProvider};
use futures::StreamExt as _;
use gpui::{AppContext, Model, ModelContext, Task};
use language::{language_settings::all_language_settings, Anchor, Buffer};
use std::time::Duration;

pub const DEBOUNCE_TIMEOUT: Duration = Duration::from_millis(75);

pub struct SupermavenCompletionProvider {
    supermaven: Model<Supermaven>,
    completion_id: Option<SupermavenCompletionStateId>,
    pending_refresh: Task<Result<()>>,
}

impl SupermavenCompletionProvider {
    pub fn new(supermaven: Model<Supermaven>) -> Self {
        Self {
            supermaven,
            completion_id: None,
            pending_refresh: Task::ready(Ok(())),
        }
    }
}

impl InlineCompletionProvider for SupermavenCompletionProvider {
    fn is_enabled(&self, buffer: &Model<Buffer>, cursor_position: Anchor, cx: &AppContext) -> bool {
        if !self.supermaven.read(cx).is_enabled() {
            return false;
        }

        let buffer = buffer.read(cx);
        let file = buffer.file();
        let language = buffer.language_at(cursor_position);
        let settings = all_language_settings(file, cx);
        settings.inline_completions_enabled(language.as_ref(), file.map(|f| f.path().as_ref()))
    }

    fn refresh(
        &mut self,
        buffer_handle: Model<Buffer>,
        cursor_position: Anchor,
        debounce: bool,
        cx: &mut ModelContext<Self>,
    ) {
        let Some(mut completion) = self.supermaven.update(cx, |supermaven, cx| {
            supermaven.complete(&buffer_handle, cursor_position, cx)
        }) else {
            return;
        };

        self.pending_refresh = cx.spawn(|this, mut cx| async move {
            if debounce {
                cx.background_executor().timer(DEBOUNCE_TIMEOUT).await;
            }

            while let Some(()) = completion.updates.next().await {
                this.update(&mut cx, |this, cx| {
                    this.completion_id = Some(completion.id);
                    cx.notify();
                })?;
            }
            Ok(())
        });
    }

    fn cycle(
        &mut self,
        _buffer: Model<Buffer>,
        _cursor_position: Anchor,
        _direction: Direction,
        _cx: &mut ModelContext<Self>,
    ) {
    }

    fn accept(&mut self, _cx: &mut ModelContext<Self>) {
        self.pending_refresh = Task::ready(Ok(()));
        self.completion_id = None;
    }

    fn discard(&mut self, _cx: &mut ModelContext<Self>) {
        self.pending_refresh = Task::ready(Ok(()));
        self.completion_id = None;
    }

    fn active_completion_text<'a>(
        &'a self,
        buffer: &Model<Buffer>,
        cursor_position: Anchor,
        cx: &'a AppContext,
    ) -> Option<&'a str> {
        let completion_text = self
            .supermaven
            .read(cx)
            .completion(buffer, cursor_position, cx)?;

        let completion_text = trim_to_end_of_line_unless_leading_newline(completion_text);

        let completion_text = completion_text.trim_end();

        if !completion_text.trim().is_empty() {
            Some(completion_text)
        } else {
            None
        }
    }
}

fn trim_to_end_of_line_unless_leading_newline(text: &str) -> &str {
    if has_leading_newline(&text) {
        text
    } else if let Some(i) = text.find('\n') {
        &text[..i]
    } else {
        text
    }
}

fn has_leading_newline(text: &str) -> bool {
    for c in text.chars() {
        if c == '\n' {
            return true;
        }
        if !c.is_whitespace() {
            return false;
        }
    }
    false
}