use std::sync::Arc;

use gpui::{AppContext, IntoElement, div};

use crate::{
    api::{self},
    app,
    component::diff_view::{DiffViewContent, DiffViewState, diff_view},
    query::{self, QueryStatus, read_query, use_query, watch_query},
    util,
};

pub(crate) struct PullRequestDiffView {
    pr_query: query::Entity<api::issues::FetchPullRequest>,
    content_diff_query: Option<query::Entity<api::repo::FetchFileDiff>>,
    diff_view_state: DiffViewState,
    diff_view_content: Option<DiffViewContent>,
    current_file_path: Option<Arc<str>>,
}

impl PullRequestDiffView {
    pub(crate) fn new(pr_id: api::issues::Id, cx: &mut gpui::Context<Self>) -> Self {
        let mut s = Self {
            pr_query: use_query(api::issues::FetchPullRequest { id: pr_id }, cx),
            content_diff_query: None,
            diff_view_state: DiffViewState::new(),
            diff_view_content: None,
            current_file_path: None,
        };
        s.on_create(cx);
        s
    }

    pub(crate) fn show_diff_for_file(
        &mut self,
        file_path: &Arc<str>,
        cx: &mut gpui::Context<Self>,
    ) {
        self.current_file_path = Some(Arc::clone(file_path));
        self.start_content_queries(cx);
    }

    fn start_content_queries(&mut self, cx: &mut gpui::Context<Self>) {
        if self.content_diff_query.is_some() {
            return;
        }
        let Some(selected_file_path) = self.current_file_path.as_deref() else {
            return;
        };

        let Some((old_file_ref, new_file_ref)) = ({
            if let QueryStatus::Loaded(pr) = read_query(&self.pr_query, cx) {
                Some((
                    api::repo::FileRef {
                        repo_slug: pr.base_repo_slug.clone(),
                        path: Arc::from(selected_file_path),
                        reff: Some(pr.base_ref.clone()),
                    },
                    api::repo::FileRef {
                        repo_slug: pr.head_repo_slug.clone(),
                        path: Arc::from(selected_file_path),
                        reff: Some(pr.head_ref.clone()),
                    },
                ))
            } else {
                None
            }
        }) else {
            return;
        };

        let content_diff_query = use_query(
            api::repo::FetchFileDiff {
                base: old_file_ref,
                head: new_file_ref,
            },
            cx,
        );
        _ = watch_query(&content_diff_query, Self::sync_content_diff_query, cx).detach();

        self.content_diff_query = Some(content_diff_query);
    }

    fn on_create(&mut self, cx: &mut gpui::Context<Self>) {
        _ = cx
            .observe(&self.pr_query, |this, _, cx| {
                this.start_content_queries(cx);
            })
            .detach();
    }

    fn sync_content_diff_query(
        &mut self,
        query: &query::Entity<api::repo::FetchFileDiff>,
        cx: &mut gpui::Context<Self>,
    ) {
        if let Some(diff) = {
            match read_query(query, cx) {
            | QueryStatus::Loaded(diff) => Some(Arc::clone(diff)),
            | _ => None,
            }
        } {
            self.load_diff_view(diff, cx);
            cx.notify();
        }
    }

    fn load_diff_view(
        &mut self,
        content_diff: Arc<util::diff::ContentDiff>,
        cx: &mut gpui::Context<Self>,
    ) {
        let theme = app::current_theme(cx);
        let old_content = content_diff.old_content.clone();
        let new_content = content_diff.new_content.clone();

        self.diff_view_state.reset(content_diff.len());
        self.diff_view_content = Some(content_diff.into());

        let theme_syntax = theme.syntax;

        if let Some(path) = &self.current_file_path {
            let path = Arc::clone(&path);
            let file_type = util::file::file_type_from_path(&path);

            let t1 = cx.background_spawn(async move {
                util::syntax_highlight::highlight_content(old_content, file_type, &theme_syntax)
            });
            let t2 = cx.background_spawn(async move {
                util::syntax_highlight::highlight_content(new_content, file_type, &theme_syntax)
            });

            _ = cx
                .spawn(async move |weak, cx| match tokio::join!(t1, t2) {
                | (Some(old_side_highlights), Some(new_side_highlights)) => {
                    _ = weak.update(cx, |this, cx| {
                        this.diff_view_state
                            .set_old_side_highlights(old_side_highlights);
                        this.diff_view_state
                            .set_new_side_highlights(new_side_highlights);
                        cx.notify();
                    });
                }
                | _ => {}
                })
                .detach();
        }
    }
}

impl gpui::Render for PullRequestDiffView {
    fn render(
        &mut self,
        _window: &mut gpui::Window,
        cx: &mut gpui::prelude::Context<Self>,
    ) -> impl gpui::IntoElement {
        let content_diff = self
            .content_diff_query
            .as_ref()
            .map(|q| read_query(q, cx))
            .unwrap_or(QueryStatus::Loading);

        match (content_diff, &self.diff_view_content) {
        | (QueryStatus::Loaded(_), Some(content)) => {
            diff_view(self.diff_view_state.clone(), content.clone()).into_any_element()
        }

        | (_, _) => div().into_any_element(),
        }
    }
}