use std::sync::Arc;

use crate::{
    api, app,
    component::{
        diff_view::{DiffViewContent, DiffViewState, diff_view},
        text::text,
    },
    query::{self, QueryStatus, read_query, use_query, watch_query},
    screen::dashboard::pull_request_file_tree::{self, PullRequestFileTree},
    util::{self},
};
use gpui::{AppContext, ParentElement, Styled, div};

pub(crate) struct PullRequestDiffView {
    selected_file_path: Option<Arc<str>>,

    pr_query: query::Entity<api::issues::FetchPullRequest>,
    file_tree_query: query::Entity<api::issues::FetchPullRequestFileTree>,
    content_diff_query: Option<query::Entity<api::repo::FetchFileDiff>>,

    diff_view_state: DiffViewState,
    diff_view_content: Option<DiffViewContent>,

    file_tree: gpui::Entity<PullRequestFileTree>,
}

pub(crate) fn new(
    pr_id: api::issues::Id,
    cx: &mut gpui::Context<PullRequestDiffView>,
) -> PullRequestDiffView {
    let mut view = PullRequestDiffView {
        selected_file_path: None,
        pr_query: use_query(api::issues::FetchPullRequest { id: pr_id.clone() }, cx),
        file_tree_query: use_query(
            api::issues::FetchPullRequestFileTree {
                id: pr_id.clone(),
                first: 100,
            },
            cx,
        ),
        content_diff_query: None,
        diff_view_state: DiffViewState::new(),
        diff_view_content: None,

        file_tree: cx.new(|cx| pull_request_file_tree::new(pr_id, cx)),
    };
    view.on_create(cx);
    view
}

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

        _ = cx
            .observe(&self.file_tree_query, |this, _, cx| {
                this.start_content_queries(cx);
            })
            .detach();

        // if pr is already loaded, start content queries
        self.start_content_queries(cx);
    }

    fn start_content_queries(&mut self, cx: &mut gpui::Context<Self>) {
        if self.content_diff_query.is_some() {
            return;
        }

        if self.selected_file_path.is_none()
            && let QueryStatus::Loaded(files) = read_query(&self.file_tree_query, cx)
        {
            self.selected_file_path = files.first().map(|file| Arc::clone(&file.path));
        }

        let Some(selected_file_path) = self.selected_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 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.selected_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::Context<Self>,
    ) -> impl gpui::IntoElement {
        let theme = app::current_theme(cx);

        let content_diff = self
            .content_diff_query
            .as_ref()
            .map(|q| read_query(q, cx))
            .unwrap_or(QueryStatus::Loading);

        match content_diff {
        | QueryStatus::Err(_) | QueryStatus::Loading => div()
            .size_full()
            .bg(theme.colors.surface)
            .p_4()
            .child(text("asd")),

        | QueryStatus::Loaded(_) => match &self.diff_view_content {
        | Some(content) => div()
            .size_full()
            .flex()
            .flex_row()
            .child(
                div()
                    .flex()
                    .w_80()
                    .h_full()
                    .border_r_1()
                    .border_color(theme.colors.border_muted)
                    .p_1()
                    .child(self.file_tree.clone()),
            )
            .child(diff_view(self.diff_view_state.clone(), content.clone())),
        | None => div(),
        },
        }
    }
}