use std::rc::Rc;

use assets::CustomIconName;
use dock::{BasePanel, DockArea, Panel, PanelEvent, add_center_panel, panel_handle};
use gpui::prelude::*;
use gpui::{
    AnyElement, App, AppContext, Context, Entity, EventEmitter, FocusHandle, Focusable, Pixels,
    Render, SharedString, Size, Subscription, WeakEntity, Window, div, px, size,
};
use gpui_component::button::{Button, ButtonVariants};
use gpui_component::dialog::{DialogDescription, DialogFooter, DialogHeader, DialogTitle};
use gpui_component::form::{field, v_form};
use gpui_component::input::{Input, InputState, Textarea, TextareaState};
use gpui_component::scroll::Scrollbar;
use gpui_component::{
    ActiveTheme, Icon, VirtualListScrollHandle, WindowExt, h_flex, v_flex, v_virtual_list,
};
use nostr::prelude::EventId;
use signed_core::{RepoStatus, activity_subject};
use signed_state::{ProfileStore, RepoStore};
use signed_ui::{SegmentButton, UserAvatar, placeholder, status_badge};
use utils::relative_time;

pub(super) mod detail;

use self::detail::IssueDetailView;

const ISSUE_ROW_HEIGHT: f32 = 73.;

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum IssueFilter {
    All,
    Open,
    Closed,
}

impl IssueFilter {
    fn matches(self, status: RepoStatus) -> bool {
        match self {
            Self::All => true,
            Self::Open => status == RepoStatus::Open,
            Self::Closed => matches!(status, RepoStatus::Closed | RepoStatus::Applied),
        }
    }
}

pub struct IssuesView {
    focus_handle: FocusHandle,
    dock_area: WeakEntity<DockArea>,
    store: Entity<RepoStore>,
    repo_name: SharedString,
    filter: IssueFilter,
    item_sizes: Rc<Vec<Size<Pixels>>>,
    visible_issues: Vec<usize>,
    counts: (usize, usize, usize),
    // A filter change notifies even when the visible rows are unchanged,
    // e.g. switching between two empty filters.
    synced_filter: IssueFilter,
    scroll_handle: VirtualListScrollHandle,
    _subscription: Subscription,
}

impl IssuesView {
    pub fn new(
        dock_area: WeakEntity<DockArea>,
        store: Entity<RepoStore>,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) -> Self {
        let repo_name = store.read(cx).name();

        let subscription = cx.observe(&store, |this, _store, cx| {
            this.rebuild(cx);
        });

        cx.defer_in(window, |this, _window, cx| {
            this.rebuild(cx);
        });

        Self {
            focus_handle: cx.focus_handle(),
            dock_area,
            store,
            repo_name,
            filter: IssueFilter::Open,
            item_sizes: Rc::new(Vec::new()),
            visible_issues: Vec::new(),
            counts: (0, 0, 0),
            synced_filter: IssueFilter::Open,
            scroll_handle: VirtualListScrollHandle::new(),
            _subscription: subscription,
        }
    }

    fn rebuild(&mut self, cx: &mut Context<Self>) {
        let filter = self.filter;

        let (visible_issues, counts) = {
            let store = self.store.read(cx);
            let mut counts = (0usize, 0usize, 0usize);

            let visible_issues: Vec<usize> = store
                .issues
                .iter()
                .enumerate()
                .filter_map(|(ix, issue)| {
                    let status = store.status_of(issue);
                    counts.0 += 1;
                    match status {
                        RepoStatus::Open => counts.1 += 1,
                        RepoStatus::Closed => counts.2 += 1,
                        RepoStatus::Draft | RepoStatus::Applied => {}
                    }
                    filter.matches(status).then_some(ix)
                })
                .collect();

            (visible_issues, counts)
        };

        let filter_changed = self.synced_filter != filter;
        let visible_issues_changed = self.visible_issues != visible_issues;
        let counts_changed = self.counts != counts;

        if !filter_changed && !visible_issues_changed && !counts_changed {
            return;
        }

        self.item_sizes = Rc::new(vec![
            size(px(0.), px(ISSUE_ROW_HEIGHT));
            visible_issues.len()
        ]);

        self.synced_filter = filter;
        self.visible_issues = visible_issues;
        self.counts = counts;

        cx.notify();
    }

    /// Open the detail panel of `issue_id` in the dock area.
    fn open_issue_detail(
        &mut self,
        issue_id: EventId,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) {
        let Some(dock_area) = self.dock_area.upgrade() else {
            return;
        };

        let panel = cx.new(|cx| IssueDetailView::new(self.store.clone(), issue_id, window, cx));

        dock_area.update(cx, |dock_area, cx| {
            add_center_panel(dock_area, panel_handle(panel), window, cx);
        });
    }

    fn render_row(&self, ix: usize, issue_ix: usize, cx: &mut Context<Self>) -> AnyElement {
        let issue = &self.store.read(cx).issues[issue_ix];
        let title = activity_subject(issue);
        let id_hex = issue.id.to_hex();
        let profile = ProfileStore::global(cx).read(cx).get(&issue.pubkey);
        let author = profile.name();
        let picture = profile.picture();
        let age = relative_time(issue.created_at);
        let status = self.store.read(cx).status_of(issue);
        let issue_id = issue.id;

        h_flex()
            .id(ix)
            .w_full()
            .gap_4()
            .px_4()
            .py_2()
            .border_b_1()
            .border_color(cx.theme().border)
            .items_start()
            .on_click(cx.listener(move |this, _event, window, cx| {
                this.open_issue_detail(issue_id, window, cx);
            }))
            .child(status_badge(status, cx))
            .child(
                v_flex()
                    .flex_1()
                    .child(
                        div()
                            .h_8()
                            .min_w_0()
                            .text_ellipsis()
                            .whitespace_nowrap()
                            .line_clamp(1)
                            .text_sm()
                            .child(title),
                    )
                    .child(
                        h_flex()
                            .h_6()
                            .gap_2()
                            .text_xs()
                            .child(
                                h_flex()
                                    .gap_1()
                                    .child(UserAvatar::new(author.clone()).picture(picture))
                                    .child(div().child(author)),
                            )
                            .child(SharedString::from("opened"))
                            .child(
                                div()
                                    .text_color(cx.theme().muted_foreground)
                                    .child(SharedString::from(&id_hex[..8])),
                            )
                            .child(SharedString::from(age)),
                    ),
            )
            .hover(|this| this.bg(cx.theme().list_hover))
            .into_any_element()
    }

    fn render_header(&self, cx: &mut Context<Self>) -> AnyElement {
        let (total, open, closed) = self.counts;

        h_flex()
            .px_4()
            .w_full()
            .gap_3()
            .border_b_1()
            .border_color(cx.theme().border)
            .bg(cx.theme().muted.opacity(0.5))
            .child(
                h_flex()
                    .h_12()
                    .gap_2()
                    .child(
                        SegmentButton::new("all", "All")
                            .icon(Icon::new(CustomIconName::GitIssueDone))
                            .count(total)
                            .selected(self.filter == IssueFilter::All)
                            .on_click(cx.listener(|this, _event, _window, cx| {
                                this.filter = IssueFilter::All;
                                this.rebuild(cx);
                            })),
                    )
                    .child(
                        SegmentButton::new("open", "Open")
                            .icon(Icon::new(CustomIconName::GitIssueOpen))
                            .count(open)
                            .selected(self.filter == IssueFilter::Open)
                            .on_click(cx.listener(|this, _event, _window, cx| {
                                this.filter = IssueFilter::Open;
                                this.rebuild(cx);
                            })),
                    )
                    .child(
                        SegmentButton::new("closed", "Closed")
                            .icon(Icon::new(CustomIconName::GitIssueClosed))
                            .count(closed)
                            .selected(self.filter == IssueFilter::Closed)
                            .on_click(cx.listener(|this, _event, _window, cx| {
                                this.filter = IssueFilter::Closed;
                                this.rebuild(cx);
                            })),
                    ),
            )
            .child(div().flex_1())
            .child(
                SegmentButton::new("new", "New issue")
                    .icon(Icon::new(CustomIconName::CirclePlus))
                    .primary()
                    .on_click(cx.listener(|this, _event, window, cx| {
                        open_new_issue_dialog(this.store.clone(), window, cx);
                    })),
            )
            .into_any_element()
    }
}

pub(super) fn open_new_issue_dialog(store: Entity<RepoStore>, window: &mut Window, cx: &mut App) {
    let subject = cx.new(|cx| InputState::new(window, cx).placeholder("Issue title"));
    let content = cx.new(|cx| TextareaState::new(window, cx).placeholder("Describe the issue..."));

    window.open_dialog(cx, move |dialog, _window, _cx| {
        let subject = subject.clone();
        let content = content.clone();
        let store = store.clone();

        dialog
            .keyboard(true)
            .close_button(true)
            .content(move |body, _window, _cx| {
                body.child(
                    DialogHeader::new()
                        .child(DialogTitle::new().child("New issue"))
                        .child(
                            DialogDescription::new()
                                .child("Report a bug, ask a question, or propose a change."),
                        ),
                )
                .child(
                    v_form()
                        .child(
                            field()
                                .label("Title")
                                .required(true)
                                .child(Input::new(&subject)),
                        )
                        .child(
                            field()
                                .label("Content")
                                .child(Textarea::new(&content).h(px(160.))),
                        ),
                )
                .child(
                    DialogFooter::new().justify_end().child(
                        Button::new("submit")
                            .primary()
                            .label("Create issue")
                            .tooltip("Create issue")
                            .on_click({
                                let subject = subject.clone();
                                let content = content.clone();
                                let store = store.clone();

                                move |_event, window, cx| {
                                    let subject = subject.read(cx).value().to_string();
                                    let content = content.read(cx).value().to_string();
                                    let subject = (!subject.is_empty()).then_some(subject);

                                    store.update(cx, |store, cx| {
                                        store.open_issue(subject, content, cx);
                                    });

                                    window.close_dialog(cx);
                                }
                            }),
                    ),
                )
            })
    });
}

impl BasePanel for IssuesView {
    fn panel_name(&self) -> &'static str {
        "issues"
    }
}

impl Panel for IssuesView {
    fn title(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
        div().child(SharedString::from(format!("{}/issues", self.repo_name)))
    }
}

impl EventEmitter<PanelEvent> for IssuesView {}

impl Focusable for IssuesView {
    fn focus_handle(&self, _cx: &App) -> FocusHandle {
        self.focus_handle.clone()
    }
}

impl Render for IssuesView {
    fn render(&mut self, _window: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
        let filter = self.filter;
        let count = self.visible_issues.len();
        let sizes = self.item_sizes.clone();
        let scroll_handle = self.scroll_handle.clone();

        v_flex()
            .size_full()
            .image_cache(gpui::retain_all("issues"))
            .child(self.render_header(cx))
            .child(
                v_flex()
                    .relative()
                    .flex_1()
                    .min_h_0()
                    .w_full()
                    .when(count > 0, |this| {
                        this.child(
                            v_virtual_list(
                                cx.entity().clone(),
                                "issues",
                                sizes,
                                move |this, range, _window, cx| {
                                    range
                                        .map(|ix| {
                                            let issue = this.visible_issues[ix];
                                            this.render_row(ix, issue, cx)
                                        })
                                        .collect()
                                },
                            )
                            .track_scroll(&scroll_handle)
                            .size_full(),
                        )
                        .child(
                            div()
                                .absolute()
                                .top_0()
                                .left_0()
                                .right_0()
                                .bottom_0()
                                .child(Scrollbar::vertical(&scroll_handle)),
                        )
                    })
                    .when(count == 0, |this| {
                        let message = match filter {
                            IssueFilter::All => "No issues",
                            IssueFilter::Open => "No open issues",
                            IssueFilter::Closed => "No closed issues",
                        };
                        this.child(placeholder(message, cx))
                    }),
            )
            .into_any_element()
    }
}