//! The application window: a vertical tab strip down the left side and the
//! active terminal filling the rest.
//!
//! The layout follows Zen Browser's vertical tabs — a persistent sidebar
//! column holding the window controls, a "New Tab" affordance, and one row
//! per tab, with the content pane inset to its right.

const std = @import("std");
const adw = @import("adw");
const gdk = @import("gdk");
const gio = @import("gio");
const glib = @import("glib");
const gobject = @import("gobject");
const gtk = @import("gtk");
const vt = @import("ghostty-vt");

const View = @import("View.zig");

const Window = @This();

const sidebar_width = 220;

alloc: std.mem.Allocator,
window: *adw.ApplicationWindow,

/// Holds one page per tab; the visible page is the active terminal.
stack: *gtk.Stack,

/// One row per tab, in the same order as `tabs`.
list: *gtk.ListBox,

tabs: std.ArrayListUnmanaged(*Tab) = .empty,

/// Monotonic counter so every tab gets a distinct GtkStack page name.
next_id: u32 = 0,

/// Set while we're programmatically changing the selection, so that the
/// resulting `row-selected` signal doesn't recurse.
updating: bool = false,

/// Set once teardown has begun, so that a session exiting mid-teardown
/// doesn't try to close a tab we're already destroying.
closing: bool = false,

/// A single tab: a view of one or more terminals, plus the sidebar row that
/// selects it.
const Tab = struct {
    window: *Window,
    view: *View,
    row: *gtk.ListBoxRow,
    label: *gtk.Label,
    name: [16]u8,
    name_len: usize,

    fn pageName(self: *const Tab) [:0]const u8 {
        return self.name[0..self.name_len :0];
    }
};

pub fn create(alloc: std.mem.Allocator, app: *adw.Application) !*Window {
    const self = try alloc.create(Window);
    errdefer alloc.destroy(self);

    const window = adw.ApplicationWindow.new(app.as(gtk.Application));
    window.as(gtk.Window).setTitle("vtabs");
    window.as(gtk.Window).setDefaultSize(1100, 720);

    self.* = .{
        .alloc = alloc,
        .window = window,
        .stack = gtk.Stack.new(),
        .list = gtk.ListBox.new(),
    };

    window.as(gtk.Widget).addCssClass("vtabs-window");

    // ---- sidebar -------------------------------------------------------
    const sidebar = gtk.Box.new(.vertical, 0);
    sidebar.as(gtk.Widget).addCssClass("vtabs-sidebar");
    sidebar.as(gtk.Widget).setSizeRequest(sidebar_width, -1);

    // The header bar lives inside the sidebar rather than spanning the
    // window, which is what gives the Zen-style look. It also carries the
    // window controls, which we still need since GTK draws its own
    // decorations on Wayland.
    const header = adw.HeaderBar.new();
    header.setShowTitle(0);
    header.as(gtk.Widget).addCssClass("flat");

    const new_tab_button = gtk.Button.newFromIconName("tab-new-symbolic");
    new_tab_button.as(gtk.Widget).setTooltipText("New tab (Ctrl+Shift+T)");
    _ = gtk.Button.signals.clicked.connect(
        new_tab_button,
        *Window,
        &onNewTabClicked,
        self,
        .{},
    );
    header.packEnd(new_tab_button.as(gtk.Widget));
    sidebar.append(header.as(gtk.Widget));

    self.list.setSelectionMode(.single);
    self.list.as(gtk.Widget).addCssClass("navigation-sidebar");
    self.list.as(gtk.Widget).addCssClass("vtabs-list");
    _ = gtk.ListBox.signals.row_selected.connect(
        self.list,
        *Window,
        &onRowSelected,
        self,
        .{},
    );

    const scroller = gtk.ScrolledWindow.new();
    scroller.setPolicy(.never, .automatic);
    scroller.as(gtk.Widget).setVexpand(1);
    scroller.setChild(self.list.as(gtk.Widget));
    sidebar.append(scroller.as(gtk.Widget));

    // ---- content -------------------------------------------------------
    self.stack.as(gtk.Widget).setHexpand(1);
    self.stack.as(gtk.Widget).setVexpand(1);
    self.stack.as(gtk.Widget).addCssClass("vtabs-content");

    const content = gtk.Box.new(.horizontal, 0);
    content.append(sidebar.as(gtk.Widget));
    content.append(self.stack.as(gtk.Widget));

    window.setContent(content.as(gtk.Widget));

    // Window-level shortcuts run in the capture phase so they are handled
    // before the focused terminal turns the key into a VT sequence.
    const shortcuts = gtk.EventControllerKey.new();
    shortcuts.as(gtk.EventController).setPropagationPhase(.capture);
    _ = gtk.EventControllerKey.signals.key_pressed.connect(
        shortcuts,
        *Window,
        &onShortcut,
        self,
        .{},
    );
    window.as(gtk.Widget).addController(shortcuts.as(gtk.EventController));

    // Free our own state once GTK is done with the window. Doing this on
    // `destroy` rather than `close-request` means no further events can
    // arrive for widgets whose user data we're about to free.
    _ = gtk.Widget.signals.destroy.connect(
        window,
        *Window,
        &onDestroy,
        self,
        .{},
    );

    try self.newTab();
    return self;
}

pub fn present(self: *Window) void {
    self.window.as(gtk.Window).present();

    // Focus has to be grabbed after the window is presented. Calling
    // grabFocus during construction silently does nothing because the
    // widget is not yet realized, which would send the first keystroke to
    // the sidebar instead of the terminal.
    if (self.activeTab()) |tab| tab.view.focus();
}

/// Open a new tab and switch to it.
pub fn newTab(self: *Window) !void {
    const tab = try self.alloc.create(Tab);
    errdefer self.alloc.destroy(tab);

    const view = try View.create(self.alloc, .{
        .on_empty = &onViewEmpty,
        .on_title = &onViewTitle,
        .ctx = tab,
    });
    errdefer view.destroy();

    const id = self.next_id;
    self.next_id += 1;

    tab.* = .{
        .window = self,
        .view = view,
        .row = gtk.ListBoxRow.new(),
        .label = gtk.Label.new("shell"),
        .name = undefined,
        .name_len = 0,
    };
    const printed = std.fmt.bufPrintZ(&tab.name, "tab{d}", .{id}) catch unreachable;
    tab.name_len = printed.len;

    // ---- sidebar row ---------------------------------------------------
    const row_box = gtk.Box.new(.horizontal, 6);
    row_box.as(gtk.Widget).addCssClass("vtabs-row");

    const icon = gtk.Image.newFromIconName("utilities-terminal-symbolic");
    row_box.append(icon.as(gtk.Widget));

    tab.label.setXalign(0);
    tab.label.setEllipsize(.end);
    tab.label.as(gtk.Widget).setHexpand(1);
    row_box.append(tab.label.as(gtk.Widget));

    const close = gtk.Button.newFromIconName("window-close-symbolic");
    close.as(gtk.Widget).addCssClass("flat");
    close.as(gtk.Widget).addCssClass("vtabs-close");
    _ = gtk.Button.signals.clicked.connect(close, *Tab, &onCloseClicked, tab, .{});
    row_box.append(close.as(gtk.Widget));

    tab.row.setChild(row_box.as(gtk.Widget));
    self.list.append(tab.row.as(gtk.Widget));

    _ = self.stack.addNamed(view.widget(), tab.pageName());

    try self.tabs.append(self.alloc, tab);

    // Only now is `tab` complete enough for the view's callbacks to use, so
    // this is the first safe moment to give the view its terminal.
    try view.addPane();

    self.refreshLabel(tab);
    self.select(tab);
}

/// Make `tab` the visible one.
fn select(self: *Window, tab: *Tab) void {
    self.updating = true;
    defer self.updating = false;

    self.stack.setVisibleChildName(tab.pageName());
    self.list.selectRow(tab.row);
    tab.view.focus();
}

fn indexOf(self: *Window, tab: *Tab) ?usize {
    for (self.tabs.items, 0..) |t, i| if (t == tab) return i;
    return null;
}

/// Close a tab, and the window along with it if it was the last one.
fn closeTab(self: *Window, tab: *Tab) void {
    if (self.closing) return;
    const index = self.indexOf(tab) orelse return;

    self.stack.remove(tab.view.widget());
    self.list.remove(tab.row.as(gtk.Widget));
    _ = self.tabs.orderedRemove(index);

    tab.view.destroy();
    self.alloc.destroy(tab);

    if (self.tabs.items.len == 0) {
        // Teardown of our own state happens in onDestroy.
        self.window.as(gtk.Window).close();
        return;
    }

    // Prefer the tab that took the closed one's place, else the new last.
    const next = @min(index, self.tabs.items.len - 1);
    self.select(self.tabs.items[next]);
}

// -------------------------------------------------------------------------
// Signal handlers

fn onNewTabClicked(_: *gtk.Button, self: *Window) callconv(.c) void {
    self.newTab() catch |err| {
        std.log.err("failed to open tab: {s}", .{@errorName(err)});
    };
}

fn onCloseClicked(_: *gtk.Button, tab: *Tab) callconv(.c) void {
    tab.window.closeTab(tab);
}

fn onRowSelected(_: *gtk.ListBox, row: ?*gtk.ListBoxRow, self: *Window) callconv(.c) void {
    if (self.updating) return;
    const selected = row orelse return;
    for (self.tabs.items) |tab| {
        if (tab.row == selected) {
            self.select(tab);
            return;
        }
    }
}

/// Refresh a sidebar row from its view's current state.
fn refreshLabel(self: *Window, tab: *Tab) void {
    _ = self;

    // GTK needs a NUL-terminated string, and titles come from the terminal so
    // they can be any length; clamp to what a sidebar row can show.
    var scratch: [192]u8 = undefined;
    const text = tab.view.label(scratch[0 .. scratch.len - 1]);

    var buf: [192]u8 = undefined;
    @memcpy(buf[0..text.len], text);
    buf[text.len] = 0;

    tab.label.setText(buf[0..text.len :0]);
    tab.label.as(gtk.Widget).setTooltipText(buf[0..text.len :0]);
}

fn onViewTitle(ctx: ?*anyopaque) void {
    const tab: *Tab = @ptrCast(@alignCast(ctx.?));
    tab.window.refreshLabel(tab);
}

/// The view lost its last pane, so the tab goes with it.
fn onViewEmpty(ctx: ?*anyopaque) void {
    const tab: *Tab = @ptrCast(@alignCast(ctx.?));
    tab.window.closeTab(tab);
}

/// GTK has finished with the window: release everything we allocated.
fn onDestroy(_: *adw.ApplicationWindow, self: *Window) callconv(.c) void {
    if (self.closing) return;
    self.closing = true;

    // Each terminal owns a session, which owns a PTY and its child process.
    // Dropping them here reaps the children rather than orphaning them.
    for (self.tabs.items) |tab| {
        tab.view.destroy();
        self.alloc.destroy(tab);
    }
    self.tabs.deinit(self.alloc);
    self.alloc.destroy(self);
}

// -------------------------------------------------------------------------
// Shortcuts

/// The tab whose terminal is currently visible.
fn activeTab(self: *Window) ?*Tab {
    const name = self.stack.getVisibleChildName() orelse return null;
    const span = std.mem.span(name);
    for (self.tabs.items) |tab| {
        if (std.mem.eql(u8, tab.pageName(), span)) return tab;
    }
    return null;
}

fn selectIndex(self: *Window, index: usize) void {
    if (index >= self.tabs.items.len) return;
    self.select(self.tabs.items[index]);
}

/// Move the selection by `delta`, wrapping around the ends.
fn cycle(self: *Window, delta: isize) void {
    if (self.tabs.items.len == 0) return;
    const current = self.indexOf(self.activeTab() orelse return) orelse return;
    const len: isize = @intCast(self.tabs.items.len);
    const next = @mod(@as(isize, @intCast(current)) + delta + len, len);
    self.selectIndex(@intCast(next));
}

fn onShortcut(
    _: *gtk.EventControllerKey,
    keyval: c_uint,
    _: c_uint,
    state: gdk.ModifierType,
    self: *Window,
) callconv(.c) c_int {
    const ctrl = state.control_mask;
    const shift = state.shift_mask;
    const alt = state.alt_mask;

    if (ctrl and shift) {
        switch (keyval) {
            gdk.KEY_T, gdk.KEY_t => {
                self.newTab() catch |err| {
                    std.log.err("failed to open tab: {s}", .{@errorName(err)});
                };
                return 1;
            },
            gdk.KEY_W, gdk.KEY_w => {
                // Closes the focused terminal. The view raises on_empty when
                // its last pane goes, which is what closes the tab.
                if (self.activeTab()) |tab| {
                    if (tab.view.focusedPane()) |pane| tab.view.closePane(pane);
                }
                return 1;
            },
            gdk.KEY_E, gdk.KEY_e => {
                if (self.activeTab()) |tab| {
                    tab.view.addPane() catch |err| {
                        std.log.err("failed to open terminal: {s}", .{@errorName(err)});
                    };
                }
                return 1;
            },
            gdk.KEY_V, gdk.KEY_v => {
                self.paste();
                return 1;
            },
            else => {},
        }
    }

    // Ctrl+Shift+arrows rearrange the focused terminal within its view. This
    // is the keyboard route to the same rearranging that dragging a pane's
    // header does.
    if (ctrl and shift) {
        const side: ?View.Side = switch (keyval) {
            gdk.KEY_Left => .left,
            gdk.KEY_Right => .right,
            gdk.KEY_Up => .top,
            gdk.KEY_Down => .bottom,
            else => null,
        };
        if (side) |s| {
            if (self.activeTab()) |tab| tab.view.moveFocused(s);
            return 1;
        }
    }

    // Ctrl+PageUp/PageDown cycles tabs, matching most tabbed terminals.
    if (ctrl and !shift) {
        switch (keyval) {
            gdk.KEY_Page_Up => {
                self.cycle(-1);
                return 1;
            },
            gdk.KEY_Page_Down => {
                self.cycle(1);
                return 1;
            },
            else => {},
        }
    }

    // Alt+1..9 jumps straight to a tab; Alt+9 is "last tab" by convention.
    if (alt and !ctrl) {
        if (keyval >= gdk.KEY_1 and keyval <= gdk.KEY_9) {
            const n = keyval - gdk.KEY_1;
            if (n == 8) {
                self.selectIndex(self.tabs.items.len -| 1);
            } else {
                self.selectIndex(@intCast(n));
            }
            return 1;
        }
    }

    return 0;
}

// -------------------------------------------------------------------------
// Paste
//
// GTK4's clipboard API is asynchronous, so the read completes on a later
// main loop turn. We resolve the destination tab at completion time rather
// than capturing it, so closing a tab mid-paste can't leave a dangling
// pointer.

fn paste(self: *Window) void {
    const clipboard = self.window.as(gtk.Widget).getClipboard();
    clipboard.readTextAsync(null, &onPasteReady, self);
}

fn onPasteReady(
    source: ?*gobject.Object,
    result: *gio.AsyncResult,
    data: ?*anyopaque,
) callconv(.c) void {
    const self: *Window = @ptrCast(@alignCast(data.?));
    const clipboard: *gdk.Clipboard = @ptrCast(@alignCast(source.?));

    var err: ?*glib.Error = null;
    const text = clipboard.readTextFinish(result, &err) orelse {
        if (err) |e| {
            std.log.warn("paste failed: {s}", .{e.f_message orelse "unknown"});
            e.free();
        }
        return;
    };
    defer glib.free(text);

    const tab = self.activeTab() orelse return;
    const terminal = tab.view.focusedTerminal() orelse return;
    const session = terminal.session;
    // Coerce to a plain slice: encodePaste dispatches on the exact type.
    const span: []const u8 = std.mem.span(text);

    // Refuse pastes containing control characters that would execute on
    // arrival (a newline in unbracketed mode runs the command immediately).
    const opts: vt.input.PasteOptions = .fromTerminal(&session.term);
    if (!vt.input.isSafePaste(span)) {
        std.log.warn("refusing unsafe paste", .{});
        return;
    }

    const parts = vt.input.encodePaste(span, opts) catch |e| {
        std.log.warn("paste encode failed: {s}", .{@errorName(e)});
        return;
    };
    for (parts) |part| session.write(part);
}