const QuitText = struct {
    const text = "Press ctrl+c to quit. Press ctrl+n to launch `vim`.";

    pub fn element(this: *@This()) App.Element {
        return .{ .ptr = this, .vtable = &.{ .content = content } };
    }

    pub fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
        _ = ctx;
        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));

        const y = 2;
        const x = size.x / 2 -| (text.len / 2);
        const anchor = (y * size.x) + x;

        for (text, 0..) |cp, idx| {
            cells[anchor + idx].style.fg = .white;
            cells[anchor + idx].style.bg = .black;
            cells[anchor + idx].cp = cp;

            // NOTE do not write over the contents of this `Container`'s `Size`
            if (anchor + idx == cells.len - 1) break;
        }
    }
};

pub fn main() !void {
    errdefer |err| log.err("Application Error: {any}", .{err});

    var gpa: std.heap.DebugAllocator(.{}) = .init;
    defer if (gpa.deinit() == .leak) log.err("memory leak", .{});

    const allocator = gpa.allocator();

    var app: App = .init(allocator, .{}, .{});
    var renderer = zterm.Renderer.Buffered.init(allocator);
    defer renderer.deinit();

    var quit_text: QuitText = .{};

    // TODO what should the demo application do?
    // - some sort of chat? -> write messages and have them displayed in a scrollable array at the right hand side?
    // - on the left some buttons?
    var box = try App.Container.init(allocator, .{
        .border = .{
            .color = .blue,
            .sides = .all,
        },
        .layout = .{
            .gap = 1,
            .padding = .vertical(2),
            .direction = .vertical,
        },
        .size = .{
            .dim = .{ .y = 90 },
        },
    }, .{});
    try box.append(try App.Container.init(allocator, .{
        .rectangle = .{ .fill = .lightgreen },
    }, .{}));
    try box.append(try App.Container.init(allocator, .{
        .rectangle = .{ .fill = .lightgreen },
    }, .{}));
    try box.append(try App.Container.init(allocator, .{
        .rectangle = .{ .fill = .lightgreen },
    }, .{}));

    var scrollable: App.Scrollable = .init(box, .disabled);

    var container = try App.Container.init(allocator, .{
        .layout = .{
            .gap = 2,
            .separator = .{ .enabled = true },
            .padding = .{ .top = 5, .bottom = 3, .left = 3, .right = 3 },
            .direction = .horizontal,
        },
    }, quit_text.element());
    try container.append(try App.Container.init(allocator, .{}, scrollable.element()));

    var nested_container: App.Container = try .init(allocator, .{
        .layout = .{
            .direction = .vertical,
            .separator = .{
                .enabled = true,
            },
        },
    }, .{});
    var inner_container: App.Container = try .init(allocator, .{
        .layout = .{
            .direction = .vertical,
        },
        .border = .{
            .color = .lightblue,
            .sides = .all,
        },
    }, .{});
    try inner_container.append(try .init(allocator, .{
        .rectangle = .{
            .fill = .blue,
        },
        .size = .{
            .grow = .horizontal,
            .dim = .{ .y = 5 },
        },
    }, .{}));
    try inner_container.append(try .init(allocator, .{
        .rectangle = .{
            .fill = .red,
        },
        .size = .{
            .grow = .horizontal,
            .dim = .{ .y = 5 },
        },
    }, .{}));
    try inner_container.append(try .init(allocator, .{
        .rectangle = .{
            .fill = .green,
        },
    }, .{}));
    try nested_container.append(inner_container);
    try nested_container.append(try .init(allocator, .{
        .size = .{
            .grow = .horizontal,
            .dim = .{ .y = 1 },
        },
    }, .{}));
    try container.append(nested_container);
    try container.append(try App.Container.init(allocator, .{
        .rectangle = .{ .fill = .blue },
        .size = .{
            .dim = .{ .x = 30 },
        },
    }, .{}));
    defer container.deinit(); // also de-initializes the children

    try app.start(.full);
    defer app.stop() catch |err| log.err("Failed to stop application: {any}", .{err});

    // event loop
    while (true) {
        const event = app.nextEvent();
        log.debug("received event: {s}", .{@tagName(event)});

        // pre event handling
        switch (event) {
            .key => |key| {
                if (key.eql(.{ .cp = 'c', .mod = .{ .ctrl = true } })) app.quit();

                if (key.eql(.{ .cp = 'n', .mod = .{ .ctrl = true } })) {
                    try app.interrupt();
                    renderer.size = .{}; // reset size, such that next resize will cause a full re-draw!
                    defer app.start(.full) catch @panic("could not start app event loop");
                    var child = std.process.Child.init(&.{"vim"}, allocator);
                    _ = child.spawnAndWait() catch |err| app.postEvent(.{
                        .err = .{
                            .err = err,
                            .msg = "Spawning $EDITOR failed",
                        },
                    });
                    continue;
                }
            },
            // NOTE errors could be displayed in another container in case one was received, etc. to provide the user with feedback
            .err => |err| log.err("Received {s} with message: {s}", .{ @errorName(err.err), err.msg }),
            else => {},
        }

        // NOTE returned errors should be propagated back to the application
        container.handle(&app.model, event) catch |err| app.postEvent(.{
            .err = .{
                .err = err,
                .msg = "Container Event handling failed",
            },
        });

        // post event handling
        switch (event) {
            .quit => break,
            else => {},
        }

        container.resize(&app.model, try renderer.resize());
        container.reposition(&app.model, .{});
        try renderer.render(@TypeOf(container), &container, App.Model, &app.model);
        try renderer.flush();
    }
}

pub const panic = App.panic_handler;
const log = std.log.scoped(.default);

const std = @import("std");
const assert = std.debug.assert;
const zterm = @import("zterm");
const input = zterm.input;
const App = zterm.App(struct {}, union(enum) {});