const QuitText = struct {
    const text = "Press ctrl+c to quit.";

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

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

        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;
        }
    }
};

const InfoText = struct {
    const text = "Press any key; Non-Ascii inputs (i.e. `Enter` or `Backspace`) to trigger an exception";

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

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

        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;
        }
    }
};

const ErrorNotification = struct {
    msg: ?[]const u8 = null,

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

    fn handle(ctx: *anyopaque, _: *App.Model, event: App.Event) !void {
        const this: *@This() = @ptrCast(@alignCast(ctx));
        switch (event) {
            .key => |key| if (!key.isAscii()) return zterm.Error.TooSmall,
            .err => |err| this.msg = err.msg,
            else => {},
        }
    }

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

        if (this.msg) |msg| {
            const row = size.y -| 2;
            const col = size.x -| 2 -| msg.len;
            const anchor = (row * size.x) + col;

            for (msg, 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;
            }

            this.msg = null;
        }
    }
};

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 threaded_io: std.Io.Threaded = .init(allocator);
    defer threaded_io.deinit();

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

    var quit_text: QuitText = .{};
    var info_text: InfoText = .{};
    var error_notification: ErrorNotification = .{};

    var container = try App.Container.init(allocator, .{
        .layout = .{
            .gap = 2,
            .padding = .{ .top = 5, .bottom = 3, .left = 3, .right = 3 },
        },
    }, quit_text.element());
    defer container.deinit();

    try container.append(try App.Container.init(allocator, .{}, info_text.element()));
    try container.append(try App.Container.init(allocator, .{}, error_notification.element()));

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

    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(),
            .err => |err| log.err("Received {s} with message: {s}", .{ @errorName(err.err), err.msg }),
            else => {},
        }

        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(try renderer.resize());
        container.reposition(.{});
        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 App = zterm.App(struct {}, union(enum) {});