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;
        }
    }
};

/// Spinner element implementation that runs a simple animation that requires
/// the continuous draw loop.
const Spinner = struct {
    counter: u8 = 0,
    index: u8 = 0,

    const map: [6]u21 = .{ '𜺎', '𜺍', '𜺇', '𜹯', '𜹿', '𜺋' };

    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 {
        const this: *@This() = @ptrCast(@alignCast(ctx));
        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));

        cells[size.x + 1].cp = map[this.index];

        this.counter += 1;
        if (this.counter >= 20) {
            this.index += 1;
            this.index %= 6;
            this.counter = 0;
        }
    }
};

const InputField = struct {
    allocator: std.mem.Allocator,
    input: std.ArrayList(u21),
    queue: *App.Queue,

    pub fn init(allocator: std.mem.Allocator, queue: *App.Queue) @This() {
        return .{
            .allocator = allocator,
            .input = std.ArrayList(u21).initCapacity(allocator, 8) catch unreachable,
            .queue = queue,
        };
    }

    pub fn deinit(this: *@This()) void {
        this.input.deinit(this.allocator);
    }

    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()) try this.input.append(this.allocator, key.cp);

                if (key.eql(.{ .cp = zterm.input.Enter }) or key.eql(.{ .cp = zterm.input.KpEnter }))
                    this.queue.push(.{ .accept = try this.input.toOwnedSlice(this.allocator) });

                if (key.eql(.{ .cp = zterm.input.Backspace }))
                    _ = this.input.pop();

                if (key.eql(.{ .cp = zterm.input.Delete }) or key.eql(.{ .cp = zterm.input.KpDelete }))
                    _ = this.input.pop();
            },
            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.input.items.len == 0) return;

        const row = 1;
        const col = 1;
        const anchor = (row * size.x) + col;

        for (this.input.items, 0..) |cp, idx| {
            cells[anchor + idx].style.fg = .black;
            cells[anchor + idx].style.cursor = false;
            cells[anchor + idx].cp = cp;

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

            if (idx == this.input.items.len - 1) cells[anchor + idx + 1].style.cursor = true;
        }
    }
};

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 input_field: InputField = .init(allocator, &app.queue);
    defer input_field.deinit();

    var quit_text: QuitText = .{};
    var spinner: Spinner = .{};

    var container = try App.Container.init(allocator, .{
        .rectangle = .{ .fill = .grey },
        .layout = .{
            .direction = .vertical,
            .padding = .all(5),
        },
    }, quit_text.element());
    defer container.deinit();

    try container.append(try App.Container.init(allocator, .{
        .rectangle = .{ .fill = .light_grey },
        .size = .{
            .grow = .horizontal,
            .dim = .{ .y = 10 },
        },
    }, input_field.element()));

    const nested_container: App.Container = try .init(allocator, .{
        .rectangle = .{ .fill = .light_grey },
    }, spinner.element());
    try container.append(nested_container);

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

    var framerate: u64 = 60;
    var tick_ms: u64 = @divFloor(time.ms_per_s, framerate);
    var next_frame_ms: u64 = 0;

    // draw loop
    draw: while (true) {
        const now_ms: u64 = @intCast(time.milliTimestamp());
        if (now_ms >= next_frame_ms) {
            next_frame_ms = now_ms + tick_ms;
        } else {
            std.Thread.sleep((next_frame_ms - now_ms) * time.ns_per_ms);
            next_frame_ms += tick_ms;
        }

        const len = blk: {
            app.queue.lock();
            defer app.queue.unlock();
            break :blk app.queue.len();
        };

        // handle events
        for (0..len) |_| {
            const event = app.queue.drain() orelse break;
            log.debug("handling event: {s}", .{@tagName(event)});
            // pre event handling
            switch (event) {
                .key => |key| {
                    log.debug("key {any}", .{key});
                    if (key.eql(.{ .cp = 'c', .mod = .{ .ctrl = true } })) app.quit();
                },
                .accept => |input| {
                    defer allocator.free(input);
                    var string = try allocator.alloc(u8, input.len);
                    defer allocator.free(string);
                    for (0.., input) |i, char| string[i] = @intCast(char);
                    log.debug("Accepted input '{s}'", .{string});
                },
                .err => |err| log.err("Received {s} with message: {s}", .{ @errorName(err.err), err.msg }),
                .focus => |b| {
                    // NOTE reduce framerate in case the window is not focused and restore again when focused
                    framerate = if (b) 60 else 15;
                    tick_ms = @divFloor(time.ms_per_s, framerate);
                },
                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 :draw,
                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 time = std.time;
const assert = std.debug.assert;
const zterm = @import("zterm");
const App = zterm.App(struct {}, union(enum) {
    accept: []u21,
});