const std = @import("std");
const builtin = @import("builtin");
const dvui = @import("dvui");
const Document = @import("models/Document.zig");
const RenderEngine = @import("render/RenderEngine.zig").RenderEngine;
const basic_models = @import("models/basic_models.zig");
const Rect_i = basic_models.Rect_i;
const Size_i = basic_models.Size_i;
const Point2_f = @import("models/basic_models.zig").Point2_f;
const Color = dvui.Color;
const tools = @import("tools.zig");
const Toolbar = @import("Toolbar.zig");
const random_document = @import("random_document.zig");
const Canvas = @This();

allocator: std.mem.Allocator,
document: *Document,
render_engine: RenderEngine,
toolbar: Toolbar,
texture: ?dvui.Texture = null,
pos: dvui.Point = dvui.Point{ .x = 400, .y = 400 },
scroll: dvui.ScrollInfo = .{
    .vertical = .auto,
    .horizontal = .auto,
},
native_scaling: bool = true,
redraw_throttle_ms: u32 = 50,
_visible_rect: ?Rect_i = null,
_zoom: f32 = 1,
_redraw_pending: bool = false,
_last_redraw_time_ms: i64 = 0,
cursor_document_point: ?Point2_f = null,
draw_document: bool = true,
/// Rect тулбара (из предыдущего кадра) для исключения кликов по нему из handleCanvasMouse.
toolbar_rect_scale: ?dvui.RectScale = null,

pub fn init(allocator: std.mem.Allocator, document: *Document, engine: RenderEngine) Canvas {
    return .{
        .allocator = allocator,
        .document = document,
        .render_engine = engine,
        .toolbar = Toolbar.init(&tools.default_tools),
    };
}

pub fn deinit(self: *Canvas) void {
    self.toolbar.deinit();
    if (self.texture) |texture| {
        dvui.Texture.destroyLater(texture);
        self.texture = null;
    }
}

fn redraw(self: *Canvas) !void {
    const full = self.getZoomedImageSize();

    const vis: Rect_i = self._visible_rect orelse Rect_i{ .x = 0, .y = 0, .w = 0, .h = 0 };

    if (vis.w == 0 or vis.h == 0) {
        if (self.texture) |tex| {
            dvui.Texture.destroyLater(tex);
            self.texture = null;
        }
        return;
    }

    const canvas_size: Size_i = .{ .w = full.w, .h = full.h };
    const new_texture = if (self.draw_document)
        self.render_engine.render(self.document, canvas_size, vis) catch null
    else
        self.render_engine.example(canvas_size, vis) catch null;

    if (new_texture) |tex| {
        if (self.texture) |old_tex| {
            dvui.Texture.destroyLater(old_tex);
        }

        self.texture = tex;
    }
    self._last_redraw_time_ms = std.time.milliTimestamp();
}

pub fn exampleReset(self: *Canvas) !void {
    self.render_engine.exampleReset();
    try self.redraw();
}

pub fn addRandomShapes(self: *Canvas) !void {
    try random_document.addRandomShapes(self.document, std.crypto.random);
    self.requestRedraw();
}

pub fn setZoom(self: *Canvas, value: f32) void {
    self._zoom = @max(value, 0.01);
}

pub fn addZoom(self: *Canvas, value: f32) void {
    self._zoom += value;
    self._zoom = @max(self._zoom, 0.01);
}

pub fn getZoom(self: Canvas) f32 {
    return self._zoom;
}

pub fn requestRedraw(self: *Canvas) void {
    self._redraw_pending = true;
}

pub fn processPendingRedraw(self: *Canvas) !void {
    if (!self._redraw_pending) return;
    if (self.redraw_throttle_ms == 0) {
        self._redraw_pending = false;
        try self.redraw();
        return;
    }
    const now_ms = std.time.milliTimestamp();
    const elapsed: i64 = if (self._last_redraw_time_ms == 0) self.redraw_throttle_ms else now_ms - self._last_redraw_time_ms;
    if (elapsed < @as(i64, @intCast(self.redraw_throttle_ms))) return;
    self._redraw_pending = false;
    try self.redraw();
}

pub fn getZoomedImageSize(self: Canvas) Rect_i {
    const doc = self.document;
    return .{
        .x = @intFromFloat(self.pos.x),
        .y = @intFromFloat(self.pos.y),
        .w = @intFromFloat(doc.size.w * self._zoom),
        .h = @intFromFloat(doc.size.h * self._zoom),
    };
}

/// Точка контента -> координаты документа.
pub fn contentPointToDocument(self: Canvas, content_point: dvui.Point, natural_scale: f32) Point2_f {
    const img = self.getZoomedImageSize();
    const px_x = content_point.x * natural_scale - @as(f32, @floatFromInt(img.x));
    const px_y = content_point.y * natural_scale - @as(f32, @floatFromInt(img.y));
    return .{
        .x = px_x / self._zoom,
        .y = px_y / self._zoom,
    };
}

/// Точка контента внутри холста.
pub fn isContentPointOnDocument(self: Canvas, content_point: dvui.Point, natural_scale: f32) bool {
    const img = self.getZoomedImageSize();
    const left_n = @as(f32, @floatFromInt(img.x)) / natural_scale;
    const top_n = @as(f32, @floatFromInt(img.y)) / natural_scale;
    const right_n = @as(f32, @floatFromInt(img.x + img.w)) / natural_scale;
    const bottom_n = @as(f32, @floatFromInt(img.y + img.h)) / natural_scale;
    return content_point.x >= left_n and content_point.x < right_n and
        content_point.y >= top_n and content_point.y < bottom_n;
}

pub fn updateVisibleImageRect(self: *Canvas, viewport: dvui.Rect, scroll_offset: dvui.Point) bool {
    const next = computeVisibleImageRect(self.*, viewport, scroll_offset);
    var changed = false;
    if (self._visible_rect) |vis| {
        changed |= next.x != vis.x or next.y != vis.y or next.w != vis.w or next.h != vis.h;
    }
    self._visible_rect = next;
    if (changed or self.texture == null) {
        return true;
    }
    return false;
}

fn computeVisibleImageRect(self: Canvas, viewport: dvui.Rect, scroll_offset: dvui.Point) Rect_i {
    const image_rect = self.getZoomedImageSize();

    const img_w: u32 = image_rect.w;
    const img_h: u32 = image_rect.h;

    const vis_w: u32 = @min(@as(u32, @intFromFloat(viewport.w)), img_w);
    const vis_h: u32 = @min(@as(u32, @intFromFloat(viewport.h)), img_h);

    const raw_x: i64 = @intFromFloat(scroll_offset.x - @as(f32, @floatFromInt(image_rect.x)));
    const raw_y: i64 = @intFromFloat(scroll_offset.y - @as(f32, @floatFromInt(image_rect.y)));

    const vis_x: u32 = @intCast(std.math.clamp(raw_x, 0, @as(i64, img_w) - @as(i64, vis_w)));
    const vis_y: u32 = @intCast(std.math.clamp(raw_y, 0, @as(i64, img_h) - @as(i64, vis_h)));

    return Rect_i{
        .x = vis_x,
        .y = vis_y,
        .w = vis_w,
        .h = vis_h,
    };
}