import type { PanelExtent as Extent, PanelView, PanelPoint as Point } from "#types/panel.types";
import { PANEL_MAX_SCALE, PANEL_MIN_SCALE } from "#configuration/constants/panel.constants";

export const ORIGIN_VIEW: PanelView = { scale: 1, x: 0, y: 0 };

const HALF = 2;

const clamp = function clamp(value: number, low: number, high: number): number {
    return Math.min(Math.max(value, low), high);
};

export const extentOf = function extentOf(element: Element): Extent {
    const rect = element.getBoundingClientRect();
    return { height: rect.height, width: rect.width };
};

export const contentExtentOf = function contentExtentOf(stage: Element, scale: number): Extent {
    const rect = extentOf(stage);
    return { height: rect.height / scale, width: rect.width / scale };
};

export const boundedView = function boundedView(view: PanelView, viewport: Extent, content: Extent): PanelView {
    const spanX = viewport.width - content.width * view.scale;
    const spanY = viewport.height - content.height * view.scale;
    return {
        scale: view.scale,
        x: clamp(view.x, Math.min(0, spanX), Math.max(0, spanX)),
        y: clamp(view.y, Math.min(0, spanY), Math.max(0, spanY)),
    };
};

export const zoomedView = function zoomedView(view: PanelView, factor: number, anchor: Point): PanelView {
    const scale = clamp(view.scale * factor, PANEL_MIN_SCALE, PANEL_MAX_SCALE);
    const ratio = scale / view.scale;
    return { scale, x: anchor.x - (anchor.x - view.x) * ratio, y: anchor.y - (anchor.y - view.y) * ratio };
};

export const fittedView = function fittedView(viewport: Extent, content: Extent, ceiling = 1): PanelView {
    if (content.width === 0 || content.height === 0) {
        return ORIGIN_VIEW;
    }
    const scale = clamp(
        Math.min(viewport.width / content.width, viewport.height / content.height, ceiling),
        PANEL_MIN_SCALE,
        ceiling,
    );
    return {
        scale,
        x: (viewport.width - content.width * scale) / HALF,
        y: (viewport.height - content.height * scale) / HALF,
    };
};

export const centerOf = function centerOf(extent: Extent): Point {
    return { x: extent.width / HALF, y: extent.height / HALF };
};

export const distanceBetween = function distanceBetween(a: Point, b: Point): number {
    return Math.hypot(a.x - b.x, a.y - b.y);
};

export const midpointOf = function midpointOf(a: Point, b: Point): Point {
    return { x: (a.x + b.x) / HALF, y: (a.y + b.y) / HALF };
};