image-studio/commands/transform.ts

import type { Rect, Vec2D } from "@core/geometry";
import { applyTransformTargetBounds } from "./transform-document";
import type { TransformHandle, TransformTarget } from "@editor/transform";
import type { Command } from "./command";
import { commandIds } from "./ids";

export type TransformBeginPayload = {
  target: TransformTarget;
  handle: TransformHandle;
  point: Vec2D;
  initialBounds: Rect;
};

export type TransformUpdatePayload = {
  point: Vec2D;
  shiftKey?: boolean;
};

export type TransformSetBoundsPayload = {
  target: TransformTarget;
  bounds: Rect;
};

export const transformBeginCommand: Command<TransformBeginPayload> = {
  id: commandIds.transformBegin,
  name: "Begin transform",
  history: { mode: "deferred", phase: "begin" },
  execute({ state }, payload) {
    return {
      ...state,
      editor: {
        ...state.editor,
        transformSession: {
          target: payload.target,
          handle: payload.handle,
          startPoint: payload.point,
          initialBounds: payload.initialBounds,
        },
      },
    };
  },
};

export const transformUpdateCommand: Command<TransformUpdatePayload> = {
  id: commandIds.transformUpdate,
  name: "Update transform",
  history: { mode: "deferred", phase: "update" },
  execute({ state }, payload) {
    const session = state.editor.transformSession;
    if (!session) return state;

    const nextBounds = transformBounds(
      session.initialBounds,
      session.handle,
      {
        x: payload.point.x - session.startPoint.x,
        y: payload.point.y - session.startPoint.y,
      },
      payload.shiftKey === true,
    );

    return {
      ...state,
      document: applyTransformTargetBounds(state.document, session.target, nextBounds),
    };
  },
};

export const transformSetBoundsCommand: Command<TransformSetBoundsPayload> = {
  id: commandIds.transformSetBounds,
  name: "Set transform bounds",
  execute({ state }, payload) {
    return {
      ...state,
      document: applyTransformTargetBounds(state.document, payload.target, normalizeRect(payload.bounds)),
    };
  },
};

export const transformEndCommand: Command = {
  id: commandIds.transformEnd,
  name: "End transform",
  history: { mode: "deferred", phase: "commit" },
  execute({ state }) {
    if (!state.editor.transformSession) return state;

    return {
      ...state,
      editor: {
        ...state.editor,
        transformSession: undefined,
      },
    };
  },
};

export const transformCommands = [transformBeginCommand, transformUpdateCommand, transformSetBoundsCommand, transformEndCommand] satisfies Command<unknown>[];

function transformBounds(bounds: Rect, handle: TransformHandle, delta: Vec2D, constrained = false): Rect {
  if (handle === "body") {
    const constrainedDelta = constrained ? constrainMoveDelta(delta) : delta;
    return { ...bounds, x: bounds.x + constrainedDelta.x, y: bounds.y + constrainedDelta.y };
  }

  let x = bounds.x;
  let y = bounds.y;
  let w = bounds.w;
  let h = bounds.h;

  if (handle.includes("w")) {
    x = bounds.x + delta.x;
    w = bounds.w - delta.x;
  }
  if (handle.includes("e")) w = bounds.w + delta.x;
  if (handle.includes("n")) {
    y = bounds.y + delta.y;
    h = bounds.h - delta.y;
  }
  if (handle.includes("s")) h = bounds.h + delta.y;

  const resized = normalizeRect({ x, y, w, h });
  if (!constrained || !isCornerHandle(handle)) return resized;

  return proportionalCornerResize(bounds, handle, resized);
}

function constrainMoveDelta(delta: Vec2D): Vec2D {
  return Math.abs(delta.x) >= Math.abs(delta.y) ? { x: delta.x, y: 0 } : { x: 0, y: delta.y };
}

function isCornerHandle(handle: TransformHandle) {
  return handle.length === 2;
}

function proportionalCornerResize(initial: Rect, handle: TransformHandle, resized: Rect): Rect {
  const aspectRatio = initial.w / initial.h;
  const widthScale = resized.w / initial.w;
  const heightScale = resized.h / initial.h;
  const scale = Math.abs(widthScale - 1) >= Math.abs(heightScale - 1) ? widthScale : heightScale;
  const w = Math.max(1, initial.w * scale);
  const h = Math.max(1, w / aspectRatio);
  const x = handle.includes("w") ? initial.x + initial.w - w : initial.x;
  const y = handle.includes("n") ? initial.y + initial.h - h : initial.y;

  return { x, y, w, h };
}

function normalizeRect(rect: Rect): Rect {
  const minSize = 1;
  return {
    x: rect.w < minSize ? rect.x + rect.w - minSize : rect.x,
    y: rect.h < minSize ? rect.y + rect.h - minSize : rect.y,
    w: Math.max(minSize, rect.w),
    h: Math.max(minSize, rect.h),
  };
}