# All files createHorizontalPosition.ts

100% Statements 330/330
100% Branches 61/61
100% Functions 7/7
100% Lines 330/330

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     import type { XCoordConfig } from "./utils.js";
    import {
      getCenterXCoord,
      getInnerLeftCoord,
      getInnerRightCoord,
      getLeftCoord,
      getRightCoord,
    } from "./utils.js";
    import type { FixedPositionOptions, HorizontalPosition } from "./types.js";

    /**
     * @internal
     */
    interface XPosition {
      left: number;
      right?: number;
      width?: number;
      minWidth?: number;
      actualX: HorizontalPosition;
    }

    /**
     * @internal
     */
    export interface FixConfig extends XCoordConfig {
      vwMargin: number;
      screenRight: number;
      disableSwapping: boolean;
    }

    /**
     * @internal
     */
    export interface CreateHorizontalPositionOptions
      extends Required<
        Pick<
          FixedPositionOptions,
          "vwMargin" | "xMargin" | "width" | "disableSwapping"
        >
      > {
      x: HorizontalPosition;
      vw: number;
      elWidth: number;
      initialX?: number;
      containerRect: DOMRect;
    }

    /**
     * Attempts to position the fixed element so that it will appear to the left of
     * the container element but also within the viewport boundaries. When swapping
     * is enabled, it will attempt to swap to the right position if it can't fit
     * within the viewport to the left. If it can't fit in the viewport even after
     * being swapped to the right or swapping is disabled, it will be positioned to
     * the viewport left boundary.
     *
     * @internal
     */
    export function createAnchoredLeft(config: FixConfig): XPosition {
      const { vwMargin, screenRight, elWidth, disableSwapping } = config;

      let left = getLeftCoord(config);
      let actualX: HorizontalPosition = "left";
      if (left >= vwMargin) {
        return { actualX, left };
      }

      const swappedLeft = getRightCoord(config);
      if (disableSwapping || swappedLeft + elWidth > screenRight) {
        left = vwMargin;
      } else {
        left = swappedLeft;
        actualX = "right";
      }

      return { actualX, left };
    }

    /**
     * Attempts to position the fixed element so that it will appear to the
     * inner-left of the container element but also within the viewport boundaries.
     * When swapping is enabled, it will attempt to swap to the right position if it
     * can't fit within the viewport to the left. If it can't fit in the viewport
     * even after being swapped to the right or swapping is disabled, it will be
     * positioned to the viewport left boundary.
     *
     * @internal
     */
    export function createAnchoredInnerLeft(config: FixConfig): XPosition {
      const { vwMargin, screenRight, elWidth, disableSwapping } = config;

      let left = getInnerLeftCoord(config);
      let actualX: HorizontalPosition = "inner-left";
      if (left + elWidth <= screenRight && left >= vwMargin) {
        return { actualX, left };
      }

      if (disableSwapping) {
        if (left + elWidth > screenRight) {
          left = screenRight - elWidth;
        } else {
          left = vwMargin;
        }

        return { actualX, left };
      }

      const swappedLeft = getInnerRightCoord(config);
      if (swappedLeft < vwMargin) {
        left = vwMargin;
      } else if (swappedLeft + elWidth > screenRight) {
        left = screenRight - elWidth;
        actualX = "inner-right";
      } else {
        left = swappedLeft;
        actualX = "inner-right";
      }

      return { actualX, left };
    }

    /**
     * Attempts to position the fixed element so that it will appear at the center
     * of the container element but also within the viewport boundaries. If the
     * centered element can't fit within the viewport, it will use the vwMargin
     * value if it overflowed to the left, it'll position to the screen right
     * boundary.
     *
     * @internal
     */
    export function createAnchoredCenter(config: FixConfig): XPosition {
      const { vwMargin, screenRight, elWidth } = config;
      let left = getCenterXCoord(config);
      if (left < vwMargin) {
        left = vwMargin;
      } else if (left + elWidth > screenRight || left < vwMargin) {
        left = screenRight - elWidth;
      }

      return { actualX: "center", left };
    }

    /**
     * Attempts to position the fixed element so that it will appear to the
     * inner-right of the container element but also within the viewport boundaries.
     * When swapping is enabled, it will attempt to swap to the inner-left position
     * if it can't fit within the viewport to the right. If it can't fit in the
     * viewport even after being swapped to the left or swapping is disabled, it
     * will be positioned to the viewport right boundary.
     *
     * @internal
     */
    export function createAnchoredInnerRight(config: FixConfig): XPosition {
      const { screenRight, vwMargin, elWidth, disableSwapping } = config;

      let left = getInnerRightCoord(config);
      let actualX: HorizontalPosition = "inner-right";
      if (left >= vwMargin) {
        return { actualX, left: Math.min(left, screenRight - elWidth) };
      }

      const swappedLeft = getInnerLeftCoord(config);
      if (disableSwapping || swappedLeft + elWidth > screenRight) {
        left = vwMargin;
      } else {
        left = Math.max(swappedLeft, vwMargin);
        actualX = "inner-left";
      }

      return { actualX, left };
    }

    /**
     * Attempts to position the fixed element so that it will appear to the right of
     * the container element but also within the viewport boundaries. When swapping
     * is enabled, it will attempt to swap to the left position if it can't fit
     * within the viewport to the right. If it can't fit in the viewport even after
     * being swapped to the left or swapping is disabled, it will be positioned to
     * the viewport right boundary.
     *
     * @internal
     */
    export function createAnchoredRight(config: FixConfig): XPosition {
      const { screenRight, vwMargin, elWidth, disableSwapping } = config;

      let left = getRightCoord(config);
      let actualX: HorizontalPosition = "right";
      if (left + elWidth <= screenRight) {
        return { actualX, left };
      }

      const swappedLeft = getLeftCoord(config);
      if (disableSwapping || swappedLeft < vwMargin) {
        left = screenRight - elWidth;
      } else {
        left = swappedLeft;
        actualX = "left";
      }

      return { actualX, left };
    }

    export interface EqualWidthOptions
      extends Pick<
        CreateHorizontalPositionOptions,
        "x" | "elWidth" | "xMargin" | "vwMargin" | "containerRect" | "initialX"
      > {
      screenRight: number;
      isMinWidth: boolean;
    }

    /**
     * @internal
     */
    export function createEqualWidth(options: EqualWidthOptions): XPosition {
      const {
        x,
        elWidth,
        xMargin,
        vwMargin,
        initialX,
        containerRect,
        screenRight,
        isMinWidth,
      } = options;

      let left = initialX ?? containerRect.left + xMargin;

      let width: number | undefined = containerRect.width - xMargin * 2;
      let minWidth: number | undefined;
      let right: number | undefined;
      if (isMinWidth) {
        minWidth = width;
        // if the fixed element has a width greater than the element it is fixed to,
        // update the width to be the fixed element's width. since the "min-width"
        // option is only possible for horizontally centered elements, need to then
        // update the `left` position again.
        if (elWidth > width) {
          left -= (elWidth - width) / 2;
          minWidth = elWidth;
        }

        width = undefined;
        const elRight = left + elWidth;
        if (elRight > screenRight) {
          left -= elRight - screenRight;
          right = vwMargin;
        }

        left = Math.max(vwMargin, left);
      }

      // going to assume that the container element is visible in the DOM and just
      // make the fixed element have the same left and right corners
      return {
        left,
        right,
        width,
        minWidth,
        actualX: x,
      };
    }

    /**
     * Creates the horizontal position for a fixed element with the provided
     * options.
     * @internal
     */
    export function createHorizontalPosition(
      options: CreateHorizontalPositionOptions
    ): XPosition {
      const {
        x,
        vw,
        vwMargin,
        xMargin,
        width,
        elWidth,
        initialX,
        containerRect,
        disableSwapping,
      } = options;

      const screenRight = vw - vwMargin;
      if (width === "min" || width === "equal") {
        return createEqualWidth({
          x,
          vwMargin,
          xMargin,
          elWidth,
          initialX,
          containerRect,
          screenRight,
          isMinWidth: width === "min",
        });
      }

      if (elWidth > vw - vwMargin * 2) {
        // if the element's width is greater than the viewport's width minus the
        // margin on both sides, just make the element span the entire viewport with
        // the margin
        return {
          left: vwMargin,
          right: vwMargin,
          actualX: x,
        };
      }

      const config: FixConfig = {
        vwMargin,
        xMargin,
        elWidth,
        initialX,
        screenRight,
        containerRect,
        disableSwapping,
      };

      switch (x) {
        case "left":
          return createAnchoredLeft(config);
        case "inner-left":
          return createAnchoredInnerLeft(config);
        case "center":
          return createAnchoredCenter(config);
        case "inner-right":
          return createAnchoredInnerRight(config);
        case "right":
          return createAnchoredRight(config);
      }
    }