import type { ReactNode } from "react";
import { createStyledContext } from "tamagui";

export type SurfaceSize = "small" | "medium" | "large";
export type SurfaceSizeIntent = SurfaceSize | "sm" | "md" | "lg";
export type SurfaceDensity = "compact" | "comfortable";
export type SurfaceIntent = { size: SurfaceSize | "unset"; density: SurfaceDensity | "unset" };

const SIZE_INTENT_ALIASES: Record<SurfaceSizeIntent, SurfaceSize> = {
  sm: "small",
  small: "small",
  md: "medium",
  medium: "medium",
  lg: "large",
  large: "large",
};

export function normalizeSurfaceSize(size: SurfaceSizeIntent): SurfaceSize {
  return SIZE_INTENT_ALIASES[size];
}

export const SurfaceContext = createStyledContext<SurfaceIntent>({
  size: "unset",
  density: "unset",
});

export const SURFACE_SIZE_RANK = { unset: 99, small: 0, medium: 1, large: 2 } as const;
export const SURFACE_DENSITY_RANK = { unset: 99, compact: 0, comfortable: 1 } as const;

/**
 * Nested surfaces/controls may inherit or go tighter (lower rank), never larger
 * than the parent (LC-68). `unset` parent = no ceiling. `unset` requested = inherit.
 */
export function clampSurfaceSize(
  requested: SurfaceSize | "unset",
  parent: SurfaceSize | "unset",
): SurfaceSize | "unset" {
  if (parent === "unset") return requested;
  if (requested === "unset") return parent;
  return SURFACE_SIZE_RANK[requested] <= SURFACE_SIZE_RANK[parent] ? requested : parent;
}

export function clampSurfaceDensity(
  requested: SurfaceDensity | "unset",
  parent: SurfaceDensity | "unset",
): SurfaceDensity | "unset" {
  if (parent === "unset") return requested;
  if (requested === "unset") return parent;
  return SURFACE_DENSITY_RANK[requested] <= SURFACE_DENSITY_RANK[parent] ? requested : parent;
}

/**
 * Declares size/density INTENT for a subtree. Nested Surfaces clamp step-down
 * only — never raw gap tokens (LC-68, LC-69). Accepts sm/md/lg aliases.
 */
export function Surface({
  size,
  density,
  children,
}: {
  size?: SurfaceSizeIntent;
  density?: SurfaceDensity;
  children?: ReactNode;
}) {
  const parent = SurfaceContext.useStyledContext();
  const nextSize = clampSurfaceSize(size ? normalizeSurfaceSize(size) : "unset", parent.size);
  const nextDensity = clampSurfaceDensity(density ?? "unset", parent.density);
  return (
    <SurfaceContext.Provider size={nextSize} density={nextDensity}>
      {children}
    </SurfaceContext.Provider>
  );
}