import {
  createContext,
  useCallback,
  useContext,
  useMemo,
  useState,
  type Dispatch,
  type ReactNode,
  type SetStateAction,
} from "react";

const SPLIT_STORAGE_KEY = "luxsin-ai-split-pct";

/** sessionStorage: left-pane route before jumping from split to full-screen `#/ai` (desktop). */
export const AI_SPLIT_RESTORE_PATH_KEY = "luxsin_ai_restore_path";

export function readAndClearAiSplitRestorePath(): string {
  try {
    const s = sessionStorage.getItem(AI_SPLIT_RESTORE_PATH_KEY);
    sessionStorage.removeItem(AI_SPLIT_RESTORE_PATH_KEY);
    if (s && typeof s === "string" && s.startsWith("/") && !s.includes("..")) return s;
  } catch {
    /* ignore */
  }
  return "/";
}
const SPLIT_MIN = 28;
const SPLIT_MAX = 72;

function clampPct(n: number) {
  return Math.min(SPLIT_MAX, Math.max(SPLIT_MIN, Math.round(n)));
}

function loadSplitPct(): number {
  if (typeof window === "undefined") return 50;
  try {
    const v = sessionStorage.getItem(SPLIT_STORAGE_KEY);
    if (v) {
      const n = parseInt(v, 10);
      if (!Number.isNaN(n)) return clampPct(n);
    }
  } catch {
    /* ignore */
  }
  return 50;
}

type AIDrawerContextValue = {
  /** Desktop split panel visible (only used when lg+ and route !== /ai) */
  open: boolean;
  setOpen: Dispatch<SetStateAction<boolean>>;
  toggle: () => void;
  /** Width share of the AI column (percent), used when split view is shown */
  splitPercent: number;
  setSplitPercent: (pct: number) => void;
};

const AIDrawerContext = createContext<AIDrawerContextValue | null>(null);

export function AIDrawerProvider({ children }: { children: ReactNode }) {
  const [open, setOpen] = useState(false);
  const [splitPercent, setSplitPercentState] = useState(loadSplitPct);

  const toggle = useCallback(() => setOpen((o) => !o), []);

  const setSplitPercent = useCallback((pct: number) => {
    const next = clampPct(pct);
    setSplitPercentState(next);
    try {
      sessionStorage.setItem(SPLIT_STORAGE_KEY, String(next));
    } catch {
      /* ignore */
    }
  }, []);

  const value = useMemo(
    () => ({ open, setOpen, toggle, splitPercent, setSplitPercent }),
    [open, splitPercent, setSplitPercent, toggle],
  );

  return (
    <AIDrawerContext.Provider value={value}>{children}</AIDrawerContext.Provider>
  );
}

export function useAIDrawer() {
  const ctx = useContext(AIDrawerContext);
  if (!ctx) {
    throw new Error("useAIDrawer must be used within AIDrawerProvider");
  }
  return ctx;
}