"use client";

import localforage from "localforage";

import type { ChatAttachment, ChatCapabilityMode, ChatReasoningEffort } from "@/lib/chat-runtime";

export type ChatComposerDraft = {
  prompt: string;
  model: string;
  reasoningEffort: ChatReasoningEffort;
  capabilityMode: ChatCapabilityMode;
  attachments: ChatAttachment[];
};

const stateKey = "chatgpt2api:chat_composer_draft_v1";
const attachmentStorage = localforage.createInstance({ name: "chatgpt2api", storeName: "chat_composer_draft" });
const attachmentKey = "attachments:v1";

export function saveChatComposerDraftState(draft: Omit<ChatComposerDraft, "attachments">) {
  if (typeof window === "undefined") return;
  try {
    window.sessionStorage.setItem(stateKey, JSON.stringify(draft));
  } catch {
    // Draft persistence is best-effort in restricted browsing modes.
  }
}

export async function saveChatComposerDraftAttachments(attachments: ChatAttachment[]) {
  if (attachments.length === 0) {
    await attachmentStorage.removeItem(attachmentKey);
    return;
  }
  await attachmentStorage.setItem(attachmentKey, attachments);
}

export async function loadChatComposerDraft(): Promise<ChatComposerDraft> {
  let raw: Partial<ChatComposerDraft> = {};
  if (typeof window !== "undefined") {
    try {
      raw = JSON.parse(window.sessionStorage.getItem(stateKey) || "{}");
    } catch {
      raw = {};
    }
  }
  const attachments = await attachmentStorage.getItem<ChatAttachment[]>(attachmentKey);
  return {
    prompt: String(raw.prompt || ""),
    model: String(raw.model || "auto"),
    reasoningEffort: ["low", "medium", "high", "xhigh"].includes(String(raw.reasoningEffort || ""))
      ? raw.reasoningEffort as ChatReasoningEffort
      : "",
    capabilityMode: ["auto", "chat", "web_search", "image_generation"].includes(String(raw.capabilityMode || ""))
      ? raw.capabilityMode as ChatCapabilityMode
      : "auto",
    attachments: Array.isArray(attachments) ? attachments : [],
  };
}

export async function clearChatComposerDraft() {
  if (typeof window !== "undefined") {
    try {
      window.sessionStorage.removeItem(stateKey);
    } catch {
      // Ignore unavailable browser storage.
    }
  }
  await attachmentStorage.removeItem(attachmentKey);
}