"use client";

import {
  useCallback,
  useEffect,
  useRef,
  useState,
  type ChangeEvent,
} from "react";
import Upload from "../../../../components/controls/Upload";
import { useMessages, useTranslation } from "../../../../contexts/MessagesContext";
import { useCreateFlow } from "../../context/CreateFlowContext";
import { CreateFlowHeaderLockup } from "../../components/CreateFlowHeaderLockup";
import { CreateFlowStepShell } from "../../components/CreateFlowStepShell";
import { CREATE_FLOW_MD_UP_COLUMN_MAX_CLASS } from "../../components/createFlowLayoutTokens";
import { fetchAuthSession } from "../../../../../lib/create/api";
import {
  createFlowUploadFailureMessageKey,
  uploadCreateFlowFile,
} from "../../../../../lib/create/uploadToServer";
import {
  COMMUNITY_AVATAR_ACCEPT,
  messageKeyForCreateFlowUploadReason,
  validateCreateFlowUploadFile,
} from "../../../../../lib/create/createFlowUploadValidation";
import {
  clearPendingCommunityAvatarFile,
  readPendingCommunityAvatarFile,
  storePendingCommunityAvatarFile,
} from "../../../../../lib/create/pendingCommunityAvatarUpload";

function hasCommunityAvatarUrl(url: string | undefined): boolean {
  return typeof url === "string" && url.trim().length > 0;
}

/** Create Community — Figma Flow — Upload. */
export function CommunityUploadScreen() {
  const m = useMessages();
  const u = m.create.community.communityUpload;
  const { markCreateFlowInteraction, state, updateState } = useCreateFlow();
  const tUpload = useTranslation("create.upload");

  const fileInputRef = useRef<HTMLInputElement | null>(null);
  const [signedIn, setSignedIn] = useState<boolean | null>(null);
  const [localPreviewUrl, setLocalPreviewUrl] = useState<string | null>(null);
  const [localFileName, setLocalFileName] = useState<string | null>(null);
  const [busy, setBusy] = useState(false);
  const [errorMessage, setErrorMessage] = useState<string | null>(null);

  useEffect(() => {
    let cancelled = false;
    void fetchAuthSession().then(({ user }) => {
      if (!cancelled) setSignedIn(Boolean(user));
    });
    return () => {
      cancelled = true;
    };
  }, []);

  useEffect(
    () => () => {
      if (localPreviewUrl) URL.revokeObjectURL(localPreviewUrl);
    },
    [localPreviewUrl],
  );

  const serverAvatarUrl = hasCommunityAvatarUrl(state.communityAvatarUrl)
    ? state.communityAvatarUrl!.trim()
    : null;
  const serverAvatarUrlRef = useRef(serverAvatarUrl);
  serverAvatarUrlRef.current = serverAvatarUrl;

  useEffect(() => {
    if (serverAvatarUrl) {
      setLocalPreviewUrl((prev) => {
        if (prev) URL.revokeObjectURL(prev);
        return null;
      });
    }
  }, [serverAvatarUrl]);

  useEffect(() => {
    let cancelled = false;
    void (async () => {
      try {
        const file = await readPendingCommunityAvatarFile();
        if (cancelled || !file) return;
        const validated = await validateCreateFlowUploadFile(
          file,
          "communityAvatar",
        );
        if (validated.ok === false) {
          await clearPendingCommunityAvatarFile();
          return;
        }
        if (cancelled) return;
        if (serverAvatarUrlRef.current) return;
        const objectUrl = URL.createObjectURL(file);
        if (cancelled) {
          URL.revokeObjectURL(objectUrl);
          return;
        }
        setLocalPreviewUrl((prev) => {
          if (prev) URL.revokeObjectURL(prev);
          return objectUrl;
        });
        setLocalFileName(file.name);
        if (!state.communityAvatarFileName) {
          updateState({ communityAvatarFileName: file.name });
        }
      } catch {
        // Missing IndexedDB / quota: leave the picker empty.
      }
    })();
    return () => {
      cancelled = true;
    };
  }, [state.communityAvatarFileName, updateState]);

  const resolveUploadError = useCallback(
    (err: unknown) => {
      const key = createFlowUploadFailureMessageKey(err);
      if (key === "errors.tooLarge") return u.fileTooLarge;
      return tUpload(key);
    },
    [tUpload, u.fileTooLarge],
  );

  const handleFileChange = useCallback(
    async (e: ChangeEvent<HTMLInputElement>) => {
      const file = e.target.files?.[0];
      e.target.value = "";
      if (!file) return;
      markCreateFlowInteraction();
      setErrorMessage(null);

      if (signedIn === true) {
        setBusy(true);
        try {
          const { url } = await uploadCreateFlowFile(file, "communityAvatar");
          setLocalPreviewUrl((prev) => {
            if (prev) URL.revokeObjectURL(prev);
            return null;
          });
          setLocalFileName(file.name);
          updateState({
            communityAvatarUrl: url,
            communityAvatarFileName: file.name,
          });
        } catch (err) {
          setErrorMessage(resolveUploadError(err));
        } finally {
          setBusy(false);
        }
        return;
      }

      const validated = await validateCreateFlowUploadFile(
        file,
        "communityAvatar",
      );
      if (validated.ok === false) {
        setErrorMessage(
          validated.reason === "tooLarge"
            ? u.fileTooLarge
            : tUpload(messageKeyForCreateFlowUploadReason(validated.reason)),
        );
        return;
      }
      try {
        await storePendingCommunityAvatarFile(file);
        setLocalPreviewUrl((prev) => {
          if (prev) URL.revokeObjectURL(prev);
          return URL.createObjectURL(file);
        });
        setLocalFileName(file.name);
        updateState({ communityAvatarFileName: file.name });
      } catch {
        setErrorMessage(tUpload("errors.generic"));
      }
    },
    [
      markCreateFlowInteraction,
      resolveUploadError,
      signedIn,
      tUpload,
      u.fileTooLarge,
      updateState,
    ],
  );

  const handlePickFile = useCallback(() => {
    if (!busy) fileInputRef.current?.click();
  }, [busy]);

  const displaySrc = serverAvatarUrl ?? localPreviewUrl;
  const hasPreview = typeof displaySrc === "string" && displaySrc.length > 0;
  const fileName =
    localFileName ??
    (typeof state.communityAvatarFileName === "string" &&
    state.communityAvatarFileName.trim().length > 0
      ? state.communityAvatarFileName.trim()
      : undefined);

  return (
    <CreateFlowStepShell
      variant="centeredNarrow"
      contentTopBelowMd="space-1400"
    >
      <div
        className={`flex flex-col items-center gap-[18px] ${CREATE_FLOW_MD_UP_COLUMN_MAX_CLASS}`}
      >
        <div className="w-full">
          <CreateFlowHeaderLockup
            title={u.title}
            description={u.description}
            justification="center"
          />
        </div>
        <input
          ref={fileInputRef}
          type="file"
          className="sr-only"
          tabIndex={-1}
          accept={COMMUNITY_AVATAR_ACCEPT}
          aria-label={hasPreview ? u.replaceButton : u.hintText}
          onChange={handleFileChange}
        />
        <Upload
          hasLabel={false}
          active={!busy}
          state={
            errorMessage ? "error" : busy ? "disabled" : "default"
          }
          hintText={
            errorMessage
              ? errorMessage
              : busy
                ? u.uploadingLabel
                : u.hintText
          }
          buttonLabel={hasPreview ? u.replaceButton : undefined}
          previewSrc={hasPreview ? displaySrc ?? undefined : undefined}
          previewAlt={u.previewAlt}
          fileName={hasPreview ? fileName : undefined}
          onClick={handlePickFile}
        />
      </div>
    </CreateFlowStepShell>
  );
}