import type { MediaKind, MediaUploadLimits, MediaUploadPolicy } from "@/api/media-upload-contracts";

export const EMERGENCY_PHOTO_MAX_BYTES = 10_000_000;
export const EMERGENCY_VIDEO_MAX_BYTES = 100_000_000;
export const EMERGENCY_VIDEO_MAX_SECONDS = 90;

const PHOTO_MIME_TYPES = new Set(["image/jpeg", "image/jpg", "image/png", "image/heic"]);

const PHOTO_EXTENSIONS = new Set([".jpg", ".jpeg", ".png", ".heic"]);

const VIDEO_MIME_TYPES = new Set(["video/mp4", "video/quicktime"]);

const VIDEO_EXTENSIONS = new Set([".mp4", ".mov"]);

export type MediaValidationProbe = (file: File) => Promise<number | null>;

export type MediaValidationResult = { ok: true } | { ok: false; reason: string };

function fileExtension(file: File): string {
  const name = file.name.toLowerCase();
  const dot = name.lastIndexOf(".");
  return dot >= 0 ? name.slice(dot) : "";
}

export function classifyMediaKind(file: File): MediaKind | null {
  const mime = file.type.toLowerCase();
  if (PHOTO_MIME_TYPES.has(mime) || PHOTO_EXTENSIONS.has(fileExtension(file))) {
    return "Photo";
  }
  if (VIDEO_MIME_TYPES.has(mime) || VIDEO_EXTENSIONS.has(fileExtension(file))) {
    return "Video";
  }
  return null;
}

/** Inclusive limit: exactly at the cap passes, one byte over fails. */
export function isMediaSizeWithinLimit(
  file: File,
  kind: MediaKind,
  limits: MediaUploadLimits,
): boolean {
  const maxBytes = kind === "Photo" ? limits.photoMaxBytes : limits.videoMaxBytes;
  return file.size <= maxBytes;
}

export function mediaOverLimitNotice(
  file: File,
  kind: MediaKind,
  limits: MediaUploadLimits,
): string {
  if (kind === "Video") {
    return `"${file.name}" exceeds the video limit (${Math.round(limits.videoMaxBytes / 1_000_000)} MB, ${limits.videoMaxSeconds} seconds).`;
  }
  return `"${file.name}" exceeds the photo limit (${Math.round(limits.photoMaxBytes / 1_000_000)} MB).`;
}

export function mediaKindLimitReachedNotice(kind: MediaKind, limits: MediaUploadLimits): string {
  const max = kind === "Photo" ? limits.maxPhotos : limits.maxVideos;
  return `${kind} limit reached (${max} per work order). Remove a file to add another.`;
}

export function emergencyMediaBatchCountError(
  file: File,
  acceptedFiles: readonly File[],
  policy?: Pick<MediaUploadPolicy, "limits" | "remaining">,
): string | undefined {
  const kind = classifyMediaKind(file);
  if (!kind || !policy) return undefined;
  const available = kind === "Photo" ? policy.remaining.photos : policy.remaining.videos;
  const alreadyAccepted = acceptedFiles.filter((accepted) => classifyMediaKind(accepted) === kind);
  if (alreadyAccepted.length < available) return undefined;
  return mediaKindLimitReachedNotice(kind, defaultLimits(policy.limits));
}

export function emergencyMediaAcceptAttribute(): string {
  return "image/jpeg,image/jpg,image/png,image/heic,video/mp4,video/quicktime,.jpg,.jpeg,.png,.heic,.mp4,.mov";
}

/**
 * Media limits apply only to Emergency/Reactive work orders; `canUpload` from the
 * server policy is authoritative and work-order binding/category are fixed by route.
 */
export function isEmergencyReactiveWorkOrderType(workOrderType: string | undefined): boolean {
  if (!workOrderType) return false;
  const normalized = workOrderType.trim().toLowerCase();
  return normalized === "emergency" || normalized === "reactive";
}

/**
 * Probe video duration from browser metadata. Returns null whenever probing or
 * preview decoding fails (e.g. some MOV files) — unknown duration proceeds to the
 * server, which enforces the cap at commit. Temporary preview URL is always revoked.
 */
export function probeVideoDurationSeconds(file: File): Promise<number | null> {
  return new Promise((resolve) => {
    const url = URL.createObjectURL(file);
    const video = document.createElement("video");
    let settled = false;

    const finish = (value: number | null) => {
      if (settled) return;
      settled = true;
      clearTimeout(timer);
      URL.revokeObjectURL(url);
      video.removeAttribute("src");
      resolve(value);
    };

    const timer = setTimeout(() => finish(null), 4_000);
    video.preload = "metadata";
    video.addEventListener("loadedmetadata", () => {
      const duration = video.duration;
      finish(Number.isFinite(duration) && duration > 0 ? duration : null);
    });
    video.addEventListener("error", () => finish(null));
    video.src = url;
  });
}

function defaultLimits(limits?: Partial<MediaUploadLimits>): MediaUploadLimits {
  return {
    photoMaxBytes: limits?.photoMaxBytes ?? EMERGENCY_PHOTO_MAX_BYTES,
    videoMaxBytes: limits?.videoMaxBytes ?? EMERGENCY_VIDEO_MAX_BYTES,
    videoMaxSeconds: limits?.videoMaxSeconds ?? EMERGENCY_VIDEO_MAX_SECONDS,
    maxPhotos: limits?.maxPhotos ?? 10,
    maxVideos: limits?.maxVideos ?? 3,
  };
}

export function emergencyMediaSizeError(
  file: File,
  limits?: Partial<MediaUploadLimits>,
): string | undefined {
  const kind = classifyMediaKind(file);
  if (!kind) return undefined;
  const resolvedLimits = defaultLimits(limits);
  return isMediaSizeWithinLimit(file, kind, resolvedLimits)
    ? undefined
    : mediaOverLimitNotice(file, kind, resolvedLimits);
}

/**
 * Validate one media file against the policy limits: kind, inclusive size caps and
 * duration when it can be probed. A failed duration probe keeps the file eligible.
 */
export async function validateMediaFileAgainstLimits(
  file: File,
  policy: Pick<MediaUploadPolicy, "limits" | "remaining">,
  probe: MediaValidationProbe = probeVideoDurationSeconds,
): Promise<MediaValidationResult> {
  const limits = defaultLimits(policy.limits);
  const kind = classifyMediaKind(file);
  if (!kind) {
    return {
      ok: false,
      reason: "Only photos (JPG, PNG, HEIC) and videos (MP4, MOV) are supported.",
    };
  }
  if (!isMediaSizeWithinLimit(file, kind, limits)) {
    return { ok: false, reason: mediaOverLimitNotice(file, kind, limits) };
  }
  const remaining = kind === "Photo" ? policy.remaining?.photos : policy.remaining?.videos;
  if (typeof remaining === "number" && remaining <= 0) {
    return { ok: false, reason: mediaKindLimitReachedNotice(kind, limits) };
  }
  if (kind === "Video") {
    const seconds = await probe(file);
    if (seconds != null && seconds > limits.videoMaxSeconds) {
      return {
        ok: false,
        reason: `"${file.name}" is longer than the ${limits.videoMaxSeconds} second video limit.`,
      };
    }
  }
  return { ok: true };
}